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

A test cross is used to find out if an individual is:

• 1 Old or young
• 2 Homozygous or heterozygous
• 3 Tall or short
• 4 Male or female

In incomplete dominance the heterozygote shows:

• 1 An intermediate phenotype
• 2 The recessive phenotype
• 3 No phenotype
• 4 The dominant phenotype

Colour blindness is more common in males because the gene is on the:

• 1 Y chromosome
• 2 Autosome
• 3 X chromosome
• 4 Mitochondria