Exam 4 Review & Notes

This is the less frequent familial form of down

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Unformatted text preview: genes are unlinked. AKer meiosis in a heterozygote for both genes, tetratypes can arise from: a) No recombina8on. b) Recombina8on between one gene and its centromere. c) A single recombina8on event between the two genes. d) A double recombina8on event between the two genes. e) A gene conversion event. 12. Two yeast genes are unlinked. AKer meiosis in a heterozygote for both genes, tetratypes can arise from: a) No recombina8on. b) Recombina3on between one gene and its centromere. c) A single recombina8on event between the two genes. d) A double recombina8on event between the two genes. e) A gene conversion event. “TT arise from a recombina8on event between one of the genes and its centromere. This event does not change the fact that we observe equal numbers of all possible spores (or gametes as in higher organisms), since the tetratype itself has equal numbers of all possible spores.” - Page 50, Dr. Zitomer’s Lecture notes 13. Two trp- yeast mutants are mated and the diploids are taken through meiosis. The resul8ng tetrads are: 40 PD, 18 TT, and 39 NPD. These two mutants: a) Complement. b) Do not complement. c) Cannot be determined 13. Two trp- yeast mutants are mated and the diploids are taken through meiosis. The resul8ng tetrads are: 40 PD, 18 TT, and 39 NPD. These two mutants: a) Complement. b) Do not complement. c) Cannot be determined If the mutants in this case did not complement, then they would lack the ability to synthesize tryptophan. Therefore, they would not grow on media lacking tryptophan. If the mutants were heterozygous for both the trp1 and trp2 genes and, therefore, can synthesize tryptophan. they will grow on media lacking tryptophan. Therefore they would be complemen8ng. Since we see expected amounts of tetrads, we can say that these two mutants were definitely complemen8ng, if they were not, there would be no resul8ng tetrads. 14. Human chromosome 2 has a piece of chromosome 8 joined to it. It probably arose from: a) An error in DNA replica8on. b) A muta8on. c) Transposon inser8on. d) Nondisjunc8on. e) Illegi8mate recombina8on. 14. Human chromosome 2 has a piece of chromosome 8 joined to it. It probably arose from: a) An error in DNA replica8on. b) A muta8on. c) Transposon inser8on. d) Nondisjunc8on. e) Illegi3mate recombina3on. In this case we are seeing two very different chromosomes joined together. Such a scenario would only arise if DNA sequences that contain only a few iden8cal nucleo8des, ended up recombining, which is in fact the defini8on of illegi8mate recombina8on. 15. Downs Syndrome occurs at a high frequency in...
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