Exam questions · Biology · Mitosis, Growth and Stem Cells
Chromosomes, Genes and DNA
- 7 exam questions
- 16 marks
- 8 quick checks
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1 Name [1 mark]
Name the part of a cell that contains the chromosomes.
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Model answer
The nucleus.
Mark scheme
- Nucleus — 1 mark
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2 State [1 mark]
State the number of chromosomes in a human body cell.
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Model answer
46 (or 23 pairs).
Mark scheme
- 46 / 23 pairs — 1 mark
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3 Name [3 marks]
Figure 1 shows how genetic material is stored in a cell. Name the structures labelled A, B and C.
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Model answer
A is the nucleus. B is a chromosome. C is a gene.
Mark scheme
- A: nucleus — 1 mark
- B: chromosome — 1 mark
- C: gene — 1 mark
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4 Describe [2 marks]
Describe the relationship between a gene and a chromosome.
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Model answer
A chromosome carries a large number of genes. A gene is a short section of the DNA that makes up a chromosome.
Mark scheme
- A chromosome carries many genes — 1 mark
- A gene is a section of the DNA of a chromosome — 1 mark
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5 Calculate [2 marks]
A fruit fly body cell has 8 chromosomes. Calculate the number of pairs of chromosomes in the cell.
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Model answer
8 ÷ 2 = 4 pairs.
Mark scheme
- Divides the number of chromosomes by 2 — 1 mark
- 4 pairs — 1 mark
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6 Describe [3 marks]
Describe how the chromosomes are arranged in a human body cell, and where they came from.
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Model answer
They are in pairs, 23 pairs in all (46 chromosomes). One chromosome in each pair came from the mother and the other from the father.
Mark scheme
- Chromosomes are in pairs — 1 mark
- 23 pairs / 46 chromosomes — 1 mark
- One of each pair from each parent — 1 mark
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7 Describe [4 marks]
Describe where DNA is found in a cell and how it is organised.
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Model answer
DNA is found in the nucleus of the cell. It is organised into chromosomes, each of which is one long, coiled DNA molecule. Each chromosome carries many genes, and a gene is a short section of DNA. In body cells the chromosomes are in pairs.
Mark scheme
- DNA is in the nucleus — 1 mark
- Organised into chromosomes — 1 mark
- Each chromosome carries many genes — 1 mark
- A gene is a section of DNA / chromosomes in pairs — 1 mark
Quick check
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1
Where are chromosomes found in a human body cell?
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B: In the nucleus
Chromosomes are in the nucleus. The cytoplasm, cell membrane and mitochondria do not contain them.
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2
What is a chromosome made of?
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C: DNA
A chromosome is a long, coiled molecule of DNA.
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3
Which of these is the smallest?
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D: A gene
A gene is a short section of DNA, which makes up part of a chromosome. A chromosome is inside the nucleus, and the nucleus is inside the cell.
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4
How many pairs of chromosomes are there in a human body cell?
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A: 23
A human body cell has 46 chromosomes, which is 23 pairs.
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5
A body cell has 18 chromosomes. How many pairs is that?
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C: 9
A pair is two chromosomes, so 18 ÷ 2 = 9 pairs.
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6
Where does each chromosome in a pair come from?
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B: One from each parent
One chromosome of each pair comes from the mother and the other comes from the father.
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7
Which statement about genes is correct?
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D: A gene is a short section of DNA
A gene is a short section of DNA. A chromosome is a long DNA molecule that carries many genes.
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8
A dog body cell has 78 chromosomes and a human body cell has 46. What does this tell you?
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A: Chromosome number is different in different species and says nothing about complexity
Different species have different numbers of chromosomes, and a larger number does not make an organism more complex. It is what the genes say that matters.