genetics: mendelian inheritance SDL Flashcards
define gene
A discreet unit of DNA which codes for a protein
define locus
The position of a gene on a chromosome
define allele
An alternative form of a gene that produces a distinguishable phenotypic effect
define genotype
The alleles contained in an organisms cells
define phenotype
The 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 dominant allele
Allele which is always expressed in the phenotype if it is present in the genotype
define recessive allele
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
define F1
First filial generation, the first hybrid offspring of two pure breeding parents
define F2
Second filial generation, the offspring from interbreeding the F1 generation
what is the law of segregation
Law of segregation: states that the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
what is the law of indipendent assortment
The law of independent assortment states that each pair of alleles segregates independently of each other pair of alleles during gamete formation
- this law only applies to genes on different, non homologous chromosomes
- genes located near each other on the same chromosome tend to be inherited together
what are linked genes
Genes located on the same chromosome that tend to be inherited together are called linked genes
- crossing over between linked alleles can produce recombinant individuals
what is incomplete dominance
both allels on a gene locus are partially expressed
what are epistatic genes
genes that mask or interfere with the effects of other genes
what is the difference between incomplete dominance and codominance
Codominance
Both alleles at a gene locus are fully expressed in the phenotype, resulting in two possible phenotypes. This is a heterozygous state, where both phenotypes are partially dominant.
Incomplete dominance
One allele for a trait is not fully expressed over its paired allele, resulting in a third phenotype that is a combination of both alleles. This is a form of intermediate inheritance.
In codominance, no allele can block or mask the expression of the other allele. In incomplete dominance, neither trait is truly dominant over the other, resulting in a blending of the two phenotypes
