Basic Principles of Genetics

Hybrid

Offspring that are the result of mating between two genetically different parents. The opposite of a purebred

Genetics

The study of gene structure and the patterns of inheritance of traits form parents to offspring

Gregor Mendel

A European monk scientist who worked with pea plants. He discovered factors and that some were dominant and others were recessive. He also discovered that alleles for the same trait separate, and genes undergo independent assortment. Finally, he learned that two identical alleles are homozygous, and two different alleles are heterozygous

Blending Theory

A theory that inherited traits blend from generation to generation

Purebred

Offspring that are the results of mating between genetically similar kinds of parents. The opposite of hybrid

Genes

Units of inheritance usually occurring on a chromosome. The units are responsible for hereditary characteristics. Sequence of DNA

Alleles

Alternate forms of the same gene

Genotype

The genetic makeup of an individual

Homozygous Genotype

A genotype consisting of two identical alleles of a gene for a particular trait

Heterozygous Genotype

A genotype consisting of two different alleles of a gene for a particular trait

Phenotype

The observable or detectable characteristics of an individual organism

Dominant Allele

The general term for an allele that masks the presence of another allele in the phenotype

Recessive Allele

The general term for an allele that is masked in the phenotype by the presence of another allele

Principle of Segregation

Gregor Mendel's principle stating that the pair of genes from each parent separate and only one gene from each parent passes on to offspring

Principle Of Independent Assortment

Gregor Mendel's principle stating that different pairs of genes are passed to offspring independently so that new combinations of genes, present in neither parent are possible

Punnet Square

A method showing all of the potential combinations of offspring genotypes that can occur and their probability given the parent genotypes

Homozygous Dominant

The term for genotype in which there are two dominant alleles

Heterozygous

The term for a genotype in which there is a dominant allele and a recessive allele

Homozygous Recessive

The term for a genotype in which there are two recessive alleles

Mendelian Genetics

The general term for inheritance patterns which can be explained by simple rules of dominance and recessiveness of genes

Polygenic Trait

A trait that is determined by the combined effect of more than one gene

Incomplete Dominance

Inheritance pattern in which a trait is expressed in the phenotype of heterozygous individuals as an apparent blend or an intermediate expression

Codominance

The inheritance pattern in which two different alleles for a trait are expressed unblended in the phenotype of heterozygous individuals

Multiple Allele Series

The inheritance pattern in which a gene has more than two alleles

Modifying Gene

Genes that can alter how certain other genes are expressed in the phenotype

Regulator Genes

Genes that can neither initiate or block the expression of other genes. They are responsible for changes that occurred in our bodies as we grow older

Incompletely Penetrant Genes

Genes whose effects does not normally occur unless certain environmental factors are present

Sex-Limited Genes

Genes that are inherited by both men and women that are normally only expressed the phenotypes of one of them

Sex-Controlled Genes

Genes that are expressed in both men and women but differently

Genome Imprinting

An inheritance pattern in which a gene will have a different effect depending on the gender of the parent from whom it is inherited

Pleiotropy

The inheritance pattern in which a single allele is responsible for a variety of traits

Stuttering Alleles Or Unstable Alleles

Defective alleles that have segments which are doubled in their transmission from generation to generation

Monozygotic Twins

Identical twins that are genetically the same

Human Genome Project

The international research effort design to discover all human genes and to determine their functions

Fertilization

When sex cells join

True Breeding

Producing offspring identical to itself

Trait

Specific characteristic

Gamete

Sex cell

Homologous

Corresponding chromosomes from each parent

Diploid

Contains two sets of homologous chromosomes

Haploid

Contains only one set of chromosomes

Meiosis

Sex cells, double division, reducing chromosomes to half

Heredity

The passing of traits from parents to their offspring

Segregation

The separation of paired alleles during meiosis so that members of each pair of alleles appear in different gametes

Test cross

First introduced by Gregor Mendel, involves the breeding of an individual with a phenotypically recessive individual, in order to determine the zygosity of the former by analyzing proportions of offspring phenotypes. Zygosity can either be heterozygous or homozygous.

Translation

The process in which ribosomes create proteins. Messenger RNA (mRNA)—produced by transcription from DNA—is decoded by a ribosome to produce a specific amino acid chain

Transcription

The process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). This takes place in the nucleus

Crossing-over

The exchange of genes between two chromosomes, resulting in non-identical chromatids that comprise the genetic material of gametes. This process occurs during Prophase I of Meiosis, just prior to chromosome alignment and splitting of the cell

Self-pollination

The pollination of a flower by pollen from the same flower or from another flower on the same plant

Cross-pollination

The transfer of pollen from the male reproductive organ of one plant to the female reproductive organ

Probability

The likelihood of an event to occur

Zygote

Egg and sperm combined

Applying Mendel's principles

Probability rules apply to genetics, and genetic problems are solved using Punnet Squares

Explain how DNA was discovered

In the early 1950s two scientists, Rosalind Franklin and Maurice Wilkins, studied DNA using x-rays. Franklin produced an x-ray photograph that allowed two other researchers, James Watson and Francis Crick to work out the 3D structure of DNA. The structure of DNA was found to be a double helix

Draw and label mitosis

Draw and label meiosis