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Genetics > Chapter 6 - Eukaryotic Linkage > Flashcards

Chapter 6 - Eukaryotic Linkage Flashcards

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Biology 101 flashcards
1
Q

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

A

Law of independent assortment

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2
Q

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

A

Synteny

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3
Q

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

A

Genetic linkage

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4
Q

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

A

Linkage groups

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5
Q

How many linkage groups do humans have?

A

24 (22 autosomal, 1 X, 1 Y)

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6
Q

This type of cross studies linkage between two genes

A

Two-factor cross

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7
Q

This type of cross studies linkages between three genes

A

Three-factor cross

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8
Q

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

A

Crossing over

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9
Q

What are three types of crossing over?

A

Single, double, multiple

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10
Q

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

A

William Bateson and Reginald Punnett

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11
Q

What two sweet pea traits did Bateson and Punnett study?

A

Flower color and pollen shape

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12
Q

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

A

No

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13
Q

During which phase of meiosis does crossing over occur?

A

Prophase I

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14
Q

Replicated sister chromatid homologs associate as these

A

Bivalents

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15
Q

Crossing over may produce these genotypes

A

Recombinant genotypes

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16
Q

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

A

Nonparental or recombinant cells

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17
Q

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

A

Recombinant offspring

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18
Q

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

A

Thomas Hunt Morgan

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19
Q

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

A

Drosophila

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20
Q

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

A

F. A. Janssens

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21
Q

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

A

Chiasmata

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22
Q

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

A

Homologous X chromosomes

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23
Q

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

A

Harriet Creighton and Barbara McClintock and Curt Stern

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24
Q

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

A

Genetic mapping

25
Q

The relative distance between linked genes is based on this

A

The likelihood that a crossover will occur between them

26
Q

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

A

Recombinant offspring

27
Q

What is the equation for gene map distance?

A

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

28
Q

What are the units of distance in genetic maps?

A

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

29
Q

One mu is equivalent to this

A

1% recombination frequency

30
Q

Genetic mapping experiments are typically accomplished by conducting this

A

Testcross

31
Q

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

A

Measurable recombination frequencies

32
Q

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

A

Three-factor cross

33
Q

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

A

Nonrecombinant phenotypes

34
Q

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

A

Double crossover phenotypes

35
Q

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

A

Single crossover phenotypes

36
Q

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

A

Double crossover

37
Q

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

A

Positive interference

38
Q

What is the expression for interference?

A

I = 1- C

39
Q

What is C in the expression for interference?

A

Coefficient of coincidence

40
Q

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

A

Expected number of double crossovers

41
Q

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

A

Fungi

42
Q

Are fungi typically haploid or diploid?

A

Haploid

43
Q

Do haploid fungal cells reproduce sexually or asexually?

A

Asexually

44
Q

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

A

Sac fungi (ascomycetes)

45
Q

Ascomycete meiosis produces four of these haploid cells

A

Spores

46
Q

A group of 4 spores is this

A

Tetrad

47
Q

This is a sac in which fungal spore tetrads are enclosed

A

Ascus

48
Q

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

A

Octad

49
Q

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

A

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

50
Q

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

A

Parental ditype (PD)

51
Q

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

A

Tetratype (T)

52
Q

If an ascus has four recombinant cells, it is this

A

Nonparental ditype (NPD)

53
Q

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

A

Nonparental ditype

54
Q

A nonparental ditype can only be produced from this

A

Double crossover

55
Q

1/4 of all double crossovers are this

A

Nonparental ditypes

56
Q

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

A

Parental ditype and tetratype

57
Q

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

A

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

58
Q

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

A

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

59
Q
A

Genetics (11 decks)

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