Introduction to genetics Ch 10

Genetics

The science of hereditary.

Allele

This is an alternative form of a single gene passed down from generation to generation

I.e Ff

Dominant

This allele

1. Appears in a homozygous dominant genotype (FF) and a heterozygous genotype(Ff)

2. Is typically expressed using capital letters (F)

3. Overshadows a recessive gene in the phenotype

Recessive

The small letter (aa). That will only appear in a homozygous recessive genotype.

Homozygous

An organism with two of the same alleles for a particular trait (YY/ yy)

Heterozygous

An organism with two different alleles for a particular trait (eg Yy)

Phentoype

The observable characteristic or outward expression of an allele pair. (eg green eyes)

Law of segregation

The two alleles for each trait separate during meiosis.

Hybrids

Heterozygous organism that are formed by breeding two species together (YY yellow peas + yy green peas = Yy yellow peas with green trait.)

Law of independent assortment

A random distribution of alleles occur during gamete formation.

Genetic recombination

The combination of genes produced by crossing over and indpendent assortment.

Polypoidy

The occurence of one/more extra sets of all chromosomes in an organism.

Selective breeding

The process by which desired traits of certain plants and animals are selected and passed on to their future generations.

In breeding

The process in which two closely related organisms are bred to have the desired traits and to eliminate the undesired ones in future generations.

Hybridization

Crossing parent organisms with different forms of a trait to produce offspring with specific desired traits. Such traits include disease resistance or faster growth periods.

Test cross

Involves breeding an organism that has an unknown genotype with one that is homozygous recessive for the desired trait. If the unknown genotype is dominant all offspring will present the dominant phenotype. If it is recessive half will have the recessive phenotype and half the dominant phenotype.

Carrier

An individual who is heterozygous for a recessive disorder.

Pedigree

A diagram that traces the inheritance of a particular trait through several generations.

Incomplete dominance

The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

Codominance

Both alleles are expressed in the heterozygous condition

Multiple alleles

Some forms of inheritance that are determined by more than two alleles.

Epistasis

This is an interaction in which one allele hides the effect of another allele.

Sex linked traits

Traits controlled by genes located on the X chromosome.

Polygenic traits

Phenotypic traits that arise from the interaction of multiple pairs of genes. Examples of these include skin colour, height, eye colour, and fingerprint pattern.