Genetics

Question 1

What is an obligate carrier?

Answer 1

Someone who may be clinically unaffected but must carry a gene mutation based on analysis of the family history

Question 2

How to know if a disease is mitochondrially inherited?

Answer 2

All children must be affected

Question 3

What is GWAS used for?

Answer 3

• To study polymorphims and polygenic disorders.
• Snips are made at genes and their significances are looked at
• Large sample size needed
• Alleles that are rare have a greater effect but those that are common, each allele has a lower effects and many are needed for an effect

Question 4

What is pleitropy?

Answer 4

a single gene that may give rise to two or more apparently unrelated effects - e.g. effects on different parts of the body

Question 5

Penetrance and expressivity

Answer 5

Penetrance – does the disease manifest?

Expressivity – how does the disease (or trait) get expressed?

Question 6

How is a karyotype made?

Answer 6

• A karyotype is a pictorial display of metaphase chromosomes
  from a mitotic cell
• When chromosomes condense they are visible under a light
  microscope
• Mitotic cells are fixed in metaphase and the chromosomes
  are stained with Giemsa dye.

Question 7

Giemsa stain

Answer 7

This stains regions with lots of Adenine (A) and thymine

(T) base pairs giving a pattern of dark bands on each chromosome

Question 8

Karyotype notation

Answer 8

-Total number chromosomes, sex chromosomes, any
extra/missing chromsomes

e. g. 46, XY
e. g. 47, XX, +21

Question 9

What can cause aneuplodies?

Answer 9

Aneuploides result from failure of separation of homologous chromosomes in anaphase I or sister chromatids in anaphase II of meiosis. This is called non-disjunction.