Paper 2: Topic 6 Inheritance, variation & evolution - Variation & evolution

Question 1

Define the term variation

Answer 1

Differences in the characteristics of individuals within a population

Question 2

State 3 causes of variation within a population

Answer 2

1. Genetics
2. Environment
3. Combination of genetics and the environment

Question 3

Explain how genetics can lead to variation in a population

Answer 3

• Different individuals will inherit different combinations of alleles
• The different combination of alleles will cause differences in the proteins that are or are not produced
• This will cause differences in the characteristics in the different individuals
• E.g. eye colour, blood group, genetic disorders such as cystic fibrosis

Question 4

Explain how the environment can lead to variation within a population

Answer 4

Different environmental factors can affect certain characteristics in individuals

e.g.

• Road accident → loss of a limb
• Exposure to UV light → affects melanin content of the skin

Question 5

Explain how genetics and the environment can lead to variation in a population

Answer 5

Individuals who possess certain genes and are exposed to certain environmental factors can have different characteristics e.g.

• skin colour (affected by UV light and gene for melanin production)
• body mass (affected by quality and quantity of diet and the genes for muscle development and growth)

Question 6

State what factors influence most physical characteristics

Answer 6

Genetics AND the environment

Question 7

State what causes variation within a population

Answer 7

Mutations

Question 8

Describe the range of variation observed in most populations

Answer 8

• Extensive
• This means there is a wide range of variants for most characteristics within a population

Question 9

Define the term ‘evolution’ Hint: 3 key parts to this definition

Answer 9

• A change in the inherited characteristics of a population over time
• Through a process of natural selection
• Which result in the formation of a new species

Question 10

Explain the theory of natural selection

Answer 10

• A mutation occurs within an individual in a population
• This causes variation to develop within a population exists
• Some individuals are more suited to their environment (due to the characteristics they possess)
• The individuals who are more suited to the environment are more successful
• These individuals are more likely to survive and breed
• These individuals will pass on the alleles for the beneficial characteristics to the their offspring
• Over a LONG period of time and MANY generations the beneficial alleles will become more common in the population
• Over time the variants that posses the best phenotypes are selected for and increase in number

Question 11

Define the term ‘selective breeding’

Answer 11

Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics

Question 12

State 2 reasons why Humans have used selective breeding for centuries

Answer 12

Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals.

Question 13

State the 4 key steps in artificial selection/selective breeding

Answer 13

• Selective breeding involves choosing parents with the desired characteristic from a mixed population
• They are bred together
• From the offspring those with the desired characteristic are bred together
• This continues over many generations until all the offspring show the desired characteristic

Question 14

Give 4 features that have been selected for in selective breeding

Answer 14

1. Disease resistance in food crops
2. Animals which produce more meat or milk
3. Domestic dogs with a gentle nature
4. Large or unusual flowers

Question 15

State 3 disadvantages of using artificial selection / selective breeding

Answer 15

1. Inbreeding can result in a reduced gene pool
2. Inbreeding can result in health problems
3. Inbreeding results in reduced variation within the population

Question 16

Explain what is meant by the expression ‘reduced gene pool’

Answer 16

The number of different alleles in a population decreases

Question 17

Explain how artificial selection can result in health problems in the population

Answer 17

• Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects
• This is because of a reduced gene pool

Question 18

Explain how artificial selection can reduce the gene pool

Answer 18

The number of alleles in the population can be decreased over time

Question 19

Explain how artificial selection can cause problems is a new disease occurs

Answer 19

• As a result of selective breeding there is less variation in a population
• So all the individuals in the population have very similar characteristics
• This means that if one individual is likely to be killed by the new disease then all the individuals in the population are also likely to die from the new disease
• This is because there is less chance of any resistant alleles being in a population

Question 20

Give 3 reasons why a gardener/farmer may use selective breeding

Answer 20

1. To produce a crop with higher yield
2. To produce a crop with more fruits
3. To produce a crop with larger fruits

Question 21

Describe the process of genetic engineering

Answer 21

A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

Question 22

Give 2 characteristics that have been genetically engineered in plants

Answer 22

1. Resistant to diseases
2. To produce bigger better fruits

Question 23

Describe an example of where bacteria have been used in genetic engineering

Answer 23

Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes

Question 24

Describe the 10 key steps in genetic engineering

Answer 24

1. The desired gene is identified
2. The gene for the desired protein is isolated (cut) from the DNA of one organisms genome using a restriction enzyme
3. Plasmids are isolated from bacteria
4. The same restriction enzyme is used to cut the plasmids
5. The cut plasmids and the desired gene are mixed together in the presence of DNA ligase
6. The DNA ligase joins the plasmid and desired gene together to form a recombinant (hybrid) plasmid
7. The recombinant/hybrid plasmid is inserted back into the bacteria
8. The bacteria are grown in large scale fermenters
9. The bacteria produce the required protein
10. The protein is extracted, purified and packaged for use

Question 25

Explain why plasmids used in genetic engineering are called vectors

Answer 25

A vector transfers something from one place to another

In this case it transfers the DNA from one organism to another

Question 26

State the 2 types of vectors that are usually used in genetic engineering

Answer 26

1. Bacterial plasmids
2. Viruses

Question 27

Give 3 examples of genetic engineering

Answer 27

1. Production of human insulin (Humulin) to treat type I diabetics
2. Production of GM crops
3. Production of specific drugs in sheep’s milk to treat disease

Question 28

Give 4 reasons scientists may want to use genetic engineering in plants

Answer 28

1. To produce a herbicide or insecticide resistant crops
2. To produce plants with larger fruits
3. To produce plants which are disease resistant
4. To produce crops with greater yield

