Chapter 12.4.1 (Exam 3) Linked Traits

Question 1

Why was Drosophila a good model system?

Answer 1

Breeds quickly; produces many offspring

Genome is sequenced

Small and cheap

Question 2

What might cause observed phenotypes in a dihybrid cross not aligning with Mendel’s second law of independent assortment?

Answer 2

Genes for different characters are on the same chromosome

Question 3

What are linked genes?

Answer 3

Genes that are on the same chromosome

Question 4

If the genes are linked (on the same chromosome), then how can we predict recombinant phenotypes ratios?

Answer 4

Recombinant offspring phenotypes appear in recombinant frequencies:

Number of recombinant offspring divided by total number of offspring

Question 5

What is recombination/crossing over?

Answer 5

Chromosomes exchange corresponding segments

The exchange involves two chromatids in the tetrad; both chromatids become recombinant

Exchange can occur at any point along the length of the chromosome

Question 6

How do recombinant frequencies relate with distance between linked genes on a chromosome?

Answer 6

Recombinant frequencies are greater for genes further apart, because an exchange event is more likely to occur between genes that are far apart

Question 7

How can location of genes on a chromosome be inferred?

Answer 7

Recombinant frequencies can be used to infer location of genes on a chromosome and make genetic maps

One map unit is equal to an average recombination frequency of 1%

Question 8

What does it mean to be a monoecious organism?

Answer 8

Organisms that possess both male and female reproductive organs within the same individual

Question 9

What does it mean to be a dioecious organism?

Answer 9

Organisms that possess male and female reproductive organs within different individuals

Question 10

How is sex determined in mammals and birds?

Answer 10

Sex is determined by one pair of sex chromosomes

Question 11

What are autosomes?

Answer 11

All chromosomes except for the sex chromosomes