Exam 2 Study Guide
Exam 2 Study Guide BIO102
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Date Created: 03/05/15
Bio 102 Exam 2 Study Guide Week 5 1St week for exam 2 material 21115 0 How fast is speciation o Gradualism versus punctuated equilibrium Darwin generally thought gradualst Fossil record shows 0 Mass extinctions followed by rapid in geological time radiations New species often appear more abruptly than predict under gradualst When might species not evolve Biodiversity about 2 million species described may be as many as 520 million total Why so many species a Increases in atmospheric oxygen allowed aerobic and anaerobic respiration b Plate tectonics created geographic isolation among species which led to allopatric speciation a Case study Australia basically an island separated by 65 MY i Lots of endemic species there c Climate change regular glacial advances and recessions a Constantly changing geographic ranges of species and environmental conditions d Mass extinctions loss of many species led to many open niches for speciation to occur e adaptive radiation evolution of ecological and phenotypic diversity within a rapidly multiplying lineage a speciation and phenotypic adaptation of an array of species exhibiting different morphological and physiological traits i Starts from single ancestor ii can exploit a range of divergent environments a Animal diversity a Cambrian explosion formation of hard outer body shells i Radiation of most modern animal phyla ii Well marked in fossil record iii Why 1 Complex predator prey relationships 2 Evolution of common body plans genes that control form Classifying animal diversity Animals Eukaryotic Multicellular Heterotrophic Obtain nutrients by eating Most animals reproduce sexually over 2000000 described extant species Phylum Chordata best known 5 95 described animal species are invertebrates 21315 Cells Introduction Outline Introduction to cells HIV life cycle Cell membrane function Basic cell structure HIV Life cycle 1 Virus binds receptors on cell membrane and enters cell Enzymes remove proteins of viral capsid 2 RT reverse transcriptase catalyzes formation of DNA complementary to viral RNA 3 New DNA strand serves as a template for complementary DNA strand 4 Double stranded DNA is incorporated into host cell s genome 5 Viral genes transcribed into mRNA Some viral DNA copied as the RNA genome for virions 6 mRNA messenger RNA translated into HIV proteins in cytoplasm 7 Capsids protein coats surround new viral RNA genomes 8 New viruses bud from host cell Questions How does HIV get into a cell Why aren t cells permeable to other things Why are cells quotalivequot and viruses not How is virus structure different from cell structure How does virus make copies of itself what cell parts does it manipulate HOW does HIV get into a cell First HIV enters through the cell membrane Cell membrane quotselectiver permeablequot Viruses and other diseases have to trick it to get in Structure Cell membrane structure remarkably similar among cell types Phospholipid bilayer Hydrophobic quotwater hatingquot tail Interact with aqueous medium Hydrophilic quotwater lovingquot head quotoilyquot core Why aren t cells permeable to other things Cells are quotselectively permeablequot Can t just let anything pass in or would get destroyed Permeability depends on proteins embedded in phospholipid bilayer Cell needs to communicate with other cells Different cell types need different materials cells also need to rid themselves of wastes Mechanisms of cell entry diffusion Particles move from area of high concentration to area of low concentration Small particles can just pass through cell membrane passive Mechanisms of cell entry osmosis Diffusion of water From high concentration to low concentration Passive When medium has higher concentration of water than cell cell is hypotonic More water in cell less solutes than medium cell is hypertonic Why don t our cells burst Mechanisms of cell entryfacilitated diffusion Substances enter protein carrier in membrane and change shape After solute moved across membrane protein returns to original shape Bigger molecules can pass through Requires no energy Mechanisms of cell entryactive transport Carrier protein binds to substance being transported and carries it to other side of membrane Most often requires energy Move substances against concentration gradient Mechanisms of cell entry endocytosis exocytosis Endocytosis substance engulfed by cell in vesicle Exocytosis substance packed up by cell and quotsent offquot HIV cell entry HIV binds to 2 cell receptor proteins in tcells Cells think it is a necessary