genetics pse

1. If every human gamete contains approximately 30,000 genes and if the forward mutation rate is between 1 x 10-5 and 1 x 10-6 new mutations per gene per generation, what is the average number of new mutations per gamete per generation? If 30,000 genes mutate at a rate between 1 x 10-5 and 1 x 10-6 new mutations per gene per generation, then there would be an average of 3 new mutations per gamete per generation. 30,000 x ((1 x 10-5 and 1 x 10-6)/2) = 3 2. What is the minimum number of single nucleotide substitutions that would be necessary for each of the following amino acid replacements? a. Trp to His The only codon for Trp is AAG, and the codons for His are CAU and CAC. This would require a minimum of a 2-base substitution, since they both have the A in the middle of the codon in common. b. Met to His The only codon for Met is AUG, and the codons for His are CAU and CAC. Since neither His codon is close to resembling the Met codon to get from Met to His requires a minimum of a 3-base substitution. 3. Show via a diagram how the product(s) of a meiotic (either I or II) nondisjunction involving the X chromosome of a human female could, when fertilized by a normal male gamete, result in an offspring with Kleinfelter’s syndrome. 4. Inversions are known to affect crossing-over. The following homologs have the indicated order (the filled and open circles indicate centromeres): •A B C D E oA D C B E a. Considering the position of the centromere, what is this sort of inversion called? This type of inversion is called paracentric inversion, because the centromere is not included in the inverted DNA strand. b. Diagram the alignment of these chromosomes during meiosis. c. Diagram the results of a single crossover between homologous genes B and C in the inversion. A crossover between B and C results in: A B C D E (normal order) A B C D A (dicentric, duplication for A, deletion for E) E B C D E (acentric, duplication for E, deletion for A) A D C B E (inverted order)