Lecture 15: Errors in Meiosis & X-inactivation Flashcards

1
Q

What is nondisjunction?

A

Failure of chromosomes to separate properly during meiosis

95% of down syndrome babies have two maternal chromosome 21

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2
Q

What is klinefelter syndrome XXY

A

individuals have an unusual number of sex chromosomes, two copy of an X and one Y.

Tall, feminine physique. Small testys

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3
Q

What is turner syndrome XO

A

Instead of two sex chromosomes they only have one. Physical manifestations, folds in the skin around the neck, some type of intellectual impairment, depends on where the x chromosome comes from.

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4
Q

If a pair of chromosomes fails to disjoin at
anaphase of meiosis I, what will be the likely
chromosome numbers (N) of the four resulting
gametes?
A) N+1, N+1, N, N.
B) N+1, N+1, N-1, N-1.
C) N+1, N-1, N, N.
D) N, N, N-1, N-1.

A

B) N+1 N+1 N-1 N-1 ??

if he said meiosis II the answer would have been C

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5
Q

What is polyploidy?

A

Possession of multiple sets of chromosomes

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6
Q

Creating a polyploid 4n raddage

A

each are going to produce gametes which is n=9 this hybrid has 18 chromosomes, if you treat the individuals so their gametes double you can produce a fertile raddage.

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7
Q

Cabbage has 2n = 18 chromosomes and turnip
has 2n = 20. Oil-seed rape is a polyploid derived
from these two Brassica species and is fully fertile. How many chromosomes would you
expect oil-seed rape to have?
A) 18
B) 19
C) 20
D) 38

A

D) 38 (because it is fertile)

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8
Q

what are the four chromosomal aberrations?

A

deletion
inversion
duplication
translocation

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9
Q

what is deletion?

A

a deletion removes a chromosomal segment

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10
Q

what is a inversion

A

an inversion reverses a segment within a chromosome

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11
Q

what is a duplication?

A

a duplication repeats a segment

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12
Q

what is translocation?

A

a translocation moves a segment from one chromosome to a non homologous chromosome

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13
Q

le jeune syndrome cri du chaat, what causes it?

A

deletion of tip of short arm of chromosome 5

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14
Q

Philadelphia translocation t (9:22)

A

95% of patients with chronic myeloid leukemia

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15
Q

TK overexpression:

A

Treatable with Gleevec in 90% of cases

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16
Q

Familial Down Syndrome from t(14:21)

A

Centric fusion =

Robertsonian translocation

17
Q
Individuals with familial Down Syndrome have
which of the following karyotypes?
A) 47 chromosomes; trisomy 21.
B) 46 chromosomes; translocation of 21.
C) 46 chromosomes; inversion of 21.
D) 45 chromosomes; monosomy 21.
A

B) 46 chromosomes; translocation of 21.

18
Q

Random inactivation of X chromosomes leads to mosaic

patterning

A
19
Q
An XXY human will:
A) exhibit Turner syndrome.
B) have a Barr body in each nucleus.
C) be an abnormal female.
D) be a monosomic.
A

A) exhibit Turner syndrome.

20
Q
A female is colour blind in one eye only. Her father is colour blind in both eyes. The cause of
the female’s condition could be:
A) X-inactivation in a heterozygote.
B) a somatic mutation.
C) damage to one eye.
D) any of the above.
A

D) any of the above