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Biology 1 > B1.7 Genetic Variation And Its Control > Flashcards

B1.7 Genetic Variation And Its Control Flashcards

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1
Q

What are the two things that affect variation?

A
  • Genetic variation.

* Environmental variation.

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2
Q

What is environmental variation?

A

•Any difference that has been caused by the conditions something lives in.

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3
Q

What are the genetic factors that affect variation?

A

•Sexual reproduction- offspring inherit characteristics.

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4
Q

What are the environmental factors that affect variation?

A
  • Nutrition.
  • Temperature.
  • Light.
  • Physical factors.
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5
Q

What is the nucleus?

A

•A large organelle found in most cells, that contains genetic information (red blood cells used to have a nucleus).

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6
Q

What does the nucleus contain?

A
  • Genetic material in the form of chromosomes.

* The human cell nucleus contains 23 pairs of chromosomes.

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7
Q

What are chromosomes?

A
  • Thread-like structures made up of DNA.

* Found in the nucleus.

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8
Q

What do chromosomes carry?

A
  • They are made of DNA.
  • They carry genes.
  • Different genes control the development of different characteristics e.g. hair colour.
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9
Q

Structures which carry information for a large number of characteristics are called?

A

•Chromosomes.

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10
Q

How many chromosomes does the human cell nucleus contain?

A

•23 pairs of chromosomes (46 all together- 23 from each parent). They are always in pairs.

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11
Q

What are genes?

A
  • Long lengths of DNA.
  • Small sections of a chromosome that control the characteristics of an organism.
  • They are passed on from parent to offspring, resulting in similar characteristics.
  • Different genes control the development of different characteristics of an organism e.g. eye colours.
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12
Q

What is a coiled up DNA?

A

•A chromosome.

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13
Q

What is an organism’s characteristics determined by?

A

•Genes inherited from their parents.
•These genes are passed on in sex cells (gametes) which the offspring develop from.
•The combination of genes from two parents cause genetic variation.
•Some characteristics are determined only by genes (e.g. violet flower colour).
•In animals these include:
-Eye colour.
-blood group.
-inherited disorder.

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14
Q

What are alleles?

A

•Different versions of the same gene.

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15
Q

What causes offspring to have the same eye colour?

A

•The dominant gene of the parents.

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16
Q

What is fertilisation?

A
  • The joining (fusing) of male and female gametes.
  • The mixture of genetic information from two parents leading to variation in offspring.
  • Genes are passed on in the gametes, from which offspring develop.
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17
Q

What is sexual reproduction?

A
  • Involves two parents.
  • They produce male and female sex cells (gametes: sperm and eggs).
  • Genetic information from two organisms (a father and a mother) is combined to produce offspring which are genetically different to either parent.
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18
Q

What are the advantages of sexual reproduction?

A
  • Variation is allowed.
  • Evolution is more likely to occur.
  • Species cannot be wiped out by a single disease.
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19
Q

Where is sperm made?

A

•In the testes.

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20
Q

Where are eggs made?

A

•In the ovaries.

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21
Q

What is asexual reproduction?

A
  • Involves only one individual as a parent.
  • There is no fusion of gametes or mixing of genetic information resulting in no variation.
  • The offspring are genetically identical to the parent-they’re clones.
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22
Q

Why do gametes have half the usual number of chromosomes?

A
  • During sexual reproduction they fuse together to form a new individual.
  • This produces variation as the individual will inherit 50% of DNA from each parent.
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23
Q

How does asexual reproduction work?

A
  • X- shaped chromosomes have two identical halves. So each chromosome splits down the middle to form two identical sets of half chromosome (i.e. two sets of DNA strands).
  • A membrane forms around each set and the DNA replicates itself to form two identical cells with complete sets of X-shaped chromosomes.
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24
Q

What are the advantages of asexual reproduction?

A
  • Suited for organisms in one place (they do not need to find a mate).
  • No risk of genetic problems in offspring.
  • They are clones.
25
Q

What are the disadvantages of asexual reproduction?

A
  • There is no variation.
  • Entire groups can be wiped out by disease.
  • Species cannot adapt to new environments.
26
Q

What are examples of asexual reproduction?

