BSC 2011 Lecture 11-15
BSC 2011 Lecture 11-15 2011
Popular in Biological Sciences II
Popular in BSC
This 4 page Class Notes was uploaded by rcg16b Notetaker on Saturday October 8, 2016. The Class Notes belongs to 2011 at Florida State University taught by Dr. Kevin Dixon in Fall 2016. Since its upload, it has received 7 views. For similar materials see Biological Sciences II in BSC at Florida State University.
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Date Created: 10/08/16
Lecture 11 Reading -‐‑ Chapter 13.1, 13.2 Concepts p 272-‐‑ 276 • Be able to distinguish between the genetic consequences of sexual and asexual reproduction o Sexual § Two parents give a unique combination of genes to offspring § Not exact replicas o Asexual § Have exact genetic copies of themselves § Produces a clone-‐‑ a group of genetically identical individuals § Genetic differences are due to mutations • Be able to distinguish the cellular processes behind asexual (mitosis)and sexual (meiosis) reproduction. o Mitosis o Meiosis • Know that chromosomes exist as homologous pairs in diploids o Chromosomes occur in pairs which implies that we have two copies of each gene • Be able to explain why meiosis produces haploid daughter cells from diploid parents • Know that sexual life cycles alternate meiosis and fertilization • Be able to explain how sexual life cycles vary in the timing of meiosis and fertilization. • Terms to Know -‐‑ Haploid, diploid, homolgous chromosome (homologous pair), sister chromatid, gamete, zygote, meiosis, fertilization, gonad, sexual reproduction, asexual reproduction, clone, spore, gametophyte, sporophyte Lecture 13 -‐‑ Meiosis Concepts • Gonad-‐‑ testes and ovaries • Haploid vs Diploid o Diploid cell (2n)-‐‑ pairs of homologous chromosomes, 2 sister chromatids at the start of meiosis/mitosis per chromosome. (original amount of chromosomes) § Homologous chromosomes -‐‑ genetically similar but not necessarily identical , they cross over each other § Sister chromatids of same chromosome -‐‑ genetically identical from S phase § Don’t confuse sister chromatids and homologous chromosomes! o Haploid cell (n)-‐‑ when the cells divide the chromosomes in half through meiosis or mitosis. • Be able to explain how meiosis produces haploid daughter cells by separating homologous pairs of chromosomes so that one homolog goes to each cell. o Sister chromatids are two copies of one chromosome o after the chromosomes duplicate in interphase, the diploid cell divides twice o this yields four haploid daughter cells • Know that meiosis consists of two stages: meiosis I and meiosis II and know that the end product of meiosis is 4 haploid cells o Meiosis I § The diploid parent cell divides into two haploid cells with duplicated chromosomes § homologous chromosomes are separated producing two cells o Meiosis II § the haploid cells with duplicated chromosomes divide into haploid cells with unduplicated chromosomes. § sister chromatids are separated § basically the same as mitosis • Know the names of the stages of meiosis and what happens in each • Know that the pairing of homologs and crossing over both occur in prophase I and be able to explain the significance of both o Homologs are aligned gene by gene o Homologs-‐‑ two chromosomes together= 4 sister chromatids o Allows for more genetic variation • Be able explain how the random assortment of homologs into daughter cells and the process of crossing over result in genetically variable gametes o Watch this!! It is less than 2 min long. -‐‑> https://youtu.be/pdJUvagZjYA o Cohesions hold together the sister chromatids o Synapsis-‐‑ when the synaptonemal complex holds one homolog tightly to the other § DNA breaks are closed up so that each broken end is joined to the corresponding nonsister chromatid § Therefore, a paternal chromatid is joined to a piece of maternal chromatid beyond the crossover point • Be able to explain the differences between mitosis and meiosis o Mitosis § Genetically identical daughter cells § Development growth and asexual reproduction § Diploid to diploid or haploid to haploid o Meiosis § Daughter cells contain a subset of parent cell’s genes § Going from diploid to haploid cells § Haploid to diploid is fertilization § Each daughter cell has one member of each homologous pair § Necessary so that the next generation has the correct amount of chromosomes o 3 major differences § Synapsis and crossing over : • occurs in meiosis during prophase I while it doesn’t occur during mitosis § Homologous pair at the metaphase plate of meiosis: • chromosomes are positioned as pairs on homologs rather than individual chromosomes as in metaphase of mitosis § Separation of homologs: • at anaphase I of meiosis, the duplicated chromosomes of each homologous pair move toward opposite poles but the sister c hromatids remain attached. In anaphase of mitosis, sister chromatids separate. § Check this diagram out! http://image.slidesharecdn.com/13 -‐‑111220234407-‐‑ phpapp01/95/biology-‐‑ch-‐‑13-‐‑11-‐‑728.jpg?cb=1324424834 (it is also in your book on page 261) • Vocabulary – Synapsis, crossing over, chiasma, meiosis I, meiosis II, segregation Readings Chapter 13.3, 13.4 Friday group assignment: • Law of Segregation • Law of Independent Assortment • Phenotypic Ratios Which of these three things is always true in all diploid, sexually reproducing systems? Law of Seg tion What factors influence the other two? Law of Independent Assortment: location of genes relative to each other Phenotypic Ratios: depend on specific circumstances Lecture 14 Mendelian Inheritance of Two Traits Probability and Inheritance Reading: Chapter 14: 267 -‐‑271. • More haploid/diploid o Haploid-‐‑ one chromosome from each type o Diploid-‐‑ two chromosomes from each type o The more homologous pairs, the more combinations (2 ) n=haploid number o n=23 for humans o if a diploid has 10 chromosomes, how many combinations are possible in gametes produced from this cell. § n=5 so 2 =32 • By able to explain why two characteristics can be inherited independently and describe the resulting pattern of inheritance. o synapsis is the joining of chromosomes in a homologous pair § prophase I results in crossing over § site of synapsis is called chiasma § DNA breaks and they e xchange pieces § Makes 4 daughter cells, two of which have recombinant chromosomes § The chromosomes join at the exact same place to exchange the same loci • If they didn’t, one would have extra copies and one would be missing some genes § This varies genetic va riation in gametes § Allows loci to segregate independently § AABb 2n=4 • A and B are on two separate chromosomes • AXA AXA • BxB bxb • Be able to explain how meiosis relates to the Law of Independent Assortment o segregation in one gene is independent of segregation in another gene o One coin flip does not affect the other, black hair does not affect length of hair (50% chance of passing on any allele) o All combinations of gametes are equally likely to be selected during meiosis • Be able to apply the sum rule and product rule of Probability correctly o Sum probability § of either one of two different probabilities occurring = P (1) + P (2) § If the word ‘or’ occurs in a statement about probabilities, then the probabilities are added § 1/8 + 1/8 + 1/8 = 3/8 (GGB, BGG, GBG) § All possibilities: o Product Probability § two independent events happening = P (event 1) X P (event 2) § If a statement about the probability contains an ‘and’ then the probabilities are multiplied § Peas • Be able to apply the rules of probability to geneti cs problems o P(Pp) = P(Pirsp second) + P(Pondp fir) = 0.5*0.5 + 0.5*0.5 = 0.25 + 0.25 = 0.5 o AaBb= four types of gametes § How do we calculate the probability? § Half gametes will have A half have a § Half have B and half have b § AB=Ab=aB=ab= 0.5*0.5=0.25 o Probabilities of the F2 genotypes § AaBB § P(Aa)*P(BB)=0.5*0.25=0.125 o Cross AAbbCcDdEe x aaBbCcDDee = AabbccDDee = 1*0.5*0.25*0.5*0.25= 0.0625
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