Practise Chromosomes. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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The nucleus of a cell contains chromosomes. Name the molecule that chromosomes are made of.
DNA
Write these structures in order of size, starting with the smallest. cell, chromosome, gene, nucleus
gene, chromosome, nucleus, cell
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
The nucleus of a cell contains chromosomes.
(a) Name the molecule that chromosomes are made of.[1]
(b) Complete the sentence. Each chromosome carries a large number of ____________ .[1]
(c) How are chromosomes normally arranged in body cells? Tick (✓) one box.[1]
In groups of three
In pairs
One of each type
Joined into one long chromosome
(d) A human body cell contains 46 chromosomes. How many pairs of chromosomes is this?[1]
Show the answer and mark scheme
(a)Answer: DNA
DNA
(b)Answer: genes
genes
(c)Answer: In pairs
(d)Answer: 23
23
Question 2Medium6 marks
Chromosomes are found in the nucleus of cells.
(a) The body cells of a fruit fly contain 4 pairs of chromosomes. How many chromosomes are in a fruit fly body cell?[1]
(b) Explain why the chromosomes in body cells are found in pairs.[2]
(c) Mature human red blood cells do not contain any chromosomes. Suggest why.[1]
(d) Describe the relationship between chromosomes, DNA and genes.[2]
Show the answer and mark scheme
(a)Answer: 8
8
(b)
one chromosome of each pair comes from the mother / egg
the other comes from the father / sperm
(c)
they have no nucleus
(d)
chromosomes are made of (long molecules of) DNA
genes are (short) sections of the DNA on a chromosome / each chromosome carries many genes
Question 3Hard7 marks
{table} shows the number of chromosomes in a body cell of different organisms.
[object Object]
(a) A student said: 'The more complex an organism is, the more chromosomes its cells contain.' Evaluate the student's statement using {table}.[3]
(b) Chimpanzees and potatoes have the same number of chromosomes. Suggest why they are very different organisms.[2]
(c) Human body cells contain about 20 000 different genes. The 46 chromosomes form 23 pairs. Assume that both chromosomes in a pair carry the same genes. Estimate the mean number of different genes carried on one chromosome.[2]
Show the answer and mark scheme
(a)
the fruit fly (simplest animal shown) has the fewest chromosomes, which supports the statement
but the potato / dog / horse / chimpanzee has more chromosomes than a human, which does not support it
conclusion: there is no clear link between complexity and chromosome number
(b)
their chromosomes carry different genes / different DNA
so they have different characteristics / make different proteins