BIOTEST6 Heredity

Flashcards to the the heredity terms.

Gene

A segment of DNA on a chromosome that codes for a specific trait.

Allele

One of a number of different forms of a gene.

Dominant

Describes a trait that covers over, or dominates, another form of that trait.

Recessive

An allele that is hidden when a dominant allele is present.

Phenotype

Physical characteristics of an organism.

Genotype

An organism's genetic makeup, or allele combinations.

Multiple Alleles

Three or more forms of a gene that code for a single trait.

Incomplete Dominance

Situation in which one allele is not completely dominant over another allele, can make an intermediate color (e.g. red x white = pink).

Codominance

A condition in which neither of the two alleles of a gene is dominant or recessive, and both show up.

Test Cross

The crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype.

Homozygous

An organism that has two identical alleles for a trait.

Heterozygous

An organism that has two different alleles for a trait.

Dihybrid Cross

A cross between individuals that have different alleles for the same gene.

Carrier

A person whose genotype includes a gene that is not expressed in the phenotype, often used in context of disease.

Sex-linked Gene

Gene located on a sex chromosome (X or Y in humans).

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family. Recessive ones often skip generations.

Polygenic Inheritance

Occurs when multiple genes determine the phenotype of a trait. Can make the characteristic seem evenly distributed (e.g., height).

Sex Chromosomes

Chromosomes that determine the sex of an individual (in humans, X and Y).

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms.

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Kleinfelter's syndrome

Males with XXY sex chromosomes, caused by nondisjunction.

Down Syndrome (Trisomy 21)

Occurs when an individual has 3 chromosomes on the 21st pair instead of 2; caused by nondisjunction.

Somatic Cell

Diploid body cells - any cell of a living organism other than the reproductive cells.

Gametes

Haploid reproductive cells.

Diploid

An organism or cell having two sets of chromosomes.

Gene Therapy

A technique that places a gene into a cell, sometimes using viruses, to correct a hereditary disease.

Transgenic Organism

Organisms that contain recombinant DNA from a different organism (also called GMOs).

Plasmid

Small, circular piece of DNA located in the cytoplasm of many bacteria used in creating transgenic organisms.

Reproductive Cloning

Using a somatic cell from a multicellular organism to make one or more genetically identical individuals.

Duplication

Change to a chromosome in which part of the chromosome is repeated.

Inversion

Mutation in which a chromosome piece reattaches to the original chromosome but in reverse orientation.

Deletion

A change to a chromosome in which a fragment of the chromosome is removed.

Translocation

Change to a chromosome in which a fragment of one chromosome attaches to a non-homologous chromosome.

Aneuploidy

Abnormal number of chromosomes, usually due to non-disjunction.

Autosomes

Any chromosome that is not a sex chromosome.