genetics lecture 8

Question 1

How is a karyotype obtained ?

Answer 1

1) Take a blood sample
2)Culture white blood cells in
growth medium 37 C
3)Add Colchicine (inhibits spindle contraction) Cells stuck in metaphase
4)Harvest cells and fix onto microscope slide
5)Stain (giemsa) and view in microscope

Question 2

what is Giemsa reagent

Answer 2

a stain that produce a distinctive banding pattern.

Question 3

G-banding of human chromosomes.

Answer 3

Chromosomes stained with Giemsa reagent, produce a distinctive banding pattern.
2)A numbering system is used to indicate positions of genes on the chromosomes p=short arm, q=long arm.
3)Each arm is divided into major sections (1, 2, etc.), and subsections.

Question 4

what causes a chromsome change in structure

Answer 4

Duplication- Occurs when a chromosome segment is duplication by mistake during chromosomal replication prior to cell division

Question 5

what causes a chromsome change in structure (2)

Answer 5

Deletions- Deletions occur when a fragment of chromosome is missing and can cause severe abnormal traits
When deletions are homozygous they are often lethal.

Question 6

what causes a chromsome change in structure (3)

Answer 6

Sequence of genes on a chromosome is reversed

Question 7

what causes a chromsome change in structure (4)

Answer 7

Translocations-
Movement of a chromosomal segment from one chromosome to another

Translocations can result in normal phenotypes as the genes are not lost.

However, the translocation event causes breakpoints, and if this occurs in-between or near an important gene, then a gene defective can occur.

Question 8

what are some diseases aassocitaed with translocations

Answer 8

Leukaemia
Downs Syndrome