Relate Genes to Trait Inheritance - Biology

$9:3:3:1$. Classic ratio for two independent traits with complete dominance.

$4$. Each heterozygous gene contributes two possible alleles to gametes.

$2^n$. Where $n$ is the number of heterozygous gene pairs.

$8$. Three heterozygous genes: $2^3 = 8$ different combinations.

Whether a dominant-phenotype individual is homozygous or heterozygous. Cross with homozygous recessive reveals the unknown genotype.

Homozygous recessive. The known genotype that reveals the unknown parent's genetics.

Heterozygous. Mixed offspring ratios indicate the parent has both allele types.

A trait controlled by a gene on the Y chromosome, passed father to son. Exclusively paternal inheritance through the male lineage only.

Genes close together on the same chromosome tend to be inherited together. Physical proximity reduces crossing over frequency between genes.

Crossing over during meiosis. Recombination frequency depends on physical distance between linked genes.

A DNA segment that encodes a functional product affecting traits. The unit of heredity that codes for proteins or RNA molecules.

An alternative version of a gene at the same locus. Different forms of the same gene, like $A$ and $a$.

A gene’s specific physical location on a chromosome. Each gene occupies a specific position on its chromosome.

The allele combination an organism has for a gene. The genetic makeup, typically written as letter combinations like $AA$ or $Aa$.

The observable trait produced by genotype and environment. The physical expression of genes influenced by environmental factors.

It has two identical alleles at that locus. Both alleles are the same, either $AA$ or $aa$.

It has two different alleles at that locus. The alleles differ, written as $Aa$ or $Bb$.

An allele expressed in the heterozygous phenotype. Usually written in uppercase and masks recessive alleles.

An allele expressed only when homozygous. Usually written in lowercase and requires two copies for expression.

Allele pairs separate during gamete formation. Each gamete gets only one allele from each pair.

Alleles of different genes assort independently in gametes. Different traits are inherited separately if genes aren't linked.

Homozygous recessive (two recessive alleles). Recessive traits need both alleles to be recessive for expression.

A heterozygote with the recessive allele but no disease phenotype. Has one recessive allele but shows the dominant phenotype.

Expected offspring genotype and phenotype probabilities. A grid showing all possible offspring combinations from a cross.

Monohybrid cross. Focuses on inheritance of a single trait.

Dihybrid cross. Examines inheritance patterns of two separate traits simultaneously.

$3:1$ (dominant:recessive). Classic ratio when dominant allele masks recessive in heterozygotes.

$1:2:1$ ($AA:Aa:aa$). Shows the actual allele combinations in offspring.

$\frac{1}{2}$. Half the offspring inherit one allele from each parent.