Chapter 14 Biology 3201 - End of Term 1st Term Assessment - Review

Genetics

Genetics

is the branch of science concerned with studying variation and inheritance of traits.

Heredity

The transmission of genetic characteristics from one generation to the next. Traits that are passed.

Selective Breeding

Ensures the transmission of certain traits.

DNA (Deoxyribonucleic acid)

The molecule that carries genetic information for the development and functioning of an organism

Traits

A distinguishing characteristic which makes individuals unique.

Gregor Mendel (1822-1884)

Father of Genetics. Austrian monk and botanist. Worked with pea plants and developed explanations for inheritance patterns.

Purebred

Species of any organisms that share similar traits. Descend from a ancestor of a distinct type.

True Breeding

An organism that will always produce offspring with certain desired traits.

Principle of Dominance

When individuals with contrasting traits are crossed, the offspring will only express the dominant trait, if the dominant trait is present.

Dominant Trait

Trait that is always expressed in spite of the presence or absence of a recessive allele.

Recessive Trait

Trait that is unusually expressed; only when two alleles for that trait are present will that trait appear.

Mendelian Ratio(s)

For single trait crosses it is 3:1. For dihybrid crosses it is 9:3:3:1.

Monohybrid Cross / Single Trait Cross

Are crosses that combine single contrasting traits.

Law of Segregation

Heritable traits are determined by pairs of alleles from each parent. Alleles separate during gamete formation, giving each offspring only one allele from each parent.

Genes

The fundamental unit of inheritance. Section of a chromosome, a piece of DNA, that codes for a particular trait.

Alleles

One of the forms in which a gene can exist. Alternate forms of the same gene. They occupy corresponding positions on homologous chromosomes.

Homozygous

The state in which both alleles for a particular gene are the same.

Heterozygous

The state in which both alleles for a particular gene are different. One dominant allele, one recessive allele.

Punnett Square

A grid used to determine the possible combinations of alleles when two parent generations are crossed. Can be used to predict the genotypes and phenotypes of the offspring.

Genotype

The genetic makeup. The combination of two alleles that an organism inherits.

Phenotype

The physical appearance of the trait. The expression of a trait as a result of inheritance.

Two Trait Cross / Dihybrid Cross

Crosses that involve two traits.

Test Cross

Used to determine the genotype of an individual, either as homozygous dominant or heterozygous dominant. Involves crossing the unknown individual with a homozygous recessive individual .

Law of Independent Assortment

It states that the inheritance of alleles for one trait does not affect the inheritance of alleles for another trait.

Incomplete Dominance

In some cases neither allele is dominant, in fact they are equally dominant. They interact to produce a new phenotype, a blending occurs.

Co-dominance

In some cases, both alleles for a trait may be dominant. As a result, both alleles are expressed in the heterozygous individual.