Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS2042 > WEEK 3: LINKAGE, RECOMB, AND GENETIC MAPPING > Flashcards

WEEK 3: LINKAGE, RECOMB, AND GENETIC MAPPING Flashcards

1
Q

if two genes are linked on the same chromosome will they assort independently?

A
  • NO!!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do genetic maps show?

A
  • The position of genes (loci) in relation to each other along the chromosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are 4 reasons why generating genetic maps are good?

A
  1. Can determine whether mutations affect different genes or not (mapping provided the first indication that there were two forms of Haemophilia)
  2. Can CLONE genes using their map position (e..g CFTR gene)
  3. Enhances our ability to predict inheritence patterns (counselling)
  4. Very useful for genome sequencing projects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is one form of Haemophilia linked to (gene) ?

A
  • The colour blindness gene
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are genes on the same chromosome said to be?

A
  • Linked
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the F2 ratio for two genes on two different homologous pairs of chromosomes?

A
  • 9:3:3:1
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Does exchange occur in linked genes?

A
  • NO - no crossing over
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which structure on the chromosome is the physical evidence of crossing over during meiosis?

A
  • Chiasmata - evidence of crossing over in Meiosis I
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Can linked genes be separated by recombination in meiosis?

A
  • YES
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

If the genes assort independently, what is the predicted phenotypic ratio in the test cross progeny?

A
  • 1:1:1:1 (unlinked)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the coupling phase known as?

A
  • When the dominant alleles of the different genes stayed together as did the recessive alleles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the repulsion phase known as?

A
  • Where one dominant and one recessive allele stay together e.g. A and b stay together and a and B stay together
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which test can be used to distinguish between independent assortment and linkage?

A
  • Chi squared test
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the recombination frequency?

A
  • The number of recombinants OVER the total progeny *100
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

If crossovers never occur between two gene loci what is the recombination frequency (RF)?

A
  • 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the maximum RF?

A
  • 50%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

If one crossover always occurred, then what would the RF be and what is this the same for?

A
  • 50%

- The same for independent assortment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why is the RF never >50?

A
  • because there are always (nearly) two non-crossover gametes from a single meiosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What can a testcross be used to measure and explain it?

A
  • RF
  • Heterozygote for two or more genes and homozygous recessive for all genes –> can determine whether recombination has occurred during gamete formation in heterozygous parent
20
Q

With test crosses to measure RF, are we looking at the gametes for one or both parents?

A
  • Only 1 parent
21
Q

In a test cross, what do the phenotypes of the zygotes equal and what does this tell us?

A
  • The genotypes of the heterozygous parent gametes

- Tells us that the phenotypes of the offspring tells us the number of RECOMBINANT and parental gametes.

22
Q

If two genes are very close together is there a small or large chance of crossover?

A
  • A SMALL chance of crossover
23
Q

if two genes are FAR APART is there a small or large chance of a crossover occurring?

A
  • A LARGE chance with lots of recombinant offspring
24
Q

What is the percentage of recbominant offspring correlated with and what is this called?

A
  • The distance between two genes

- Called the MAP distance

25
Q

What is map distance defined as?

A
  • The distance between two loci that will generate 1% of recombination between them
  • Units are Map UNITS (mu)
26
Q

What do double crossovers make long distances in terms of accuracy?

A
  • They make them inaccurate

- Double crossovers cancel out the recombinants for distant markers

27
Q

Does recombination frequency= crossover frequency?

A
  • NO
  • recombination frequency= recombinant gametes in progeny
  • crossover frequency= two sister chromatids
28
Q

When genes are very far apart on the same chromosome, why does the RF no longer accurately measure the distance between them?

A
  • Because of double recombinants
29
Q

At what RF % do we need to do a statistical test (Chi2) to determine if the genes are linked or not?

A
  • > 25% need to do a test for linkage
30
Q

What is the GENERAL genetic hypothesis?

A
  • That the genes are UNLINKED and we do the chi squared test to see if they are linked or not
  • Linked= we do not support
  • Unlinked= we support
31
Q

Why is mapping human genes difficult and from this, what is it restricted to analysis of ?

A
  • Because of the small numbers of progeny.
  • Can’t perform desired number of crosses
  • Restricted to analysis of pedigrees
32
Q

What is the Coefficient of coincidence (C)?

A
  • the observed number of doubles (crossovers)/ expected number of doubles
33
Q

What is positive interference?

A
  • Where the observed number of crossovers was less than the expected
  • One crossover interferes with another occurring nearby
  • Thus reducing the number of double recombinants
34
Q

What is the equation for the degree of interference?

A
  • 1- coefficient of coincidence (C)
35
Q

What does a degree of interference (I) of 0.6 mean?

A
  • That 60% of second crossovers were “prevented” from occurring
36
Q

What are the C and I values for no double crossovers resepctively?

A
  • 0 and 1
37
Q

What are the C and I values for the same number of double crosovers expected respectively?

A
  • > 1 and <0
38
Q

What are the C and I values respectively for more double crossovers than expected?

A
  • > 1 and <0
39
Q

What does an I value of less than 0 mean?

A
  • the occurrence of one crossover occurring is causing ADDITIONAL crossovers to occur
40
Q

Can crossover occur in MITOSIS??

A
  • YES occasionally

- Produces new combinations of alleles

41
Q

What happens if MITOTIC crossover occurs early in development?

A
  • It will give rise to a patch of tissue with characteristics different to the rest –> MITOTIC CLONE
42
Q

What do mitotic clones allow for?

A
  • Developmental genetecists to follow cell line lineages (providing that the gene product stays within the cell–> genes action is autonomous)
43
Q

What does crossover in MITOSIS play a role in?

A
  • Important in cancer–> tumour suppressor genes
44
Q

What does mitotic recombination allow us to create?

A
  • Create mosaic animals (basically heterozygous) –> but have mutant tissues
45
Q

What is intragenic recombination and which organisms does it occur in ?

A
  • Where the unit of recombination is smaller than the gene and recombination is measured between two close genes.
  • Occurs in all organisms but hard to measure

BMS2042 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions