B14 - variation and evolution fact test

Question 1

what is variation

Answer 1

the differences in phenotypes in a population

Question 2

what differences can variation be due to

Answer 2

• the genes they have inherited (genetic causes)
• conditions in which they have developed (environmental)
• combination of genes and the environment

Question 3

what do all variants arise from

Answer 3

mutations
most have no effect on the phenotype but some influence the phenotype and very few determine phenotype

Question 4

what is evolution

Answer 4

evolution is a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

Question 5

how does evolution by natural selection happen

Answer 5

1. there is variation between organisms
2. the best adapted have an advantage
3. these organisms are more likely to survive and reproduce
4. they pass on useful alleles to offspring
5. the useful characteristics becomes more common in the population

Question 6

what is natural selection described as

Answer 6

survival of the fittest because if you have an advantage, you are more likely to survive and reproduce, passing on your advantageous alleles to your offspring

Question 7

when are 2 organisms from the same ancestor become classed as different species

Answer 7

when they become so different in phenotype that they can no longer interbreed to produce fertile offspring

Question 8

what is selective breeding

Answer 8

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

Question 9

what are the steps involved in selective breeding

Answer 9

1. decide desirable characteristics
2. choose parents with desirable characteristics and breed them together
3. select best offspring and breed them together
4. repeat the process continuously over many generations until all of the offspring show desired characteristics

Question 10

what are some characteristics desired in animals

Answer 10

• produce more meat or milk
• animals with gentle temperaments
• aesthetic
• without specific genetic defects

Question 11

what are some characteristics desired in food crops

Answer 11

• disease resistant
• bigger yield of fruit

Question 12

what are the characteristics desired in plants

Answer 12

big or unusual coloured flowers

Question 13

what can selective breeding lead to

Answer 13

‘inbreeding’ where some breeds are particularly prone to disease or inherited defects

Question 14

what is genetic engineering (genetic modification)

Answer 14

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

Question 15

what have plant cells been engineered for

Answer 15

• resistant to diseases, pests and herbicides
• produce bigger better fruits/increased yield of fruit
• have more nutritional value e.g golden rice

Question 16

what have bacterial cells been engineered to produce

Answer 16

useful substances such as human insulin to treat diabetes

Question 17

what is the process of genetic engineering

Answer 17

1. genes from chromosomes are cut out using restriction enzymes leaving sticky ends (short sections of exposed, unpaired bases)
2. a virus or bacterial plasmid is cut using the same restriction enzyme to also create sticky ends. this also creates an antibiotic marker gene
3. the loop and gene sticky ends are joined together by DNA ligase enzymes
4. the combined loop is placed in a vector, such as a bacterial cell and then allowed to multiply as it will now contain the modified gene

Question 18

in plants, where is the vector placed into

Answer 18

meristematic cells which can then produce identical copies of the modified plant

Question 19

what are concerns about genetically modified crops

Answer 19

• effect on populations of wildflower and insects
• some people feel the effects of eating GM crops on human health have not been fully explored

Question 20

how is genetic modification used in medicine

Answer 20

• may be possible to cure genetic disorders
• this is called gene therapy and involves transferring normal genes into patients so the correct proteins are produced

Question 21

what are the benefits of genetic modification

Answer 21

• faster and more efficient way of getting the same results as selective breeding
• improve crop yields or crop quality, which is important in developing countries. this may help reduce hunger around the world
• introduce herbicide resistance, which results in less herbicides being used as weeds are quickly and selectively killed
• insect and pest resistance can be developed and inserted into the plant . the plant produces toxins which would discourage insects from eating the crop
• sterile insects could be created such as a mosquito. they would breed, leading to infertile offspring. this may help with the spread of diseases, such as malaria, dengue fever and the zika virus

Question 22

what are the risks of genetic modification

Answer 22

• transfer of the selected gene into other species, what benefits one plant could harm another
• some believe it’s not ethical to interfere with nature in this way
• GM crop seeds are often more expensive and so people in developing countries can’t afford them
• GM crops could be harmful e.g. toxins from the crops have been detected in some people’s blood
• pollen produced by the plants could be toxic and harm insects that transfer it between plants

Question 23

what are the 4 types of cloning methods

Answer 23

cuttings, tissue culture, adult cell cloning and embryo transfers

Question 24

what are cuttings

Answer 24

cuttings from a plant can be used to make identical new plants

Question 25

what is tissue culture

Answer 25

• using small groups of cells from part of a plant to grow identical new plants
• this is important for preserving rare plant species or commercially in nurseries
• tissue sample scraped from plant, placed in agar growth medium containing nutrients and auxins, samples develop into tiny plantlets which are planted into compost

Question 26

what is adult cell cloning

Answer 26

• remove an egg cell from a donor sheep
• remove nucleus from sheep you wish to clone
• insert the DNA into the donor egg cell
• electric shock to allow the cells to divide
• insert back into the uterus

Question 27

what is an embryo transfer

Answer 27

• a developing embryo is removed from a pregnant animal at an early stage, before the embryo’s cells have had time to become specialised
• the cells are separated, grown for a while in a lab then transported into host mothers - producing identical offspring