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BGM1004-Genetics > BGM1004/L10 Sex in Genetics > Flashcards

BGM1004/L10 Sex in Genetics Flashcards

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Biology 101 flashcards
1
Q

Give 2 advantages to asexual reproduction.

A

Fast cycle
Less energy required than sexual reproduction

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2
Q

Give an advantage to sexual reproduction.

A

Gives new gene combinations

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3
Q

Give 2 disadvantages to sexual reproduction.

A

Time & energy to find a mate
Potential of breaking apart favourable gene combinations

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4
Q

What kind of reproduction drives natural selection?

A

Sexual reproduction

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5
Q

What kind of reproduction gives an advantage in harsh environments?

A

Sexual reproduction

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6
Q

What are the products of spermatogenesis according to the Protenor mode of sex determination?

A

7 chromosomes with 1X
6 chromosomes without X

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7
Q

What is another name for the Protenor mode of sex determination?

A

XX/X0

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8
Q

What are the products of spermatogenesis according to the Lygaeus mode of sex determination?

A

6 autosomes + X OR
6 autosomes + Y

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9
Q

What is another name for the Lygaeus mode of sex determination?

A

XX/XY

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10
Q

What is the term for the sex that produces unlike gametes? (In humans = male sex)

A

Heterogametic

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11
Q

Give 2 species in which the female is the heterogametic sex.

A

Moths
Butterflies
Some fish
Most birds

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12
Q

What nomenclature is commonly used to describe a heterogametic female?

A

ZW

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13
Q

What nomenclature is commonly used to describe a homogametic male?

A

ZZ

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14
Q

What was the outcome of the Tijo experiment (1956)?

A

Improved method of preparing human metaphase chromosomes (karyotyping)

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15
Q

What results in variation in numbers of X chromosomes?

A

Nondisjunction (failure of X chromosomes to separate properly during meiosis)

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16
Q

What genotypes result in Klinefelter syndrome?

A

47,XXY, 48,XXXY, 48,XXYY, 49,XXXXY and 49,XXXYY

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17
Q

What genotypes result in Turner syndrome?

A

45,X0

18
Q

Give 3 symptoms of Klinefelter syndrome.

A

Tall stature
Slightly feminised physique
Tendency to lose chest hair
Breast development
Testicular atrophy
Female-type public hair pattern

19
Q

Give 3 symptoms of Turner syndrome.

A

Short stature
Small fingernails
Shortened metacarpal IV
No menstruation
Poor breast development
Rudimentary ovaries

20
Q

How did X and Y chromosomes likely begin their existence?

A

Ordinary autosomes

21
Q

How many proteins are encoded by the Y chromosome for male fertility?

A

At least 26

22
Q

What are PARs (pseudoautosomal regions)?

A

Regions that share homology with X chromosome

23
Q

What is MSY?

A

Male-specific region of Y that does not synapse with X chromosome

24
Q

What is SRY?

A

Sex-determining region Y, producing testis determining factor (TDF)

25
Q

In what species is sex determined by incubation temperature?

A

All crocodile
Most turtles
Some fish

26
Q

How does temperature determine sex in some species?

A

Activity of enzymes and inhibitors control production of steroid hormones such as oestrogen

27
Q

What is dosage compensation?

A

Mechanism to keep X-linked gene doses similar between males and females

28
Q

How is dosage compensation achieved?

A

X chromosome inactivation

29
Q

How many X chromosomes are active in a given organism?

A

All but 1

30
Q

What is the number of Barr Bodies in a given organism?

A

X(n-1)

31
Q

What is a Barr Body?

A

Condensed X chromosome with RNA attached

32
Q

What is the Lyon Hypothesis (1961)?

A

Inactivation is random at an early point in development
Once inactivated, all progeny cells have the same X chromosome inactivated

33
Q

What is anhidrotic ectodermal dysplasia?

A

X-linked mutation causing absence of sweat glands

34
Q

How does anhidrotic ectodermal dysplasia present in men?

A

Men carrying dominant allele (D) have no sweat glands

35
Q

How does anhidrotic ectodermal dysplasia present in heterozygous females?

A

Mosaic of D and d sectors across the body

36
Q

Where is X chromosome inactivation initiated?

A

XIC (X-inactivation centre)

37
Q

What are the key products from the XIC? (2)

A

Xist
Tsix

38
Q

What is the function of Xist?

A

Progressive coating of one X chromosome spreading outwards from XIC

39
Q

What does the coating of an X chromosome lead to?

A

Packaging into heterochromatin

40
Q

Approximately what percentage of genes escape inactivation?

A

15%

BGM1004-Genetics (22 decks)

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