Inheritance

Question 1

What are the types of variations?

Answer 1

• Continous
• Discontinuous

Question 2

What are the properties of continuous variation?

Answer 2

• Affected by genes & environmental factors
• A range of phenotypes exist b/w 2 extremes
• They can change over time(e.g. skin color, body mass, height of plant, size of leaves
• Many genes can control one single characteristic
• Plotted on a histogram or a bell-shaped curve

Question 3

What are the properties of discontinuous variation?

Answer 3

• Only controlled by genes
• Phenotypes are clear-cut with no intermediates.
• Controlled by a few genes, e.g., blood group, eye color, color of seeds in pea plant, etc.
• Plotted on a bar graph

Question 4

What are the properties of DNA?

Answer 4

• Double helix
• Nucleotides
• 4 bases(A,T,C,G)
• Base pairing maintains double helix shape (A-T) & (C-G)

Question 5

Define gene.

Answer 5

A small section of DNA that controls the production of one specific protein/controls one specific characteristic

Question 6

Describe the sequence of bases.

Answer 6

• The sequence of bases in DNA/gene determines the sequence of amino acids in a protein.
• The sequence of amino acids in a protein determines the shape of the protein and hence its function.
• e.g., enzymes have specific shapes which allow them to carry out specific functions

Question 7

Define allele.

Answer 7

Different versions of some genes are called alleles

Question 8

Define a homologous pair.

Answer 8

• A pair of chromosomes that carries some type of genes on the same gene locus
• One chromosome is maternal, the other one is paternal.

Question 9

Define genotype.

Answer 9

The 2 alleles of a gene present in an individual

Question 10

Define phenotype.

Answer 10

The physically observable features.

Question 11

Why are observed ratios often different from expected ratios?

Answer 11

• Sample sizes are usually small
• Fertilization is a random process.

Question 12

Define gene mutation.

Answer 12

• Random change in the base sequence of a gene/DNA that results in the production of an altered protein

Question 13

What is the advantage of mutation?

Answer 13

• Gives superior features to an organism, giving an adaptation and survival advantage, and may lead to natural selection

Question 14

What is the disadvantage of mutation?

Answer 14

• Can lead to diseases

Question 15

What is sickle cell anaemia?

Answer 15

• A disease caused by a gene mutation
• The gene responsible for Hb production has been altered, resulting in abnormal Hb production.

Question 16

In sickle cell anaemia (SCA), what happens to red blood cells?

Answer 16

• Red blood cells have a lower surface area, due to which oxygen transport decreases. This results in:
• The rate of aerobic respiration is decreasing
• less ATP produced
• lethargic, breathless, less stamina.

Question 17

What are the reasons for mutations?

Answer 17

• Chemicals (e.g., Tar)
• Radiation (gamma radiation)

Question 18

What are the sources of variations in sexually reproducing organisms?

Answer 18

• Mutations
• Meiosis
• Random Mating
• Random fertilization
• Environmental factors

Question 19

What are the types of selections?

Answer 19

• natural selection
• Artificial selection