Unit 3

Question 1

What is the purpose of selective breeding?

Answer 1

Improves plant and animal characteristics for sustainable food production, increasing food yield, nutritional value, pest/disease resistance, and ability to thrive in different environments.

Question 2

What is the purpose of field trials?

Answer 2

To compare performance of cultivars/treatments and evaluate GM crops.

Question 3

What are the key features of field trials?

Answer 3

1. Selection of treatments ensures valid comparisons.
2. Replicates account for variability and improve reliability.
3. Randomisation eliminates bias.

Question 4

Define ‘gene’.

Answer 4

A section of DNA coding for a trait.

Question 5

What is an allele?

Answer 5

Different forms of a gene.

Question 6

What is a genotype?

Answer 6

Genetic makeup (e.g., BB, Bb, bb).

Question 7

What is a phenotype?

Answer 7

Physical trait (e.g., tall, short).

Question 8

What does homozygous mean?

Answer 8

Two identical alleles (BB or bb).

Question 9

What does heterozygous mean?

Answer 9

Two different alleles (Bb).

Question 10

What is a dominant allele?

Answer 10

Masks recessive allele (B).

Question 11

What is a recessive allele?

Answer 11

Expressed only if both alleles are recessive (bb).

Question 12

What is a monohybrid cross?

Answer 12

P (Parent generation) → F1 (First generation) → F2 (Second generation).

Question 13

How do Punnett Squares help in breeding?

Answer 13

They predict offspring genotypes and phenotypes.

Question 14

What is the expected phenotype ratio from two heterozygous parents (Tt x Tt)?

Answer 14

3:1 phenotype ratio.

Question 15

What are the risks of inbreeding?

Answer 15

Inbreeding depression, reduced fertility, poor survival, and genetic disorders.

Question 16

What is crossbreeding?

Answer 16

Mixing different breeds/cultivars to improve characteristics.

Question 17

What are F1 hybrids?

Answer 17

Uniform heterozygous individuals produced from crossbreeding.

Question 18

What is hybrid vigour?

Answer 18

Increased disease resistance, growth, and yield in F1 hybrids.

Question 19

Why are F1 hybrids not usually bred together?

Answer 19

F2 offspring show too much variation.

Question 20

What is genetic engineering?

Answer 20

Transfer of genetic material from one organism to another.

Question 21

How does genome sequencing help in genetic engineering?

Answer 21

It helps identify desirable genes.

Question 22

What is recombinant DNA technology?

Answer 22

Inserts single genes into crop plants.

Question 23

What is an example of a gene used for pest resistance?

Answer 23

Bt toxin gene.

Question 24

What is an example of a gene used for herbicide tolerance?

Answer 24

Glyphosate resistance gene.

Question 25

Why do farmers use selective breeding?

Answer 25

To improve characteristics of plants and animals for better food production.

Question 26

What traits do breeders select?

Answer 26

Traits that enhance yield, nutritional value, and resistance to pests/diseases.

Question 27

What makes a good field trial?

Answer 27

Valid comparisons through treatment selection, replication, and randomisation.

Question 28

What are the risks of inbreeding?

Answer 28

Accumulation of harmful recessive alleles leading to reduced fertility and genetic disorders.

Question 29

How does crossbreeding benefit animals and plants?

Answer 29

By producing hybrids with improved traits such as disease resistance and growth.

Question 30

Why are F1 hybrids not usually bred together?

Answer 30

They produce offspring with too much variation.

Question 31

How is genetic engineering used in crops?

Answer 31

By transferring desirable genes to enhance traits like pest resistance and herbicide tolerance.