Biology Flashcards: Use Probability For Trait Frequency

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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.

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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: 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 2: 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 3: 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 4: 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 5: 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 6: 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 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: 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 9: Which option best explains why drift is stronger in small populations than large ones?

Answer: Sampling error is larger when the number of breeders is small. Fewer breeding individuals means larger random variation.

Flashcard 10: 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 11: 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 12: 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 13: Which assumption of Hardy–Weinberg is violated when alleles change due to copying errors?

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

Flashcard 14: 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 15: Identify whether a population is evolving if $p$ changes from $0.40$ to $0.45$ in one generation.

Answer: Yes; a change in allele frequency indicates evolution. Any change in allele frequency indicates evolutionary forces.

Flashcard 16: What is the probability interpretation of $2pq$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen individual is heterozygous $Aa$. Probability of getting one $A$ and one $a$ allele.

Flashcard 17: 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 18: 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 19: 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 20: What is mutation as a source of variation?

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

Flashcard 21: What is the founder effect?

Answer: Genetic drift when a new population is started by few individuals. Small founding group may not represent original diversity.

Flashcard 22: 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 23: 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 24: 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 25: What is the probability interpretation of $p$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen allele from the gene pool is $A$. Represents sampling probability from the allele pool.

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: What is the Hardy–Weinberg genotype frequency equation?

Answer: $p^2 + 2pq + q^2 = 1$. Expansion of $(p + q)^2$ for random mating probabilities.

Flashcard 28: Identify the expected frequency of carriers $Aa$ if $q^2 = 0.01$ in Hardy–Weinberg.

Answer: $2pq = 0.18$. If $q^2 = 0.01$, then $q = 0.10$, $p = 0.90$, $2pq = 0.18$

Flashcard 29: What is the probability interpretation of $p^2$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen individual is $AA$. Independent probability of getting $A$ from both parents.

Flashcard 30: Identify $p$ if $q^2 = 0.16$ in Hardy–Weinberg equilibrium.

Answer: $p = 0.60$. If $q^2 = 0.16$, then $q = 0.40$, so $p = 0.60$

Flashcard 31: 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 32: 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 33: 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 34: 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 35: Identify whether allele frequency can change by chance alone in a small population.

Answer: Yes; genetic drift can change allele frequency by chance. Random sampling of gametes causes frequency fluctuations.

Flashcard 36: Identify the probability of an offspring being $Aa$ from parents $Aa \times Aa$.

Answer: $\frac{1}{2}$. Punnett square shows $Aa$ outcome in 2 of 4 boxes.

Flashcard 37: What is meant by microevolution?

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

Flashcard 38: 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 39: Which assumption of Hardy–Weinberg is violated when alleles change due to copying errors?

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

Flashcard 40: Which assumption of Hardy–Weinberg is violated when survival differs by genotype?

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

Flashcard 41: Which option best describes how gene flow usually affects differences between populations?

Answer: It reduces differences by making allele frequencies more similar. Migration homogenizes allele frequencies across populations.

Flashcard 42: What is the probability interpretation of $p^2$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen individual is $AA$. Independent probability of getting $A$ from both parents.

Flashcard 43: 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 44: What is directional selection?

Answer: Selection favoring one extreme phenotype, shifting the mean. Population mean moves toward the favored extreme.

Flashcard 45: What is the probability interpretation of $q^2$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen individual is $aa$. Independent probability of getting $a$ from both parents.

Flashcard 46: 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 47: 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 48: What is gene flow?

Answer: Movement of alleles between populations via migration and breeding. Immigration and emigration transfer alleles between populations.

Flashcard 49: What is selection pressure?

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

Flashcard 50: What is the Hardy–Weinberg genotype frequency equation?

Answer: $p^2 + 2pq + q^2 = 1$. Expansion of $(p + q)^2$ for random mating probabilities.

Flashcard 51: What is stabilizing selection?

Answer: Selection favoring intermediate phenotypes, reducing variation. Extreme variants are eliminated, average is favored.

Flashcard 52: 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 53: 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 54: Identify $p$ if $q^2 = 0.16$ in Hardy–Weinberg equilibrium.

Answer: $p = 0.60$. If $q^2 = 0.16$, then $q = 0.40$, so $p = 0.60$

Flashcard 55: 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 56: 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 57: 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 58: Which option best explains why drift is stronger in small populations than large ones?

Answer: Sampling error is larger when the number of breeders is small. Fewer breeding individuals means larger random variation.

Flashcard 59: What is selection pressure?

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

Flashcard 60: What is genetic drift?

Answer: Random change in allele frequencies due to chance events. Sampling error in small populations causes frequency fluctuations.

Flashcard 61: 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 62: What is the probability interpretation of $q^2$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen individual is $aa$. Independent probability of getting $a$ from both parents.

Flashcard 63: Which option best describes how gene flow usually affects differences between populations?

Answer: It reduces differences by making allele frequencies more similar. Migration homogenizes allele frequencies across populations.

Flashcard 64: Identify whether a population is evolving if $p$ changes from $0.40$ to $0.45$ in one generation.

Answer: Yes; a change in allele frequency indicates evolution. Any change in allele frequency indicates evolutionary forces.

Flashcard 65: What is meant by microevolution?

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

Flashcard 66: What is the bottleneck effect?

Answer: Genetic drift after a sharp population size reduction. Surviving individuals may not represent original diversity.

Flashcard 67: 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 68: What is fitness in evolutionary biology?

Answer: Relative reproductive success of a genotype or phenotype. Higher fitness means more offspring in next generation.

Flashcard 69: 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 70: What is mutation as a source of variation?

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

Flashcard 71: 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 72: 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 73: 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 74: Identify the probability of an offspring being $aa$ from parents $Aa \times aa$.

Answer: $\frac{1}{2}$. Test cross produces 50% heterozygous, 50% recessive.

Flashcard 75: Identify the expected $aa$ genotype frequency if $q=0.30$ in Hardy–Weinberg.

Answer: $q^2 = 0.09$. Calculate $q^2 = (0.30)^2 = 0.09$

Flashcard 76: 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 77: Identify the expected frequency of carriers $Aa$ if $q^2 = 0.01$ in Hardy–Weinberg.

Answer: $2pq = 0.18$. If $q^2 = 0.01$, then $q = 0.10$, $p = 0.90$, $2pq = 0.18$

Flashcard 78: 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 79: Identify the expected $aa$ genotype frequency if $q=0.30$ in Hardy–Weinberg.

Answer: $q^2 = 0.09$. Calculate $q^2 = (0.30)^2 = 0.09$

Flashcard 80: 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 81: What is the probability interpretation of $p$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen allele from the gene pool is $A$. Represents sampling probability from the allele pool.

Flashcard 82: Identify whether allele frequency can change by chance alone in a small population.

Answer: Yes; genetic drift can change allele frequency by chance. Random sampling of gametes causes frequency fluctuations.

Flashcard 83: Identify the probability of an offspring being $Aa$ from parents $AA \times aa$.

Answer: $1$. All offspring inherit $A$ from one parent, $a$ from other.

Flashcard 84: Which assumption of Hardy–Weinberg is violated when survival differs by genotype?

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

Flashcard 85: 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 86: 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 87: 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 88: 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 89: What is the probability interpretation of $2pq$ in Hardy–Weinberg equilibrium?

Answer: Probability a randomly chosen individual is heterozygous $Aa$. Probability of getting one $A$ and one $a$ allele.