Question

Which of these statements is incorrect?

Syntenic genes are located on the same chromosome.

Independent assortment results in recombinant chromosomes.

You can reliably predict the relative genetic distance from genes’ physical distance on a chromosome.

Linked genes are always syntenic.

What is the relative genetic distance between two linked genes if the recombination frequency is 0.49?

0.49 cM

4.9 cM

49 cM

490 cM

What statement best explains the distortion in Mendelian ratios observed by Bateson & Punnett in 1905? (Reminder: they found an overrepresentation of F2 offspring showing both dominant or recessive phenotypes, and an underrepresentation of offspring displaying one dominant and one recessive phenotype)

Human error: they should have been more careful about their experimental setup.

Gene linkage: Genes for flower color and pollen shape are physically close on the same chromosome, leading to a breakdown in the independent assortment of the alleles for these traits.

Chromosome crossover: Homologous recombination of two chromatids during meiosis caused the alleles to shuffle, resulting in a breakdown of the independent assortment of the alleles for those genes.

Random variation: No two situations are alike. In finite populations, you are going to get some variation across a mean.

When determining the relative genetic distance between two genes, why is dihybrid back-cross preferable over traditional dihybrid cross?

9:3:3:1 phenotypic ratio is easier to work with than 1:1:1:1 ratio.

Genotypes of the offspring can be determined based on their phenotype.

If the genes are independently assorted, the dihybrid back-cross would result in only 2 genotypes in the F1 generation.

B and C

Why do we map genes?

To understand how genes interact with each other

Comparative genomics analysis

To determine the genotype of an organism

All of the above

Answer 1

Answer 1

You can reliably predict the relative genetic distance from genes’ physical distance on a chromosome

Answer 2

49 cM (because 1% recombination equals distance of 1 map unit)

Answer 3

Gene linkage: Genes for flower color and pollen shape are physically close on the same chromosome, leading to a breakdown in the independent assortment of the alleles for these traits.

Answer 4

Genotypes of the offspring can be determined based on their phenotype.

Answer 5

All of the above