B1.7 Genetic Variation and its Control

Question 1

What is genetic variation?

Answer 1

The inheritance of characteristics from parents - these are determined by genes

Question 2

What are genes?

Answer 2

Codes inside your cells that control how you’re made

Question 3

How are genes passed onto offspring?

Answer 3

Sex cells containing genes from the mother and father combine to develop offspring

Question 4

Why are no two species genetically identical?

Answer 4

Due to the genes which determine an offspring’s characteristics coming from two different individuals

Question 5

What are examples of characteristics inherited only by genes - in both plants and animals? (4)

Answer 5

A flower being violet in colour (plants), eye colour, blood group and inherited disorders (animals)

Question 6

What is environmental variation?

Answer 6

The environment an organism lives and grows in, can cause differences between members of the same species

Question 7

What are examples of environmental variation?

Answer 7

Your toes being eaten off, getting a suntan, having yellow leaves - anything which is caused by the conditions of the environment

Question 8

Is height determined by environmental variation or genetic variation?

Answer 8

Both - an animals or plants max height is determined by genes, but weather it actually reaches that height is determined by the environmental factors e.g. how much food it gets.

Question 9

Is intelligence determined by environmental variation or genetic variation?

Answer 9

Both - there are theories that show your maximum possible IQ is determined by genes, but whether you reach this level of IQ is determined by environmental factors e.g. your upbringing and school life

Question 10

Is health determined by environmental variation or genetic variation?

Answer 10

Both - some people are more likely to get certain diseases due to their genes, but environmental factors like whether you smoke or much junk food you eat can also affect health

Question 11

What do the nuclei in cells contain?

Answer 11

Genetic material - the instructions you need to grow and develop

Question 12

How is genetic material stored in nuclei?

Answer 12

In chromosomes

Question 13

How are chromosomes found?

Answer 13

In pairs

Question 14

How many chromosomes does a human cell contain?

Answer 14

23 pairs - 46 in total

Question 15

What are chromosomes long lengths of?

Answer 15

Chromosomes are long lengths of a molecule called DNA

Question 16

Where is DNA found in chromosomes?

Answer 16

It is coiled up to form the arms of the chromosomes

Question 17

What does chromosomes carry?

Answer 17

Genes - which are short sections of DNA

Question 18

What are different versions of the same genes called?

Answer 18

Alleles

Question 19

What is sexual reproduction?

Answer 19

The combination of genetic information from two organisms (a father and a mother) to produce offspring which are genetically different to either parent

Question 20

What are gametes? What do they contain?

Answer 20

Sex cells e.g. egg and sperm cells in animals - each gamete contains 23 chromosomes which is half the number of chromosomes in a normal cell

Question 21

What is fertilisation?

Answer 21

The fusion of gametes to form a cell with the full number of chromosomes (half from the father and half from the mother)

Question 22

Why do offspring inherit features from both parents?

Answer 22

Because they receive a mixture of chromosomes from both parents

Question 23

Can you sum up sexual reproduction?

Answer 23

Sexual reproduction involves the fusion of male and female gametes. Because there are two parents, the offspring contain a mixture of their parents’ genes and are genetically different to their parents

Question 24

What is asexual reproduction?

Answer 24

When an ordinary cell divides in two - the new cells have exactly the same genetic information as the parent celll

Question 25

How does asexual reproduction work?

Answer 25

1. X-shaped chromo’ have 2 identical halves
2. Each chromo’ is split down the middle to form two identical sets of ‘1/2 chromosomes’ - a membrane forms around each set
3. The DNA then replicates itself to form two identical cells with completes sets of X-shaped chromosomes

Question 26

How do plants and animals grow and produce replacement cells?

Answer 26

With asexual reproduction

Question 27

How do bacteria and certain plants produce offspring?

Answer 27

With asexual reproduction

Question 28

Can you sum up asexual reproduction?

Answer 28

There’s only one parent. There’s no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. The offspring are genetically identical to the parent - they’re clones

Question 29

What is cloning?

Answer 29

The making of an exact (genetically identical) copy of an organism

Question 30

What are the two ways of cloning a plant?

Answer 30

Cuttings and tissue culture

Question 31

Describe the process of ‘cuttings’ when cloning a plant

Answer 31

Cuttings from a good parent plant, are used to produces genetically identical copies of the parent plant

Question 32

What benefits are there to using ‘cuttings’ to clone plants? (2)

Answer 32

The plants can be produced quickly and cheaply

Question 33

Describe the process of ‘tissue culture’ when cloning a plant

Answer 33

Plant cells are put in a growth medium with hormones, and they grow into new plants (or clones of the parent plant)

Question 34

What benefits are there to using ‘tissue culture’ to clone plants? (3)

Answer 34

They grow very quickly, they require very little space and they can be grown all year

Question 35

What are the two ways of cloning an animal?

Answer 35

Embryo transplants, and adult cell cloning

Question 36

Describe the process of ‘embryo transplants’ when cloning an animal

Answer 36

An embryo is created, then split many times in the early stages to form clones - the cloned embryos can then be inserted into a host mother to continue developing

Question 37

Describe the process of ‘adult cell cloning’ when cloning an animal

Answer 37

An unfertilised egg has its genetic material removed (its nucleus), and then a complete set of chromosomes from an adult body cell is inserted into the ‘empty’ egg cell - an electric shock is then used to make the egg divide like a normal embryo

Question 38

What happens after the embryo has received an electric shock in ‘adult cell cloning’?

Answer 38

Once it has become a ball of cells, it’s implanted into the uterus of a surrogate mother, where it grows into a genetically identical copy of the original adult body cell

Question 39

What benefits are there to cloning? (3)

Answer 39

It allows you to achieve an ideal offspring with known characteristics e.g. a cow which produces a lot of milk can be cloned for a farmer, the study of cloning gives us a greater understanding of the development of the embryo, and cloning could be used to preserve endangered species

Question 40

What are the concerns with cloning?

Answer 40

Gives a ‘reduced gene pool’, so a new disease could potentially wipe out a population as they may all have no allele resistant to the disease, cloned animals aren’t as healthy as the originals and people are worried that humans might be cloned in the future

Question 41

What is genetic engineering?

Answer 41

The idea to copy a useful gene from one organism’s chromosome into the cells of another

Question 42

How does genetic engineering work? (2 steps)

Answer 42

1. A useful gene is ‘cut’ from one organism’s chromosome using enzymes
2. Enzymes are then used to cut another organism’s chromosome and then to insert the useful gene

Question 43

What is an example of when genetic engineering is used?

Answer 43

The human insulin gene can be inserted into bacteria to produce human insulin, which can then be given to be people with diabetes

Question 44

What are GM crops?

Answer 44

Genetically modified crops which have had their genes modified

Question 45

Why are crops genetically modified? (3)

Answer 45

To make them resistant to viruses, insects and herbicides

Question 46

What is gene therapy?

Answer 46

The treatment of disorders by inserting working genes into sufferers

Question 47

What is an example of genetic engineering used in animals?

Answer 47

Sheep have been genetically engineered to produce drugs in their milk that can be used to treat human diseases

Question 48

What are the benefits of GM crops? (2)

Answer 48

They can increase the yield of a crop, and they can be engineered to contain nutrients which there is a lack of in developing countries e.g. ‘golden rice’

Question 49

What are the concerns with GM crops? (3)

Answer 49

They affect biodiversity around farmland as they affect the number of weeds and plants in the area (and so the population of insects), not everyone is convinced that growing GM crops are safe, and it is thought that transplanted genes may get out into the natural environment e.g. herbicide resistant weeds, making ‘superweeds’