Pre- IB Biology Unit 7: Mendelian Genetics

Asexual Reproduction

Process of reproduction involving a single parent that results in offspring that are genetically identical to the parent

Gene

\n A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Sexual Reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents.

Allele

a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.

Dominant

Describes a trait that covers over, or dominates, another form of that trait. (Always expressed)

Recessive

Describes a trait that is covered over, or dominated, by another form of that trait and seems to disappear.

Homozygus

Having two identical alleles for a particular gene (The same AA or aa

Heterozygus

An organism that has two different alleles for a trait (Different Aa)

Genotype

An organism's genetic makeup, or allele combinations. (Ex. AA, aa, Aa)

Phenotype

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Fertilization

The action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote. (Sexual Reproduction)

Gametes

A mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

Principal of Dominance

Mendel's second conclusion, which states that some alleles are dominant and others are recessive.

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete.

Law of independent Assortment

Each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random.

Carrier

A person whose genotype includes a gene that is not expressed in the phenotype. (Always Heterozygous)

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family. (Circle= Female, Square= Male, and half shaded= carrier)

Complete Dominance

A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.

Incomplete Dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Codominance

A condition in which both alleles for a gene are fully expressed. ( Speckled Chicken)

Multiple Allele

Three or more forms of a gene that code for a single trait. A gene that has more than two alleles.

Polygenic Traits

Characteristics that are influenced by more than one pair of genes.

Sex Linked Traits

A trait associated with a gene that is carried only by the male or female parent.

Heredity

The passing on of physical or mental characteristics genetically from one generation to another.