inheritence Flashcards
what is a monohybrid inheritance
the inheritance of a single characteristic controlled by one gene, each parent having two alleles for that gene
what is Mendel’s first law
the characteristics of an organism are determined by alleles which occur in pairs, only one of a pair of alleles can be present in a single gamete
give an example of a homozygous dominant and a homozygous recessive gene
HH
hh
give an example of a heterozygous gene
Hh
what is a test/back cross
used to tell if a dominant phenotype is heterozygous or homozygous by crossing it with a homozygous recessive
if it is homozygous all offspring will have a dominant phenotype
if it is heterozygous half offspring will show the recessive phenotype
what is meant by pure breeding
a variety bred for several generations with itself so all individuals are homozygous, all offspring will have the same phenotype as their parents
what is codominance
when both alleles express themselves equally in the heterozygote phenotype
outline what is meant by multiple alleles
when there are more than two alleles for one gene for example blood groups Ia, Ib and Io
what is sex linkage
when genes have their loci only on the X chromosome
therefore males only have one copy of the gene (XY) and females have two (XX)
in sex linkage what will happen if the male gains a recessive allele
the male only has one copy of the gene, therefore the recessive allele will always be expressed
give an example of well known sex-;inked traits
red-green colour blindness and
haemophilia
what is dihybrid inheritance
the inheritance of two genes located on two different chromosomes with each gene having two alleles
what is Mendel’s second law of independent assortment
either one of a pair of contrasted characteristics may combine with either pair during gamete formation
what is autosomal linkage
this is a dihybrid cross where both the genes are located together on the same chromosome therefore in a heterozygous organism only 2 different gametes can be formed
