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Lecture 10

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Biology 1001A

Lecture 10:  How to get serious about learning   Make a plan to stay sharp  Make gold. Make questions.  Get help: Office hours, forum  Concept Fixes  Study groups  Make classes count  Clicker Question   Which ones are haploid?  Haploid means you have just 1 copy of each chromosome (or the homologue)   one copy of each homologue  doesn't matter if the chromosome is replicated or not  same size same shape is homologue  1 is haploid, 3 is haploid  2 is wrong because the 2 large chromosomes and 2 small chromosomes can pair up  List of mechanisms to generate genomic diversity   Mutations  Transposition (Mobile elements)  Copy number variation (Ex. slippage)  Ability of repair damage (Ex. Dimers) and DNA polymerase  Repairing double stranded breaks create copy number variations in a genome  Meiosis (Sexual recombination)   Sexual reproduction itself (Recombination in meiosis is a very controlled/precise mutation when DNA recombines during meiosis)  Creating a zygote (n+n=2n)  Random segregation of homologous chromosomes at anaphase I of meiosis  Random segregation of the chromatids of replicated chromosomes at meiosis II is a third mechanism for generating diversity  CNVs from unequal crossing-over in meiosis (Genetic Recombination)  Independent assortment happens in meiosis I  Crossing over in meiosis 1 can make some alleles go away for your children since genes close to each other on the same chromosome have a low probability of recombination since XXXXXXX ("Repaired" chromosome with none of the nasty alleles)  Zygotes bring DNA from 2 different cells into the same cell   Create variation  Homologous chromosomes carry the same genes in the same places, but different alleles   karyotypes are cut and paste by human, put together same size same shape from largest to small   homologues have the same genes in the same places  how homologues are the same and different  X X  Pair of homologous chromosomes have 2 pairs of sister chromatids and 2 chromatids  In meiosis I, chromosome number is reduced from diploid to haploid (n)   Reductional division of meiosis because it reduces the chromosome number from diploid to haploid  In meiosis II, cells divide to give products with 1C amount of DNA but the chromosome number is not (equational division)   the amount is reduced from 2 C to 1 C   in Animals life cycle, the zygote divides by mitosis   Meiosis only makes gametes in animals  In animal life cycles, the zygote divides by mitosis  in Plants life cycle, the zygote and the spores divide by mitosis   The product of meiosis are spores (not gametes)  They make a gametophyte through mitosis  The gametophyte makes gametes through mitosis   plants make gametes by mitosis  Gametophytes are haploid and divide by mitosis  Gametophytes actually makes gametes  in some Fungi/algae, the zygote divides by meiosis   The gametes are made by mitosis  The zygote divides by meiosis into spores which grows into a gametophyte by mitosis  fungi/algae are haploid in their life cycle  Plants and fungi/algae are reversed from humans  sexual reproduction is not necessary in the biological world  In prophase of meiosis I, replicated homologues pair and recombine   Sex = sexual recombination = reproduction  bring to people's DNA together  Prophase 1 is sexual recombination  Recombination during meiosis cuts and pastes DNA backbones   Red/blue are homologous since they have very similar base sequences  Recombination enzymes creates nicks (cuts) in the backbones  The backbones are switched, the red goes on the blue and the blue goes onto the red  the cross over are not on sister chromatids, only on homologues pai
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