7.1 - Inheritance Flashcards
Hardy Weinberg equations
p squared + 2pq + q squared = 1
p + q = 1
(p squared = homozygous dominant
q squared = homozygous recessive
2pq = heterozygous)
Hardy Weinberg assumptions
- no selective advantage
- large population
- random mating
- no mutation
- no emigration/immigration
Monohybrid
- 1 gene
- 3:1 ratio
Dihybrid
- 2 genes
- 2 heterozygous = 2:3:3:1 ratio
common examples: pea plants, drosophila
Autosomal linkage
- chromosome not sex-linked
- 2 heterozygous = 2:3:3:1 ratio
- stay together during independent segregation unless crossing over occurs
Define autosome
chromosome that is not sex-linked
Sex linkage
alleles specific to sex (X and Y) chromosomes
female = XX, male = XY
written with X/Y then small letter to represent allele
common examples: colourblindness, haemophilia, family trees/pedigree charts
Define allelomorphic
when a gene has more than 2 potential alleles
Epistasis
allele of one gene masks expression of another in the phenotype
common examples: enzymes, colour, flow chart
Codominance/multiple alleles
written with capital letter then small letter (sometimes with a dash e.g Bbb’)
common examples: colour, shape/structural/physical feature, blood group
Why chi-squared
categorical data
Suggest two causes of genetic variation
crossing over, independent segregation
Why are phenotypic ratios often not the same as the expected ratios?
crossing over, linked genes
(monohybrid) = random fertilisation, small population size
Define phenotype
characteristic due to genetic constitution due to environment
What does it mean when genes are linked?
they are located on the same chromosome
