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Genetics Test I - Jourdan > Sex Determination and Sex Linkage > Flashcards

Sex Determination and Sex Linkage Flashcards

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0
Q

Sex:

A

Refers to sexual phenotype

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1
Q

How many sex chromosomes doe platypus have?

A

10 sex chromosomes: 10X or 5X/5y

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2
Q

Sex determination:

A

The mechanism by which sex is established

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3
Q

Hermaphroditism:

A

Reers to the condition in which both sexes are present in the same organism

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4
Q

Monoecious

A

Production of both male and female gametes in the same individual

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5
Q

Dioecious

A

Production of either male or female gametes in the same individual

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6
Q

What are the types of chromosomal sex-determining systems?

A

XX-XO sex determination
XX-XY
ZZ-ZW
Haplodiploidy

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7
Q

Sexual reproduction

A

Alternates between haploid and diploid states

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8
Q

How many sexual phenotypes do most organisms have?

A

Two, male and female

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9
Q

Describe XX-XO system

A 
Chromosomal sex-determination system
Heterogametic sex=males (XO)
    Males have only one sex chromosome 
Homogametic sex = Female XX
Grasshoppers
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10
Q

Describe XX-XY system

A

Chromosomal sex-determination system
X and Y chromosomes are not homologous-genes located on each are different
X and Y pair during meiosis: Pseudoautosomal regions-Located at both tips of human X and Y chromosomes

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11
Q

Pseudoautosomal regions:

A

Regions where pairing occurs between X and Y chromosomes since they are not homologous. Located at both tips of human X and Y chromosomes

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12
Q

Where are X and Y chromosomes homologous?

A

ONLY at pseudoautosomal regions

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13
Q

Describe the ZZ-ZW sex determination

A

Chromosomal sex-determination system
Female-heterogametic
Male-homogametic
Found in birds, moths, some butterflies, some isopods, some amphibians, some fishes

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14
Q

What are Armadillidium vulgare?

A

Isopods
Females ZW
Males ZZ
Wolbachia are bacteria that is transmitted through egg cytoplasm to the offspring
This bacteria converts males to females
Males that have been converted to females still retain ZZ genotype

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15
Q

Why might the converting of males to females in isopods be advantageous to bacteria Wolbachia?

A

Because the bacteria is transmitted through egg cytoplasm, so the more females to make eggs the more bacteria can spread

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16
Q

Describe haplodiploidy

A 
Chromosomal sex-determination system
No sex chromosomes; Sex is based on # of sets of chromosomes 
Haploid somatic set - male
Diploid somatic set - female 
Bees, wasps, ants, some hymenoptera

Males develop from unfertilized eggs; mitosis
Females from fertilized eggs

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17
Q

Describe genic sex-determining system

A

No sex chromosomes, only the sex-determining genes
Genes at one or more loci determine the sex of the individual
Found in some plants, fungi, protozoans, and fish

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18
Q

Give some examples of environmental sex determination

A

Limpets

Turtles

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19
Q

What are crepidula fornicate?

A

Common slipper limpet
As larva, they swim around to find an unoccupied substrate (i.e. rock) with no other limpets. The first swimming larva to settle becomes a female and produces chemicals that attract other larva

Other larvae settle on top of it and become males that mate with the female below

After a while, these males transform into females and attract other “males”

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20
Q

What are common slipper limpet examples of?

A

Environmental sex-determining system

And sequential hermaphroditism

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21
Q

How is turtle sex determined?

A

They are part of the environmental sex-determining system

Turtles in warm temperatures produce females during certain times of the year

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22
Q

How are alligators’ sex determined?

A

Environmental sex-determining by producing males in warm temperatures during certain times of the year

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23
Q

How many pairs of chromosomes do Drosophila have? How many of them are autosomes vs sex chromosomes?

A

Three pairs autosomes

One pair of sex chromosomes

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24
Q

How many chromosomes do Drosophila have?

A

8

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25
Q

Normally what sex chromosomes do males and females have in Drosophila?

A

Females have two X chromosomes

Males have X and Y chromosome

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26
Q

What does the presence of Y chromosome determine in Drosophila?

A

Does NOT determine maleness

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27
Q

What is each fly’s sex determined by?

A

By the balance between genes on autosomes and genes on X chromosome

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28
Q

What is the genic balance system?

A

Balance between genes on autosomes and genes on X chromosome

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29
Q

What do X chromosomes contain in Drosophila?

A

Genes with female-producing effects

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30
Q

What do autosomes in Drosophila contain?

A

Genes with male-producing effects

31
Q

What is the sex of an XX AA Drosophila?

A

Female

*1:1 ratio

32
Q

What is the sex of XY AA Drosophila?

A

Male

*1:2 ratio

33
Q

What is the sex of XO AA Drosophila?

