lect23__meiosis

lect23__meiosis - Reductionist Cell Division: Meiosis...

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1 Reductionist Cell Division: Meiosis Biology 2A Mitosis = asexual division a Makes “identical clones” ` # of chromosomes per daughter cell is the same as found in original (parent) cell ` Information in each chromosome is the same as that of parent cell Diploidy: another strategy to delay the mutational meltdown One haploid cell with a mutation can fuse with a different haploid cell The two are unlikely to have the same mutation Joining (becoming diploid) ‘hides’ mutations from selection The GOOD copy of the gene makes enough protein to keep the cell alive Hides the faulty gene – faulty gene is ‘recessive’ Recessive genes have no affect on phenotype Which could be diploid? A. B. C. BOTH Which could be diploid? A. B. C. D. A and B only E. A, B and C could all be diploid How many copies of a gene (say, alleles for the first enzyme of glycolysis), exist in a diploid cell (that has not replicated its DNA?) A. 1 B. 2
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2 How many copies of a gene (say, alleles for the first enzyme of glycolysis), exist in a haploid cell (that has not replicated its DNA)? A. 1 B. 2 Avoiding Muller’s Ratchet while maintaining a large genome a 1. Multiple chromosomes allow independent assortment of mutations. ` Some daughter cells end up with more mutations, and some with less. ` Selection can then remove multiple mutations per death ` Possibility of ‘resetting’ some cells genomes so that they have fewer mutations than the average cell a 2. Diploidy allows mutations to be hidden from selection. ` Can work with multiple chromosomes to increase probability of resetting the genome represents a centromere represents a mutation Diploid cells can ‘hide’ mutations The “good” copy of the gene could produce enough protein … That the mutated copy has no affect on phenotype The good gene is termed ‘dominant’ and the mutated gene is termed ‘recessive’ DNA replication Cell division Affects of assortment during mitosis in a Diploid Cell with 2 types of chromosomes All four daughters might survive! DNA replication Cel division represents a centromere represents a mutation Cell division Normal? Purify + Reset Affects of assortment during mitosis in a Diploid Cell with n=2 chromosomes What is a chromatid? A. The same thing as a chromosome B. One half of a replicated chromosome C. Any DNA-protein complex.
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3 What is an example of a pair of alleles? A. Any two DNA sequences B. Any two discrete DNA sequences, carried on homologous chromosomes C. Two DNA sequences that are alternate forms of the same gene a What is the relationship among DNA, an allele, and a chromosome? ` A. A chromosome contains hundreds of alleles, which are composed of protein. ` B. A chromosome contains hundreds of alleles,
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lect23__meiosis - Reductionist Cell Division: Meiosis...

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