protein and quotlet it inquot Why are cells alive and viruses not Viruses do not have means of replicating themselves Protein coat enzymes DNA or RNA Cells quotfundamental unit of lifequot membrane Organelles nucleus eukaryotic and ways to make proteins and replicate themselves Week 6 2 39 week for exam 2 material 21815 Reading Notes Cell Structure and Function Uni ed Cell Theory Proposed by Matthias Schleiden and Theodor Schwann All living things are composed of one or more cells the cell is the basic unit of life and new cells arise from existing cells Prokaryotic Cells 0 Does not contain a Nucleus or any other membranebound organelle o The DNA is found in the central part of the cell called the nucleoid 0 Mostly single celled Eukaryotic Cells 0 Have membranebound nucleus 0 Many membranebound organelles like Endoplasmic reticulum Golgi apparatus Chloroplasts Mitochondria 0 Several rodshaped chromosomes Cytoplasm is the entire region of a cell between the plasma membrane and the nuclear envelope doublemembrane structure that takes most of the outer most portion of the nucleus 0 Consists of 7080 water although it has a semisolid consistency which comes from the proteins in it o Nucleus o The most prominent organelle in the cell 0 Houses the cells DNA and directs synthesis of ribosomes and proteins 1 Ribosomes o Responsible for protein synthesis 0 Appear as a single tiny dots or a cluster 1 Mitochondria o The powerhouse or energy factories of the cell and are responsible for making adenosine triphosphate ATP the cell s main energy carrying molecule 0 Double membrane organelles o Vesicles and Vacuoles o Membranebound sacs that function in storage and transport 0 Vacuoles are somewhat larger than vesicles 0 The membranes of vesicles can fuse with either plasma membrane or other membrane systems within the cell 0 some agents such as enzymes within plant vacuoles break down macromolecules and the membrane of a vacuole does not fuse with the membranes of other cellular components 0 Animal cells vs Plant cells 0 Plant cells have a cell wall while animal cells don t 0 Both have cell membranes 0 Animal cells have lysosomes the cell s 39garbage disposal while in plants the digestive process happens in the vacuoles 0 Plant cells have chloroplasts which are the plant cell s organelles that carry out photosynthesis Lecture outline Creature of the day Ayeaye pronounced eyeeye 0 Type of lemur o Madagascar 0 Has a multipurpose digit that taps on wood to nd food and listens for vibrations inside that could mean movement of food 0 Cell structure and function 0 Once in how does HIV complete its life cycle 0 Basics of cell communication Cells Part 2 structure and function Talked about the cell membrane 0 If glycoprotein matches the cell the virus is able to enter the cell because the glycoprotein is like a key that has to match 0 Once HIV is in what does it do 0 Utilizes several cell organelles to complete it s life cycle 0 Can use HIV life cycle to understand cell structure Once in the cell HIV proteins and RNA released into cytoplasm Cytoplasm 0 Mostly water This is where the quothumans are mostly waterquot 7580 comes from because all of our cells are mostly water or a liquid 0 Also contains proteins amp other chemicals 0 Cell organelles oating in it Cells change shape 0 Reverse transcription next 0 Once in the cytoplasm HIV uses enzyme reverse transcriptase to change from RNA to DNA Animal cells controlled by DNA AZT drugs block the enzyme from completing this action so the proteins don t assemble properly and cant spread using that cell Once in cytoplasm HIV uses enzyme reverse transcriptase to change from RNA to DNA Animal cells controlled by DNA HIV then moves to nucleus Nucleus 0 Control center of cell 0 Contains chromosomes hereditary material 0 Surrounded by nuclear envelope 0 Has nuclear pores Allow communication with cell protein synthiesis HIV gets into nuclear pore don t know exactly how 0 Once in nucleus HIV uses enzyme integrase to insert itself into cell s DNA Then starts making proteins to make copies of itself 0 Proteins are made in ribosomes some ribosomes in cytoplasm others in rough endoplasmic reticulum endoplasmic reticulum ER 0 Complex network of tubes and sacs o 2 types Lquotsmoothquot Small percentage Lipids and carbohydrates made 2 quotroughquot Mostly rough Ribosomes make it bumpy 0 Site of protein synthesis So HIV makes necessary proteins eg RT enzyme in rough ER 0 then has to transport these proteins into cytoplasm 0 proteins enter transport vesicles that quotbudquot from rough ER to golgi apparatus 0 Components like lipids to assemble new virions made in smooth ER 