3.7.1 Inheritance Flashcards
Define genotype
The genetic constitution of an organism
Define phenotype
The expression of an organism’s genetic constitution, combined with its interaction with the environment
What is an allele
Different version of the same gene
What is meant by codominant alleles
2 dominant alleles that both contribute to the phenotype, either by showing a blend of both characteristics or the characteristics appearing together
Define monohybrid inheritance
Where one phenotypic characteristic is controlled by a single gene
Define dihybrid inheritance
Where 2 phenotypic characteristics are determined by two different genes present on 2 different chromosomes at the same time
What is meant by sex linkage
Where an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual
Why are males more likely to express a recessive sex linked allele
Most sex linked alleles are located on the X chromosome
Therefore males only get one copy of the allele, so will express this characteristic even if its recessive
Since females get 2 alleles this is less likely
Which parent do males inherit sex linked characteristics from
Their mother, since the Y chromosome can only come from their father. Therefore if the mother is heterozygous for sex linked alleles, she is a carrier and may pass the trait on
What is meant by autosomal linkage
Where 2 or more genes are located on the same chromosome. In this case only one homologous pair is needed for all 4 alleles to be present. For genes that arent linked, 2 homologous pairs are needed
What is meant by epistasis
Where 2 non linked genes interact, with one gene either masking or suppressing the other gene
Define the 2 types of epistasis
Recessive epistasis - where 2 homozygous recessive alleles mask expression of another allele
Dominant epistasis - where 1 dominant allele masks expression of multiple other alleles
What is the chi squared test
A statistical test to find out whether the difference between observed and expected data is due to chance or a real effect
What are the criteria for the chi squared test
Data placed in discrete catagories
Large sample size
Only raw count data allowed ie not %
No data values equal 0
How can we use a chi squared test in relation to the content of this topic
We can compare expected phenotypic ratios with observed ratios to test our understanding of how different genes and alleles are inherited
