Chapter 16 and 18 Notes
Chapter 16 and 18 Notes BIOL 2601 - 01
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BIOL 2601 - 01
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This 6 page Class Notes was uploaded by Suzanne Notetaker on Wednesday October 28, 2015. The Class Notes belongs to BIOL 2601 - 01 at Youngstown State University taught by Dr. Asch in Fall 2015. Since its upload, it has received 42 views. For similar materials see General Biology in Biology at Youngstown State University.
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Date Created: 10/28/15
Chapter 16 Simple Patterns of Inheritance Mendel s Laws of Inheritance Experiments with pea plants variable traits selffertilizing large owers Singlefactor cross experiment follows only single trait P generation truebreeding parents F1 generation offspring of P cross monohybrids differ parents by one trait F2 generation Fl selffertilizers recessive trait reappears Three Important Ideas 1 Traits are dominant hybrids and recessive 2 Genes unit factors and alleles gene has two variant forms a Every individual has two genes for a character trait 3 Segregation of alleles two copies of gene by F1 segregate from each other each sperm or egg carries one allele F2 traits follow 31 ratio Mendel s Law of Segregation Two copies of a gene separate from each other during the transmission from parent to offspring Genotype and Phenotype Genotype genetic composition of an individual TThomozygous dominant tthomozygous recessive Ttheterozygous Phenotype9physicalbehavioral characteristics TT and Tttall ttdwarf Punnett Square Step 1 Write down genotypes of parents Step 2 Write down possible gametes each paret ca I g 7 Step 3 Create empty Punnett square Step 4 Fill in possible genotypes Images provided by Dr Asch YSU BIOL 2601 Chapter 16 F15 Twofactor Cross Follows inheritance of two different traits Can determine linkage Possible patterns 1 Two genes are linked 2 Two genes are independent Dihybrid offspring offspring are hybrids With respect to both traits 9331 ratio data for F2 hybrids is consistent With independent assortment Law of Independent Assortment Alleles of different genes assort independently of each other during gamete formation Chromosome Theory of Inheritance Chromosomes contain DNA Chromosomes are replicated and passed from parent to offspring Nucleus of diploid cell contains two sets of chromosomes homologous pairs At meiosis one member of each chromosome pair segregate into each daughter nucleus Gametes are haploid cells U PP P Chromosomes and Segregation Mendel s Law of Segregation explained by pairing and segregation of homologous chromosomes during meiosis Locus 9physical location of a gene on a chromosome Chromosomes and Independent Assortment Law of Independent Assortment explained by behavior of chromosomes during meiosis Random alignment of chromosome pairs during meiosis I leads to IA of genes found on different chromosomes Sex Chromosomes and Xlinked Inheritance Found in many but not all species With two sexes Sex Determination XY system males XY and females XX XO system males X or X0 and females XX ZW system males 22 or females ZW not all chromosomal mechanisms involve sex chromosomes other mechanisms exist e g sex controlled by environment Plants some have single type of plant male and female gametophytes Others sexually distinct plants male or female gametophytes only Xlinked Traits Humans X chromosome larger and carries more genes than Y Genes found on X but not Y Xlinked genes Males are hemizygous for Xlinked genes a Hemophilia A recessive a Disease allele encodes defective version of a clotting protein Molecular Basis of Different Inheritance Patterns Understanding gene function at molecular level explains differences in inheritance patterns Simple Mendelian inheritance Alleles dominant or recessive Phenotypes ratios follow Mendel s laws Incomplete dominance Heterozygote shows intermediate phenotypes hypothesis of blending Neither allele is dominant Codominance Multiple alleles three or more variants in population Phenotype depends on Which two alleles are inherited both phenotypes fully expressed Chapter 18 Genetics of Viruses and Bacteria Genetic Properties of Viruses Nonliving particles with nucleic acids and required assistance to reproduce First virus discovered tobacco mosaic virus Viruses Nucleic acid enclosed in protein coat Vary greatly in characteristics host range structure genome composition Differences Host Range number of species and cell types that can be affected Structural capsid