Chapter 6 - Eukaryotic Linkage

Question 1

The transmission of genes close to one another on the same chromosome violates this Mendelian law

Answer 1

Law of independent assortment

Question 2

This term refers to two or more genes that are physically linked on the same chromosome

Answer 2

Synteny

Question 3

Genes located close together on a chromosome tend to be transmitted as a unit, influencing inheritance patterns in this phenomenon

Answer 3

Genetic linkage

Question 4

Chromosomes are called this, as they contain a group of genes that are linked together

Answer 4

Linkage groups

Question 5

How many linkage groups do humans have?

Answer 5

24 (22 autosomal, 1 X, 1 Y)

Question 6

This type of cross studies linkage between two genes

Answer 6

Two-factor cross

Question 7

This type of cross studies linkages between three genes

Answer 7

Three-factor cross

Question 8

Genes that are far apart on the same chromosome may independently assort from each other due to this

Answer 8

Crossing over

Question 9

What are three types of crossing over?

Answer 9

Single, double, multiple

Question 10

In 1905, these two scientists conducted a cross in sweet peas involving two different traits

Answer 10

William Bateson and Reginald Punnett

Question 11

What two sweet pea traits did Bateson and Punnett study?

Answer 11

Flower color and pollen shape

Question 12

Did Bateson and Punnett obtain the expected 9:3:3:1 phenotypic ratio in the F2 generation for their two-factor sweet pea crosses?

Answer 12

No

Question 13

During which phase of meiosis does crossing over occur?

Answer 13

Prophase I

Question 14

Replicated sister chromatid homologs associate as these

Answer 14

Bivalents

Question 15

Crossing over may produce these genotypes

Answer 15

Recombinant genotypes

Question 16

These are haploid cells that contain a combination of alleles not found in the original chromosomes

Answer 16

Nonparental or recombinant cells

Question 17

These offspring are produced by the exchange of DNA between two homologous chromosomes during meiosis in one or both parents, leading to a novel combination of genetic material

Answer 17

Recombinant offspring

Question 18

The first direct evidence of linkage came from studies conducted by this scientist

Answer 18

Thomas Hunt Morgan

Question 19

Thomas Hunt Morgan studied body color, eye color and wing length inheritance patterns in this organism

Answer 19

Drosophila

Question 20

Thomas Hunt Morgan considered the previous studies of this cytologist to explain his data

Answer 20

F. A. Janssens

Question 21

Janssens microscopically observed these and proposed that crossing over involves a physical exchange between homologous chromosomes

Answer 21

Chiasmata

Question 22

Morgan realized that crossing over between these chromosomes was consistent with his data

Answer 22

Homologous X chromosomes

Question 23

These three scientists performed crosses involving two linked genes to obtain direct evidence that genetic recombination is due to crossing over

Answer 23

Harriet Creighton and Barbara McClintock and Curt Stern

Question 24

This is performed to determine the linear order of linked genes along the same chromosome

Answer 24

Genetic mapping

Question 25

The relative distance between linked genes is based on this

Answer 25

The likelihood that a crossover will occur between them

Question 26

Experimentally, the percentage of these is correlated with the distance between the two genes

Answer 26

Recombinant offspring

Question 27

What is the equation for gene map distance?

Answer 27

Map distance = # of recombinant offspring/Total # of offspring x 100

Question 28

What are the units of distance in genetic maps?

Answer 28

Map units (mu) [or centiMorgans (cM)]

Question 29

One mu is equivalent to this

Answer 29

1% recombination frequency

Question 30

Genetic mapping experiments are typically accomplished by conducting this

Answer 30

Testcross

Question 31

Multiple crossovers set a quantitative limit on these as the physical distance increases

Answer 31

Measurable recombination frequencies

Question 32

Data from this type of cross can also yield additional information about map distance and gene order

Answer 32

Three-factor cross

Question 33

In the offspring of crosses involving linked genes, these phenotypes occur most frequently

Answer 33

Nonrecombinant phenotypes

Question 34

In the offspring of crosses involving linked genes, these phenotypes occur least frequently

Answer 34

Double crossover phenotypes

Question 35

In the offspring of crosses involving linked genes, these phenotypes occur with intermediate frequency

Answer 35

Single crossover phenotypes

Question 36

This crossover separates the gene in the middle from the other two genes at either end

Answer 36

Double crossover

Question 37

This term refers to the decreased probability that a second crossover will occur near a first crossover

Answer 37

Positive interference

Question 38

What is the expression for interference?

Answer 38

I = 1- C

Question 39

What is C in the expression for interference?

Answer 39

Coefficient of coincidence

Question 40

The coefficient of coincidence (C) is the observed number of double crossovers divided by this

Answer 40

Expected number of double crossovers

Question 41

Much of our earliest understanding of genetic recombination comes from the genetic analysis of this group of organisms

Answer 41

Fungi

Question 42

Are fungi typically haploid or diploid?

Answer 42

Haploid

Question 43

Do haploid fungal cells reproduce sexually or asexually?

Answer 43

Asexually

Question 44

These fungal cells have been particularly useful to geneticists because of their unique style of sexual reproduction

Answer 44

Sac fungi (ascomycetes)

Question 45

Ascomycete meiosis produces four of these haploid cells

Answer 45

Spores

Question 46

A group of 4 spores is this

Answer 46

Tetrad

Question 47

This is a sac in which fungal spore tetrads are enclosed

Answer 47

Ascus

Question 48

Some fungi species form this many spores following a mitotic division of a tetrad

Answer 48

Octad

Question 49

What characteristic of asci makes them good for genetic researchers to study?

Answer 49

All the spores within one ascus are the product of a single meiotic division

Question 50

If an ascus has a tetrad with nonrecombinant allele arrangements, it is said to have this

Answer 50

Parental ditype (PD)

Question 51

If an ascus has two nonrecombinant and two recombinant cells, it is called this

Answer 51

Tetratype (T)

Question 52

If an ascus has four recombinant cells, it is this

Answer 52

Nonparental ditype (NPD)

Question 53

If two genes assort independently, the number of asci with a parental ditype is expected to equal the number of asci with this

Answer 53

Nonparental ditype

Question 54

A nonparental ditype can only be produced from this

Answer 54

Double crossover

Question 55

1/4 of all double crossovers are this

Answer 55

Nonparental ditypes

Question 56

These two tetrad classifications are ambiguous and can be derived in two different ways

Answer 56

Parental ditype and tetratype

Question 57

What is the formula for finding map distances from fungal tetrad analysis (without accounting for double crossovers)?

Answer 57

Map distance = Nonparental ditypes (NPD) + 1/2 * Tetratypes (T) / Total number of asci * 100

Question 58

What is the more precise way to calculate map distance using fungal tetrads, accounting for double crossovers?

Answer 58

Map distance = Single crossover tetrads + 2 * Double crossover tetrads / Total number of asci * 0.5 * 100