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Chapter 4 COPY Flashcards

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1
Q
A
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2
Q

What cellular process produces a recombination of linked genes?

A

Recombination

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3
Q

What are recombinant frequencies diagnostic of?

A

Linkage

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4
Q

How can an analysis of recombinant frequencies generate a chromosome map?

A

By determining the distance between genes based on recombination frequencies

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5
Q

How are recombination maps used in conjunction with physical DNA maps?

A

To provide a detailed understanding of gene locations and functions

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6
Q

Why is obtaining a map of gene positions on chromosomes important?

A

For strain building, discovering gene function, and interpreting evolutionary mechanisms

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7
Q

What is the significance of gene position in strain building?

A

It is crucial for building complex genotypes for experimental or commercial applications

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8
Q

How does knowing a gene’s position help in discovering its function?

A

It allows for defining the gene at the DNA level and understanding its underlying function

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9
Q

What can variations in gene arrangement indicate in related species?

A

Differences in evolutionary mechanisms

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10
Q

What are linked genes?

A

Genes that are located on the same chromosome

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11
Q

Who performed a dihybrid selfing to study inheritance in sweet peas?

A

Bateson and Punnett

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12
Q

What did Morgan propose to explain the co-inheritance of certain gene alleles?

A

Gene linkage

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13
Q

What is a test cross?

A

A cross where a tester only contributes recessive alleles to the progeny

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14
Q

What does a recombinant frequency of less than 50% indicate?

A

That genes are linked

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15
Q

What is crossing over?

A

The process where homologous chromosomes exchange parts during meiosis

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16
Q

What is the cis conformation?

A

When two dominant alleles are present on the same homolog

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17
Q

What is the trans conformation?

A

When two dominant alleles are on different homologous chromosomes

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18
Q

Who provided evidence that crossing over is a breakage and rejoining process?

A

Harriet Creighton and Barbara McClintock

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19
Q

What is the significance of chiasmata?

A

Sites where crossing over occurs

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20
Q

What are map units also known as?

A

Centimorgans (cM)

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21
Q

What does 1 map unit (centimorgan) represent?

A

A distance between genes for which 1 in 100 products of meiosis is recombinant

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22
Q

What does a three-point testcross determine?

A

If three genes are linked, their order, and genetic distance in map units

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23
Q

In a three-point testcross, what type of tester is used?

A

Triply recessive tester

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24
Q

What do multiple crossovers in a meiocyte indicate?

A

That several crossovers can occur along a chromosome pair

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25
What is the relationship between longer regions and crossover frequency?
Longer regions have more crossovers and thus higher recombinant frequencies
26
What does the chi-square test analyze in linkage studies?
The statistical significance of the observed versus expected ratios of offspring
27
What is the role of molecular markers in mapping?
They help identify specific locations of genes on chromosomes
28
What is the definition of recombination frequency (Rf)?
The percentage of recombinants observed in the test cross progeny
29
True or False: A recombinant frequency of 50% indicates linkage.
False
30
Fill in the blank: The distance between adjacent genes or markers is based upon _______.
Recombination frequencies
31
What is a three-point testcross?
A genetic cross involving three loci to determine gene linkage and order
32
In a three-point testcross, what are the parental genotypes represented by?
v+/v ∙ cv+/cv ∙ ct+/ct ♀ X v/v ∙ cv/cv ∙ ct/ct ♂
33
What is the significance of recombinant genotypes?
They indicate the occurrence of crossover events between linked genes
34
Fill in the blank: Recombinant Frequency for v and cv loci = _______.
268/1448 X 100 = 18.5%
35
What is the recombinant frequency for v and ct loci?
191/1448 X 100 = 13.2%
36
What is the recombinant frequency for cv and ct loci?
93/1448 X 100 = 6.4%
37
True or False: The gene order is arbitrary in a three-point testcross.
True
38
What is deduced from the double recombinant class in a three-point testcross?
The middle gene is the allele pair that has 'flipped' position
39
What does the gene order v ct cv imply?
It indicates the relative positions of the genes on the chromosome
40
What is the general pattern for three linked genes in terms of genotype frequency?
8 genotypes: 2 high frequency, 2 intermediate, 2 second intermediate, 2 low frequency
41
How is the recombinant frequency calculated?
Number of recombinant offspring divided by total number of offspring, multiplied by 100
42
What is the implication of the additivity of recombinant frequencies?
The sum of individual recombinant frequencies does not equal the total recombinant frequency
43
Fill in the blank: For the v and cv loci, recombinants = _______.
18.5%
44
What does a double recombinant genotype result from?
Two crossover events occurring between linked genes
45
What is the total number of gametes produced in the testcross?
1448
46
What does 'R' represent in the context of recombinant genotypes?
Recombinant offspring
47
What is the role of reiterative mapping in genetics?
To build complex recombination maps based on multiple testcrosses
48
True or False: The three-point testcross helps establish gene order on a chromosome.
True
49
What does the notation v+, cv+, and ct+ indicate?
Wild-type alleles for the respective loci
50
Fill in the blank: The middle gene in a three-point testcross is determined by _______.
Inspection of the double recombinant class
51
What is the recombinant for loci?
ct is the allele pair that has flipped position in the double recombinant class.
52
What does reiterative mapping build?
Complex recombination maps.
53
What is the percentage of DNA sequence identity between two individuals?
About 99.9% identical.
54
What constitutes almost all of the .1% difference in DNA sequences?
Single nucleotide differences.
55
What are molecular heterozygotes?
Individuals at many sites in their genome with different alleles.
56
Define a molecular marker.
DNA difference between 2 chromosomes that does not produce visibly different phenotypes.
57
What are single nucleotide polymorphisms (SNPs)?
DNA differences at a single nucleotide position between individuals.
58
How many SNPs are estimated to be in the human genome?
About 3 million.
59
What are silent SNPs?
SNPs within genes that have no effect on phenotype but are useful for mapping.
60
What is a test cross?
A cross used to determine linkage between genes.
61
What do restriction enzymes do?
Cut DNA at specific sequences.
62
What is RFLP?
Restriction fragment length polymorphism.
63
What are simple sequence length polymorphisms (SSLPs)?
Repetitive DNA where the number of consecutive repeats differs.
64
What are the two types of SSLPs?
* Minisatellite markers * Microsatellite markers
65
What does PCR stand for?
Polymerase Chain Reaction.
66
What are the three steps in the PCR process?
* Denature DNA strands * Pair primers to specify the segment * Synthesize new DNA strands.
67
What is the unit of measure for genetic maps?
Centimorgan (cM).
68
What is the unit of measure for physical maps?
Kilobase (kb).
69
What is the null hypothesis in chi-square tests?
That there is no difference among groups.
70
What does a chi-square test estimate?
Whether observed data indicates linkage or occurs by chance.
71
What occurs if the difference in chi-square is less than or equal to 5%?
The null hypothesis is true.
72
What do genetic maps rely on?
Recombination frequencies.
73
How do physical maps differ from genetic maps?
Physical maps are based on the actual DNA sequence.
74
What are the key applications of genome sequencing?
* Assembling DNA sequences * Identifying genes based on sequence characteristics * Identifying homologous genes.

genetics (12 decks)

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