0 Golgi apparatus UPS of the cell Sorting and labeling them by zip code and then ship them out ribosomes Directs proteins and lipids to nal destinations in cell quotsorting and shipping stationquot So HIV uses the golgi apparatus to sort and ship proteins and lipids to form new virions HIV virions assembled and parts leave cell by exocytosis Other important cell components 0 Mitochondria the quotpower plantsquot of the cell The energy source of the cell 0 Mitochondrial DNA Animals versus plant cells 3 Main differences 1 Plants have a cell wall in addition to plasma membrane 2 Plants have chloroplasts for making sugars or quotfoodquot for the plant 3 Plants cells have vacuoles Cellular communication 0 Cells in multicellular organisms are specialized Although they are specialized they do not operate in isolation Thus cells must communicate with one another 0 Brain feels quotpainquot 0 You pull hand away from heat 0 quotsignaling moleculesquot proteins and chemicals used for communication Signaling molecules 0 Received by quottarget cellsquot 0 2 types of receptors 1 ln membrane 0 Hydrophilic molecules bind to receptors at cell surface 2 Inside cell 0 Hydrophobic molecules pass through membrane Types of signaling molecules 1 Shortrange affect only cells around them 0 Have short life span 0 Eg nitric oxide expansion of blood vessel walls or vasodilation lowers blood pressure 2 Longrange can travel through blood 0 Longer life span 0 Eg hormonesadrenaine testosterone estrogen etc o Eg adrelanine response See frightening stimulus eg snake Brain sends signal to adrenal gland on kidney produce adrenaline Adrenaline goes to liver Liver breaks down glucose Adrenaline goes to heart Beats more increasing blood ow Why are bacteria such as anthrax toxic P P FWN They interfere with intercellular communication Anthrax toxin blocks action of kinase an enzyme that cuts up proteins 0 Once kinase is inactivated the cell cannot respond to external signals 0 Cell eventually dies How can snake venom kill you Cobra venom has neurotoxins that block signals among nerve cells 0 quotpostsynaptic blockquot 0 Results in muscle freeze diaphrang Leads to dif culty breathing which can lead to respiratory arrest Key points The cell is the basic unit of life 0 Cellular structure in eukaryotes is complex 0 Each cell has an organized interworking group of parts to perform cell functions 0 Depending on the type of cell different proteins will be synthesized and cellular structure varies Cells are specialized and need to communicate 0 Short range or longrange signaling molecules 22015 Cell Division and Cancer Lecture Lecture Outline Creature of the day Peacock Spider o Twerking spider 0 Weird blue butt 0 Moves arms kind of looks like its dancing 0 Warning colors Week 7 3ml week of exam 2 material 22315 Cell division and Cancer Creature of the day Grumpy frog 0 African rain frog Blob sh 0 Deep sea sh of Australia Angler sh 0 Deep sea sh with modi ed n that is a lure bio luminescent to see 0 Star nosed mole o E Canada and NE America good swimmer sensitive tentacles The cell cycle 0 Cell division mitosis 0 Cancer abnormal cell division 0 Cell division meiosis 0 Sex cell gamete formation Cancer is caused by abnormal cell division Cell division is part of a normal cellular process Cell cycle normal Most of the time cells are in interphase Steps of interphase are o 61 cell growth amp normal metabolism 0 S DNA replication amp chromosome duplication o 62 growth amp preparation for mitosis S phase initiates division in chromosomes 0 S phase before mitosis DNA replicates amp into 2 sister chromatids connected by a centromere Chromosomes 0 DNA is tightly wound in chromosomes contained in cell nucleus 0 Each species has different numbers and shapes of chromosomes quotka ryotypequot 0 Most animals are diploid meaning that they carry 2 copies of chromosomes 0 Pars of chromosomes are called homologous 12 meters of DNA packed in cell size of 5 micrometers 0 Each species has different numbers amp shapes of chromosomesgt quotka ryotypequot 0 Most animals are diploid meaning that they carry 2 copies of chromosomes 0 Pairs of chromosomes 1 from mom and 1 from dad are called homologous 0 Cells in human body except eggs amp sperm contain 46 chromosomes each During S phase chromosomes double making 4 copies Then G phase Then 4 stages of mitosis 1 Prophase 2 Metaphase 3 Anaphase 4 Telophase Prophase First stage of mitosis Chromatin condenses amp becomes visible in nucleus Centrosomes move to opposite poles of cell Microtubules begin to grow out from centrosomes Metaphase middle Chromosomes attach to spindle bers at centromeres Chromosomes