FINNEGAN

Question 1

What process leads to the inheritance of novel alleles on DIFFERENT chromosomes?

Answer 1

Independent assortment of chromosomes at meiosis I

Question 2

What process leads to the inheritance of new combinations of alleles on the SAME chromosomes?

Answer 2

A chiasma at meiosis

Question 3

What happenes in meiosis I?

Answer 3

Chromosomes replicate, form 2 chromatid pairs and then the two chromosomes form bivalents

Question 4

Define bivalent

Answer 4

a pair of homologous chromosomes.

Question 5

What happens in meiosis II?

Answer 5

microtubules attach to cetromeres, leaving 4 products and supposedly 2 products

Question 6

If parental genotypes AA BB and aa bb produce progeny of AB, ab, Ab and aB, which are the recombinants and which are parental? How come?

Answer 6

AB and ab are parentals

Ab and aB are recombinants

• independent assortment at bivalent level

Question 7

Parents AA bb x aa BB produce?

Which are recombinants?

Answer 7

Ab ab (parental)

AB ab (recombinants)

Question 8

The frequency of recombination between genes on different chromosomes is what? Always?

Answer 8

50%

YES

Question 9

Chiasma

Answer 9

Where paired chromosomes remain in contact during the first metaphase of meiosis at which corssing over and exchange of genetic material can occur between strands.

Question 10

Genes that show < 50% recombination are said to be….

Answer 10

Linked (on the same chromosome)

Question 11

Recombinants come in ____

Answer 11

Pairs

Question 12

How is recombination frequency calculated?

Answer 12

No. recombinants/ expected progeny

Question 13

1cM = 1% recombination = ______

Answer 13

1 map unit

Question 14

Max frequency of recombination between any 2 genes is what?

Answer 14

50%

Question 15

Parental phenotypes are the most ____

Answer 15

common

Question 16

Double recombinant frequencies are the most ____

Answer 16

uncommon

Question 17

Crossing over gives __________ products

Answer 17

reciprocal

Question 18

Why does genetic map never add up to distance between furthest away genes?

Answer 18

correct for double recombinants

Question 19

Top tip for working with 3 point test cross tables

Answer 19

always write out the full genotypes of parents

Question 20

How can you tell which gene is in the middle of a genetic map for linked genes?

Answer 20

look at double recombinants and see which remain parental

Question 21

What does it mean for the coefficient of coincidence to be below 1 ?

How is it calculated?

Answer 21

less double recombinants than expected

OBSERVED freq of doubles/ EXPECTED freq of doubles

Question 22

What is interference?

Calculated?

Answer 22

Crossing over one time in a chromosome makes it less likely for a second cross over on the same chromosome

1 - coefficient of coincidence

Question 23

Is recombination uniform among individuals/ species?

Answer 23

NO

• varies greatly between species
• varies between sexes

BUT distribution is not random

Question 24

What is a physical map?

Answer 24

The actual length of the gene distances in base pairs

Question 25

Why is the female genetic map longer ?

Answer 25

There is more recombination points, more chiasma perhaps?

Question 26

What stabilises bivalents at meiosis I?

Answer 26

Chiasma

Question 27

What holds sister chromosomes together?

Answer 27

Cohesin

Question 28

Is it possible for mitotic recombination to occur? Why?

Can lead to…

Answer 28

YES
When the chromosomes line up in mitosis to be separated, they can also line up differently/flipped

As a result of this, there can be a loss of heterozygosity

Question 29

Describe the use of a complementation test

Answer 29

if two mutant homozygotes are crossed and produce wild type offspring, then the mutations are in different genes and complementation has occurred

Question 30

What is intragenic complementation?

Answer 30

result of a gene coding for an enzyme that is an homomultimer (has more than one protein subunit)
- This means that alleles of the same gene can complement

Question 31

Structure of a T4 bacteriophage

Answer 31

• head with packaged DNA
• collar
• tube
• sheath covers a tail
• base plate

Question 32

How are T4 phages used for complementation tests?

Answer 32

plaques on a lawn of bacteria
- due to lysis

• it is key in this experiment that recombination is given time to occur, hence why it is isn’t recombination as then they would be able to grow immediately

Question 33

Distinguish between a genetic map and a physical map

Answer 33

Genetic and physical maps illustrate the arrangement of genes and DNA markers on a chromosome. The relative distances between positions on a genetic map are calculated using recombination frequencies, whereas a physical map is based on the actual number of nucleotide pairs between loci.