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Genetics Lecture > Variation in Chromosome Number > Flashcards

Variation in Chromosome Number Flashcards

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1
Q

What is a euploid cell?

A

A cell that contains multiple of one complete set of chromosomes.
A “normal” amount of chromosomes.

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2
Q

What does euploidy look like in humans?

A

In human cells, one complete set consists of one of each autosome and one sex chromosome, and two complete sets consist of two of each autosome and two sex chromosomes (either XY or XX).

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3
Q

How many pairs of chromosomes do humans need to be fully functional?

A

23 pairs

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4
Q

How many complete sets of chromosomes are in euploid and haploid cells?

A

One complete set

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5
Q

How many complete sets of chromosomes are in euploid and diploid cells?

A

Two complete sets

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6
Q

What is an aneuploid cell?

A

Any variation from a euploid cell.
An abnormal amount of chromosomes.

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7
Q

What are the most common types of aneuploidies?

A

Trisomy and monosomy

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8
Q

What is a monosomy?

A

Having one copy of one chromosome

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9
Q

What is a trisomy?

A

Having three copies of one chromosome

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10
Q

How does aneuploidy affect late-stage cancer cells?

A

Many late-stage cancer cells have numerous aneuploidies but do not die from these.

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11
Q

What happens if all of an individual’s cells are aneuploid?

A

This situation is detrimental to the individual

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12
Q

What do aneuploidies affect?

A

Aneuploidy does not affect the cell itself. It affects the surrounding cell and development.
Basically bad interaction with neighbors, but functions perfectly.

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13
Q

Aneuploidies involving which chromosomes are more severe?

A

Autosomes, not sex chromosomes

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14
Q

What percentage of aneuploidies are observed in live births?

A

0.3% of all live births

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15
Q

What are the most common autosomal aneuploidies?

A

Trisomy 13, 18, and 21

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16
Q

What syndrome is caused by trisomy 21? At what frequency?

A

Down syndrome; 1 in 800 live births

17
Q

What syndrome is caused by trisomy 18? At what frequency?

A

Edwards syndrome; 1 in 6000 live births

18
Q

What syndrome is caused by trisomy 13? At what frequency?

A

Patau syndrome; 1 in 15000

19
Q

What is a stillbirth?

A

Death of a fetus after the 20th week, but before birth

20
Q

What is a spontaneous abortion/miscarriage?

A

Death of a fetus after 6-8 weeks to the 20th week

21
Q

Death prior to 6-8th week

A

Similar to stillbirth/miscarriages
Usually occurs before woman knows she is pregnant
Hard to study

22
Q

What percentage of aneuploidies are observed in stillbirths?

A

4%
Seen in trisomy 13, 18, and 21

23
Q

What percentage of aneuploidies are observed in spontaneous abortions?

A

35%
Seen in trisomy 16, 21, and 22

24
Q

What is the reason that autosomal monosomies are rarely observed in spontaneous abortions, stillbirths, or live births?

A

Autosomes are necessary for the development of fetuses. Having a monosomy in an autosome means the dosage of that chromosome is insufficient to continue development (i think)

25
Q

What are the three most common sex chromosome trisomies?

A

XXX
XXY
XYY

26
Q

What syndrome is caused by XXX? At what frequency?

A

Triple X
1 in 1000 females

27
Q

What syndrome is caused by XYY? At what frequency?

A

Jacob’s Syndrome
1 in 1000 males

28
Q

What syndrome is caused by XXY? At what frequency?

A

Klinefelter syndrome
1 in 650 males

29
Q

What is XO?

A

A sex chromosome monosomy
O refers to a missing sex chromosome

30
Q

What syndrome is caused by XO? At what frequency?

A

Turner’s syndrome
1 in 2500 females

31
Q

Which occurs more in spontaneous abortions/stillbirths: Sex chromosome trisomies or XO?

A
32
Q

What is nondisjunction?

A

The failure of dyads or monads to segregate properly during meiosis I or meiosis II

33
Q

When can nondisjunction occur?

A

Either meiosis I or meiosis II

34
Q

What happens during meiosis I nondisjunction?

A

Two dyads within the same tetrad do not separate.
There will be aneuploid four gametes produced. Two gametes will have an extra chromosome and produce a trisomy. Two will be missing a chromosome a produce a monosomy.

35
Q

What happens during meiosis II nondisjunction?

A

Two monads within the same dyad do not separate.

Genetics Lecture (17 decks)

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