The direction of shell coiling in the snail Lymnea s determined by a maternal ef
ID: 225978 • Letter: T
Question
The direction of shell coiling in the snail Lymnea s determined by a maternal effect gene for which the dextral allele is dominant to the sinistral allele In a cross in which the phenotype of the snail contributing eggs was sinistral, all F_1 progeny are dextral a) What was the genotype of the snail that contributed eggs? b) These dextral F_1 progeny are self-fertilized and they produce an F_2 generation comprising 50% dextral and 50% sinistral snails. What was the genotype of the sperm donor in the initial cross? (Don't forget to show your work here) Double-stranded DNA is wrapped around 8 _____ which collectively form _____, which are organized into structures called _____ The Meselson-Stahl experiment was designed to discriminate between three alternative models of DNA synthesis (see Chapter 11 section 1 for details). If the dispersive model were correct, would the researchers have obtained two separate bands of DNA following replication in the^14N medium? If you answered yes, how many generations would this have taken? If you answered no explain your answer. If a region of the genome is said to be CpG rich, what does this mean in terms of base composition? a) What type of chromatin would you expect to find in this region? b) Would you expect this region to replicate early or late in S-phase? Gene conversion can produce ratios of alleles that differ from Mendelian expectations Imagine a gene with two alleles that differ by one base: allele 1 is CAATT and allele 2 is CAGTT. Draw a) the two alleles with their complementary base pairs b) the outcome of a crossover that produces a mismatched base pair in each allele c) the outcome of mismatch repair that results in a ratio of 3 copies of allele 1 for every one copy of allele 2.Explanation / Answer
4. a. The genotype of the egg contributing gene was Sinstral.
b. The genotype of the initial sperm donor was dextral.
5. Double stranded DNA is wrapped around 8 histones, which collectively form chromatosome, which are organized into structures called chromosome.
6. No, they would not have obtained two separate band if the dispersive model was correct. So many discrete bands would have appeared if the discrete model was correct.
7. The region is said to be rich in GC composition.
a. The chromatin present in this region is said to be heterochromatin
b. The region will replicate in the late S- phase.