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Flashcards in FINNEGAN Deck (33)
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1
Q

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

A

Independent assortment of chromosomes at meiosis I

2
Q

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

A

A chiasma at meiosis

3
Q

What happenes in meiosis I?

A

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

4
Q

Define bivalent

A

a pair of homologous chromosomes.

5
Q

What happens in meiosis II?

A

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

6
Q

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?

A

AB and ab are parentals

Ab and aB are recombinants

  • independent assortment at bivalent level
7
Q

Parents AA bb x aa BB produce?

Which are recombinants?

A

Ab ab (parental)

AB ab (recombinants)

8
Q

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

A

50%

YES

9
Q

Chiasma

A

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.

10
Q

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

A

Linked (on the same chromosome)

11
Q

Recombinants come in ____

A

Pairs

12
Q

How is recombination frequency calculated?

A

No. recombinants/ expected progeny

13
Q

1cM = 1% recombination = ______

A

1 map unit

14
Q

Max frequency of recombination between any 2 genes is what?

A

50%

15
Q

Parental phenotypes are the most ____

A

common

16
Q

Double recombinant frequencies are the most ____

A

uncommon

17
Q

Crossing over gives __________ products

A

reciprocal

18
Q

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

A

correct for double recombinants

19
Q

Top tip for working with 3 point test cross tables

A

always write out the full genotypes of parents

20
Q

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

A

look at double recombinants and see which remain parental

21
Q

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

How is it calculated?

A

less double recombinants than expected

OBSERVED freq of doubles/ EXPECTED freq of doubles

22
Q

What is interference?

Calculated?

A

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

1 - coefficient of coincidence

23
Q

Is recombination uniform among individuals/ species?

A

NO

  • varies greatly between species
  • varies between sexes

BUT distribution is not random

24
Q

What is a physical map?

A

The actual length of the gene distances in base pairs

25
Q

Why is the female genetic map longer ?

A

There is more recombination points, more chiasma perhaps?

26
Q

What stabilises bivalents at meiosis I?

A

Chiasma

27
Q

What holds sister chromosomes together?

A

Cohesin

28
Q

Is it possible for mitotic recombination to occur? Why?

Can lead to…

A

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

29
Q

Describe the use of a complementation test

A

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

30
Q

What is intragenic complementation?

A

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

31
Q

Structure of a T4 bacteriophage

A
  • head with packaged DNA
  • collar
  • tube
  • sheath covers a tail
  • base plate
32
Q

How are T4 phages used for complementation tests?

A

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
33
Q

Distinguish between a genetic map and a physical map

A

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.