Inheritance

A cross between a heterozygous and a homozygous recessive individual (Aa x aa) gives the phenotypic ratio:

• 1 1 : 1
• 2 3 : 1
• 3 9 : 3 : 3 : 1
• 4 All the same

A dihybrid cross of two heterozygotes gives a phenotypic ratio of:

• 1 3 : 1
• 2 9 : 3 : 3 : 1
• 3 1 : 2 : 1
• 4 1 : 1

Haemophilia is carried on the:

• 1 Mitochondria only
• 2 X chromosome
• 3 Chromosome 21
• 4 Y chromosome

The sex of a human child is determined by the:

• 1 Environment
• 2 Egg
• 3 Mother's age
• 4 Sperm

Down syndrome is caused by an extra copy of chromosome:

• 1 18
• 2 X
• 3 13
• 4 21