PEDIGREE ANALYSIS

Question 1

What is a propositus?

Answer 1

member of the family that firsts comes to geneticist’s attention

Question 2

Tell tale signs that a trait is X linked recessive from a pedigree?

Answer 2

• all affected daughters MUST have a heterozygous mother and a hemizygous father
• many more males show phenotype than females
• NONE of an affected male’s offspring are affected but all of his daughters are carriers

Question 3

Tell tale signs that a trait is X linked dominant?

Answer 3

• affected males pass condition on to ALL daughters but none of their sons
• affected heterozygous females married to unaffected males pass condition to half sons and half daughters

Question 4

What is a sex influenced/ limited trait?

Answer 4

phenotypes differ between sexes but the gene inheritance pattern is autosomal

Question 5

Restriction site and cleavage site are two ____ properties

Answer 5

separate

Question 6

What is an RFLP?

Answer 6

restriction fragment length polymorphism

- differ in the presence of absence of a restriction recognition site

Question 7

what is a dominant negative mutation?

Answer 7

mutant gene phenotype product interferes with the wild type product and prevents function

Question 8

What is haploinsufficiency?

Answer 8

gene product is insufficient because of normal allele and prevents wild type phenotype being expressed

Question 9

Haemophilia is an _ - ___ recessive gene that is caused by a loss of restriction site in the middle of a factor ___ gene.

Answer 9

x- linked

VIII

Question 10

What is co-dominance?

Answer 10

• when the products of both alleles are expressed in phenotype
  eg. blood type AB has a contribution from A and B

Question 11

What is incomplete dominance?

Answer 11

When the phenotype produced is an intermediate of both phenotypes

Question 12

what is penetrance?

Answer 12

probability the genotype will yield the phenotype at all

Question 13

What is expressivity?

Answer 13

the extent to which the phenotype is expressed

Question 14

Multifactorial traits depend on the interaction between multiple genes and the ____.

Answer 14

environment

Question 15

What is GWAS? Used for?

Answer 15

genome wide association studies

• find single nucleotide polymorphisms, and aim to identify genes/ differences in DNA sequences between affected individuals and normal individuals for a trait

Question 16

Huntingdon’s disease is an autosomal __(a)__ disease that shows __(b)__ expressivity. This can prove genetic __(c)___ due to varieties in the size of the unstable allele. Poly-__(d)___ chains increase through generations and the gene gets __(e)___.

Answer 16

a) dominant
b) variable
c) anticipation
d) glutamine
e) larger

Question 17

How does PCR work?

Answer 17

1) pairs of primers on opposite strands are extended towards eachother
2) strands are heated to denature to generate single stranded templates (95 degrees)
3) temp lowered to 55 degrees for annealing of the primers
4) raised to 72 degrees for DNA polymerase action

Question 18

What does consanguineous mean?

Answer 18

descend from shared ancestor