line up in middle of cell Anaphase Daughter chromosomes separate Pulled by spindle bers to opposite sides of cell Telophase Spindle bers dissolve New nuclei form 0 Ring of actin laments forms around nuclei Cytokinesis breaks 2 daughter cells apart 0 Technically not a part of mitosis Cancen Now that we know normal cell division process how does cancer occur 1 single cell loses control of mitosis 2 divides uncontrollany producing daughter cells with same problems a if contained at this stage tumor called benign 3 if these cancerous cells spread to other parts of body tumor is malignant Why don t we see cells dividing out of control all the time Cell division is heavily regulated Genes that produce proteins involved in cell division called protooncogenes Tumor suppressor genes prevent cells from dividing For cell to divide protooncogenes must be turned on and tumor suppressor genes off Certain types of DNA damage cause cell to lose control of mitosis How a cell turns cancerous 1 Protooncogenes become oncogenes which cause excessive cell division 0 works with single mutation 2 Damage to tumor suppressor genes 0 both copies have to be damaged Cancer related to lifestyle 0 Study 44000 pairs of twins 0 most important contributor to cancer risk was environment including lifestyle and behavior Risk factors see Table 115 Behavioral changes can reduce risk of many types of cancer Cigarette smoking leading cause of cancer mortality in US Tobacco smoke has 40 known carcinogens People who quit smoking before age 50 reduce risk of dying by 50 0 Skin cancer 0 By far most common 0 1 million new cases per year in US 0 Risk goes up dramatically each time sunburned o WEAR SUNSCREEN Queensland Australia 0 Ozone layer thin protects against UV B 0 13 people get skin cancer Types Carcinoma generally not malignant but should be removed Melanoma bad news Meiosis division of gametes Produces gametes eggs and sperm 0 Key just like mitosis but 2 cellular divisions before second division DNA does NOT replicate Major differences from mitosis 0 ends up in 1 copy of chromosomes haploid in eggs and sperm versus 2 copies diploid from mitosis in rest of somatic cells Results in 4 daughter cells Meiosis causes variation Sexual reproduction fusion of gametes causes variation in offspring New chromosome combinations from parents Variation also caused by crossing over 00000 homologous chromosomes switch sections creating new combinations Key points 0 Cancer is caused by abnormal cell division mitosis Cell division is a normal part of the cell cycle that is kept in check by regulatory genes Mitosis allows division of somatic all cells but gametes results in 2 diploid daughter cells Meiosis allows formation of gametes eggs and sperm Results in 4 haploid gametes New terms Gametes cells produced for sexual reproduction eggs and sperm Diploid 2 copies of chromosomes also called 2N found in somatic non sexceHs Haploid 1 copy of chromosomes also called N found in gametes Crossing over when sister chromatids exchange chunks of chromosome during meiosis Interphase noncell division phase except in S phase when DNA and chromosomes replicate Chromosome packet of tightly wound DNA Homologous chromosomes matching chromosomes inherited from each parent Chromatid when chromosomes replicate sister chromatids are the copies Centromere place where sister chromatids are connected before the separate during anaphase Spindle bers attach to centromeres and help drag copied chromosomes to opposite sides of cell 0 during anaphase Cytokinesis furrowing 39pinching off of cell membrane to complete cell division process 22515 Immunity and Vaccines Reading Notes 0 A more technical term for germs are pathogens 0 Pathogens include Bacteria viruses protists some fungi and multicellular animals like parasites 0 Different genetic versions of pathogens are called strains Immune System System built to protect body against pathogens 0 External defenses made up of physical and chemical barriers on the surface of the body these are the rst line of the immune system 0 Internal or lnnate immune system Gets kicked into gear when the external defenses fail 0 Adaptive Immune System Layer of innate immune system Acts in a highly speci c manner against pathogens Remembers rst encounter with certain strain of pathogen and then specialized defense cells are put against those certain strains of pathogens Immune Memory feature of adaptive immune system The capacity to remember the rst encounter of certain strains of pathogens to know which specialized defense cells to send to fend of the pathogen Lecture Notes The air we breathe is full of germs Pathogens