1. Under which of the following conditions would genes on the same chromosome as

Question

1. Under which of the following conditions would genes on the same chromosome assort independently? • double crossovers in the region of interest • genes widely separated on the same chromosome • sex linkage • genes on the same chromosome cannot assort independently

2. Harriet Creighton and Barbara McClintock observed that one strain of corn had a chromosome with a dark staining knob on one end and an extra piece on the other. Associated with this chromosome were the dominant gene C (colored) on the knob end and the recessive wx (starchy) on the other end. Chromosomes without the unusual features carried alternate alleles c (colorless) and Wx (Waxy). Which of the following crosses allowed them to quantify the recombination rates between these two genes? • recombinant assay • monohybrid • testcross • three point cross

3. Which of the following chromosomes would Creighton and McClintock have observed in progeny with colorless, waxy phenotypes? • knob present, extra piece present • knob present, extra piece absent • knob absent, extra piece absent • knob absent, extra piece present

4. Which of the following conditions would cause phenotypic recombination without crossing over? • double crossovers in the region of interest • genes widely separated on the same chromosome • sex linkage • genes located on different chromosomes

5. Under which of the following conditions is it valid to equate the number of recombinant progeny with the number of crossovers between two genes? • less than 15% of the progeny are recombinant • less than 30% of the progeny are recombinant • genetic interference is less than 15% • genetic interference in greater than 15%

6. A testcross is usually preferred over a dihybrid cross to map genes. The advantage of using this type of cross is • not all genes respond to a dihybrid cross • the outcome is simplified by controlling the gametic combinations in one parent • dihybrid crosses produce a greater number of phenotypic combinations • phenotypes in other crosses are not sufficiently correlated with genotypes

7. Which chromosome mutations involve exchange between two non-homologous chromosomes? • deletion • duplication • inversion • translocation

8. Large deletions are lethal when they are ______, while small deletions are lethal when they are ______. • both heterozygous and homozygous - homozygous only • homozygous only - homozygous only • both homozygous and heterozygous - heterozygous only • heterozygous only - both heterozygous and homozygous

9. In heterozygotes for translocation, which of the following segregation patterns during meiosis would produce viable gametes? • alternate • adjacent • aneuploid • breakpoint

Explanation / Answer

1) Answer: Double crossovers in the region of interest would allow chromosome to assort independently.

2) Answer: Test cross would determine the recombination rates between these two genes.

3) Answer: Knob present, extra piece present. Knob is present at the end of tha chromosome and an extra piece at the other.

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