Chapter 6: Genetic Linkage & Mapping in Eukaryotes

Question 1

the transmission of ____ on the same chromosome violates Mendel’s law of independent assortment.

Answer 1

• genes but the actually chromosomes separate through independent assortment.

Question 2

What is synteny?

Answer 2

when two or more genes are located on the same chromosome and are physically linked.
- thomas hunt morgan

Question 3

Chromosomes are called ___

Answer 3

Linkage groups - since they contain a group of genes that are linked together

Question 4

In humans, how many linkage groups do males and females have?

Answer 4

Males - 25; 22 autosomal, X chromosome, Y chromosome, mitochondria
Females - 24: 22 autosomal, X chromosome, mitochondria

Question 5

What is a two factor and three factor cross?

Answer 5

Two factor - linkage between two genes
Three factor - linkage between three genes

Question 6

what is a test cross?

Answer 6

a heterozygote x homorecessive (all traits are homo)

Question 7

What is the expected ratio for a heterozygote and homorecessive test cross?

Answer 7

1:1:1:1

Question 8

A/a * B/b x a/a * b/b
1. what is the predicted progeny ratio?
2. what is the recombinant frequency?
3. Is it linked or mendel?

Answer 8

1. 1:1:1:1
2. 9.8%
3. Linked because less than 50%

Question 9

What does the * (should be a dot) mean?

Answer 9

We don’t know if they are linked
If they are linked write it as AB/ab.

Question 10

what groups are there in a 3 factor cross?

Answer 10

1. Nonrecombinant - lowest #s - happens most frequently
2. double cross over - parental (less frequently)
3. single cross over

Question 11

What is mitotic recombination?

Answer 11

• Mitosis does not involve the homologous pairing of of chromosomes to form bivalents.
• crossing over during mitosis does occur on rare occasions in which it may produce a pair of recombinant chromosomes that have a new combinant of alleles