Question 1:

The correct answer is D. 1 Red : 2 Pink : 1 White.

Explanation:
This is an example of incomplete dominance (neither allele is dominant).

• RR = Red

• WW = White

• RW = Pink

Cross between two pink flowers (RW × RW):

Genotypes:

• RR (Red) → 1

• RW (Pink) → 2

• WW (White) → 1

Phenotype ratio: 1 Red : 2 Pink : 1 White → Matches D.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 2:

The correct answer is B. The red and white alleles are codominant.

Explanation:
In the example given, crossing red (RR) with white (WW) produces pink offspring (RW). This is not simple dominance because neither allele masks the other — instead, both contribute to the phenotype, producing an intermediate trait. This is incomplete dominance, but the question says "neither allele is dominant to the other" and then lists "codominant" as an option.

In strict terms:

• Codominance – both alleles are expressed separately in heterozygotes (e.g., red and white patches).

• Incomplete dominance – heterozygous phenotype is a blend (e.g., pink).

However, many GCSE-style questions describe the situation as "codominant" when they mean neither is dominant and both affect the phenotype (even if the result is a blend). Given the options:

• A. Red allele is dominant to white – False; otherwise, RW would be red, not pink.

• B. Red and white alleles are codominant – Best match in the options, since the question states neither is dominant and the result is a mix.

• C. White allele is sex linked – No evidence; this is an autosomal trait.

• D. White allele is dominant to red – False; otherwise, RW would be white, not pink.

Thus, B is the intended best answer.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 3:

The correct answer is C. Three.

Explanation:
Human ABO blood groups are controlled by three different alleles:

• Iᴬ (produces A antigen)

• Iᴮ (produces B antigen)

• Iᴼ (produces no antigen)

These three alleles combine in pairs to produce the four blood types (A, B, AB, O).

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 4:

The correct answer is C. Iᴼ is recessive to both Iᴬ and Iᴮ.

Explanation:
In the ABO blood group system:

• Iᴬ and Iᴮ are codominant (both expressed when present together → blood group AB).

• Iᴼ is recessive to both Iᴬ and Iᴮ, meaning it is only expressed in the phenotype when two Iᴼ alleles are present (blood group O).

• If an Iᴼ allele is paired with Iᴬ, the person has blood group A (Iᴬ masks Iᴼ).

• If paired with Iᴮ, the person has blood group B (Iᴮ masks Iᴼ).

Checking the options:

• A. Iᴬ is dominant over Iᴮ – False; they are codominant.

• B. Iᴼ is dominant over Iᴬ – False; Iᴼ is recessive.

• C. Iᴼ is recessive to both Iᴬ and Iᴮ – True.

• D. Iᴮ is dominant over Iᴬ – False; they are codominant.

Thus, C is correct.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 5:

The correct answer is B. Woman: IᴬIᴼ, Man: IᴼIᴼ.

Explanation:

• The woman is heterozygous for blood group A → genotype IᴬIᴼ (since Iᴬ is dominant, she has blood group A, but carries Iᴼ as well).

• The husband has blood group O → genotype must be IᴼIᴼ (two recessive alleles; O is the only possibility).

Checking the options:

• A. Woman IᴬIᴬ, Man IᴼIᴼ – Woman is homozygous A, not heterozygous → incorrect.

• B. Woman IᴬIᴼ, Man IᴼIᴼ – Correct ✅.

• C. Woman IᴬIᴮ, Man IᴼIᴼ – Woman would be blood group AB (codominant), not A → incorrect.

• D. Woman IᴼIᴼ, Man IᴬIᴼ – Woman would be group O, man would be group A → incorrect.

Thus, B is correct.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 6:

We have:

• Woman: heterozygous blood group A → IᴬIᴼ

• Man: blood group O → IᴼIᴼ

• Child: blood group AB → genotype must be IᴬIᴮ

Step 1 – Can this child's genotype come from these parents?

Possible gametes from woman: Iᴬ or Iᴼ
Possible gametes from man: Iᴼ only

Possible offspring genotypes:

• Iᴬ from woman + Iᴼ from man → IᴬIᴼ (blood group A)

• Iᴼ from woman + Iᴼ from man → IᴼIᴼ (blood group O)

There is no way to get IᴬIᴮ (AB) from these parents, because the man cannot contribute Iᴮ (he only has Iᴼ).

Step 2 – Which statement cannot be true?

A. The boy’s genotype is IᴬIᴮ – This must be true for a child with blood group AB. This is factually correct for the child’s type, but does it conflict with parentage?

B. The woman is the child’s mother – Possible; she could be the mother (she could pass Iᴬ), but then the father must provide Iᴮ, which this man cannot. So not a conflict of fact — she could be mother if father is someone else.

C. The man is the child’s father – Impossible with blood group AB child, because the man has Iᴼ only. Therefore, this statement cannot be true.

D. The boy’s phenotype is blood group AB – This is a given fact (child is AB). This is true about the child, regardless of parentage.

The question asks: Which of the following statements cannot be true?
It means: given what we know, which statement is false or impossible?

• C is impossible because a man with blood group O cannot have a biological child with blood group AB.

✅ Correct answer: C

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 7:

Correct Answer: A. Carrier female with normal vision

Reasoning: Mary is represented by a circle (female) that is half-shaded. According to the legend, this symbol identifies a carrier of color blindness. Carriers of X-linked recessive traits generally have normal vision because they possess one functional dominant allele.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 8:

Correct Answer: A. She is red green colour blind

Reasoning:

B is true: Alison has a color-blind son. Since her husband is unaffected (XY), the son must have inherited the color-blind gene from Alison. Thus, she is a carrier (heterozygous).

C is true: Harry and Peter are her brothers, and both are shaded red (color blind).

D is true: Since her father (Roy) is unaffected, he could only give her a normal X chromosome. Therefore, her color-blind allele must have come from her mother, Mary.

A is false: As a carrier with one normal allele, Alison has normal vision, not color blindness.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 9:

Correct Answer: C. 50%

Reasoning:

• Alison's genotype: X^BX^b (Carrier)

• Partner's genotype: X^BY (Unaffected male)

• Daughters' possibilities: They will all receive an X^B from their father.

• From Alison, they have a 50% chance of receiving the normal allele (X^BX^B) and a 50% chance of receiving the color-blind allele (X^BX^b), making them carriers.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 10:

The correct answer is D. a rare random change in genetic material that can be inherited.

Explanation:
A mutation is a change in the DNA sequence. It is generally rare, occurs randomly, and can be inherited if it happens in the gametes (sex cells). Not all mutations are harmful — some are neutral or even beneficial. However, the definition in basic biology emphasizes that mutations are heritable changes in genetic material.

• A – Incorrect; mutations are not necessarily frequent.

• B – Incorrect; many mutations can be inherited if they occur in germ cells.

• C – Incorrect; not all mutations are harmful.

• D – Correct; matches the standard definition.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.