Practise reading human karyotypes to identify sex chromosomes, distinguish typical XX and XY patterns, and recognize extra or missing sex chromosomes.
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?
XX
XY
Y
YY