Chromosomes and Development

Question 1

What is the largest cause of congenital anomalies?

Answer 1

Mendelian disorders

Question 2

2 points that are susceptible to errors in mitosis

Answer 2

DNA replication

Chromosome segregation

Question 3

2 essential features of meiosis

Answer 3

Chromosomal pairing

DNA exchange

Question 4

When does a cell go from diploid to haploid

Answer 4

At the end of meiosis 1

Homologous pairs separate

Question 5

Non-disjunction

Answer 5

In meiosis (1 or 2)
Erros in chromosome segregation
Whole chromosome loss or gain

Question 6

What factor is a risk for non-disjunction?

Answer 6

Mother’s age

Increases as she ages

Question 7

When is meiosis halted in oogenesis?

Answer 7

At the end of MI (end of embryogenesis)
During MII (until just before ovulation)
Resumes after ovulation is triggered by fertilization

Question 8

When does the oocyte number peak?

Answer 8

Embryonic week 20

Question 9

Aneuploidy

Answer 9

Gain or loss of an entire chromosome

Question 10

How to identify:

1. Aneuploidy
2. Insertions or deletions
3. Copy number variants

Answer 10

1. Whole chromosome
2. Cytogenic resolution
3. Submicroscopic (chromosome microarray)

Question 11

3 examples of structural variants

Answer 11

Translocations
Inversions
Complex rearrangements

Question 12

2 types of translocations and what they mean

Answer 12

Reciprocal (exchange of broken segments)

Robertsonian (fusion of 2 acrocentric chromosomes near the centromere)

Question 13

Where does the problem with translocations occur?

Answer 13

If they occur in germ cells they can cause unbalanced genetic information in the progeny

Question 14

What are the 5 acrocentric chromosomes?

Answer 14

13, 14, 15, 21, 22

Question 15

Robertsonian translocations are
1. balanced
2. unbalanced
when you have how many chromosomes?

Answer 15

1. 45

2. 46

Question 16

Turner syndrome

Answer 16

Missing an X chromosome

Infertility, short stature, cardiac problems, but normal intelligence

Question 17

Chromosomal microarray

Answer 17

Gain or loss of 0.25-10Mb (or more) of a genome
Take patient DNA, label with probe on slide that has reference DNA
DNA is either labelled with a different colour (measure the balance) or the same colour (measure the brightness)

Question 18

Williams Syndrome

Answer 18

Deletion in chromosome 7

Intellectual disability, short stature, different behaviour and appearance