7C - genotypes and phenotypes (copy)

Inheritance

The process by which genetic information is passed from parents to offspring.

Genotype

The genetic infromation for a particular trait

• These are the 2 alleles an organism has for a particular trait.

• e.g. TT, Tt, tt

Phenotype

The visible expression of the genetic make-up of an organism

• This is any distinct property of an organism – physical, chemical, physiological or behavioural

• e.g. ‘Tall,’ ‘Blood Type B,’ ‘posses 70% beta proteins’ etc.

Dominant

Only require a single copy of the allele in order to be expressed in the phenotype.

• E.g. black hair = B

Recessive

Two alleles must be present in the gnotype for the trait to be shown. If there is only one recessive allele, it will be masked or hidden by the dominant allele.

Complete dominance

A pattern of dominance where only the dominant allele from the genotype of a heterozygous individual is expressed in the phenotype of that organism.

• dominant and recessive

Homozygous

If an organism has 2 copies of an allele that are the same

• homozygous dominant (BB) / recessive (bb)

Heterozygous

If an organism has 2 different alleles.

• Bb - carrier of the recessive gene (display dominant)

Codominance

Occurs when both alleles from the genotype are fully expressed in the phenotype of a heterozygote.

• both alleles can be thought of as dominant and neither allele can mask the expression of the other.

• brown cow x white cow = roan cow (spotted brown and white).

Incomplete dominance

a pattern of dominance where neither allele from the genotype of a heterozygous individual is dominant and both are expressed in an intermediate phenotype

• White flower x red flower = pink flower.

sex-linked genes

Genes that are located on a sex chromosome

•  are inherited differently than autosomal traits