Lecture 12 - Introduction to Chromosomal Disorders

Question 1

What are the two major types of chromosomal disorders?

Answer 1

1. Numerical chromosomal disorders

2. Structural chromosomal disorders

Question 2

Down Syndrome falls under what major category of chromosomal disorders?

Answer 2

Numerical chromosomal disorder - trisomy 21

Question 3

Which numerical chromosomal disorder has a higher mortality rate - Trisomy 13 or Trisomy 18?

Answer 3

Trisomy 13

Question 4

Cri Du Chat syndrome falls under what major category of chromosomal disorders?

Answer 4

Structural chromosomal disorders - deletion of part of chromosome 5

Question 5

What disorder results from a deletion of part of chromosome 4, in which 85-90% of cases are de novo mutations?

Answer 5

Wolf-Hirschhorn syndrome

Question 6

What is the term for late-replicating condensed chromatin sitting on the nuclear membrane?

Answer 6

heterochromatin (“Barr bodies” also an acceptable answer)

Question 7

The ___ chromosome is a submetacentric chromosome with 150 million base pairs encoding over 1400 genes.

Answer 7

X chromosome

Question 8

The ____ chromosome is an acrocentric chromosome with over 50 million base pairs and codes for over 200 genes.

Answer 8

Y chromosome

Question 9

Many of the genes on the Y chromosome are related to what two processes?

Answer 9

1. Sex determination

2. Spermatogenesis

Question 10

In mammals all but one X chromosome is inactivated in the blastocyst. The inactive X chromosomes become what?

Answer 10

Barr bodies

Question 11

Which abnormality would NOT result in a child with Kleinfelter Syndrome (47, XXY)?

A. Paternal meiosis I
B. Paternal meiosis II
C. Maternal meiosis I
D. Maternal meiosis II

Answer 11

B.

Question 12

A paracentric inversion:

A. Causes the centromere position to be altered
B. Prevents meiotic crossover formation on the affected chromosome
C. Engages both chromosome arms
D. Can lead to broken chromosomes during meiosis

Answer 12

D.