Reproduction Practice Questions

Potato plants can reproduce without producing flowers or seeds. A new potato plant grows from a tuber (a swollen underground stem) of the parent plant. The new plant is genetically identical to the parent.

DNA is a polymer made from units called nucleotides.

Figure 1 shows one nucleotide from a DNA molecule.

A student extracted DNA from a kiwi fruit using the method below.

• Step 1 Mash the peeled kiwi fruit in a beaker.
• Step 2 Add a solution containing detergent (washing-up liquid) and salt, and mix gently.
• Step 3 Filter the mixture into a test tube.
• Step 4 Slowly pour ice-cold ethanol down the side of the test tube so that it forms a layer on top of the filtrate.

A horse has a diploid chromosome number of 64. Gametes are produced in the ovaries and testes of horses by meiosis.

Proteins are made in two stages: transcription and translation.

Part of the coding DNA of a gene has the base sequence:

$T - A - C \quad G - G - A \quad C - T - T$

A short length of mRNA has the base sequence:

$A U G \quad G C U \quad U A U \quad C C G$

The table shows the amino acids coded for by some mRNA codons.

Codon	Amino acid
AUG	methionine
GCU	alanine
UAU	tyrosine
CCG	proline
CAG	glutamine

Gene P codes for a protein that makes the purple pigment in the flowers of a plant.

Three varieties of this plant have different versions of the non-coding DNA found in front of gene P. The table shows the results of an investigation into these three varieties.

Variety	Variant in the non-coding DNA in front of gene P	Relative amount of mRNA from gene P	Flower colour
A	none	100	deep purple
B	variant 1	45	pale purple
C	variant 2	5	white

The coding DNA of gene P is identical in all three varieties.

An enzyme is made from a chain of amino acids. Part of the mRNA coding for this enzyme has the base sequence:

normal: $A U G \quad C A U \quad G G A \quad U C U$

In one person, a genetic variant in the coding DNA of the gene changes this mRNA sequence to:

variant: $A U G \quad C G U \quad G G A \quad U C U$

Codon	Amino acid
AUG	methionine
CAU	histidine
CGU	arginine
GGA	glycine
UCU	serine

The histidine in the normal enzyme is part of the active site.

Aphids are small insects that feed on plant sap.

In spring and summer, when plants are growing quickly, female aphids reproduce asexually. Each female produces large numbers of offspring that are genetically identical to her.

In autumn, male and female aphids are produced and they reproduce sexually. The fertilised eggs survive the cold winter and hatch in the following spring.