GENETICS SPEEDRUN

What is a gene?

A DNA sequence that codes for a protein or RNA molecule.

What is an allele?

A variant form of a gene.

What is a locus?

The position of a gene on a chromosome.

What is genotype?

An organism’s genetic makeup.

What is phenotype?

The observable traits of an organism.

What is dominance?

An allele that is expressed in a heterozygote.

What is recessiveness?

An allele expressed only in a homozygote.

What is codominance?

When both alleles in a heterozygote are fully expressed.

What are multiple alleles?

More than two possible alleles for a gene in a population.

What does Mendel’s Law of Segregation state?

Alleles separate during gamete formation.

What does Mendel’s Law of Independent Assortment state?

Alleles of different genes assort independently if unlinked.

What is a monohybrid cross phenotypic ratio for Aa × Aa?

3:1 phenotype, 1:2:1 genotype.

What is the phenotypic ratio for a dihybrid cross (RrTt × RrTt) with independent assortment?

9:3:3:1.

What is the purpose of a test cross?

To determine an unknown genotype by crossing with a homozygous recessive.

How is X-linked recessive inheritance recognised in pedigrees?

Mostly males affected, skips generations.

How is X-linked dominant inheritance recognised?

Affected males pass trait to all daughters, no sons.

How to calculate frequency of affected females in X-linked recessive?

Female freq = (male freq)².

If male freq of an X-linked recessive is 0.10, what is female freq?

0.01 (1%).

What is the rule for probability problems in genetics?

Multiply probabilities for independent events.

In the dog coat colour hierarchy As > ay > at, what genotype produces sandy coat?

ayay or ayat.

What does recombination frequency (RF) measure?

Genetic distance between linked genes in map units.

Formula for recombination frequency.

(RF) = (Number of recombinants ÷ Total offspring) × 100.

What does RF < 50% indicate?

Genes are linked.

What does RF ≈ 50% indicate?

Independent assortment.

What is p in Hardy–Weinberg?

Frequency of dominant allele.

What is q in Hardy–Weinberg?

Frequency of recessive allele.

What is p + q equal to?

1.

What is p² in Hardy–Weinberg?

Frequency of homozygous dominant genotype.

What is 2pq in Hardy–Weinberg?

Frequency of heterozygous genotype.

What is q² in Hardy–Weinberg?

Frequency of homozygous recessive genotype.

If q² = 0.04, what is p?

q = 0.2, p = 0.8.

How to calculate p(M) allele frequency from MM, MN, NN counts?

p(M) = [2×MM + MN] / (2×total).

How to calculate p(N) allele frequency from MM, MN, NN counts?

p(N) = [2×NN + MN] / (2×total).

What is the gene pool?

Total number of all alleles for a given gene in a population.

How to find total alleles in a population?

Population size × 2.

What is the key to solving multiple allele problems?

Follow the given dominance hierarchy exactly.

What’s the first step in pedigree analysis?

Identify inheritance pattern before calculating probabilities.

List common exam traps in genetics.

Mixing male/female X-linked probabilities, forgetting to square for females, assuming genes are unlinked without checking RF.