Home / iGCSE Biology (0610)-17.2 Mitosis – iGCSE Style Questions Paper 4

iGCSE Biology (0610)-17.2 Mitosis – iGCSE Style Questions Paper 4

IGCSE Biology (0610) Practice Questions Paper 4 - All Chapters
Question

Mitosis and meiosis are both important processes for life.
(a) Complete the sentences about mitosis and meiosis.
Mitosis is a type of nuclear division which produces genetically identical cells.
It is important for growth, ……………………………………. of tissues and
……………………………………. reproduction.
Just before mitosis the chromosomes are replicated and then the chromosomes
……………………………………. so that the chromosome number is maintained in each daughter cell.
Meiosis is another type of nuclear division that is involved in the production of gametes. The chromosome number is halved from ……………………………………. to haploid resulting in genetically different cells. The fusion of the nuclei of two gametes formed by meiosis forms a ……………………………………. . This process is known as ……………………………………. .
(b) Mutations are a source of genetic variation in a population.
(i) Describe what is meant by a gene mutation.
(ii) State two examples of how mutation rates can be increased.

▶️ Answer/Explanation
Solution

(a)

  • Mitosis is important for growth, repair of tissues and asexual reproduction.
  • Chromosomes separate to maintain the diploid number in daughter cells.
  • Meiosis halves the chromosome number from diploid to haploid.
  • Fusion of gametes forms a zygote, a process called fertilisation.

Explanation: Mitosis ensures genetic consistency for growth and repair, while meiosis introduces variation via haploid gametes. Fertilisation restores diploidy, combining genetic material from two parents.

(b)(i) A gene mutation is a random change in the base sequence of DNA.

Explanation: Mutations alter the genetic code, potentially affecting protein synthesis. They can be neutral, beneficial, or harmful, driving evolutionary variation.

(b)(ii) Two examples:

  • Ionising radiation (e.g., X-rays, UV light)
  • Chemicals (e.g., mustard gas, benzene)

Explanation: Mutagens like radiation and chemicals increase mutation rates by damaging DNA or interfering with replication.

Question

(a) Mitosis is a type of nuclear division.
Fig. 5.1 is a series of photomicrographs showing a cell dividing by mitosis.

(i) State the change that has occurred to the mass of DNA immediately before mitosis in
Fig. 5.1.
(ii) Estimate the time when the chromosomes shown in Fig. 5.1 begin to separate.
(b) Meiosis is another type of nuclear division.
Describe how the nuclei in cells produced by meiosis differ from the nuclei in cells produced
by mitosis.
(c) Stem cells divide by mitosis during the growth of an embryo.
Describe the role of stem cells in the growth of an embryo.
(d) An embryo develops into a fetus.
Outline the processes of labour and birth.

Answer/Explanation

Answer:

(a)
(i) doubles ;
(ii) 34–39 minutes ;

(b) are genetically different (from each other and the parent cells) ;
(produce) haploid (nuclei) ;
ref. to reduction division / chromosome number being halved ;

(c) ref. to unspecialised cells ;
that can become specialised ;
ref. to expression of genes in specialised cells ;
AVP ; e.g. continually divide

(d) breaking of the amniotic sac ;
amniotic fluid is released ;
contraction of (the muscles in the) uterus (wall) ;
dilation of the cervix ;
passage through the vagina ;
(tying and) cutting the umbilical cord ;
delivery of the afterbirth / placenta ;
AVP ;

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