Biology Flashcards: Use Probability For Inheritance Predictions

What this deck covers

This deck focuses on Use Probability For Inheritance Predictions, 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: What is $P(A_{bb})$ in the cross $AaBb \times AaBb$ with independent assortment?

Answer: $\frac{3}{16}$. Dominant for A, recessive for B in dihybrid cross.

Flashcard 2: What is $P(\text{all 3 children show dominant phenotype})$ if each has probability $\frac{3}{4}$?

Answer: $\left(\frac{3}{4}\right)^3=\frac{27}{64}$. Independent events multiply: $\left(\frac{3}{4}\right)^3$.

Flashcard 3: What is $P(\text{both children are } aa)$ if each child has $P(aa)=\frac{1}{4}$ and births are independent?

Answer: $\frac{1}{16}$. Independent events multiply: $\frac{1}{4} \times \frac{1}{4}$.

Flashcard 4: What is the probability rule that justifies multiplying probabilities across different genes in a dihybrid cross?

Answer: Independent assortment (treat events as independent). Genes on different chromosomes assort independently during meiosis.

Flashcard 5: What is the genotype ratio from a monohybrid cross $Aa \times Aa$?

Answer: $1AA:2Aa:1aa$. Classic Mendelian ratio from heterozygous parents.

Flashcard 6: What is $P(Aa)$ for the cross $Aa \times Aa$?

Answer: $\frac{1}{2}$. Heterozygous offspring from two heterozygous parents.

Flashcard 7: What is $P(AAbb)$ in the cross $AaBb \times AaBb$ (independent assortment)?

Answer: $\frac{1}{16}$. Homozygous dominant A, homozygous recessive b.

Flashcard 8: What is $P(\text{roan})$ for codominance in $C^RC^W \times C^RC^W$?

Answer: $\frac{1}{2}$. Heterozygotes express both red and white alleles simultaneously.

Flashcard 9: What is $P(\text{at least one } aa)$ in two children if each has $P(aa)=\frac{1}{4}$?

Answer: $1-\left(\frac{3}{4}\right)^2=\frac{7}{16}$. Use complement rule: 1 minus probability of no $aa$ children.

Flashcard 10: What is the probability an offspring receives allele $a$ from a homozygous recessive parent $aa$?

Answer: $1$. Homozygous parent only has one allele type.

Flashcard 11: What is the probability an offspring receives allele $A$ from a heterozygous parent $Aa$?

Answer: $\frac{1}{2}$. Equal probability of transmitting either allele.

Flashcard 12: What does the probability of an event represent in genetics problems?

Answer: The likelihood that a specific genotype or phenotype occurs. Probability quantifies the chance a genetic outcome will occur.

Flashcard 13: What is $P(\text{offspring has genotype } aaBb)$ in $AaBb \times AaBb$ (independent assortment)?

Answer: $\frac{1}{8}$. Homozygous recessive a, heterozygous B.

Flashcard 14: What is $P(\text{dominant phenotype})$ for $Aa \times Aa$ with complete dominance?

Answer: $\frac{3}{4}$. Both $AA$ and $Aa$ show dominant phenotype.

Flashcard 15: What is the genotype ratio from a monohybrid cross $Aa \times Aa$?

Answer: $1AA:2Aa:1aa$. Classic Mendelian ratio from heterozygous parents.

Flashcard 16: What is $P(\text{at least one recessive phenotype})$ in $Aa \times Aa$?

Answer: $\frac{1}{4}$. Recessive phenotype probability in monohybrid cross.

Flashcard 17: What is the genotype ratio for the ABO cross $I^Ai \times I^Bi$?

Answer: $\frac{1}{4}$ each: $I^AI^B$, $I^Ai$, $I^Bi$, $ii$. Each genotype appears in $\frac{1}{4}$ of offspring.

Flashcard 18: What is $P(\text{intermediate phenotype})$ for incomplete dominance in $Rr \times Rr$?

Answer: $\frac{1}{2}$. Heterozygotes ($Rr$) show the intermediate pink phenotype.

Flashcard 19: What is $P(Aa)$ for the cross $Aa \times Aa$?

