Lecture 15: Errors in Meiosis & X-inactivation

Question 1

What is nondisjunction?

Answer 1

Failure of chromosomes to separate properly during meiosis

95% of down syndrome babies have two maternal chromosome 21

Question 2

What is klinefelter syndrome XXY

Answer 2

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

Tall, feminine physique. Small testys

Question 3

What is turner syndrome XO

Answer 3

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.

Question 4

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.

Answer 4

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

if he said meiosis II the answer would have been C

Question 5

What is polyploidy?

Answer 5

Possession of multiple sets of chromosomes

Question 6

Creating a polyploid 4n raddage

Answer 6

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.

Question 7

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

Answer 7

D) 38 (because it is fertile)

Question 8

what are the four chromosomal aberrations?

Answer 8

deletion
inversion
duplication
translocation

Question 9

what is deletion?

Answer 9

a deletion removes a chromosomal segment

Question 10

what is a inversion

Answer 10

an inversion reverses a segment within a chromosome

Question 11

what is a duplication?

Answer 11

a duplication repeats a segment

Question 12

what is translocation?

Answer 12

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

Question 13

le jeune syndrome cri du chaat, what causes it?

Answer 13

deletion of tip of short arm of chromosome 5

Question 14

Philadelphia translocation t (9:22)

Answer 14

95% of patients with chronic myeloid leukemia

Question 15

TK overexpression:

Answer 15

Treatable with Gleevec in 90% of cases

Question 16

Familial Down Syndrome from t(14:21)

Answer 16

Centric fusion =

Robertsonian translocation

Question 17

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.

Answer 17

B) 46 chromosomes; translocation of 21.

Question 18

Random inactivation of X chromosomes leads to mosaic

patterning

Question 19

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.

Answer 19

A) exhibit Turner syndrome.

Question 20

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.

Answer 20

D) any of the above