BIOL 3452 Principles of Genetics - Mendel's Principles Vocabulary Flashcards (Video Notes)

Vocabulary-style flashcards covering Mendelian genetics concepts and related terms from the lecture notes.

Gene

A region of DNA that encodes a protein or RNA; the basic unit of heredity.

Allele

An alternative form of a single gene.

Genotype

The set of alleles that an individual has for a given trait (e.g., YY, Yy, yy).

Phenotype

The observable trait or characteristic (e.g., yellow or green seeds).

Homozygote

An organism with two identical alleles for a trait (YY or yy).

Heterozygote

An organism with two different alleles for a trait (Yy).

Dominant allele

An allele whose trait is expressed in the phenotype when present; often functional.

Recessive allele

An allele whose trait is expressed only when two copies are present; may be nonfunctional.

Pure-breeding lines

Lines that produce offspring with the same trait generation after generation; used for crosses.

Monohybrid cross

Cross between pure-breeding lines differing in one trait; reveals segregation of alleles.

Dihybrid cross

Cross between individuals heterozygous for two genes (e.g., YyRr) to test independent assortment.

Reciprocal cross

Crosses with the parental sexes reversed to test inheritance patterns.

Testcross

Cross with a homozygous recessive to reveal the unknown genotype of the other parent.

Punnett square

A grid used to visualize segregation and random union of alleles.

Law of Segregation

Alleles separate during gamete formation; fertilization is random.

Law of Independent Assortment

Genes on different chromosomes assort independently; yields expected dihybrid ratios like 9:3:3:1.

Product rule

Probability of two independent events occurring together equals the product of their probabilities.

Sum rule

Probability of either of two mutually exclusive events equals the sum of their probabilities.

Phenotypic ratio 3:1

In the F2 generation of a monohybrid cross, about 3 dominant-phenotype to 1 recessive-phenotype.

Genotypic ratio 1:2:1

In the F2 generation of a monohybrid cross, genotypes appear as 1:2:1 (YY:Yy:yy).

Multihybrid cross

Cross involving more than two genes; number of possible gametes is 2^n.

Artificial selection

Humans direct mating to enhance desirable traits through selective breeding.

Homunculus

A discredited theory that offspring traits are contributed by a miniature organism in sperm.

Blended inheritance

A discredited idea that parental traits blend permanently in offspring.

Huntington disease

A dominant human genetic disease causing progressive neurodegeneration.

Cystic fibrosis

A recessive genetic disease caused by CFTR mutation, leading to thick mucus and organ impairment.

CFTR

A protein that regulates chloride ion transport across membranes; mutated in CF.

Pedigree

A family tree diagram used to analyze inheritance patterns (dominant or recessive) in humans.

Incomplete dominance

A form of inheritance where alleles are not fully dominant or recessive, resulting in a heterozygous phenotype that is an intermediate blend of the homozygous phenotypes (e.g., a red flower and a white flower produce pink offspring).

Codominance

A form of inheritance where both alleles are expressed equally and distinctly in the phenotype of a heterozygote (e.g., human ABO blood groups, where A and B alleles are codominant).

Multiple alleles

When a gene has more than two alleles present in a population (e.g., ABO blood group system has three alleles: I^A, I^B, and i).

Polygenic inheritance

When a single trait is controlled by two or more genes, often resulting in a continuous range of phenotypes (e.g., human height or skin color).

Epistasis

When the expression of one gene is affected by another gene (e.g., a gene for pigment production might be epistatic to a gene for pigment color).

Linked genes

Genes located on the same chromosome that tend to be inherited together because they are physically close to each other. They do not assort independently.

Sex-linked inheritance

The inheritance of traits determined by genes located on the sex chromosomes (X or Y), often leading to different inheritance patterns in males and females (e.g., colorblindness, hemophilia).

Carrier

An individual who is heterozygous for a recessive allele and does not express the trait but can pass it on to offspring.