Answer: $\frac{1}{2}$. Heterozygous offspring from two heterozygous parents.

Flashcard 20: What is $P(A_{bb})$ in the cross $AaBb \times AaBb$ with independent assortment?

Answer: $\frac{3}{16}$. Dominant for A, recessive for B in dihybrid cross.

Flashcard 21: What is the phenotype ratio for incomplete dominance in the cross $Rr \times Rr$?

Answer: $1$ red : $2$ pink : $1$ white. Heterozygotes show a blended intermediate phenotype.

Flashcard 22: What is $P(\text{exactly one } aa)$ in two children if each has $P(aa)=\frac{1}{4}$?

Answer: $2\times\frac{1}{4}\times\frac{3}{4}=\frac{3}{8}$. Binomial probability: one success, one failure, times 2 orders.

Flashcard 23: What is $P(\text{recessive phenotype})$ in the test cross $Aa \times aa$?

Answer: $\frac{1}{2}$. Half the offspring are recessive in test cross.

Flashcard 24: What is the complement rule for a genetic outcome that does not occur?

Answer: $P(\text{not }A)=1-P(A)$. The probability of not getting an outcome equals 1 minus its probability.

Flashcard 25: What is $P(\text{dominant phenotype})$ for $Aa \times Aa$ with complete dominance?

Answer: $\frac{3}{4}$. Both $AA$ and $Aa$ show dominant phenotype.

Flashcard 26: What is the addition rule for mutually exclusive genetic outcomes?

Answer: $P(A \text{ or } B)=P(A)+P(B)$. Mutually exclusive outcomes add their probabilities.

Flashcard 27: What is $P(aa)$ for the cross $Aa \times Aa$ with complete dominance?

Answer: $\frac{1}{4}$. Only $aa$ shows recessive phenotype in complete dominance.

Flashcard 28: What is $P(aa)$ for the cross $Aa \times Aa$ with complete dominance?

Answer: $\frac{1}{4}$. Only $aa$ shows recessive phenotype in complete dominance.

Flashcard 29: What does the probability of an event represent in genetics problems?

Answer: The likelihood that a specific genotype or phenotype occurs. Probability quantifies the chance a genetic outcome will occur.

Flashcard 30: What is $P(\text{roan})$ for codominance in $C^RC^W \times C^RC^W$?

Answer: $\frac{1}{2}$. Heterozygotes express both red and white alleles simultaneously.

Flashcard 31: What does "heterozygous" mean for a single gene with two alleles?

Answer: Two different alleles (for example, $Aa$). One dominant and one recessive allele at the same locus.

Flashcard 32: What is the multiplication rule for independent genetic events?

Answer: $P(A \text{ and } B)=P(A)\times P(B)$. Independent events multiply their individual probabilities.

Flashcard 33: What is the genotype ratio for the ABO cross $I^Ai \times I^Bi$?

Answer: $\frac{1}{4}$ each: $I^AI^B$, $I^Ai$, $I^Bi$, $ii$. Each genotype appears in $\frac{1}{4}$ of offspring.

Flashcard 34: What is $P(\text{recessive phenotype})$ for the cross $AA \times Aa$?

Answer: $0$. Homozygous dominant parent cannot produce recessive offspring.

Flashcard 35: What is $P(aabb)$ in the cross $AaBb \times AaBb$ with independent assortment?

Answer: $\frac{1}{16}$. Recessive phenotype for both traits in dihybrid cross.

Flashcard 36: What is $P(aa)$ for the cross $Aa \times aa$?

Answer: $\frac{1}{2}$. Half the offspring get recessive allele from homozygous parent.

Flashcard 37: What is $P(\text{not recessive phenotype})$ in $Aa \times Aa$ with complete dominance?

Answer: $\frac{3}{4}$. Complement of recessive phenotype probability.

Flashcard 38: What is $P(\text{dominant for both})$ using the product rule if $P(A_)=\frac{3}{4}$ and $P(B_)=\frac{3}{4}$?

Answer: $\frac{9}{16}$. Multiply independent probabilities: $\frac{3}{4} \times \frac{3}{4}$.