Question 29

Define a insecticide

Answer 29

A chemical that selectively kills insects

Question 30

Define a herbicide

Answer 30

A chemical that selectively kills plants e.g. broad leaved plants

Question 31

Define a pesticide

Answer 31

A chemical that selectively kills pests e.g. aphids

Question 32

Give one example of genetic engineering in embryos

Answer 32

To insert a corrected gene into the ovum or early embryo to prevent certain genetic diseases

Question 33

Give 7 concerns some people have with GM crops

Answer 33

1. We do not yet know the long-term effect of consuming GM food i.e. they may have negative impacts on human health
2. Consumption of GM food may trigger allergies in some people
3. The modified crops may susceptible to changes in the environment in the future as they have a reduced gene pool
4. The gene may be passed between different plant species and ‘escape’ into wild plants and other crops
5. GM crops will reduce the biodiversity in the areas where they are grown
6. The long term effect on other organisms in the food chain is unknown e.g. effect on insects that feed on the GM plants
7. Transplanted herbicide resistant genes may spread to other plants and lead a new ‘super weed’ variety

Question 34

Give 3 reasons why some people are in favour of GM crops

Answer 34

1. It can be used to produce food that is rich in certain nutrients e.g. high vitamin A content. These nutrient rich foods can then be made available to people in countries with poor diets to prevent malnutrition
2. There are no studies to date that indicate ther are long-term side effects of consuming GM foods
3. It can help provide food security for a growing human population

Question 35

Give an example where a GM crop has been used to help reduced disease

Answer 35

• The use of GM rice called ‘golden rice’
• Which is rich in Vitamin A
• To prevent a specific form of blindness In developing countries which have poor diet and rely heavily on rice

Question 36

State the two methods that can be used to clone plants

Answer 36

1. Tissue culture
2. Cuttings

Question 37

Define the term ‘tissue culture’

Answer 37

The process of using small groups of cells from part of a plant to grow identical new plants

Question 38

Give 2 uses of tissue culture

Answer 38

This is important for

• preserving rare plant species
• producing large numbers of genetically identical plants commercially in nurseries

Question 39

Describe how tissue cultures are carried out

Answer 39

• A few plant cells are selected from the plant with the desirable characteristics
• The cells are placed in a growth medium which contains nutrients and growth hormones
• The cells grow into plantlets
• Which are genetically identical i.e. clones

Question 40

Give 4 advantages of using tissue culture

Answer 40

1. Only a few cells are needed
2. Many (100s) genetically identical plants can be produced from one parent plant
3. The technique only requires a small amount of space to produce many plants
4. The technique can be used throughout the year

Question 41

Give 4 disadvantages of using tissue culture

Answer 41

1. The procedure requires specific skills and equipment
2. The cloned plants will all be susceptible to the same diseases
3. There will be a reduced gene pool in the plants
4. The technique is slower (than cuttings) as the cells need time to divide and differentiate to become established plants

Question 42

Define the term ‘clone’

Answer 42

• Individuals which have the same genetic information (DNA)
• And therefore have the same characteristics

Question 43

Explain why gardeners may use cuttings

Answer 43

• Simple method
• Which is used to produce many identical new plants from a sinlge parent plant

Question 44

Give 4 advantages of using cuttings

Answer 44

1. It is a simple procedure
2. No technical apparatus is required
3. It is a cheap technique
4. It is a quick process (as plants form roots quickly to give an independent plant)

Question 45

Give 3 disadvantages of using cuttings

Answer 45

1. Only a limited number of cuttings can be taken from any one parent plant
2. So cuttings produces a lot less plants than tissue culture (10s compared to 100s)
3. The cloned plants will all be susceptible to the same diseases
4. There will be a reduced gene pool in the plants

Question 46

State the 2 techniques that can be used to clone animals

Answer 46

1. Embryo transplants
2. Adult cell cloning

Question 47

Define the term ‘embryo transplants’

Answer 47

A process which splits apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers

Question 48

Describe the 7 main steps when carrying out embryo transplants

Answer 48

1. Sperm cells from a male with the desirable characteristics are collected
2. Ova from a female with the desirable characteristics are collected
3. The sperm are then used to fertilise the ova to form a zygote
4. The zygote divides by mitosis and develops into an embryo
5. The embryo is then split into many smaller groups of cells (clones)
6. The clones are then implanted into the uterus of other females (surrogate mothers)
7. The cloned embryos then develop into new individuals which are all genetically identical

Question 49

State the advantage of using embryo transplants

Answer 49

Hundreds of genetically identical offspring can be produced each year from one prize male and one prize female e.g. bull and cow

Question 50

Describe the 5 main steps in adult cell cloning

Answer 50

1. The nucleus is removed from an unfertilised egg cell
2. The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
3. An electric shock stimulates the egg cell to divide to form an embryo
4. These embryo cells contain the same genetic information as the adult skin cell
5. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development

Question 51

State 3 concerns some people have with the use of animal cloning techniques Applies to both adult cell cloning and embryo transplants

Answer 51

1. The production of clones reduces the gene pool
2. The variation within the population decreases
3. If a new disease occurs then the entire population may be wiped out (killed) as there is less chance of having an allele that provides resistance to the disease

Question 52

State 3 reasons why some people are in favour of using animal cloning techniques

Answer 52

1. The study of animal clones can mean scientists can gain a greater understanding of embryo development, ageing and age-related disorders
2. Clones may be less healthy and may be more prone to disorders related to old age
3. Concerns exist that the technique could be applied to Humans in the future