Define:

Genotype

The alleles possessed by an organism

Phenotype

All the characteristics of an organism

Dominant allele

An allele which has the same effect on the phenotype whether it is present in the homozygous or heterozygous state

Recessive allele

An allele which only has an effect on the phenotype when present in homozygous state

Codominant alleelle

Allelees which have a partial effect on the phenotype when present in heterozygotes but a greater effect in homozygotes

Locus

The particular position on homologous chromosomes of a gene

Homozygous

Having two identical alleles of a gene

Heterozygous

Having two different alleles of a gene

Carrier

An individual that has a recessive allele of a gene that does not have an effect on the phenotype

Test Cross

Testing a suspected heterozygote by crossing with a known homozygous recessive

Punnet Grid

Pedigree Chart

a record of ancestry or purity of breed

State that some genes have more than two alleles

Describe ABO blood groups as an example of co-dominance and multiple alleles

Co-dominant alleles- alleles which have a partial effect on the

phenotype when present in heterozygous state but have a greater effect in

homozygotes.

An example is in the alleles controlling the BO blood group system in humans.

The ABO system is controlled by 3 alleles; I , I and I .

I produces A antigens

I produces B antigens

I produces no antigens

There are 2 such alleles present in each person and therefore 6 combinations,

which are:

I I = A

I I = A The I and I alleles show equal dominance

I I = B with respect to one another (i.e. the are

I I = AB co-dominant), but each is dominant to I .

I I = O Inheritance follows normal Mendelian

I I = B patterns.

Outline how the sex chromosomes determine gender by referring to the inheritance of x and y chromosomes of humans

Xy = male

Xx = female

State that some genes are present on the x chromosome and absent from the shorter y chromosome

Define sex linkage

Genes carried on sex chromosomes

State two examples of sex linkage

State that a human female can be heterozygous or homozygous, with respect to sex-linked genes

Explain that female carriers are heterozygous for x-linked alleles

Calculate and predict the genotypic and phenotypic ratios of offspring of monohybrid crosses involving any of the above patterns of inheritance

Deduce the genotypes or phenotypes of individuals in pedigree charts