Inherited change Flashcards
What is the genotype
the genetic constitution of an organism
What is a phenotype
The expression of the genotype and its interaction with the environment
What is an allele
A variation of a particular gene
How are multiple alleles caused
mutations in a gene that occur at different positions in the gene
How can alleles be homozygous
alleles at a specific locus can be homozygous if they are the same type of allele
How can alleles be heterozygous
alleles at a specific locus can be heterozygous if they are a different type of allele
What is a dominant allele
an allele that is always expressed in the phenotype of a heterozygote, so only one copy is needed for expression
What is a recessive allele
an allele is not expressed in the phenotype of a heterozygote, so 2 copies are needed for the allele to be expressed
What are codominant alleles
When both alleles are equally as dominant and equally expressed in the phenotype
e.g. blood type
How to use test crosses to identify an unknown genotype
unknown genotype crosses with a homozygous recessive individual
if all offspring have dominant phenotype, the unknown genotype is homozygous dominant
is some have the dominant phenotype and some have recessive phenotype, unknown phenotype is heterozygous
When would you use a dihybrid cross
to identify the inheritance of 2 different genes
What is autosomal linkage
Where 2 or more genes are located on the same autosome
therefore less likely to be separated during crossing over so are likely to be inherited together
therefore offspring are more likely to resemble the parental genotype
What is sex linkage
Gene is located on the X chromosome
therefore males are more likely to have recessive conditions as they only require 1 copy of the recessive sex linked allele for expression
What is epistasis and what are the suppressing and suppressed genes called
the interaction between 2 genes where one genes masks the expression of the other gene in the phenotype
suppressing gene is called the epistatic gene and the suppressed gene is called the hypostatic gene
epistatic interactions can be dominant or recessive
What happens in dominant epistasis
expression of dominant allele of epistatic gene masks the expression of hypostatic gene
