CAIE IGCSE Biology 17 Inheritance Questions

Review DNA, genes, protein synthesis, mitosis, meiosis and monohybrid inheritance through diagrams, crosses and data.

Covered syllabus points

17.1 Chromosomes, genes and proteins 17.2 Mitosis 17.3 Meiosis 17.4 Monohybrid inheritance

[Maximum number: 6]

(a)

A scientist investigated sexual reproduction in flowering plants.

Fig. 2.1 shows the procedure for crossing two plants of the same species.

The scientist collected the seeds and germinated them. The leaves and flowers of the offspring plants showed phenotypic variation as they were not all identical to the parent plants.

The scientist then investigated the chromosomes of all the offspring plants and found that they had exactly the same number of chromosomes as the parent plants.

[ 2 ]

(i)

Define the term chromosome.

[ 2 ]

(b)

The plant Camellia japonica has flowers that can be white, red or a mixture of these two colours. When red-flowered plants are crossed with white-flowered plants, all the offspring plants have flowers with petals that are a mixture of red and white, as shown in Fig. 2.2.

Fig. 2.2

- The gene for petal colour in C. japonica is given the symbol P.
- The allele for white petals is given the symbol $\mathbf{P W}^{\mathbf{W}}$ .
- The allele for red petals is given the symbol $\mathbf{P R}^{\mathbf{R}}$ .

[ 4 ]

(i)

Table 2.1 shows the phenotypes of three different pairs of parent plants.

Complete Table 2.1 by giving all the possible genotypes of the offspring plants that could be produced by these parent plants.
.

Table 2.1

[ 3 ]

phenotype of male parent	phenotype of female parent	all the possible genotypes of offspring plants produced by this cross
red petals	red petals	PRPR;
white petals	red petals	PRPW;
petals that are both red and white	petals that are both red and white	$\mathrm{P}^{\mathrm{R}} \mathrm{P}^{\mathrm{R}}, \mathrm{P}^{\mathrm{R}} \mathrm{P}^{\mathrm{W}}, \mathrm{P}^{\mathrm{W}} \mathrm{P}^{\mathrm{W}}$ ;

(ii)

State the type of inheritance that is shown by petal colour in C. japonica.

[ 1 ]

[Maximum number: 1]

The graph shows how the mass of DNA per cell changes before, during and after a nuclear division in a diploid cell.

Figure for Question 2 — CAIE IGCSE Biology

Which row describes the type of nuclear division and the chromosome number of the daughter cells shown in the graph?

type of nuclear
division

chromosome
number of
daughter cells
produced

meiosis

diploid

meiosis

haploid

mitosis

diploid

mitosis

haploid

[Maximum number: 1]

Which statement about meiosis is correct?

Meiosis produces diploid cells.

Meiosis produces genetically identical cells.

Meiosis produces gametes.

Meiosis produces cells for growth of tissues.

[Maximum number: 7]

Colour blindness is a characteristic that is inherited. Colour blindness is more common in males than in females.

Fig. 6.1 is a pedigree diagram showing the inheritance of colour blindness in a family.

Fig. 6.1

(a)

Define the term inheritance.

[ 1 ]

(b)

Using the symbols B and b, state the genotypes of individual 5 and individual 8 in the pedigree diagram.

5

8

[ 3 ]

1 correct use of X and Y in responses for individual 5 and individual 8 ;
2 correct X allele given for individual 5: $\mathbf{X}^{\mathbf{b}} \mathbf{Y} / \mathbf{b}$ ;
3 correct X allele given for individual 8: $\mathrm{X}^{\mathrm{B}} \mathrm{Y}$ / B ;

(c)

Individual 3 is a carrier of colour blindness because she has one copy of the allele for colour blindness but has normal colour vision.

Describe the evidence from Fig. 6.1 that shows that individual 3 is a carrier.

[ 3 ]

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