Diagnostics Lec 6

Question 1

What is the Y chromosome and what is it responsible for

Answer 1

One of two sex chromosomes, present in males only. It is smaller in size than the X chromosome and likely contains 50-60 genes.

It is responsible for the development of a fetus into a male and for male fertility.

Question 2

What are the two regions within the Y chromosome

Answer 2

Male specific region
Pseudo-autosomal region

Question 3

What genes are found in the male specific region and what do they do

Answer 3

SRY gene:
male determining, causes. testes to form

Azoospermia factor (AZF) gene:
encode proteins involves in sperm production

Question 4

what is found in the pseudo-autosomal region

Answer 4

homology to the X chromosome

Question 5

What is infertility

Answer 5

inability to conceive after 12 months of unprotected intercourse

Question 6

What is Klinefelter syndrome

Answer 6

the most common cause of male infertility

Question 7

How does Klinefelter syndrome occur

Answer 7

Results from an extra X chromosome obtained (eg XXY)
Changing of the hormonal environment during adolescence
Leading to progressive degeneration of the testicular environment

Question 8

What is Y chromosome microdeletions

Answer 8

when a segment of the Y chromosome is absent

Question 9

Outline the features of Y chromosome microdeletions

Answer 9

A segment of the Y chromosome is absent
Identified as AZFa (the most proximal segment), AZFb (middle), and AZFc (distal)
Next most common are microdeletions of the Y chromosome
1/4000 men

Question 10

How is the absence of the Y chromosome segment screened

Answer 10

using a simple sequence Tagged Sites (STS) based PCR assay

Question 11

What are sequence tagged sites

Answer 11

DNA sequences of known sequences and known locations on a chromosome database, they are easily amplified by PCR

Question 12

What can be designed based on the sequence in the database

Answer 12

oligonucleotide primers

Question 13

Primers are complemetary to unique sequences but can flank any sequence, including what

Answer 13

microsatellite repeats

Question 14

STS can be used to examine what

Answer 14

the structural integrity of parts of chromosomes

Question 15

slide

Answer 15

9

Question 16

What can be identified on a normal male

Answer 16

Peaks at every point

Question 17

What can be identified on a normal female

Answer 17

Only one STS is amplified (ZFY_ZFX) = one peak

Question 18

What can be seen after deletiuon of EZFb and AZFc

Answer 18

• No PCR fragments with STS primers 1, 2, 6, 7, 8, 11
• Corresponds to deletion of AZFb and AZFc region of the§ Y chromosome
• Partial deletion is responsible for sterility in this case

Question 19

Required date interpretation from graphs

Answer 19

on slides