Edexcel IGCSE Biology 3.26 Sex chromosomes
Practise interpreting sex chromosomes in karyotypes, tables and calculations to identify sex and chromosome-number differences.
- Syllabus
- First assessment 2019
- Course
- Biology 4BI1
Exam points
- identify male or female karyotypes from XX, XY or the presence of a Y chromosome
- describe chromosome differences in karyotypes, including missing or extra sex chromosomes
- calculate ratios or frequencies from birth data and syndrome incidence figures
3.26 Sex chromosomes question 1
Reflexes are responses that protect the body and involve the central nervous system (CNS).
The photograph shows a breed of dog called a border collie.
Some border collies have a genetic condition called sensory neuropathy.
Border collies with sensory neuropathy may be injured as their reflexes do not work well.
Sensory neuropathy is caused by a recessive allele, n . The dominant allele for not having sensory neuropathy is N .
The diagram shows a family pedigree for some border collies.
Sex determination in dogs is controlled in the same way as in humans.
Which combination of sex chromosomes is present in the body cells of a male dog?
A
XX
B
XY
C
Y
D
YY
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