6.2.4 multiple alleles Flashcards
define condominance
where both alleles present in genotype of heterozygous individual contribute to phenotype
define multiple alleles
characteristics for which there are 3 or more alleles in population gene pool
what causes many genes to have more than 2 alleles
huge changes can happen anywhere within the gene
when does a gene have multiple alleles
when 3 or more alleles at specific gene locus
how many alleles can someone possess in pair of homologous chromosomes
2 alleles - 1 at each gene locus
examples of multiple alleles
- inheritance of ABO blood groups in humans
- coat colour of rabbits
describe inheritance of ABO blood groups in humans as an example of multiple alleles
- 4 blood groups (phenotypes) = A, B, AB, O
- determined by 3 allles of single gene on chromosome 9
- gene encodes isoagglutinogen on surface of erythrocytes
- alleles present in human gene pool = IA, IB, IO
- IA & IB are dominant to IO (recessive)
- if IA & IB present in genotype, both contribute to phenotype
- any individual will only have 2 of 3 alleles within genotype
which alleles are required parents to produce children with any of 4 blood groups
- man of blood group A
- woman of blood group B
- all heterozygous at gene locus
IBIO (woman) x IAIO (man) produces:
IBIA (group AB) IBIO (group B) IAIO (group A) IOIO (group O)
describe how coat colour in rabbits is an example of multiple alleles
- coat colours include:
1. wild type coat colour (grey base, yellow band & black tip)
2. albino (no pigment = white fur)
3. chinchilla (silvery grey - lack yellow band)
4. himalayan (white, black feet/ears/nose/tail) - coat colours determined by 1 gene with 4 alleles
- dominant hierarchy:
1. agouti (C) dominant to all alleles
2. chinchilla (Cch) dominant to himalayan (Ch)
3. albino (c) recessive to all alleles
results of crossing albino & agouti rabbits
look on notes
results of crossing albino & himalayan
look at notes
