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Genetics - MCB 104 > Sex Chromosomes > Flashcards

Sex Chromosomes Flashcards

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1
Q

What are the two types of sex chromosomes?

A

X and Y chromosome. Y chromosome is much shorter than the X chromosome.

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2
Q

What is the difference between autosomes and sex chromosome aneuploidies?

A

Autosome aneuploidies [presence of abnormal number of autosomes in a cell] are not that common and do not live successfully.

Sex chromosome aneuploidies [presence of abnormal number of X or Y chromosomes in a cell] are common and they survive successfully.

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3
Q

What is an aneuploidy?

A

presence of abnormal number of chromosomes in a cell

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4
Q

What sex chromosomes do females carry? males?

A

2 X chromosomes = XX 1 X and 1 Y chromosome = XY

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5
Q

What do aneuploidy phenotypes tell us?

A

That the Y chromosome carries the dominant maleness gene. (SRY or TDF)

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6
Q

Which gene in the Y chromosome determines sex in eutherian mammals?

A

SRY gene

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7
Q

Turner Syndrome

  1. Karyotype?
  2. Number of chromosomes per cell?
  3. Incidence?
  4. Phenotypes?
A
  1. XO
  2. 45
  3. 1 in 5000 females
  4. Physical and cognitive abnormalities, sterility
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8
Q

Triple X syndrome

  1. Karyotype?
  2. Number of chromosomes per cell?
  3. Incidence?
  4. Phenotypes?
A
  1. XXX
  2. 47
  3. 1 in 1000 females
  4. None
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9
Q

Kleinfelter Syndrome

  1. Karyotype?
  2. Number of chromosomes per cell?
  3. Incidence?
  4. Phenotypes?
A
  1. XXY
  2. 47
  3. 1 in 650 males
  4. Reduced fertility
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10
Q

XYY Syndrome

  1. Karyotype?
  2. Number of chromosomes per cell?
  3. Incidence?
  4. Phenotypes?
A
  1. XYY
  2. 47
  3. 1 in 1000 males
  4. Increased stature
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11
Q

What are the most common sex chromosome anueploidies?

A
  1. Turner Syndrome
  2. Triple X syndrome
  3. Kleinfelter syndrome
  4. XYY Syndrome
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12
Q

During sex determination, one of the X chromosome is randomly deactivated in females so that all cells only have one active X chromosome. Why is it important for the X chromosome to be deactivated in females?

A

Dosage compensation.

Y chromosome contains 200 male specific genes

X chromosome contains ~1400 genes that function in both sexes, mostly.

To level the plainfield and for equality purposes, one of the X chromosome is randomly deactivated.

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13
Q

Label the arrow.

How do we know which marking is activated and which is deactivated?

A
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14
Q

But when does dosage compensation take place in females? OR when does random X inactivation occur?

A

X inactivation occurs after many cell divisions have already occured during the Blastocyst stage.

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15
Q

Why or How are human females called Mosaics?

A

the random X chromosome inactivation. Because of this X inactivation, all women are natural mosaics: although all their cells have the same two chromosomes, one from each parent, the mother’s X copy works in some cells, while the father’s X works in the others.

This is how dosage is compensated for.

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16
Q

How are Tortoiseshell and calico cats an example of random X inactivation?

A

If a female has XBXb genotype, then according to the dosage compensation theory, all cells may randomly have either XB activated or Xb activated. If the former is activated, then you get black patch, if latter is activated then you get orange patch. Because the female has both types of cells [with either one or the other activated] they exhibit appear mosaic.

Human females are also mosaic even if we cannot see the mosaicness phenotypically.

17
Q

Male calico cats also exist. Why?

A

Since they have been talking about sex chromosomes and their aneuploidies in this lecture, it has something to do with that. So I am guessing males that have aneuploidy XXY? Think in this manner. because dosage compensation will happen regardless. and XXY are viable but sterile.

18
Q

How does sex determination and dosage compensation vary among species?

A
19
Q

How do compensations vary among animals?

A
20
Q

traits of sex linked dominant inheritance?

Also notice how the map looks like

A
21
Q

traits of X linked recessive inheritance

A

1) shows up primarily in males
2) transmitted from female carriers to sons
3) half of daughters of female carriers are carriers
4) NOT transmitted from affected males to sons

22
Q

What causes Hemophilia A and how is it transmitted?

A

defect in clotting protein “Factor VIII” and is an X linked recessive disease

23
Q

Hemophilia A primarily shows up in males. How does a female III 9 have it?

A
24
Q

What inheritance pattern is depicted by this map? and what are the traits?

A

X linked dominant

25
Q

What is sex linkage?

A

is the hallmark of a sex linked gene is sex linked transmission or inheritance.

26
Q

What about here?

A

autosomal trait sex restricted. But how do you identify these?!!!

27
Q

What does this image tell us about the BRCA2 gene?

A

This BRCA2 inheritance is the same pattern as depicted in card 26.

28
Q

What trait is exhibited here?

A

Mitochondrial trait - sex biased.

women pass it on to all her children, males and females alike but affected males do not pass them on to their children whether males or females.

Genetics - MCB 104 (5 decks)

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