Genetic inheritance Flashcards
Define gene
discreet unit of DNA which codes for a protein
Define allele
an alternative form of a gene that produces a different phenotypic effect
Define locus
the position of a gene on a chromosome
Define genotype
alleles contained in an organisms cells
Define phenotype
characteristics of an organism determined by its genotype and its environment
Define homozygous
an organism which possesses 2 identical alleles of the same gene
Define heterozygous
An organism which possesses 2 different alleles of the same gene
Define dominance
allele which is always expressed in the phenotype if it is present in the genotype
Define recessive
allele which is only expressed in the phenotype when the dominant allele is not present
Define codominance
When both alleles affect the phenotype of a heterozygous individual
Describe the law of independent assortment
states that each pair of alleles segregates independently of each other pair of alleles during gamete formation
In what situations may inheritance of a gene deviate from simple medelian patterns
When alleles display incomplete dominance/codominance
When a gene has more than 2 alleles
When a gene produces multiple phenotypes
Describe the effect of incomplete dominance
The phenotype of F1 hybrids is between the phenotypes of the 2 parental varieties
what is epistasis?
a gene at one locus alters the phenotypic expression of a gene at a second locus
Give an example of epistasis
Mice:
- one gene determines coat colour e.g., black or brown
- another gene determines if pigment will be deposited in the hair - colour or no colour
