BIO 121: General Biology - Study Guide
BIO 121: General Biology - Study Guide BIO 121
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This 9 page Study Guide was uploaded by Holden Hershey on Friday October 17, 2014. The Study Guide belongs to BIO 121 at Syracuse University taught by Wiles in Fall. Since its upload, it has received 161 views. For similar materials see General Biology in Biology at Syracuse University.
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Date Created: 10/17/14
Cell DivisionMitosis Cell Division how unicellular organisms reproduce Multicellular organisms depend on cell division for their development from a fertilized egg and for growth and repair Part of the cell cycle ordered sequence of events in the le of a cell Most Cell Division Results in Geneticallv Identical Daughter Cells Genome genetic material DNA of a cell quotPartitioned among chromosomes one DNA molecule associated w many proteins Chromatin complex of DNA and proteins Exist in dy ferent forms of condensation at different times Animals Gametes one set of chromosomes Somatic Cells two sets of chromosomes Cells replicate their genetic material before they divide Each daughter cell receives a copy of the DNA Chromosomes are duplicated prior to division quotProduces 2 sister chromatids chromatids joined by sister chromatid cohesion and held tightly by centromeres When the cohesion is broken the chromatids separate during cell division becoming the chromosomes of the daughter cells Eukarvotic Cell Division Mitosis Division of the Nucleus Cytokinesis Division of the Cytoplasm Process of Mitosis Interphase GISG2 GI Cell growth Q DNA synthesis Cell continues to grow Replication of Chromosomes G2 Cell completes preparations for cell division Nuclear Envelope encloses the nucleus Centrosomes are formed each contains two centrioles Organize the microtubules of the spindle Prophase Chromatin fibers become tightly coiled Nucleoli disappear Identical sister chromatid pairs appear Mitotic Spindle forms Prometaphase Nuclear Envelope breaks apart Microtubules invade the nuclear area Each of the two chromatids have a kinetochore protein structure the centromere Microtubules jerk back and forth in preparation for metaphase Metaphasechromosomes are aligned at the metaphase plate Metaphase Plate equal distant between spindles Each chromatid has a kinetochore connected Sister chromatids are pulled apart by the shortening of the microtubules Sister chromatids separate motor proteins move along the kinetochore microtubules to opposite ends of the cell AnaphaseShortest stage Cohesion proteins are cleaved Microtubules shorten Chromosomes pull apart Telophase 2 daughter nuclei form in the cell Nuclear Envelope reappears Completion of Mitosis division of the nucleus Cytokinesisdivision of the cytoplasm Animal cells Use of Cleavage Furrow Plant cells Use of a Cell Plate M itosisCytokinesis Terms defined Mitotic Spindle made up of microtubules Controls chromosome movement during mitosis Arises from the centrosomes Spindle microtubules amp asters Some spindle microtubules attach to the metaphase plate Centromereconstricted region Joins sister chromatids Kinetochoreprotein to which microtubules bind Attached to centromere Homologous Chromosomes similar chromosomes from separate parents Diploid Cell chromosomes are paired homologous chromosomes Similar in length shape and other features Haploid Cells contain only one member of each of the homologous chromosome pair Genesinformation units in chromosomes Instructions for the building of a protein Locussite of a gene in the chromosome Alleles dyferent forms of a gene Same loci on homologous chromosomes Crossing Over between homologous nonsister chromosomes Exchanges segments of DNA strands Results in genetic recombination Gene Pairs Diploid individuals genes have pairs of alleles On homologous chromosomes Homozygous two identical alleles Heterozygous two different alleles MitosisMeiosis Mitosis single nuclear division2 identical daughter cells no Crossing Over Meiosis two nuclear divisionsFour haploid cellsCrossing over occurs Prophase I Binary F ission in Bacteria 1 DNA is replicated 2 Cell begins to elongate 3 Replication is almost complete Cell begins to divide plasma membrane begins to pinch Produces two identical prokaryotic cells Some of the proteins involved in bacterial binary fission are related to Eukaryotic Actin quotubulin Likely that Mitosis evolved from Prokaryotic cell division Study of unicellular eukaryotes shows that they may use similar methods as past ancestors Eukarvotic Cell Cvcle is regulated by a Molecular Control Svstem Signaling molecules in the cytoplasm regulates cell process Cell Cvcle Control Svstem Molecularly based Cyclic changes in regulatory proteins work