are disease causing agents and can be found on almost any surface we touch 0 Pathogens include viruses bacteria and protists as well as some fungi and multicellular animals Given that bacteria viruses and fungi are everywherewhy aren t we always sick Animals possess an immune system that protects them against most infectious agents o 3 lines of defense External defenses on the surface of the body are the rst ineof defense in animals Internal defense system Innate immune system is the second line of defense Adaptive immune system third line of defense highly speci c with specialized defense cells 1St line of defense skin and mucous Skin provides general protection Mucus traps microbes amp debris in respiratory tract Cilia lining walls sweep away mucus amp foreign matter Bypassing 1St line of defense easy for many pathogens 0 Many pathogens take advantage of breaks in the skin to gain entry to their hosts 0 Other pathogens are vectored by blood feeding hosts 0 Yet others are ingested by breathing 2nOI line of defense innate immunitv 1 Phagocytosis Macrophages modi ed white blood cells engulf amp digest microbes by phagocytosis 2 Cellular defenses Natural killer cells i Modi ed white blood cells ii Do not kill normal cells bc they recognize self proteins in cell membrane iii Kill antigens by releasing poreforming proteins iv Dissolve cell membrane amp it leaks to death 3 In ammation Symptoms i Reddening increased blood ow ii Swelling leaky capillaries iii Heat increased metabolism and phagocytosis iv Pain pressure or damage to nerve endings Process i Skin is torn ii Damaged cells and mast cells release histamine iii Histamine makes blood vessels leaky iv Macrophages squeeze through leaky vessels and engulf bacteria by phagocytosis v Platelets help seal off wound clotting 4 Fever 0 Effective part of body s defense against infection 0 Most bacteria viruses adapted to 986 37 C for replication 0 Raising body temperature reduces replication rate of invaders o Bacteria need iron at higher temps growth reduced 0 Higher temperature increases white blood cell activity Fever induces production of interferon travels to uninfected cells amp increases resistance to virus attack 3rOI line of defense adaptive immunity The adaptive immune system has two types of responses 1 Antibodymediated immunity uses B cells to make antibodies 2 Cellmediated immunity uses T cells to destroy cells harboring pathogens 0 Adaptive immunity Involves 3 steps 1 Immune system recognizes invader antigen 2 Immune system launches attack 3 Immune cells retain a memory of that invader 2 main players white blood cells 1 B cells 0 Mature in bone marrow 2 T cells 0 Mature in thymus 0 Step 1 immune system recognizes antigen Antigens are 0 Foreign molecule 0 Unique for each type of foreign invader 0 Unique shapes on cell surface 0 Different lymphocytes recognize a speci c antigen 0 Receptor on this membrane 0 Similar to a lock and key 0 Step 2 Antigens enters body Nonspeci c defenses attack 0 Adaptive immune response 0 About two weeks to develop 0 B cells and T cells become activated Bearing receptors speci c for antigen 0 Results in clonal selection 0 Antibody production antibodymediated immunity 0 T cells that match antigen replicate cellmediated immunity 0 Step 3 immune memory 0 B cells 0 Produce antibodies speci c for antigen Active complement proteins destroy cells by making hole in their plasma membranes Increase phagocytosis Neutralize toxins and viruses 0 B and T cells that bind to the speci c antigen have now have replicated o Disproportionately represented among population of white blood cells 0 B cells are producing antibodies o Circulating in blood Tcells 0 Memory Helper Tcells show antigens to other cells in immune system 0 Memory Cytotoxic Tcells destroy own bodies own cells that are infecteddamaged Blind to infected cells Release poreforming proteins and dissolve cell membrane Antigens 0 Foreign molecule Unique for each type of foreign invader Unique shapes on cell surface Different lymphocytes recognize a speci c antigen 0 Receptor on this membrane 0 Similar to a lock and key Antibodymediated immunity 0 memory B cells produce antibodies speci c for antigen Activate complement proteins make holes in plasma membranes 0 Increase phagocytosis Antibodies bind directly to antigens neutralizing toxins and proteins Cellmediated immunity 0 Memory Helper Tcells show antigens to other cells in immune system 0 Memory Cytotoxic Tcells destroy bodies own cells that are infected damaged Bind to infected cells 0 Release poreforming proteins and dissolve cell membrane the body the immune system The second time a pathogen