Biology Flashcards: Use Probability For Trait Frequency

What this deck covers

This deck focuses on Use Probability For Trait Frequency, giving you a quick way to review the definitions, rules, and examples that matter most for Biology.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Which Hardy–Weinberg term corresponds to the expected frequency of homozygous recessive $aa$?

Answer: $q^2$. Probability of inheriting $a$ from both parents is $q \times q$.

Flashcard 2: What condition describes Hardy–Weinberg equilibrium in terms of allele frequencies?

Answer: Allele frequencies remain constant across generations. No evolutionary forces acting means stable frequencies.

Flashcard 3: Which assumption of Hardy–Weinberg is violated when individuals choose mates by phenotype?

Answer: Random mating. Mate choice by traits creates non-random breeding patterns.

Flashcard 4: Which assumption of Hardy–Weinberg is violated when many individuals enter or leave a population?

Answer: No migration (no gene flow). Movement changes local allele frequencies through mixing.

Flashcard 5: Which assumption of Hardy–Weinberg is violated when alleles change due to copying errors?

Answer: No mutation. New alleles arise spontaneously, changing frequencies.

Flashcard 6: Which assumption of Hardy–Weinberg is violated when survival differs by genotype?

Answer: No natural selection. Differential survival/reproduction changes allele frequencies.

Flashcard 7: Which assumption of Hardy–Weinberg is violated when population size is very small?

Answer: Infinitely large population (no genetic drift). Small populations experience random sampling effects.

Flashcard 8: Identify the allele frequency $q$ if $f(AA)=0.36$, $f(Aa)=0.48$, and $f(aa)=0.16$.

Answer: $0.40$. $q = 1 - p = 1 - 0.60 = 0.40$

Flashcard 9: Identify the expected genotype frequencies if $p=0.50$ and $q=0.50$ in Hardy–Weinberg.

Answer: $p^2=0.25$, $2pq=0.50$, $q^2=0.25$. Equal allele frequencies produce maximum heterozygosity.

Flashcard 10: What is meant by microevolution?

Answer: Change in allele frequencies within a population over time. Evolution within populations, not between species.

Flashcard 11: Identify the expected $AA$ genotype frequency if $p=0.70$ in Hardy–Weinberg.

Answer: $p^2 = 0.49$. Calculate $p^2 = (0.70)^2 = 0.49$

Flashcard 12: What is natural selection in terms of trait frequency?

Answer: Nonrandom change in trait frequency due to differential fitness. Favorable traits increase, unfavorable traits decrease.

Flashcard 13: Which Hardy–Weinberg term corresponds to the expected frequency of heterozygotes $Aa$?

Answer: $2pq$. Two ways to get $Aa$: $A$ from mom, $a$ from dad or vice versa.

Flashcard 14: What is mutation as a source of variation?

Answer: Random DNA change that creates new alleles. Introduces novel alleles into the gene pool.

Flashcard 15: What is selection pressure?

Answer: Environmental factor that affects survival or reproduction. External conditions that determine survival and reproduction.

Flashcard 16: What is meant by microevolution?

Answer: Change in allele frequencies within a population over time. Evolution within populations, not between species.

Flashcard 17: Identify the probability of an offspring being $aa$ from parents $Aa \times Aa$.

Answer: $\frac{1}{4}$. Punnett square shows $aa$ outcome in 1 of 4 boxes.

Flashcard 18: What equation must allele frequencies satisfy for a two-allele gene?

Answer: $p + q = 1$. All alleles must sum to 100% of the gene pool.

Flashcard 19: What is the formula for allele frequency $q$ of allele $a$ using genotype frequencies?

Answer: $q = f(aa) + \frac{1}{2}f(Aa)$. Homozygotes contribute 1 copy, heterozygotes contribute 0.5.

Flashcard 20: What is the formula for allele frequency $p$ of allele $A$ using genotype frequencies?

Answer: $p = f(AA) + \frac{1}{2}f(Aa)$. Homozygotes contribute 1 copy, heterozygotes contribute 0.5.

Flashcard 21: What is the definition of phenotype frequency in a population?

Answer: Proportion of individuals showing a specific trait (phenotype). Observed by counting individuals displaying each trait.

Flashcard 22: What is the definition of genotype frequency in a population?

Answer: Proportion of individuals with a specific genotype. Measured by counting individuals with each genotype.

Flashcard 23: Identify the most likely outcome if selection strongly favors allele $A$ over many generations.

Answer: Allele $A$ increases in frequency; $a$ decreases. Consistent selection pressure drives directional change.

Flashcard 24: Which Hardy–Weinberg term corresponds to the expected frequency of homozygous dominant $AA$?

Answer: $p^2$. Probability of inheriting $A$ from both parents is $p \times p$.

Flashcard 25: What is the probability of showing a recessive phenotype from parents $Aa \times Aa$?

Answer: $\frac{1}{4}$. Recessive phenotype requires $aa$ genotype ($q^2$).

Flashcard 26: Identify the allele frequency $p$ if $f(AA)=0.36$, $f(Aa)=0.48$, and $f(aa)=0.16$.

Answer: $0.60$. $p = f(AA) + \frac{1}{2}f(Aa) = 0.36 + 0.24 = 0.60$

Flashcard 27: Identify $q$ if the recessive genotype frequency is $q^2 = 0.09$ in Hardy–Weinberg.

Answer: $q = 0.30$. Take square root of $q^2$: $\sqrt{0.09} = 0.30$

Flashcard 28: Identify $p$ if $q = 0.30$ for a two-allele Hardy–Weinberg population.

Answer: $p = 0.70$. Since $p + q = 1$: $p = 1 - 0.30 = 0.70$

Flashcard 29: Identify the expected heterozygote frequency if $p=0.70$ and $q=0.30$.

Answer: $2pq = 0.42$. Calculate $2 \times 0.70 \times 0.30 = 0.42$

Flashcard 30: Identify the expected $AA$ genotype frequency if $p=0.70$ in Hardy–Weinberg.

Answer: $p^2 = 0.49$. Calculate $p^2 = (0.70)^2 = 0.49$