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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
How many chromosomes do Drosophila have?
8
25
Normally what sex chromosomes do males and females have in Drosophila?
Females have two X chromosomes | Males have X and Y chromosome
26
What does the presence of Y chromosome determine in Drosophila?
Does NOT determine maleness
27
What is each fly's sex determined by?
By the balance between genes on autosomes and genes on X chromosome
28
What is the genic balance system?
Balance between genes on autosomes and genes on X chromosome
29
What do X chromosomes contain in Drosophila?
Genes with female-producing effects
30
What do autosomes in Drosophila contain?
Genes with male-producing effects
31
What is the sex of an XX AA Drosophila?
Female | *1:1 ratio
32
What is the sex of XY AA Drosophila?
Male | *1:2 ratio
33
What is the sex of XO AA Drosophila?
Male
34
What is the sex of XXY AA Drosophila ?
Female
35
What is the sex of XXX AA Drosophila?
Metafemale
36
What is the sex of XXXY AA Drosophila?
Metafemale
37
What is the sex of XX AAA Drosophila?
Intersex
38
What is the sex of XO AAA Drosophila?
Metamale
39
What is the sex of XXXX AAA Drosophila?
Metafemale
40
What is the role of X chromosomes in humans?
Contains genetic information essential for both sexes; At least one copy of an X is required
41
Where is the male determining gene in humans?
On Y chromosome
42
What does the absence of Y chromosome in humans result in?
Female phenotype
43
Where are the genes affecting fertility located in humans?
On the X and Y chromosome
44
What do human females usually need to be fertile?
Two X chromosomes
45
What might the additional copies of X chromosome upset in humans?
Upset normal development in both males and females
46
What is the name of the sex-determining region of the Y chromosome in humans?
Sry gene
47
What does the Sry gene cause?
Neutral gonads to develop into testes
48
When was the Sry gene found?
1990
49
What does the Sry gene encode?
Encodes a protein that binds to DNA and causes a sharp bend in the molecule
50
What other genes besides Sry play a role in fertility and development of sex differences in humans?
X-linked, Y-linked, and autosomal genes
51
What reproductive organ produces testosterone?
Testes
52
What does testosterone cause during embryonic development?
Causes embryonic tissue to develop into male characteristics
53
In order for testosterone to cause embryonic tissues to develop into male characteristics, what receptor must be present? Where is this receptor?
Androgen receptor and it is encoded by a gene on the X chromosome
54
If the androgen receptor is muted in a male, what happens?
The embryo is supposed to be male but develops into an XY female because the testosterone receptor is mutated
55
What is turner syndrome?
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
What is androgen-insensitivity syndrome?
The androgen receptor is mutated | XY female
57
How often does turner syndrome occur?
1 in 3000
58
How often does Klinefelter syndrome occur?
1 in 1000
59
What is Klinefelter syndrome?
``` XXY, XXXY, XXYY Male Usually small testes Reduce facial and pubic hair Often taller than normal Sterile Usually of normal intelligence ```
60
Who discovered X linked white eyes in drosophila?
Thomas Hunt Morgan
61
Who explained deviations from expected drosophila offspring was bc of nondisjunction?
Calvin Bridges (morgan's student)
62
Who discovered the Barr body?
Murray Barr
63
Who proposed that the Barr body was the inactive X chromosome?
Mary Lyon
64
What is the Lyon hypothesis?
That the barr body is the inactive X chromosome
65
When does the X inactivation take place in humans?
First few weeks of development
66
Once the X chromosome is inactivated in humans, it ________
Remains inactive in all descendants of the first cell
67
How is X inactivation brought about?
By the action of Xist (X inactivation specific transcript)
68
Where is Xist located?
On the X chromosome
69
What does Xist produce?
Produces an RNA molecule that coats the X chromosome annd induces X inactivation
70
Coating the X chromosome with Xist RNA cause:
Removal of acetyl groups from histone proteins Methylation of histones Alteration of histone composition
71
What escapes inactivation during X inactivation?
Pseudoautosomal region
72
In cats, random inactivation of X chromosomes early in embryonic development produces what?
A patchy distribution for the expression of X-linked characteristics as demonstrated in tortoiseshell cats
73
What determines orange color in cats?
Single x-linked locus
74
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
B
75
What is the sexual phenotype of a fruit fly that has XXYYY sex chromosomes and two sets of autosomes?
Female
76
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
X+Y

Genetics Test I - Jourdan (6 decks)

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