A

Male

34
Q

What is the sex of XXY AA Drosophila ?

A

Female

35
Q

What is the sex of XXX AA Drosophila?

A

Metafemale

36
Q

What is the sex of XXXY AA Drosophila?

A

Metafemale

37
Q

What is the sex of XX AAA Drosophila?

A

Intersex

38
Q

What is the sex of XO AAA Drosophila?

A

Metamale

39
Q

What is the sex of XXXX AAA Drosophila?

A

Metafemale

40
Q

What is the role of X chromosomes in humans?

A

Contains genetic information essential for both sexes; At least one copy of an X is required

41
Q

Where is the male determining gene in humans?

A

On Y chromosome

42
Q

What does the absence of Y chromosome in humans result in?

A

Female phenotype

43
Q

Where are the genes affecting fertility located in humans?

A

On the X and Y chromosome

44
Q

What do human females usually need to be fertile?

A

Two X chromosomes

45
Q

What might the additional copies of X chromosome upset in humans?

A

Upset normal development in both males and females

46
Q

What is the name of the sex-determining region of the Y chromosome in humans?

A

Sry gene

47
Q

What does the Sry gene cause?

A

Neutral gonads to develop into testes

48
Q

When was the Sry gene found?

A

1990

49
Q

What does the Sry gene encode?

A

Encodes a protein that binds to DNA and causes a sharp bend in the molecule

50
Q

What other genes besides Sry play a role in fertility and development of sex differences in humans?

A

X-linked, Y-linked, and autosomal genes

51
Q

What reproductive organ produces testosterone?

A

Testes

52
Q

What does testosterone cause during embryonic development?

A

Causes embryonic tissue to develop into male characteristics

53
Q

In order for testosterone to cause embryonic tissues to develop into male characteristics, what receptor must be present? Where is this receptor?

A

Androgen receptor and it is encoded by a gene on the X chromosome

54
Q

If the androgen receptor is muted in a male, what happens?

A

The embryo is supposed to be male but develops into an XY female because the testosterone receptor is mutated

55
Q

What is turner syndrome?

A

Human that develops as XO (45 chromosomes)
Female with underdeveloped sex characteristics
Low hairline
Broad chest
Folds on neck
Usually sterile
Usually of normal intelligence

56
Q

What is androgen-insensitivity syndrome?

A

The androgen receptor is mutated

XY female

57
Q

How often does turner syndrome occur?

A

1 in 3000

58
Q

How often does Klinefelter syndrome occur?

A

1 in 1000

59
Q

What is Klinefelter syndrome?

A 
XXY, XXXY, XXYY
Male
Usually small testes
Reduce facial and pubic hair
Often taller than normal
Sterile
Usually of normal intelligence
60
Q

Who discovered X linked white eyes in drosophila?

A

Thomas Hunt Morgan

61
Q

Who explained deviations from expected drosophila offspring was bc of nondisjunction?

A

Calvin Bridges (morgan’s student)

62
Q

Who discovered the Barr body?

A

Murray Barr

63
Q

Who proposed that the Barr body was the inactive X chromosome?

A

Mary Lyon

64
Q

What is the Lyon hypothesis?

A

That the barr body is the inactive X chromosome

65
Q

When does the X inactivation take place in humans?

A

First few weeks of development

66
Q

Once the X chromosome is inactivated in humans, it ________

A

Remains inactive in all descendants of the first cell

67
Q

How is X inactivation brought about?

A

By the action of Xist (X inactivation specific transcript)

68
Q

Where is Xist located?

A

On the X chromosome

69
Q

What does Xist produce?

A

Produces an RNA molecule that coats the X chromosome annd induces X inactivation

70
Q

Coating the X chromosome with Xist RNA cause:

A

Removal of acetyl groups from histone proteins
Methylation of histones
Alteration of histone composition

71
Q

What escapes inactivation during X inactivation?

A

Pseudoautosomal region

72
Q

In cats, random inactivation of X chromosomes early in embryonic development produces what?

A

A patchy distribution for the expression of X-linked characteristics as demonstrated in tortoiseshell cats

73
Q

What determines orange color in cats?

A

Single x-linked locus

74
Q

How does the heterogametic sex differ from the homogametic sex?

a. the heterogametic sex is male; homogametic sex is female
b. gametes of the heterogametic sex have different sex chromosome; gametes of homogametic sex have the same sex chromosome
c. gametes of the heterogametic sex all contain a Y chromosome
d. gametes of the homogametic sex all contain an X chromosome

A

B

75
Q

What is the sexual phenotype of a fruit fly that has XXYYY sex chromosomes and two sets of autosomes?

A

Female

76
Q

What was the genotype of the few live F1 red-eyed males obtained by Bridges when he crossed a white-eyed female with a red-eyed male

A

X+Y

Genetics Test I - Jourdan (6 decks)

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