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Course: Edexcel A Level Biology A (SNAB) 9BI0
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Edexcel A Level Biology A (SNAB) 9BI0

Topic 1 · Lifestyle, Health and Risk

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Topic 2 · Genes and Health

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Topic 3 · Voice of the Genome

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Topic 4 · Biodiversity and Natural Resources

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Topic 5 · On the Wild Side

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Topic 6 · Immunity, Infection and Forensics

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Topic 7 · Run for your Life

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Topic 8 · Grey Matter

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Quiz

3.3.3 Genes and Linkage – Exam questions

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  • Questions count: 12
  • Passing grade: B+
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1.
Which statement best describes Gene linkage?
Genes on the same chromosome tend to be inherited together.
An offspring with a combination of alleles not seen in either parent, produced by crossing over.
Having more than two complete sets of chromosomes.
A heterozygote who does not show a recessive condition but can pass it on.
2.
Why is a double recessive used in a test cross to measure linkage?
It is always linked
It increases crossing over
It gives only recessive alleles, so offspring phenotypes show the gametes of the other parent
It makes all offspring dominant
3.
Which hypothesis suits a fruit-fly linkage experiment?
Body colour and wing shape genes will show fewer than 50% recombinant offspring
Flies are small
Wings are useful
Flies breed
4.
Why are fruit flies commonly used in linkage studies?
They have no chromosomes
They are polyploid
They breed quickly and produce many offspring
They live for decades
5.
Using the table, what is the recombination frequency between genes A and B?
87%
6.5%
50%
13%
6.
What does the test-cross table show about genes A and B?
They are unlinked
They are on different chromosomes
They are linked, about 13 map units apart
They are 87 map units apart
7.
Using the recombination frequencies in the table, what is the gene order?
P – R – Q
Q – P – R
P – Q – R
R – P – Q
8.
On the chromosome map, which pair of genes is least likely to be separated by crossing over?
Dr Dabour Hub Academy - figure 1
A and B
A and C
All equally likely
B and C
9.
The graph shows recombination frequency against gene distance. Why does it level off near 50%?
Dr Dabour Hub Academy - figure 2
Very distant genes behave as if unlinked, and RF can never exceed 50%
Crossing over stops at long distances
Genes merge at 50%
Linked genes always give 100%
10.
In a linkage test cross, the number of recombinant offspring is the _____.
independent variable
dependent variable
karyotype
autosome
11.
Genes on the same chromosome are said to be _____.
polyploid
homozygous
recessive
linked
12.
A recombination frequency of 50 per cent indicates that two genes _____.
are on the Y chromosome
are very close together
behave as if unlinked
are always inherited together
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Part of Topic 3 · Voice of the Genome — see every lesson and quiz in this unit.
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