varies in shape and complexity some have viral envelope from host cell plasma membrane Genome DNA vs RNA single stranded vs double stranded linear vs circular Reproduction Viruses aren t alive Viral reproductive cycle can be different among types of viruses Viral Reproductive Cycle 1 Attachment phage binds to proteins in outer bacterial cell membrane a Specific for one kind of cell 2 Entry phage iniects in DNA into the bacterial cytoplasm a Some fuse with cell membrane 6 g HIV b Some expressed immediately 0 Virus proceed to synthesis OR integrate 3 Integration integrate into chromosomes via integrase a Host cell carrying a prophage may undergo repeated division lysogenic cycle i To end lysogenic cycle and switch to lytic cycle phage DNA is excised b Alternatively may skip lysogenic cycle and proceed to step 4 4 Synthesis of Viral Components phage DNA circularizes host chromosomal DNA is degraded 5 Viral Assembly phage components assemble help of noncapsid proteins to make new phages 6 Release Lysozyme causes cell lysis and new phages released from broken cell LysogenvLatencv in bacteriophage Some viruses can integrate genomes into host chromosome Prophageprovirus is inactive or latent Most viral genes are silenced When host cell replicates also copies prophage Lysogenic cycle integration replication and excision temperate phages not virulent Lytic cycle synthesis assembly and release On rare occasions a 219th may be excised from host chromosome 4a New phages can 1 Phage injects its bind to bacterial DNA into cells cytoplasm 391 8 LYTIC LYSOGENIC 3a Cell lyses and 2a Phage DNA directs 21 F hage DNA 3b limnhgstEA f releases the new the synthesis of Integrates Into lselclo ledw en phages my new phages or host chromosome prophage C V1 CS quot w 4 AIDS and HIV Human inmmunodeficiency Virus HIV is the causative agent of acquired immune deficiency syndrome AIDS AIDS spread by 1 Sexual contact primarily 2 Transfusion of infected blood 3 Sharing needles 4 Infected mother AIDS Virus destroys White blood cell called helper T cell role in immune system HIV reverse transcriptase lacks proofreading function makes more errors create mutant HIV strands difficult to create vaccine Origin of Viruses Theories 1 Viruses evolved from macromolecules inside living cells 2 Regressive evolution 3 Evolved in parallel With cellular organisms Viriods singlestranded circular RNA molecule that infect plants cells replicate in host nucleus or chloroplast Prions converts normal proteins PrPC to abnormal form PrPSC to form fibrils Genetic Properties of Bacteria single type of organism may more than one copy of chromosome depends on species and growth typically 14 identical chromsomes Nucleoid9region where tightly packed bacterial chromosome found Bacterial Chromosomes molecules of doublestranded DNA circular shorter few thousand genes mostly structural single origin of replication Plasmids small circular pieces of DNA that exist independently of bacterial chromosome occur naturally in main bacteria strands and few eukaryotes replicated independently provide growth advantages Episome9plasmid that can integrate into bacterial chromosome Types 1 Resistance R factors resistance against antibiotics and other toxins 2 Degradative enable bacterium to digest and utilize unusual substance 3 Colplasmids encode colicines proteins kill other bacteria 4 Virulence turn bacterium into pathogenic strain 5 Fertility F factors allow bacteria to mate Reproduction of Bacteria by binary fission identical copy of mother s genetic material not involve genetics from two different parents Gene Transfer Between Bacteria Genetic diversity mutations or genetic transfer 1 Conjugation direct physical interaction transfers genetic material from donor to recipient a Donor contain F factor that can be transferred to recipient i F factors carry several genes that require conjugation ii F has factor F39 does not iii Sex pili made by F that bind to F39 1 Contact made pili shorten to draw cells closer 2 One F factor transferred other stays in donor 3 Both replicate 2 Transformation DNA released from bacterium taken up by another a Only competent cells with competence factors facilitate binding of DNA fragments to bacterial cell surface uptake DNA and incorporate imported DNA 3 Transduction virus transfer genetic info from one bacterium to another a Usually error in phage lytic cycle b Newly assembled phages incorporate piece of host DNA instead Vertical Gene Transfer genes are passed from one generation to the next among individual s of the same species