CHAPTER 6

Question 1

Synteny

Answer 1

two or more genes located on the same chromosome and are physically linked

Question 2

Genetic Linkage

Answer 2

Genes close together on a chromosome are transmitted as a unit
Influences inheritance patterns

Question 3

Linkage groups

Answer 3

-Chromosome, because they contain a group of genes linked together
-Represent number of types of chromosomes in a species

Question 4

Two-factor cross

Answer 4

Studies linked between 2 genes

Question 5

Three-factor cross

Answer 5

Studies linked between 3 genes

Question 6

Crossing over

Answer 6

Genes far apart on the same chromosome independently assort from each other

Question 7

Bateson and Punnett Discovery

Answer 7

Some genes are linked on the same chromosome

Question 8

Genetic linkage occurs because

Answer 8

Genes that are close together on the same chromosome tend to be transmitted together to offspring

Question 9

How does linkage in diploid eukaryotic species change during meiosis?

Answer 9

Crossing over during prophase I exchanges DNA segments between non-sister chromatids, altering linkage and creating recombinant genotypes.

Question 10

What do haploid cells retain about alleles?

Answer 10

Retain the same combination of alleles as the original chromosomes, with linked alleles unaltered in gametes.

Question 11

Nonparental / Recombinant cells

Answer 11

Haploid cells that contain a combination of alleles not in the original chromosomes

Question 12

Two ways that the genetic recombination occurs:

Answer 12

1. Two gene on the same chromosome, crossing over during meiosis
2. Two gene on different chromosomes

Question 13

Recombinant offspring

Answer 13

Those produced due to a crossover event during the gamete formation in at least one parent

Question 14

What evidence did Morgan provide for X-linked genes?

Answer 14

Inheritance patterns differed between sexes and male offspring inherited X-linked traits from their mothers.

Question 15

What did Creighton, McClintock, and Stern demonstrate about genetic recombination?

Answer 15

Evidence that genetic recombination results from crossing over by examining chromosomes for observable exchanges between linked genes.

Question 16

Locus

Answer 16

Position of a gene or genetic marker on a chromosome.

Question 17

Genetic Mapping

Answer 17

Determines the linear order of linked genes along the same
chromosome

Question 18

Genetic maps uses

Answer 18

1. Understand complexity of genetic organization
2. Molecular geneticist to clone genes
3. Understand evolutionary relationship
4. Diagnosis/Treatment
5. Predict inherited diseases
6. Improve agriculturally strains

Question 19

How is the relative distance between linked genes determined?

Answer 19

The relative distance is based on the likelihood of a crossover occurring between them.

Question 20

What is the correlation between recombinant offspring and gene distance?

Answer 20

A higher percentage of recombinant offspring indicates that genes are far apart, while fewer recombinants suggest that genes are close together.

Question 21

How does the distance between genes affect recombinant offspring?

Answer 21

Genes that are far apart result in many recombinant offspring, while close genes produce very few recombinants.

Question 22

map distance calculation in genetic mapping

Answer 22

Map distance = (number of recombinant offspring / total offspring) × 100

Question 23

What are the units for map distance?

Answer 23

Map distances are in map units (mu) or centiMorgans (cM), with 1 mu equal to a 1% recombination frequency.

Question 24

Whats does the testcross data estimate?

Answer 24

It estimates the distance between two genes

Question 25

How do multiple crossovers affect recombination frequencies?

Answer 25

Multiple crossovers limit measurable recombination frequencies; a testcross can yield a maximum of 50% recombinant offspring.

Question 26

What happens to genes 50 mu apart or greater?

Answer 26

follow the Law of Independent Assortment.

Question 27

What does the analysis of the F2 generation in linked gene crosses reveal?

Answer 27

-Nonrecombinant phenotypes occur most frequently -single crossover phenotypes occur with intermediate frequency -double crossover phenotypes are the least frequent

Question 28

How does the product rule apply to predicting double crossovers?

Answer 28

The product rule calculates the likelihood of a double crossover by multiplying the probabilities of each single crossover, treating them as independent events

Question 29

positive interference

Answer 29

When a crossover in one segment reduces the likelihood of a second crossover in a nearby segment.

Question 30

Fungi

Answer 30

-typically haploid (1n) -reproduce asexually

Question 31

Diploid zygote (2n)

Answer 31

Two haploid cells fuse to form it. Diploid zygote goes through meiosis to produce 4 haploid spores

Question 32

Spores

Answer 32

Meiosis produces four haploid cells

Question 33

Tetrad

Answer 33

Group of 4 spores

Question 34

Ascus

Answer 34

Sac where spores are enclosed in

Question 35

Octad

Answer 35

Ascus that contains eight ascospores

Question 36

What are the three types of tetrads that can form after meiosis?

Answer 36

1. Parental ditype (PD) 2. Tetratype (T) 3. Nonparental ditype (NPD)

Question 37

Parental ditype (PD)

Answer 37

Four haploid spores with nonrecombinant alleles.

Question 38

Tetratype (T)

Answer 38

Two nonrecombinant cells and two recombinant cells.

Question 39

Nonparental ditype (NPD)

Answer 39

Four cells with recombinant genotypes.

Question 40

What is expected in asci if two genes assort independently?

Answer 40

The number of parental ditype (PD) asci will equal the nonparental ditype (NPD) asci, resulting in 50% recombinant spores.

Question 41

What types of asci are produced when two genes are linked?

Answer 41

-No crossover: Parental ditype (PD) -Single crossover: Tetratype (T) -Double crossover: Any of the three types, depending on the chromatids involved

Question 42

Why is crossing over less likely in mitosis than in meiosis?

Answer 42

Mitosis does not involve homologous chromosome pairing, so crossing over is much rarer.

Question 43

Mitotic recombination

Answer 43

Pair of recombinant chromosomes that have a new combination of alleles

Question 44

What happens if mitotic recombination occurs early in embryonic development?

Answer 44

Recombinant chromosomes are passed to daughter cells, potentially creating a tissue patch with different characteristics from the rest of the organism.

Question 45

What does mitotic recombination involve?

Answer 45

The exchange of chromosomal regions between homologs during the division of somatic cells.