Lecture 9/25 - E2

Question 1

How do you calculate the distance for the gene in the middle?

Answer 1

r = non-parental
Add up the observed values for the single recombination events and the double recom events
The double recombination need to be doubled
Divide r by the total number observed

Question 2

Can we know the left to right order or just which gene is in the middle?

Answer 2

Just which gene is in the middle

Question 3

Determine the gene order from a ABD/abd x abd/abd cross.
ABD: 36%
abd: 34%
Abd: 1%
aBD: 1%
ABd: 12%
abD: 16%

Answer 3

First, which appears at the smallest frequency?
Abd and aBD
Which gene is different from the parents?
A and a
Therefore the a allele is the middle gene
- Cannot determine left to right order

Question 4

What is interference?

Answer 4

When the observed and expected number of double recombinants differ.

Question 5

Given a gene arangement of A-B-C and observed recombinant frequences of 0.18 between A&B and 0.136 between B&C. What is the expected number of double recombinants?

Answer 5

Multiple the two values:

0.18 x 0.136 = 0.025

Question 6

What is the coefficient of coincidence (c) and how is it calculated?

Answer 6

Measure of the difference between observed and expected

c = observed/expected

Question 7

How do you calculated interference (I) in recombination?

Answer 7

1 - c

Question 8

What does it mean in I is greater than 0

Answer 8

Positive interference - lower levels of recombination than expected

Question 9

What does it mean in I is less than 0

Answer 9

Negative interference - higher levels of recombination than expected

Question 10

For ABC/abc you find that recombination, r, between AB is 0.04 and between BC is 0.02. The expected rate of souble recombination is …

Answer 10

0.04 x 0.02 = 0.0008

Question 11

For ABC/abc you observe 0.16 double ecombinants instead of 0.08. The coefficient of coincidence is…

Answer 11

Observed / Expected

0.16 / 0.08 = 2

Question 12

A coefficient of cofidence of 2 indicates…

Answer 12

Interference = 1-c = 1 - 2 = -1

-1 means there was negative interference

Question 13

Is there more recombination in males or females?

Answer 13

Females

Question 14

Where do both males and females show reduced recombination?

Answer 14

At the Centromere

Question 15

What is a cold spot?

Answer 15

Where there is reduced recombination between genes (shrinks genetic map)

Question 16

What is a hot spot?

Answer 16

Where there is more recombination between genes (expands genetic map)

Question 17

What is allelic phase?

Answer 17

The order of alleles of two or more genes that are on the same homolog (mom or dad’s original chromosome)