enters responds quickly and rigorously l sE 39 Q 3 12 w 5 In In a and the overall response 2 g is relatively weak 3 E 39 1 IE 2 a or E a 1 4 Weeks The rst time a pathogen enters the body it takes several days for the Vaccines immune response to build to its peak Va CC i nes W O rk by simulating adaptive immunity by exposing people to antigens Two types of vaccines live a live virus or bacterium is used although attenuated Attenuated pathogens are usually missing key genes that make the host sick Dead or antigen pathogen is not alive or perhaps just antigen is in vaccines IMMUNITY IN VERTEBBRATES IMMUNE SYSTEM External Internal Defenses Defenses F H I 39 I Physical Chemical Innate Adaptive barriers barriers immunity immunity I l 1st line Antibody Cell Phagocytosis l In ammation mediated mediated immunity immunity 2nol line Discover Biology Sle Figure 322 3nd I i 2012 W W Norton 8 Company Inc Review types of immune cells Nonspeci c Macrophages White blood cells that engulf invading microbes amp alert other immune cells Neutrophils phagocytic white blood cells Natural killer cells WBCs that destroy infected cells Speci c B cells Lymphocytes that produce antibodies Plasma cells secrete antibodies into bloodstream Memory B cells provide future immunity T cells Lymphocytes that regulate response Cytotoxic T cells destroy speci c targeted cells HelperT cells stimulate immune responses Memory T cells provide future immunity 22715 Lecture Notes Plague Outline 0 General info 0 Characteristics quotThe Big Ideaquot Several human factors are responsible for the emergence and proliferation of emergent diseases Infectious diseases Pathogens are 0 Infect living things 0 Prior to 1944 in wars like the civil war WWI and WWII more people died from infections than from trauma 0 On march 1 1944 P zter opened the rst commercial plant for large scale production of penicillin by submerged culture in Brooklyn NY Characteristics of emerging diseases 0 Relative risk of viruses highest 0 High mutation rates 0 Bacteria protozoa an fungi intermediate 0 Helminths lowest relative risk 0 Most emerging human pathogens gt75 are zoonotic Drivers of emergence Changes in land use or agricultural practices 0 Example Nipah vuris Vectored by ying foxes Changes in human demographics and society 0 Example SARS severe acute respiratory syndrome 20022003 8098 cases worldwide 0 Poor population health HIV Malnutrition Pathogen evolution 0 Example evolution of antibiotic resistence Wild life trade 0 Climate change 0 Climate wamring can mean geographic range shifts of disease vectors Multidrug resistence Multdrug resistence has led to increasing incidence of disease with renewed virulence reemerging diseases Antibiotics not only losing power but evolving to infections that are mutating lnectious diseases Consequences 6th leading cause of species extinctions Other 5 Habitat loss Invasive species Pollution Overexploitation Global climate change wewwe Week 8 last week for exam 2 material 3215 Inheritance Lecture notes Creature 0f the day Narwhal Inheritance Outline Traits Human phenotype genotypes 0 Genetic variation 0 Meiosis How are traits inherited O Mendel s law of segregation O Mendel s law of independent assortment Widows peak dominant trait Detached earlobes dominant trait Attached earlobes recessive trait Leonardo DiCaprio and Parker Posey s phenotypes are detached earlobes widows peak Matt Damon s phenotype is attached earlobes widows peak So phenotype is a description of physical appearance Genotype is the genetic basis for appearance and other unseen traits What do dominant and recessive mean First we need to look at a cell Chromosomes are found in the nucleus 0 Human chromosomes are in pairs we are diploid 0 One pair of chromosomes homologous 0 Locus locations of a particular gene on a chromosome 0 Allele different forms of a gene at a locus 0 Homozygous 2 copies same allele eX Blueblue 0 Heterozygous 2 copies different alleles eX Red green Let s say red allele means detached earlobes are green allele means attached gt Remember attached earlobes are dominant traits gt So the person s genotype is red green BUT their phenotype is detached earlobes 0 Green is masked This locus codes for hairline widows peak dominant straight hairline recessive gt Now lets say the blue genotype means straight hairline phenotype gt This person will have straight hairline results only when both alleles are blue 0 Dominant allele one dominant allele in the genotype automatically eXpressed in the phenotype masks recessive 0 Recessive allele both copies on homologous chromosomes must be same for recessive to be eXpressed in the phenotype