PS5-Key - Problem Set 5-ANSWER Key BILD1 FA 2009 Problem 1:...

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Problem Set 5-ANSWER Key BILD1 FA 2009 Problem 1: A. Haploids only have one copy of any given gene, so they can never be heterozygous. Without the interaction between the two alleles in one organism, no determination can be made of which is dominant and which is recessive. B. When homologous chromosomes line up on the metaphase I plate, they do it randomly. If you have copy A and copy B of every chromosome, there is no rule directing all A’s to go right and all B’s to go left. It is a mix and match system and you can end up with any combination of A’s and B’s in a gamete. This is called Independent Assortment, meaning the homologous distribute randomly between the forming gametes. If there are genes on two different chromosomes, they will also appear to assort independently because of the random chromosome separation. C. Locus: The gene location on a chromosome Allele: Variations at a locus, meaning differences in the DNA code. F1 generation: Filial One. This is the first generation of offspring in a genetic cross. D. A homozygote has two copies of the same allele for a given gene. A heterozygote has two different alleles for the gene. E. Since Purple flowers are the dominant phenotype, our plant could be either PP (homozygous dominant) or Pp (heterozygous). To test which type it is, we should do a test cross, when the Purple flowered plant is crossed to a homozygous recessive (pp), white flowered plant. Since we know the only gametes made by the white plant will pass on the p allele to the offspring, we can conclude that all P alleles that show up as purple flowers in the F1 generation are from the unknown Purple plant. By counting the number of purple F1’s we can determine the genotype of the purple parent. F. For Aa: A and a gametes. For AaMm: AM, Am, aM, and am gametes. Problem 2: A. grey (GG) male X white (gg) female B. F1 pups: Gg (grey) X Gg (grey) G G g g Grey White Gg Gg Gg Gg Genotype of Pups Æ Grey Gg Æ grey fur G g G g Grey Grey GG Gg Gg gg ¼ GG pups Æ Grey (true breeding) ½ Gg pups Æ Grey ¼ gg pup Æ White (true breeding) ½ of the pups will be true breeding for their coat color
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C. For grey pups, there are two possible genotypes: GG and Gg.
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This note was uploaded on 12/17/2009 for the course BIOL 1 taught by Professor Patrick during the Fall '09 term at CSU Northridge.

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PS5-Key - Problem Set 5-ANSWER Key BILD1 FA 2009 Problem 1:...

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