Biology-Module 8

Sex Chromosomes

Chromosomes that determine the sex of an individual.

Autosomes

Chromosomes that do not determine the sex of an individual

Autosomal inheritance

inheritance of a genetic trait not on a sex chromosome.

True Breeding

If an organism has a certain characteristic that is always passed on to its offspring we say that this organism bred true with respect to that characteristic.

Sex-linked inheritance

Inheritance of a genetic trait located on the sex chromosomes.

Genotype

Two letter set that represents the alleles an organism possesses for a certain trait

Monohybrid cross

A cross between two individuals, concentrating on only one definable trait.

Dihybrid cross

A cross between two individuals, concentrating on two definable traits.

Pedigree

A diagram that follows a particular phenotype through several generations.

Homozygous genotype

A genotype in which both alleles are identical.

Heterozygous genotype

A genotype with two different alleles.

Genetic disease carrier

A person who is heterozygous in recessive genetic disorder.

Antigen

A protein that, when introduced in the blood, triggers the production of an antibody.

Mutation

A radical chemical change in one or more alleles.

Change in chromosome structure

A situation in which a chromosome loses or gains genes during meiosis.

Change in chromosome number

A situation in which abnormal cellular events in meiosis lead to either none of a particular chromosome in the gamete or more than one chromosome in the gamete.

Mendel's Principles for Genetics:

1. The traits of an organism are determined by its genes. 2. Each organism has two alleles that make up the genotype for a given trait. 3. In sexual reproduction, each parent contributes ONLY ONE of its alleles to its offspring. 4. In each genotype, there is a dominant allele. If it exists in an organism, the phenotype is determined by that allele.

Dominant allele

An allele that will determine phonotype if just one is present in the genotype.

Recessive allele

An allele that will not determine the phono type unless the genotype is homozygous in that allele.

Allele

One pair of genes that occupies the same position on homologous chromosomes.

Phenotype

The observable expression of an organism's genes.