Home / iGCSE Biology (0610)-17.1 Chromosomes, genes and proteins – iGCSE Style Questions Paper 1

iGCSE Biology (0610)-17.1 Chromosomes, genes and proteins – iGCSE Style Questions Paper 1

IGCSE Biology (0610) Practice Questions Paper 1 - All Chapters

Question

An individual has the genotype $Bb$.

What is the correct description of this genotype?

(A) heterozygous, with two different alleles of the same gene
(B) heterozygous, with two different genes of the same allele
(C) homozygous, with two different alleles of the same gene
(D) homozygous, with two different genes of the same allele
▶️ Answer/Explanation
The genotype $Bb$ consists of two different versions of a single gene, known as alleles (one dominant $B$ and one recessive $b$). When an organism has two different alleles for a specific trait, it is described as heterozygous. In contrast, homozygous would mean having two identical alleles, such as $BB$ or $bb$. Options B and D are technically incorrect because “alleles” are versions of a gene, not the other way around. Therefore, the description in option A perfectly matches the biological definition of a heterozygous state.
✅ Answer: (A)

Question

Which statement describes inheritance?

(A) organisms which are not pure-breeding
(B) the difference between homozygous and heterozygous genotypes
(C) the genetic information in dominant alleles
(D) the transmission of genetic information from generation to generation
▶️ Answer/Explanation

Inheritance is defined as the process by which genetic information is passed on from parents to their offspring. This biological mechanism ensures that traits and characteristics are carried forward through successive generations via DNA. While terms like “homozygous” or “dominant alleles” describe specific states or types of genetic data, they do not define the overarching process of transfer itself. Option (D) accurately captures this fundamental concept of biological continuity.

✅ Answer: (D)

Question

What happens to the lining of the human uterus in the days before the release of an egg cell?
A   It breaks down.
B   It is lost from the body.
C   It thickens.
D   It thins.
▶️ Answer/Explanation
Detailed solution

The correct answer is C.

Explanation:

Before the release of an egg (ovulation), the body enters the proliferative phase of the menstrual cycle. Increased levels of the hormone estrogen cause the uterine lining, or endometrium, to repair and grow. This process involves the development of new blood vessels and tissues, causing the lining to thicken. This preparation ensures that the uterus is ready to support the implantation of a fertilized egg. Consequently, options A and B describe menstruation, while C correctly identifies the pre-ovulatory growth.

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