Alleles, Genes and Phenotypes Flashcards
how are different alleles made?
alleles arise through mutations
what is a “wild type” allele?
the default phenotype
what is the dominance hierarchy?
B > b > b’
what is incomplete dominance?
heterozygotes may have a blended phenotype, e.g. blue fruit + red fruit = purple fruit
what is codominance?
when two alleles produce different different phenotypes are both expressed, e.g. blood groups
some alleles are dominant to some and codominant to others
What are pleiotropic alleles?
alleles that create multiple phenotypes
Name an example of how phenptypes can be determined by more than one gene’s genotype
in cats the brown gene can be modified by the dilute gene
what is epistasis?
the phenotypic expression of one gene is influenced by products from other genes, e.g. labradors: B (black fur) dominant over b (brown); E (pigment) dominant over e (no pigment). if ee, fur is yellow regardless of Bb alleles -> E is epistatic to B
how does the environment affect phenotypes?
light, temperature, nutrition can influence the phenotype, e.g. point restriction coat colour in siamese cats
what is a qualitative trait?
discrete quality that is controlled by one locus
what are quantitative traits?
trait is influenced by many loci and the environment
what is gene linkage?
alleles on the same chromosome are more likely to be inherited together as they are physically linked, so it is unlikely that recombination will break them up
what is a parental phenotype?
same phenotype as parents (often due to gene linkage)
what is a recombinant phenotype?
a phenotype that differs from parents’
how do you calculate the recombinant frequency?
number of recombinant offspring divided by total number of offspring
what can recombinant frequencies be used for?
to infer the location of genes on a chromosome and create genetic maps
what does homogametic mean?
two copies of a X chromosome (XX)
what does heterogametic mean?
one copy of each chromosome (XY)
-> gene is hemizygous
