Variation

Question 1

Causes of variation

Answer 1

• alleles that individuals have inherited
  = genetic causes eg hair colour
• environment
  = eg language
• combination of genes and the environment
  = height

Question 2

Define mutations

Answer 2

Random changes to DNA

Question 3

Examples of selective breeding

Answer 3

• dogs
  = more gentle
• food crops
  = disease resistant
• cows
  = more milk
• plants
  = larger flowers

Question 4

Stage 1 of selective breeding

Answer 4

• take a mixed population of species and select largest female and male
• breed together
  = sexual reproduction produces variation in offspring
• offspring will be mix of larger and smaller
• select largest male and female offspring and breed together
• breed until all offspring large

Question 5

Problem with selective breeding

Answer 5

If we breed closely related animals or plants then we can get inbreeding
= cause some breeds to be prone to disease or inherited defects

Question 6

Describe genetic engineering

Answer 6

Genes from one organism are cut out and transferred to cells of a different organism eg bacteria

Question 7

GM crops function

Answer 7

Produce a greater yield than normal

Question 8

Stages of genetic engineering

Answer 8

• identify the gene we want to transfer
• use enzymes to isolate gene
• transfer gene into vector eg virus or plasmid
• desired gene transferred into target organism
• organism cells take up vector and useful gene it contains
  = produce protein that gene codes for

Question 9

Why do we do genetic engineering at early stages of embryo

Answer 9

Make sure all of the cells receive the transferred gene
= organism develops with characteristic that we want

Question 10

Adv of cloning plants

Answer 10

Because clone is genetically identical to original plant we know exactly what clone’s characteristics will be

Question 11

Describe cuttings cloning method

Answer 11

• small piece of plant removed and dipped into rooting powder
  = contains plant hormones
  = encourages plant to develop roots
  = produce genetically identical clone of starting plant

Question 12

Describe tissue culture cloning method

Answer 12

• take plant we want to clone and divide plant into hundreds of tiny pieces
• each piece contains small number of cells
• small groups of cells incubated with plant hormones
  = stimulate plant to grow and develop into fully grown clones
• conditions must be sterile
  = reduce entry of microorganisms

Question 13

Why do we need sterile conditions

Answer 13

Don’t want to introduce any microorganisms such as bacteria or fungi

Question 14

Why is tissue culture used in commercial farming

Answer 14

Allows growers to produce thousands of genetically identical plants quickly and cheaply
= can be certain they will get desired characteristics as they’re clones
Preserve rare species of plants

Question 15

Describe embryo transplants

Answer 15

• start with sperm of animal with desired characteristics
• fertilisation produces fertilised egg
• allow egg to develop into an early stage embryo
• cells must not start to specialise
• use glass rod to spilt embryo into 2
• transplant embryos into host mothers
  = two identical clones

Question 16

Problem with embryo transplant

Answer 16

As we start with sperm and an egg
= can’t be certain that offspring will have desired characteristic

Question 17

Benefit of adult cell cloning

Answer 17

Cloning from an adult
= we know characteristics clone will have

Question 18

Stages of adult cell cloning

Answer 18

• remove a cell from animal we want to clone
• remove nucleus of cell that contains genetic info of animal were cloning
• take unfertilised egg cell from same species
• remove nucleus from unfertilised egg and throw it away
• insert nucleus from original adult body cell into empty egg cell
• give egg cell an electric shock
• makes egg cell divide to form an embryo
• when embryo developed it’s inserted into the womb of an adult female to continue development

Question 19

Why was Darwin’s theory not accepted

Answer 19

• at time people believed god made all animals and plants
• not enough evidence
• not understand how genetics are inherited

Question 20

Describe Lamark’s theory

Answer 20

When characteristic regularly used it becomes more developed
= strengthened characteristic passed on to offspring

Question 21

Why was Lamark wrong

Answer 21

Changes that occur in an organisms lifetime can’t be passed onto offspring

Question 22

How does speciation work

Answer 22

Need a geographical barrier to separate a population into 2
= prevent interbreeding between populations

Question 23

Describe gene therapy

Answer 23

Giving person the healthy version of a gene

Question 24

Problem and solution of gene therapy

Answer 24

Faulty gene would be in all cells
= hard to transfer new gene to every cell

Could transfer the gene at early stage of development eg egg or embryo stage
= as person grows healthy gene passed into all other cells

Question 25

Pros and cons of GM crops

Answer 25

Pros
- crops with desirable characteristics
= more fruits for LICs
- can make sure plants make special nutrients
Eg golden rice has beta carotene to prevent blindness
- increase growth rates of plants and yield

Cons
- don’t know how they can affect health
- chance plants make way to wild and out compete local plants
= change whole ecosystem

Question 26

Examples of genetic engineering

Answer 26

• bacteria produce hormone insulin to treat diabetes
• crops resistant to disease, insects etc
• drugs in sheep milk to extract and treat diseases

Question 27

Pros and cons of cloning

Answer 27

Pros
- produces lots of offspring with specific desirable feature
- study of clone could help research into embryo development
- bring back species that are extinct

Cons
- may lead to human cloning
- clones have low survival rate
- clones have genetic problems
- reduced gene pool

Question 28

Why does clone of adult cell cloning look nothing like mother

Answer 28

Clone contains none of her genetic material