Use the diagram to explain why cystic fibrosis is caused by a recessive allele.

1
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?
2
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.
3
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.
4
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
5
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6
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.