Intro to genetics and punnet squares Flashcards
what is genetics
genetics is the study of how, in all living things, the characteristics and qualities of parents are given to their children by their genes.
how many copies of genes does all organisms receive
they receive two copies of each gene, one from each parent
what are alleles
alleles are alternative forms of genes
what does alleles control
alleles control the contrasting characteristics of each trait
what are the two types of alleles
dominant or recessive
describe a dominant allele
dominant alleles are symbolised by capital letters and they will always express/show themselves
describe a recessive allele
recessive alleles are symbolised by lowercase letter and they only express/show themselves in the absence of dominant alleles
what is genotype
e genetic makeup (combination of alleles) of an organism
what is phenotype
the physical features/appearance of an organism
what is the link between phenotype and genotype
phenotype is the expression of genotype
eg: If the genotype is TT, the plant’s
phenotype is tall
If the genotype is tt, the plant’s
phenotype is short
what does homozygous mean
homozygous (pure bred) means that an organism has two identical alleles for a trait
eg: BB, bb
BB – both alleles are dominant, so
homozygous dominant.
bb – both alleles are recessive, so
homozygous recessive.
what does heterozygous mean
heterozygous (hybrid) means that organism has two different alleles for a trait.
eg: Bb
In this case the recessive allele is
hidden by the dominant allele
and is not expressed.
Who is the Punnet Square named after?
Reginald Punnet
