Genetics

Question 1

What are the structures of an animal cell

Answer 1

Cell membrane - controls what enters and leaves the cell.
Nucleus - contains the DNA (chromosomes)
Cytoplasm - where chemical reactions take place
Mitochondria - respiration occurs here
Chromosomes - DNA is arranged into long, coiled molecules called chromosomes

Question 2

How many chromosomes do human body cells have

Answer 2

46 chromosomes ( 23 pairs )

Question 3

How many chromosomes do sex cells have?

Answer 3

Human sex cells have half (23)

Question 4

What is a gene?

Answer 4

A gene is a section of a chromosome that codes for a particular characteristic. E.g. eye colour, shape of nose, curly straight hair etc.

Question 5

What forms do we inherit the gene?

Answer 5

We inherit two forms. One from our mother and one from our father.

Question 6

What is the name of the form of the gene?

Answer 6

It is called an allele

Question 7

If an individual has 2 identical alleles (e.g. BB, tt ) for a characteristic ( e.g. two blue eyes alleles ) the are said to be H for this characteristic.

Answer 7

They are said to be Homozygous.

Question 8

Selective breeding definition

Answer 8

Selective breeding involves CHOOSING PARENTS with particular DESIRABLE CHARACTERISTICS to breed TOGETHER and produce offspring with more desirable characteristics.

Question 9

What are the steps to selective breeding?

Answer 9

1. DECIDE WHICH CHARACTERISTICS are important ( desirable characteristics ) e.g. blue flowers.
2. CHOOSE PARENTS that show these characteristics and BREED THEM TOGETHER.
3. SELECT THE OFFSPRING that have the desired characteristics to breed the next generation.
4. REPEAT THE PROCESS continuously ( over a number of years ).

Question 10

Advantages of selective breeding

Answer 10

• INCREASED MILK/MEAT YIELD from cattle.
• Can create NEW VARIETIES of crops.
• DISEASE RESISTANCE in food crops or garden plants.
• Produce DOMESTICATED ANIMALS e.g. labradoodle

Question 11

Disadvantages of selective breeding

Answer 11

• Can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects.
• Because of the smaller genetic pool selective bred organisms are MORE LIKELY TO PASS ON HARMFUL RECESSIVE ALLELES.
• There they are more likely to be SUSCEPTIBLE TO DISEASES.

Question 12

What is genetic engineering

Answer 12

Genetic engineering is a process which involves:

• Changing the genes of an organism
• By INTRODUCING A GENE from another organism to give a desired characteristic.
• An organism where genes have been altered is called a ‘GENETICALLY MODIFIED ORGANISM’

Question 13

Stages of genetic engineering

Answer 13

SELECT the desired characteristic.

ISOLATE the gene responsible for the characteristic ( using enzymes ).

INSERT this gene into another organism ( e.g. a bacterium ).

REPLICATION of the organism.

Question 14

Stages in Nuclear Transfer Cloning

Answer 14

1. Take a NORMAL BODY CELL ( contains full amount of chromosomes ) from the organism to be closed and REMOVE THE NUCLEUS.
2. Take an EGG CELL from another organism and REMOVE THE NUCLEUS ( and discard it).
3. INSERT the nucleus of the normal body cell into the empty egg cell.
4. ELECTRIC SHOCK is given to stimulate cell division.
5. IMPLANT this embryo into uterus of a SURROGATE organism to develop into a clone.