Year 9 Biology - Genetics

Question 1

What is the Cell Membrane?

Answer 1

The cell membrane is the outer-most layer of an animal cell and controls what enters and leaves the cell.

Question 2

What is a Chromosome?

Answer 2

A Chromosome is a strand/piece of DNA which is coiled molecule (is like thread).

Question 3

What is a Nucleus?

Answer 3

The nucleus contains all the DNA and Chromosomes that the person has in them in every single other nucleus.

Question 4

What is a gene

Answer 4

A gene is a section of a chromosome that codes for a protein or a particular characteristic. Each form of a gene is called an allele.

Question 5

Cytoplasm

Answer 5

Is where chemical reactions take place in a cell.

Question 6

Mitochondria

Answer 6

Mitochondria is where respiration takes place/occurs.

Question 7

How many Chromosomes does the average human have in each cell?

Answer 7

Normal Cells:
46 (23 pairs) in normal cell

Sex Cells (gametes)
23 in a normal Sperm/Egg cell

Question 8

What are Homozygous alleles?

Answer 8

If an individual has 2 identical alleles (e.g BB, tt) for a characteristic (e.g a blue allele and a brown allele) then they are said to be homozygous for this characteristic.

Question 9

What are Heterozygous alleles?

Answer 9

If an individual has 2 identical alleles (e.g Bb, Tt) for a characteristic (e.g a blue allele and a brown allele) then they are said to be heterozygous for this characteristic.

Question 10

How to draw a Genetic Cross (steps)

Answer 10

(Question:)

Key:

Parent Phenotype: (Male x Female)
Parent Genotype: (XY x XX)
Possible Sex Cells (gametes) : (XY in sperm cell, XX in egg cell)

Then Draw Genetic Cross/Diagram:

Offspring Phenotype: (Male, Male, Female, Female)
Offspring Genotype: (XY, XY, XX, XX)
Probability: (50% Male, 50% Female)

Question 11

What is Selective Breeding Definition

Answer 11

Slective Breeding involves choosing parents with particular desirable characteristics to breed together and produce offspring with more desirable characteristics.

Question 12

Stages involved with Selective Breeding

Answer 12

1. You decide which characteristics are important (desirable characteristics) e.g blue flowers
2. Choose the parents that show this phenotype (or characteristics) and breed them together.
3. Select the offspring that have the desired characteristic to breed the next generation.
4. Repeat this process continually (over a number of years).

Question 13

Advantages of Selective Breeding:

Answer 13

• Increased meat/milk yield from cattle (which may increase profits for farmers)
• Can create new varieties of (good) crops
• Disease resistance in food crops of garden plants e.g soya beans
• Can produce domesticated animals with gentle nature e.g labradoodle dog

Question 14

Disadvantages of Selective Breeding:

Answer 14

• Selective Breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease of inherited defects
• Because of the smaller gene pool, selective bred organisms are more likely to pass on harmful genetic alleles
• There, they are more likely to be susceptible to diseases.

Question 15

What is Genetic Engineering?

Answer 15

Genetic Engineering is process that involves changing the genes of an organism, or by introducing a gene from another organism to give a desired characteristic.

An organism whose genes have been altered is called a ‘genetically modified organism’

Question 16

Stages in Genetic Engineering

Answer 16

1. Select the desired characteristic
2. Isolate the gene responsible for the characteristic (using enzymes to cut it out)
3. Insert this gene into another organism (e.g a bacterium)
4. Replication of the organism (let it divide itself over a certain period of time)

Question 17

What is Cloning?

Answer 17

Cloning is where you remove a cell from an organism and then use it to put into an egg cell for it to then grow and be identical to that original organism.

Question 18

How to Clone a Mammal (Nuclear Transfer Cloning)

Answer 18

1. Take a normal body cell (contains full amount if chromosomes) from the organism to be cloned, but remove the nucleus and keep it
2. Take an egg cell from another organism and remove the nucleus and discard it.
3. Insert the nucleus of the body cell (the animal to be cloned) into the now empty egg cell
4. Give the egg cell with it’s new nucleus an electric shock, so it thinks it’s fertilised and then let it divide into an embryo
5. The insert the embryo into an organism’s uterus that has similar gene type, or is the same species, and then wait for the surrogate organism to give birth to the originally cloned organism