Flashcard 39: What is the expected phenotype ratio in a test cross $Aa \times aa$ (complete dominance)?

Answer: $1$ dominant : $1$ recessive. Equal probability of dominant and recessive phenotypes.

Flashcard 40: What is the classic dihybrid phenotype ratio from $AaBb \times AaBb$ (independent assortment)?

Answer: $9:3:3:1$. Standard ratio for two independent genes with complete dominance.

Flashcard 41: What is the probability an offspring receives allele $A$ from a heterozygous parent $Aa$?

Answer: $\frac{1}{2}$. Equal probability of transmitting either allele.

Flashcard 42: What is $P(\text{not recessive phenotype})$ in $Aa \times Aa$ with complete dominance?

Answer: $\frac{3}{4}$. Complement of recessive phenotype probability.

Flashcard 43: What is $P(\text{type AB})$ for the ABO cross $I^Ai \times I^Bi$?

Answer: $\frac{1}{4}$. Only $I^AI^B$ genotype produces type AB blood.

Flashcard 44: What is $P(Aa)$ for the cross $AA \times aa$?

Answer: $1$ (all offspring are $Aa$). Only possible genotype when crossing homozygous dominant with recessive.

Flashcard 45: What is $P(\text{offspring has genotype } Aabb)$ in $AaBb \times AaBb$ (independent assortment)?

Answer: $\frac{1}{8}$. Heterozygous A, homozygous recessive b.

Flashcard 46: What is the phenotype ratio for incomplete dominance in the cross $Rr \times Rr$?

Answer: $1$ red : $2$ pink : $1$ white. Heterozygotes show a blended intermediate phenotype.

Flashcard 47: What is $P(\text{all 3 children show dominant phenotype})$ if each has probability $\frac{3}{4}$?

Answer: $\left(\frac{3}{4}\right)^3=\frac{27}{64}$. Independent events multiply: $\left(\frac{3}{4}\right)^3$.

Flashcard 48: What is $P(\text{dominant for both})$ using the product rule if $P(A_)=\frac{3}{4}$ and $P(B_)=\frac{3}{4}$?

Answer: $\frac{9}{16}$. Multiply independent probabilities: $\frac{3}{4} \times \frac{3}{4}$.

Flashcard 49: What is $P(aaB_)$ in the cross $AaBb \times AaBb$ with independent assortment?

Answer: $\frac{3}{16}$. Recessive for A, dominant for B in dihybrid cross.

Flashcard 50: What does "homozygous recessive" mean for a single gene with two alleles?

Answer: Two recessive alleles (for example, $aa$). Two copies of the recessive allele at the same locus.

Flashcard 51: What is $P(\text{intermediate phenotype})$ for incomplete dominance in $Rr \times Rr$?

Answer: $\frac{1}{2}$. Heterozygotes ($Rr$) show the intermediate pink phenotype.

Flashcard 52: What is $P(\text{recessive phenotype})$ for the cross $AA \times Aa$?

Answer: $0$. Homozygous dominant parent cannot produce recessive offspring.

Flashcard 53: What is $P(\text{offspring is heterozygous at both loci } AaBb)$ in $AaBb \times AaBb$?

Answer: $\frac{1}{4}$. Heterozygous at both loci in dihybrid cross.

Flashcard 54: What is the phenotype ratio for codominance in the cross $C^RC^W \times C^RC^W$?

Answer: $1$ red : $2$ roan : $1$ white. Both alleles are expressed simultaneously in heterozygotes.

Flashcard 55: What is $P(\text{offspring has genotype } Aabb)$ in $AaBb \times AaBb$ (independent assortment)?

Answer: $\frac{1}{8}$. Heterozygous A, homozygous recessive b.

Flashcard 56: What is $P(\text{at least one } aa)$ in two children if each has $P(aa)=\frac{1}{4}$?

Answer: $1-\left(\frac{3}{4}\right)^2=\frac{7}{16}$. Use complement rule: 1 minus probability of no $aa$ children.

Flashcard 57: What is the probability of producing gamete $AB$ from genotype $AaBb$ (independent assortment)?

