BIOL2222 Genetics Lab: Key Vocabulary Flashcards

Vocabulary flashcards covering Mendelian genetics, maize genetics, and chi-square concepts from the lecture notes.

Mendel's Law of Segregation

During meiosis, homologous chromosomes separate so each gamete receives a single allele for each gene.

Mendel's Law of Independent Assortment

Genes on different chromosomes assort independently during gamete formation.

Punnett Square

A diagram used to predict offspring genotype and phenotype frequencies from parental genotypes.

Genotype

An organism's genetic makeup; the specific alleles it carries.

Phenotype

The observable traits or characteristics resulting from genotype and environment.

Allele

A variant form of a gene at a given locus.

Locus

The specific location of a gene on a chromosome; plural is loci.

Diploid

Cell or organism with two sets of chromosomes (2n).

Haploid

Cell with a single set of chromosomes (n).

Homologous Chromosomes

Chromosome pairs with the same genes at the same positions, one from each parent.

Homozygous

Two identical alleles for a gene (e.g., AA or aa).

Heterozygous

Two different alleles for a gene (e.g., Aa).

Dominant

The allele that masks the recessive allele in a heterozygote.

Recessive

The allele whose phenotype is masked in a heterozygote.

Epistasis

Gene interaction where one gene modifies or masks the phenotypic effect of a gene at a different locus.

Dominant Epistasis

A dominant allele of one gene masks the expression of alleles of another gene.

Recessive Epistasis

The recessive alleles of one gene mask the effects of alleles at another gene.

Complementary Genes

A set of genes (A, C, R) that must each have at least one dominant allele to produce pigment.

CI gene

A dominant epistatic gene that inhibits aleurone color production regardless of A, C, or Pr.

Aleurone

The pigmented middle layer of the corn kernel; color depends on gene interactions.

Endosperm

Triploid nutritive tissue inside the kernel; pigment can color it and it provides embryo nutrition.

Pericarp

Outer layer of the corn kernel; often colorless and not the source of kernel color.

A, C, R genes

Genes required for aleurone pigment production; need at least one dominant allele at each locus to produce pigment.

Pr gene

Locus controlling anthocyanin pigment color in the aleurone; Pr yields purple pigment when expressed.

Y gene

Gene controlling carotenoid pigment production in the endosperm; Y gives yellow pigment.

Su gene

Gene controlling starch type in the endosperm; Su yields starchy/smooth/opaque kernels; su yields sugary/wrinkled.

Monohybrid cross

Cross involving one gene; expected genotype ratio 1:2:1 and phenotype ratio 3:1.

Dihybrid cross

Cross involving two genes; independently assorting, often yields a 9:3:3:1 phenotype ratio.

P generation

Parental generation in a genetic cross; usually true-breeding for studied traits.

F1 generation

First filial generation; offspring of the P cross; often all heterozygous for studied traits.

F2 generation

Second filial generation; offspring from crossing F1 individuals; shows segregation.

Monoecious

Plant that produces both male and female flowers on the same plant (e.g., corn).

Gametes

Sex cells (sperm and egg) that are haploid and fuse to form a zygote.

Chi-square

Statistical test to compare observed vs. expected frequencies under a hypothesis.

Null hypothesis

Assumes observed differences are due to random chance.

Alternative hypothesis

Assumes observed differences reflect a real, non-random effect.

Degrees of freedom

In chi-square tests, df = number of categories minus 1.

Observed (O)

Actual counts obtained from experimental data.

Expected (E)

Counts expected under the hypothesized inheritance pattern.

Chi-square equation

X2 = sum[(O − E)2 / E] over all categories.

9:3:3:1 ratio

Classic phenotypic ratio for a dihybrid cross with independent assortment.

Genotype ratio 1:1:2:2:4:2:2:1:1

Genotype distribution for certain two-gene (dihybrid) crosses (example: R/r with Su/su).