as a cell cycle clock CyclinCyclin dependent kinases CDKs Clock has specific checkpoints where the cell cycle stops InternalExternal signaling in transduction pathways Eukarvotic Chromosomes Nucleosome Histone protein bead wrapped in DNA Organized into coiled loops Held together by nonhistone scaffolding protein Eight histone bound together by I DNA I Nucleosome In a stringbead formation Genetics Offspring acquire 2enes from Darents bv inheriting Chromosomes Each gene in an organism s DNA exists at a specific locus on a chromosome In asexual reproduction a single parent produces genetically identical offspring by mitosis Sexual Reproduction combines genes from 2 parents leading to genetically diverse offspring Human Somatic Cells diploid2sets of 23 chromosomes one from each parent Human diploid cells have 22 homologous pairs of autosomes and on pair of sex chromosomes XX femalesXY Males Ovaries quotestes produce haploid gametes by meiosis Each gamete has 23 chromosomes n23 During fertilization an egg and sperm unite forming a diploid 2n46zygote Develops into a multicellular organism by mitosis Sexual le cycles differ in the timing of meiosis relative to fertilization and in the point of the cycle in which and organism is produced by mitosis Meiosis reduces the number of Chromosome sets from Diploid to HaDloid Two cell divisions Meiosis I Meiosis II Produce 4 haploid daughter cells The number of chromosome sets is reduced from 2 diploid to 4 haploid during Meiosis I the reduction division Diploid 2n46 Haploid n23 Mendel s Two laws of Inheritance Parents pass on to their offspring discrete genes that refrain their identity through generations Law of Se gregation genes have alternative forms or alleles In meiosis the two alleles of a gene separate also in gamete formation Explains the 3 1 ratio in F2 phenotypes observed when monohybrids self pollinate Each organism inherits 1 allele for each gene from each parent Heterozygous Aa AaBbC c A Dominant a Recessive Homozygous AA aa AABBC C aabbcc dominant allele does not mask genotype of recessive but it controls the phenotype considered to be true breeding Law of Independent Assortment The pair of alleles for a given gene segregates into gametes independently of the pair of alleles for any other gene In a cross between dihybrids individuals heterozygous for two genes the offspring have four phenotypes 93393I ratio Probabilitv Laws govern Mendelian Inheritance Multiplication Rule probability of two or more events occurring together is equal to tge product of the individual probabilities of the independent single events Addition Rule probability of an event that can occur in two or more independent mutually exclusive ways is the sum of the individual probabilities Complete Dominance of one allele heterozygous phenotype same as that of homozygous dominant PP or Pp Incomplete Dominance of either allele heterozygous phenotype intermediate between the two homozygous phenotypes Example Red Flower breeds with a white flower to produce a pink flower CodominanceBoth phenotypes expressed in heterozygotes Example Blood type AB or IquotA IquotB Multiple Alleles in the population some genes have more than two alleles Example ABO blood group alleles IquotA IquotB Iquot0 PleitroQy one gene affects multiple phenotypic characters Example Sickle Cell disease EQistasis Phenotypic expression of one gene affects the expression of another gene Example BbEe x BbEe Polvgenic Inheritance a single phenotypic character is affected by two or more genes Expression of a genotype can be affected by environmental influences resulting in a range of phenotypes Polygenic characters that are also influence by the environment are called multifactorial characters An organisms overall phenotype including its physical appearance internal anatomy physiology and behavior reflects its overall genotype and unique environmental history Even in more complex inheritance patterns Mendel s fundamental laws of segregation and independent assortment still apply Analysis of family pedigrees can be used to deduce the possible genotypes of individual and make predictions about future offspring Such predictions are statistical probabilities Heterozygous carriers of genetic disorders Many human diseases are multifactorial meaning they have both environmental and genetic influences that do not exactly apply to Mendel s theory of independent assortment Amniocentesis Chronic Villus Sampling can indicate whether a suspected disorder is present in a fetus Other genetic tests can be performed after birth Gene Expression Dominant Allele masks expression of recessive allele Phenotype appearance Genotype genetic constitution Mendel s Principle of Segregation two alleles of a gene separate during Meiosis and an egg or a sperm