Genetics

Question 0

Define the term genotype

Answer 0

The alleles present within cells of an individual for a particular trait/characteristic

Question 1

Define the term phenotype

Answer 1

The characteristics expressed by the organism (caused by the genotype)

Question 2

Define the term dominant allele

Answer 2

Expressed in the phenotype even if a different allele for the same gene is present

Question 3

Define the term recessive allele

Answer 3

Only expressed in the phenotype if no dominant allele is present

Question 4

Define the term co dominant

Answer 4

Alleles are co dominant if they both contribute to the phenotype

Question 5

Define the term heterozygous

Answer 5

Two different alleles

Question 6

Define the term homozygous

Answer 6

Two copies of the same allele

Question 7

Define the term linkage

Answer 7

• Genes for different characteristics that are present at different loci on the same chromosome
• The combination of alleles are usually inherited together because they segregate together in meiosis

Question 8

How should a genetic diagram be laid out?

Answer 8

1. Parental phenotype
2. Parental genotype
3. Gametes
4. Punnet square
5. F1 phenotype (ratio)
6. F1 genotype
7. Gametes
8. Punnet square
9. F2 genotype ratio
10. F2 phenotypic ratio

Question 9

What is sex linkage?

Answer 9

If the gene for the characteristic is on the sex chromosome

Question 10

Define the term homogametic

Answer 10

Women XX

Question 11

Define the term heterogametic

Answer 11

Men XY

Question 12

What causes haemophilia?

Answer 12

Could be a recessive allele of a gene, that codes for a faulty version of the protein factor.

X^H - normal X^h - haemophilia

Question 13

What is a monohybrid cross?

Answer 13

• parents - homozygous dominant x homozygous recessive (NN X nn)
• f1 generation - all heterozygous offspring (Nn)
• f2 generation phenotypic ratio 3 : 1 (dominant : recessive)

Question 14

What is a dihybrid cross?

Answer 14

• parents - homozygous dominant x homozygous recessive (NNGG x nngg)
• f1 generation - all heterozygous offspring (NnGg)
• f2 generation - 9 : 3 : 3 : 1 (dominant both : dominant 1st recessive 2nd : recessive 1st dominant 2nd : recessive both)

Question 15

What is a co dominant cross?

Answer 15

• parents - homozygous for one allele x homozygous for other allele (H^n H^n x H^s H^s)
• f1 generation - all heterozygous offspring (H^n H^s)
• f2 generation - 1 : 2 : 1 (homozygous for one allele : heterozygous : homozygous for the other allele)