Errors in meiosis and X-activation - 15

Question 1

What are the 6 chromosomal abnormalities

Answer 1

Non-disjunction
Aneuploidy
Deletion
Duplication
Inversion
Translation

Question 2

What is Aneuploidy and a consequence

Answer 2

Abnormal number of a particular chromosome. Causes down syndrome (trisomy 21)

Question 3

What is deletion and a consequence

Answer 3

Removes a chromosomal segment (Lejeune syndrome)

Question 4

What is translocation and a consequence

Answer 4

moves a segment from one chromosome to a non-homologous chromosome, causes over expression of a gene (Philadelphia translocation)

Question 5

What is non-disjunction and a consequences

Answer 5

Failure of chromosomes to separate during meiosis. (Kleinfeld and turners)

Question 6

What are the two options for non-disjunction

Answer 6

If during | daughter cells will be 2(n+) and 2(n-). If during || then daughter cells will be 2(n), 1(n+) and 1(n-)

Question 7

What is inversion and a consequence

Answer 7

Reverses a segment and causes problems in meiosis (haemophilia A)

Question 8

What is Duplication

Answer 8

May cause gene to not function properly (over expression of gene)

Question 9

Explain familial down syndrome

Answer 9

Fusion of two non homologous chromosomes. This will produce a large range of gamets. 1 lethal, 1 normal, 1 translocation carrier and 1 that presents down syndrome

Question 10

Explain Philadelphia translocation

Answer 10

Can lead to leukaemia (95%) When the gene can’t be turned off or regulated

Question 11

Define polyploidy

Answer 11

possession of multiple sets of chromosomes (This is autoploidy in organisms that can self fertilize) Triploids are sterile as they don’t produce viable gamets

Question 12

Explain effect of odd number of chromosomes in meiotic segregation

Answer 12

an cause Philadelphia translocation and familial down syndrome.

Question 13

Why does X-inactivation occur

Answer 13

Girls will inherit one X chromosome from mother and father. Both have the same genes so only one needs to be inactive

Question 14

What happens in X-inactivation

Answer 14

Either the maternal or the paternal X chromosome will be condensed and inactivated

Question 15

Why are women stripped

Answer 15

Which X chromosome is inactivated is random so each cell with have a different active one. If these had phenotypes coded on them we would see them represented in striated patterns.