Transcript genetics_data_interpretation

Use the diagram to explain why cystic fibrosis is
caused by a recessive allele.
Could the locus for the allele be on the X
chromosome?
Coat colour in cats is controlled by a single gene. This
gene has two alleles – B which results in black
coloured fur and G which results in ginger fur.
Use the information above to explain why tortoishell
cats are never male.
Tall, cut-leaved tomato plants are crossed with dwarf,
potato leaved plants giving in the F1 generation nothing but
tall, cut-leaved plants.
These are allowed to cross with each other producing in the
F2 generation 926 tall, cut-leaved; 288 tall, potato-leaved;
293 dwarf, cut-leaved; and 104 dwarf, potato-leaved.
In fruit flies, normal wings are produced by the
dominant allele M and miniature wings by the
recessive allele m.
Pure-breeding, female flies with normal wings were
crossed with male flies having miniature wings. All
the offspring had normal wings.
The offspring were allowed to interbreed and the
following results were obtained.
105 normal, females
52 normal, males
46 miniature-winged, males
male affected with haemophilia
unaffected male
1
2
Rhesus
positive
3
4
Rhesus
positive
8
Rhesus
negative
Rhesus
positive
unaffected female
Rhesus
negative
5
6
Rhesus
positive
Rhesus
positive
7
Rhesus
positive
9
10
11
Rhesus
positive
Rhesus
positive
12
Rhesus
negative
Rhesus
positive
1
2
Give evidence from the
diagram that night blindness
could be a recessive
condition.
If night blindness is a
recessive condition, explain
why it cannot be sex linked.
3
Female with
night blindness
Male with
normal sight