genes, chromosomes and cell division

Question 1

Balanced chromosome rearrangement

Answer 1

All the chromosomal material is present

Question 2

Unbalanced chromosome rearrangement

Answer 2

• Extra or missing chromosomal material, usually 1 or 3 copies of gene
• Causes major developmental problems

Question 3

Aneuploidy

Answer 3

• Whole extra or missing chromosome
• X chromosome aneuploidy better tolerated because of X chromosome inactivation

Question 4

Translocation

Answer 4

Rearrangement of chromosomes

Question 5

Robertsonian translocation

Answer 5

• Two acrocentric chromosomes stuck end to end
• Increased risk of trisomy in pregnancy

Question 6

Reciprocal translocation

Answer 6

Two broken off chromosome pieces of non-homologous chromosomes are exchanged

Question 7

Insertions and deletions

Answer 7

• Missing or duplicated material
• Microdeletions - too small to be seen on chromosome using light microscope

Question 8

what is somatic mosaicism

Answer 8

Refers to the occurrence of two genetically distinct populations of cells within an individual, derived from a post-zygotic mutation
- May only affect a portion of the body
- Not transmitted to progeny
- Somatic mosaicism for a chromosomal abnormality could contribute to cancer
- Changes could activate an oncogene or delete a tumour suppressor

Question 9

Down’s syndrome karyotype

Answer 9

47XY +21

Question 10

miscarriage karyotype

Answer 10

47 XY +14

Question 11

Edward syndrome, trisomy 18 karyotype

Answer 11

47 XY +18

Question 12

Turner syndrome karyotype

Answer 12

45 X