will only receive one allele Mendel s Principle of Independent Assortment Alleles of different loci are distributed randomly into gametes Recombination presents generations that were not present during the parent generation Random orientation of chromosomes during Meiosis I controls where they end up as gametes Monohybrid cross Q you take two heterozygous hamsters you get a 3 1 ration in the expression of the phenotypes but a I 392I expression of the genotypes Test Cross can reveal the organisms genotype Linked Genes groups of genes that are on the same chromosome tend to be inherited together two loci lined closely together same pair of homologous chromosomes independent assortment does not apply Recombination of Linked Genes can result from crossing over in Meiotic Prophase I Crossing Over breaking and rejoining of homologous chromosomes Linkage Map Linkage map of a chromosome shows the relative locations of genes on a chromosome measures the frequency of recombination between linked genes more likely the farther they are apart X and Y Chromosomes determines sex in mammals X bearing egg Y bearing Sperm X Chromosome important genes for males and females Male receives all x linked genes from mom Females receives all x linked genes from both parents Multiple Genes alleles of many loci may interact Norm of Reaction a range of phenotypic possibilities from a single genotype under different environmental conditions Blood Count infectionaltitude level of fitness Studies of Columbia Professor Morgan on Mendel s Laws Morgan worked with Drosophila Melanogaster Fruit Fly led to the Chromosome Theorv of Inheritance Genes are located on chromosomes behavior of chromosomes during meiosis accounts for Mendel s law Sex Linked genes Unique Patterns of Inheritance Chromosomally based sex Sex in mammas is determined by whether or not a Y is present InsectsBirdsFish have dyferent systems Sex chromosomes carry sex linked genes most on the x chromosome x lined Males inherit recessive xlinked alleles will express the trait from mother color blindness One of the two x chromosomes in a female deactivates during the development of the embryo This deactivated x chromosome becomes highly condensed into a Barr Body Linked genes tend to be inherited together because they are located near each other on the same chromosome Offspring from a F I dihybrid testcross parental ages have the same combination of traits as those in the P generation Recombination types exhibit new combinations of traits not expressed in F1 individuals or individuals from the P generation For genetically linked genes crossing over between non sister chromatids during Meiosis I accounts for the observed recombinants always less than 50 of the total Order of genes on a chromosome and the relative distances between them can be deduced from recombination frequencies observed in genetic crosses this data allows the construction of linkage maps a type of genetic map the further apart genes are the more likely their allele combinations will be recombined during cross over Alterations of Chromosome Number or structure cause some genetic disorders Aneuploidy abnormal chromosome number can result from nondisjunction during meiosis When a normal gamete unites with one containing two copies or no copies of a particular chromosome the resulting zygote and its descending cells either have one extra copy of that chromosome trisomy 2nI or are missing a copy monosomy 2nI Polyploidy more than two complete sets of chromosomes can result from nondisjunction during meiosis Chromosome breakage can result in alterations of chromosome structure deletions duplications inversions translocations Change in number of chromosomes per cell or in the structure of the individual chromosomes can effect the phenotype and in some cases lead to disorders Such alterations cause Downs Syndrome Usually due to trisomy of the 21 S chromosome Certain cause cancers associated with chromosomal translocations and various other diseases Inheritance Patterns that are an exception to Standard Mendelian Inheritance in mammals the phenotypic effects of a small number of particular genes depend on which allele is inherited from each parent a phenomenon called Genomic ImDrintin2 imprints are formed during gamete production with the result that one allele either maternal or paternal is not expressed in offspring The inheritance of traits controlled by genes present in mitochondria and plastids depend solely on the maternal parent because the zygotes cytoplasm containing these organelles comes from the egg Some diseases affecting the nervous system and the muscular system are caused by defects I mitochondrial genes that prevent the cells from making enough ATP
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