m 0 I can roll my tongue dominant but my mom cant recessive 0 Let s say now R is the allele for rolling and r is the allele for not 0 Can my dad roll his tongue 0 Yes 0 What s my mom s genotype 0 Has to be rr 0 What s my dad s genotype 0 We don t know could be Rr or RR Meiosis division of gametes 0 Produces gametes eggs and sperm 0 Key just like mitosis but two cellular divisions 0 Before second division DNA does NOT replicate 0 Major differences from mitosis O Ends up in 1 copy of chromosomes haploid in eggs and sperm 0 Versus 2 copies diploid from mitosis in rest of somatic cells 0 Results in 4 daughter cells Meiosis causes variation 0 Sexual reproduction fusion of gametes causes variation in offspring 0 New chromosome combinations from parents 0 Variation also caused by crossing over 0 Homologous chromosomes switch sections creating new combinations Meiosis causes variation by creating new chromosome combinations 0 Homologous chromatids can cross over 0 Sexual reproduction causes variation in offspring 0 New chromosome combinations from parents 1 et from mom and dad Gregor Mendal 18221884 0 Augustinian monk Austria 0 Studies on plant hybridizationinheritance 0 Laid foundation for modern genetics 0 Results published in 1865 O BUT ignored until 1900 Mendel s rst experiment pemnts with purple and white owers 1 trz 1 Removed stamens from purple ower prevent selffertilization Transferred pollen from white to purple ower Plants made seeds Planted seeds and observed offspring Fl phenotypes Bred Fls together Observed F2 grandchild phenotypes 0 Results F1 generation all purple F2 generation 3 purple 111 white purple dominant white recessive 0 These experiments resulted in Medel s principle of segregation 0 Pairs of alleles segregate separate during gamete formation when eggs and sperm 9959 are made fusion of gametes at fertilization creates allele pairs again Key concepts 0 Phenotype vs genotype 0 Dominant vs recessive 0 Other genetics terms 0 Principle of segregation 0 Principle of independent assortment Glossary of Genetics Terms genotype genetic type what genes a person has for a particular trait usually represented by 2 alleles for example genotype Ff phenotype physical appearance in uenced by one or many genes for example a person with genotype Ff or ff has freckles which is their phenotype gene segment of DNA that codes for a particular protein allele different forms of a gene chromosome tightly wound up DNA that contains many loci and therefore many genes homologous chromosomes pairs of chromosomes that contain the same genes inherit one from mom and one from dad diploid 2 copies of chromosomes and hence the genes on them homozygous 2 copies of the same allele eg FF or ff on homologous chromosomes heterozygous different alleles on homologous chromosomes eg Ff Punnett square determines offspring genotypes by matching up parental genotypes Genetics Concepts dominant if one dominant allele is present in the genotype it is automatically expressed in the phenotype although there are 2 copies in diploid organisms it masks the other allele on the other chromosome Freckles are a dominant trait so if a person has either genotype FF or Ff they will have the freckle phenotype recessive for a recessive allele to be eXpressed it has to be present on both chromosomes No freckles are recessive so a person must have the genotype ff to have no freckles as their phenotype codominant both copies are eXpressed e g red gene on one chromosome and white gene on another chromosome gt genotype redwhite but phenotype pink A plant with codominant ower color genes would have red owers if the genotype is RR white owers if the genotype is WW and pink owers if the genotype is RW 34 15 Genetic Disorders Creature of the Day Acacia Ant Lecture outline Mendel s law of independent assortment Other types of dominance o Incomplete dominance o Codominance Polygenic traits 0 Continuous phenotypes Genetic disorders 0 Types 0 Inheritance patterns Mendel s second experiment quotdihybrid crossquot green or yellow peas and round or wrinkled peas 2 traits F1 generation got all yellow round peas so yellow and round were dominant F2 generation not 31 ratio as in purplewhite pea ower experiments 0 Got 9331 ratio 9 yellowround 3 yellowwrinkled 3 greenround 1 greenwrinkled o This is because there are 2 different loci and chromosomes sort independently so all possible gametes are formed Chromosomes sort independently so all possible gametes formed 0 These experiments resulted in Mendel s principle of the independent assortment 0 He knew something other than segregation was going on 0 Each pair of alleles segregates