Key Concepts in Genetics and Meiosis

Diploid

A cell containing two complete sets of chromosomes- one from each parent.

Haploid

A cell containing only a single set of chromosomes.

Meiosis

A form of cell division where the daughter cells receive HALF the DNA of the parent cell (makes haploid gametes).

Cross over

Process in which two homologous chromosomes transfer/exchange DNA during meiosis (results in recombinant chromosomes).

Homologous chromosomes

Chromosomes that are: -About the same size -Have the same type of genes in the same location (One inherited from the biological mother, the other inherited from the biological father).

Gamete

Reproductive cells of animals or plants.

Nondisjunction

An error in meiosis in which chromosomes fail to separate properly. Can occur in Meiosis I (homologous chromosomes fail to separate) OR Meiosis II (sister chromatids fail to separate).

Genome

A full set of genetic information that an organism carries in its DNA.

Fertilization

When the egg and sperm cell fuse to form a zygote.

Genetics

The study of biological inheritance (how traits are passed from one generation to the next, and the variation in these traits).

Gene

A sequence of DNA → codes for a protein → determines a trait. Passed from parent to offspring. Found on chromosomes.

Allele

One or more versions of a gene that control the same characteristic.

Independent assortment

Genes for different traits segregate independently during formation of gametes.

Segregation

A parent can only pass one allele for each trait to its offspring.

Punnett Square

A way of showing what gene combinations could result from a genetic cross.

Principle of dominance

Alleles can be dominant or recessive. -Dominant = Version of the trait that is always visible in offspring. Can mask (hide) the presence of a recessive allele. -Recessive = The non-dominant allele. Trait will be HIDDEN in the presence of a dominant allele.

Homozygous

Two identical alleles for a particular trait.

Heterozygous

Two different alleles for a particular trait.

Phenotype

Your physical traits (what we "see").

Genotype

Your genetic makeup (the alleles) in our DNA.

Incomplete dominance

One allele is not completely dominant over another.

Codominance

BOTH alleles contribute to the phenotype.

Polygenic trait

Trait controlled by two or more genes.

Sex chromosome

Chromosomes that determine an individual's biological sex.

Autosome

The remaining 44 human chromosomes.

Sex-linked gene

A gene located on a sex chromosome.

Karyotype

Pictures of an individual's complete set of chromosomes.

Pedigree

A chart that shows the presence/absence of a trait within a family across several generations.