Genetics

Question 1

Rhesus factor

Answer 1

monogenetic trait controlled by a dominant allele

Rh+: antigen on erythrocytes
Rh-: lacking antigen

Question 2

Rhesus antibodies

Answer 2

Rh- recognises the antigen as foreign, therefore the immune system will attack it

Rh- woman can become pregnant with Rh+ child
when Rh+ blood enters the maternal blood stream, immune system produces Rh+ antibodies
Following pregnancy can result in Rh+ antibodies crossing the placenta and attacking the foetal blood stream (anaemia, jaundice)

Question 3

Genetic disorders

Answer 3

Huntington’s disease
Neuro-degenerative disease, appearing around 40 - 50% inheritance

Albinism
Failure to produce pigmentation

Haemophillia Type A
affects blood clotting

Question 4

Environmental pressure effects

Answer 4

Tray-sachs disease
recessive autosomal trait - homozygotes lack an enzyme leading to an accumulation of lipids in nervous system
Heterozygotes give resistance to TB, those with the allele had high survival rates within ghettos

Question 5

Source of variation

Answer 5

random assortment of chromosomes during meiosis
crossing over of chromosomes
non disjunction
maturation
random fertilisation

Question 6

random assortment of chromosomes

Answer 6

duplicated pairs of chromosomes line up randomly during the first meiotic division - final sex cells could contain more or less chromosomes from the paternal/maternal lines

Question 7

chiasma (crossing over)

Answer 7

chromatids may be swapped during the first meiotic division

results in recombination

Question 8

non-disjunction

Answer 8

chromosomes pairs or single chromosomes may not separate during meiosis - results in too many or too little chromosomes in the gametes
Trisomy - inheriting an extra copy of a chromosomes
Monosomy - missing a chromosome

Question 9

Random fertilisation

Answer 9

any sperm can fertilise any egg

Question 10

Blood group inheritance

Answer 10

A and B are co-dominant, O is recessive

6 blood group genotypes, 4 blood group phenotypes