independently of one another during gamete formation Other important experiments concepts Codominance o In heterozygotes both traits are expressed o Illustrated in Mendel s third experiment with snapdragons White red parental owers made pink offspring Polygenic 0 But most traits are not coded for single genes 0 Traits in uenced by many genes are quotpolygenicquot Ex Skin color arm length eye color etc Let s say skin color is codominant and in uenced by 3 genes Types of Dominance Complete dominance Incomplete Dominance Codominance Codominance example ABO Blood Types 0 Gene that controls ABO type codes for enzyme that dictates structure of a glycolipid on blood cells 0 Two alleles Aand 3 are codominant when paired Third allele 1 is recessive to others 0 0 blood is the universal donor blood because it lacks a protein that restricts most blood types so anyone is able to take 0 blood Incomplete Dominance Mendel s 3rOI experiment with snapdragons 0 When mixed red and white snapdragons F1 generation was pink intermediate 0 F2 generation has 121 ratio 0 of homozygous red 0 to heterozygous pink 0 to homozygous white But most traits are not coded for by single genes quotpolygenicquot traits in uenced by multiple genes 0 Ex Skin color arm length eye color etc 0 Human skin color is codominant and in uenced by 3 gene 0 The greater the number of genes and environmental factors that affect a trait the more continuous the variation in versions of that trait Genetic disorders Inherited conditions that cause mild to severe medical problems 0 Why don t they disappear Mutation introduces new rare alleles ln heterozygotes harmful allele can be masked so it can still be passed on to off spring Medicine can keep people with severe conditions alive to reproduce Genetic disorders types 1 Singlegene mutations o 60008000 known disorders 0 1 in about 200 births inherited predictably o Eg cystic brosis sickle cell anemia Huntington s disease 2 Multifactorial or quotpolygenicquot o Combinations of environmental factors amp mutations in multiple genes 0 Eg breast cancer associated genes found on chromosomes 6 11 13 141517 and 22 0 Nature of complex gene interactions make very complicated 3 Chromosomal o Duplication o Inversion o Translocation o Deletion o Nondisjunction 4 Mitochondrial o Relatively rare Inheritance patterns Autosomal in nonsex chromosome recessive inheritance patterns 0 If parent are both heterozygous child will have 25 chance of being affected EX CF Autosomal dominant trait often appears in every generation 0 Eg Achondroplasia homozygotes usuaIIy stillborn Heterozygotes display a type of dwar sm Have short arms and legs relative to other body parts Achondroplasia o Autosomal dominant inheritance o Homozygotes usuaIIy stillborn XIinked recessive carried on X chromosome only 0 Males show disorder more than females 0 Son cannot inherit disorder from his father 0 Examples of Xlinked traits Color blindness Inability to distinguish among some or all colors Hemophilia Bloodclotting disorder 17000 maIes has aIIeIe for hemophilia A 0 Was common in European royal families Chromosomal disorders 1 Duplication part of a chromosome is repeated and passed on to the offspring 2 Inversion a linear stretch of the DNA is inverted in the chromosome 3 Translocations one piece of chromosome can end up on another chromosome 4 Deletion loss of a segment of a chromosome most are IethaI or cause serious disorder 5 Non disiunction a problem during meiosis when homologous chromosomes do not separate properly during anaphase l b causes some gametes to have n1 chromosomes in humans 24 or n1 chromosomes 22 causes aneuploidy in offspring 2n 1 or 2n 1 i Major cause of human reproductive failure IiMost human miscarriages are aneuploids iii Types of aneuploidy LDown syndrome a Trisomy of chromosome 21 b Mental impairment and a variety of additional defects c Can be detected before birth d Risk dramatically when mother over age 35 2 Turner syndrome a Inheritance of only one X XO b 98 spontaneously aborted c Survivors are short infertile females i No functional ovaries ii Secondary sexual traits reduced iii May be treated with hormones surgery 3 Klinefelter Syndrome a XXY condition b Results mainly from nondisjunction in mother 67 c Phenotype is tall males i Sterile or nearly so ii Feminized traits sparse facial hair somewhat enlarged breasts iii Treated with testosterone injections 4 Jacob syndrome XYY a Taller than average males b Most otherwise phenotypically normal c Some mentally impaired d Once thought to be predisposed to criminal behavior but studies now discredit
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