Answer: $\frac{1}{4}$. Each of four possible gamete types equally likely.

Flashcard 58: What is $P(\text{type O})$ for the ABO cross $I^Ai \times I^Bi$?

Answer: $\frac{1}{4}$. Only $ii$ genotype produces type O blood.

Flashcard 59: What is P(A_B_) in the cross $AaBb \times AaBb$ with independent assortment?

Answer: $\frac{9}{16}$. Dominant phenotype for both traits using independent assortment.

Flashcard 60: What does "homozygous recessive" mean for a single gene with two alleles?

Answer: Two recessive alleles (for example, $aa$). Two copies of the recessive allele at the same locus.

Flashcard 61: What is the multiplication rule for independent genetic events?

Answer: $P(A \text{ and } B)=P(A)\times P(B)$. Independent events multiply their individual probabilities.

Flashcard 62: What does "heterozygous" mean for a single gene with two alleles?

Answer: Two different alleles (for example, $Aa$). One dominant and one recessive allele at the same locus.

Flashcard 63: What is $P(\text{both children are } aa)$ if each child has $P(aa)=\frac{1}{4}$ and births are independent?

Answer: $\frac{1}{16}$. Independent events multiply: $\frac{1}{4} \times \frac{1}{4}$.

Flashcard 64: What is the complement rule for a genetic outcome that does not occur?

Answer: $P(\text{not }A)=1-P(A)$. The probability of not getting an outcome equals 1 minus its probability.

Flashcard 65: What is $P(aaB_)$ in the cross $AaBb \times AaBb$ with independent assortment?

Answer: $\frac{3}{16}$. Recessive for A, dominant for B in dihybrid cross.

Flashcard 66: What is $P(\text{dominant phenotype})$ in the test cross $Aa \times aa$?

Answer: $\frac{1}{2}$. Half the offspring show each phenotype in test cross.

Flashcard 67: What is the classic dihybrid phenotype ratio from $AaBb \times AaBb$ (independent assortment)?

Answer: $9:3:3:1$. Standard ratio for two independent genes with complete dominance.

Flashcard 68: What is the phenotype ratio for codominance in the cross $C^RC^W \times C^RC^W$?

Answer: $1$ red : $2$ roan : $1$ white. Both alleles are expressed simultaneously in heterozygotes.

Flashcard 69: What is the addition rule for mutually exclusive genetic outcomes?

Answer: $P(A \text{ or } B)=P(A)+P(B)$. Mutually exclusive outcomes add their probabilities.

Flashcard 70: What is a test cross used to determine in inheritance probability problems?

Answer: Whether a dominant-phenotype individual is heterozygous or homozygous. Reveals hidden genotype by crossing with homozygous recessive.

Flashcard 71: What is the expected phenotype ratio in a test cross $Aa \times aa$ (complete dominance)?

Answer: $1$ dominant : $1$ recessive. Equal probability of dominant and recessive phenotypes.

Flashcard 72: What is the phenotype ratio with complete dominance from $Aa \times Aa$?

Answer: $3$ dominant : $1$ recessive. Dominant allele masks recessive in heterozygotes.

Flashcard 73: What is $P(Aa)$ for the cross $Aa \times aa$?

Answer: $\frac{1}{2}$. Half heterozygous, half homozygous recessive offspring.

Flashcard 74: What is the probability an offspring receives allele $a$ from a homozygous recessive parent $aa$?

Answer: $1$. Homozygous parent only has one allele type.

Flashcard 75: What is the phenotype ratio with complete dominance from $Aa \times Aa$?

Answer: $3$ dominant : $1$ recessive. Dominant allele masks recessive in heterozygotes.

Flashcard 76: What is $P(\text{exactly one } aa)$ in two children if each has $P(aa)=\frac{1}{4}$?

Answer: $2\times\frac{1}{4}\times\frac{3}{4}=\frac{3}{8}$. Binomial probability: one success, one failure, times 2 orders.

Flashcard 77: What is the probability rule that justifies multiplying probabilities across different genes in a dihybrid cross?

Answer: Independent assortment (treat events as independent). Genes on different chromosomes assort independently during meiosis.