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
define
Allele
different forms of a particular gene, found at the same ocus on a chromosome
state
number of alleles per gene in diploid organisms
2
Define
dominant allele
an allele whose characteristics will always appear in the phenotype, whether one or two are present
define
recessive allele
an allele whose characteristic only appears in the phenotype if no dominant allele is present
define
codominant alleles
2 dominant alleles that both contribute to the phenotype, either by showing a blend of both characeristic or the characteristics appearing together
contrast
homozygous and heterozygous
homozygous = both alleles are dominant or both are recessive
heterozygous = one allele is dominant and the other is recessive
define
monohybrid inheritance
when one phenotypic characteristic is controlled by a single gene
define
dihybrid inheritance
when two phenotypic characteristics are determined by two different genes present on two different chromosomes at the same time
define
sex-linkage
when an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual
explain
why males are more likely to express a recessive sex-linked allele
most sex-linked alleles are located on the X chromosome so males only get one copy of the allele and will express this characteristic even if it’s recessive. Females have two alleles so this is less likely
state and explain
which parent males inherit sex-linked characteristics from
mother, as the Y chromosome can only come from their father so if the mother is heterozygous for sex-linked alleles, she is a carrier and may pass on the trait
define
autosomal linkage
when 2 or more genes are located on the same (non-sex) chromosome. Only 1 homologous pair is needed for all 4 alleles to be present. For genes that aren’t linked, 2 homologous pairs are needed
define
epistasis
when 2 non-linked genes interact with 1 gene either masking or suppressing the other gene
define
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
define
chi-squared test
a statistical test to find our whether the difference between observed and expected data is due to chance or a real effect
state
criteria for chi-squared test
- data placed in discrete categories
- large sample size
- only raw count data
- no data values equal 0
explain
how chi-squared test is performed
formula results in a number which is compared to a critical value, if number is greater or equal to critical value, there is a significant difference.
explain
use of chi-squared test in relation to inheritance
comparison of expected phenotypic ratios with observed ratios to test understanding of how different genes and alleles are inherited
