Genetics Notes Review

This set of flashcards covers key genetic terms and definitions based on the lecture notes on foundational genetics concepts.

Gregor Mendel

Founder of modern genetics who studied the inheritance of traits in pea plants.

Allele

A version of a gene that can cause different traits, such as yellow or green peas.

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

Dominant allele

An allele that is expressed when two different alleles are present.

Recessive allele

An allele that is expressed only when two copies are present.

Gene

A section of DNA that provides instructions for making proteins.

Trait

A physical or behavioral characteristic influenced by genes.

Law of Segregation

During gamete formation, allele pairs separate so that a sperm or egg carries only one allele for each trait.

Punnett Square

A diagram that shows the possible genotypes of offspring from a genetic cross.

Dihybrid Cross

A genetic cross that examines two traits at once, resulting in a 9:3:3:1 phenotypic ratio.

Monohybrid Cross

A genetic cross that examines the inheritance of a single trait.

Test Cross

A method to determine the genotype of an organism exhibiting a dominant trait by crossing it with a homozygous recessive.

Probability

The likelihood that an event will occur, used in genetics to predict inheritance outcomes.

Independent assortment

The principle stating that allele pairs segregate independently during gamete formation.

Chromatin

Loose, messy DNA in the nucleus, existing when the cell isn’t dividing.

Chromosome

Neatly packed DNA that forms thick, X-shaped structures before cell division.

Sister chromatids

Identical halves of a duplicated chromosome, connected in the middle.

Homologous chromosomes

A pair of chromosomes that are the same size and shape, containing the same types of genes.

Genotype

The genetic constitution of an organism, represented by letters (e.g., YY, Yy, yy).

Phenotype

The observable physical traits of an organism, influenced by genotype.

Non-Mendelian Genetics

Patterns of inheritance that do not follow Mendel's simple rules of dominant and recessive traits.

Incomplete Dominance

Neither allele is fully dominant; traits blend together.

Codominance

Both alleles are equally expressed in the phenotype.

Genetic Linkage

Genes that are located on the same chromosome and tend to be inherited together.

Multiple Alleles

More than two allele options for a gene, such as the ABO blood group.

Polygenic Inheritance

Many genes control one trait, leading to a range of phenotypes.

Sex-Linked Traits

Traits that are associated with genes located on the sex chromosomes, typically on the X chromosomes.

Crossing Over

The exchange of segments of DNA between homologous chromosomes during meiosis, contributing to genetic variation.

Crossover Frequencies

The frequency at which crossover events happen, measured in percentages to create genetic maps.

Nondisjunction

The failure of chromosomes to separate properly during meiosis, leading to disorders like trisomy and monosomy.

Trisomy 21

A condition where an individual has three copies of chromosome 21, also known as Down's Syndrome.

Klinefelter's Syndrome

A genetic condition in males characterized by one extra X chromosome (XXY).

Turner's Syndrome

A genetic condition in females where one of the X chromosomes is missing or partially missing (X0).

Karyotype

A laboratory technique that produces an image of an individual's complete set of chromosomes, used to identify chromosomal abnormalities.

X chromosome inactivation

The process by which one of the two X chromosomes in females is randomly silenced, preventing the dosage imbalance of X-linked genes.