practice_midterm_key

practice_midterm_key - Biology 105 Introduction to Genetics...

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Biology 105: Introduction to Genetics Page 1 Midterm Fall 2004 KEY Part I. Definitions Hemizygous: The genotype for genes present only in one copy in an otherwise diploid organism; e.g. X-linked genes in a male. Prophase I: Beginning of meiosis I; chromosomes condense and crossing-over occurs. Karyotype: Visual description of the complete set of chromosomes in one cell of an organism. Interference: A phenomenon where a cross-over in one part of the chromosome lowers the probability of a second cross-over nearby. Mitosis: A form of cell division where one diploid parent cell yields two genetically identical diploid daughter cells.
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Part II Short Answer (Answer 5 out of the 6) 1. In humans, achondroplastic dwarfism and neurofibromatosis are extremely rare autosomal dominant conditions. If a woman with achondroplasia marries a man with neurofibromatosis, what genotypes and phenotypes could be predicted in their children and in what proportions? (these genes are unlinked) f A / + ; + / + x m + / + ; N / + f A ; + + ; + m 1/4 normal + / + ; + / + A / + ; + / + ; 1/4 dwarf A / + ; + / + + ; N + / N + / N 1/4 neuro + / + ; + / N 1/4 dwarf A / + ; + / N + neuro A / + ; + / + ; + ; + + / + + / + 2 . A-------------20MU-------------------B----------5MU----------C An AABBCC female is crossed with an aabbcc male and the resulting F1 progeny are backcrossed to aabbcc individuals. What fraction of the F2 will be heterozygous for all three genes? I II A B C a b c a b c a b c 0.80 x 0.95 x 0.5 = 0.38 NO cross overs in only want progeny with ABC regions I AND II gamete from female f m
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3 . A unique species of fish containing only one large chromosome is discovered. Describe the ratios and classes of progeny (with respect to ploidy) produced when a triploid member of this species is crossed to a diploid member of this species. 1/2 progeny will be triploid 1 /2 progeny will be diploid 4. For two genes far apart on the same chromosome, 50MU is the maximum distance. Why? Recombination occurs at the 4 strand stage and involves only 2 of 4 chromatids. 5.
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This note was uploaded on 04/15/2008 for the course BIO 105 taught by Professor Sullivan during the Fall '08 term at UCSC.

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practice_midterm_key - Biology 105 Introduction to Genetics...

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