A
  • Bacteria or yeast cells use binary fission.
  • Plants use runners, bulbs or vegetative propagation.
  • Some invertebrates like starfish and hydra produce asexual offspring.
27
Q

What are clones?

A

•Genetically identical individuals.

28
Q

How can plants be cloned?

A
  • Gardeners can take cuttings from good parent plants, and then plant them to produce genetically identical copies (clones) of the parent plant.
  • These plants can be produced quickly and cheaply.
29
Q

How can plants be cloned by tissue culture?

A
  • Few plant cells are put in a growth medium with hormones, and they grow into new plants- clones of the parent plant.
  • These plants can be made very quickly, in very little space, and be grown all year.
30
Q

What does tissue culture involve?

A

•Using small groups of cells from a part of a plant to grow new plants.

31
Q

What do embryo transplants involve?

A
  • Splitting apart cells from a developing animal embryo before they become specialised.
  • The identical embryos are then implanted into the wombs of host mothers.
32
Q

Describe the process of animal cloning using embryo transplants? (Between a bull and a cow)

A
  • Sperm cells are taken from a prize bull and egg cells are taken from a prize cow.
  • The sperm is then used to artificially fertilise an egg cell.
  • The embryo that develops is then split many times to form clones before any cells become specialised.
  • These clone embryos can then be implanted into lots of host cows where they grow into baby calves (which will be genetically identical to each other).
33
Q

What is the offspring of animal cloning always?

A

•The offspring is always a clone of the male parent as the genetic information of the father is used.

34
Q

What are the advantages of embryo transplants in animals?

A

•The technique could be used to produce high yielding products.
•It is faster than the traditional way of breeding animals- herds of animals can be produced faster.
•The study of animal clones could lead to
greater understanding of the development of the embryo, and of ageing and age-related disorders.

35
Q

What are the disadvantages of embryo transplants in animals?

A
  • People do not want this procedure used in humans.

* It could provide more embryos for scientific testing which causes ethical problems.

36
Q

How can animals be cloned by adult cell cloning?

A
  • The nucleus is removed from an unfertilised egg cell.
  • It is replaced with the nucleus of an adult cell (e.g. skin cell).
  • An electric shock is used to start the cell division to form embryo cells.
  • These embryo cells contain the same genetic information as the adult cell.
  • When the embryo has developed into a ball of cells it is inserted into the uterus of an adult female to continue its development.
  • This technique was used to create Dolly- the famous cloned sheep.
37
Q

Why is an adult cell used in adult cell cloning?

A

•Adult cells contain 46 chromosomes.

38
Q

What are the advantages of adult cell cloning?

A
  • It can be used to clone animals of desired characteristics.
  • It could be used to save animals from extinction.
39
Q

What are the disadvantages of adult cell cloning?

A
  • People don’t want designer babies.
  • If it is used in farming, it produces more genetically identical individuals reducing the gene pool and if there is a disease an entire population can be wiped out.
40
Q

What is genetic engineering?

A

•Using genes from chromosomes of humans and other organisms cut out using enzymes and transferred to cells of other organisms.

41
Q

What is genetic engineering used in?

A
  • Vaccine production.
  • Production of insulin for diabetics.
  • GM crops.
42
Q

Describe the process of genetic engineering.

A
  • Cut out the insulin gene from the chromosome of a human cell using an enzyme.
  • Remove a ring of DNA from a bacterium and open it up using the same enzyme.
  • Insert the insulin gene into the plasmid using another enzyme. Enable a bacterium to take up the altered DNA.
  • Put the bacterium in a fermenter, and it multiples many times. Each new bacterium contains the insulin gene.
  • The bacteria produce insulin which can be extracted.
43
Q

How can genes be transferred into animals and plants?

A

•The same method (genetic engineering uses enzymes to cut and paste genes) could be used to transfer useful genes into animals and plants at the very early stages of their development (i.e. shortly after fertilisation).

44
Q

List the issues listed with cloning:

A

Few different alleles in a population:
•Cloning quickly gets you lots of ‘ideal’ offspring but you also get a ‘reduce gene pool’- this means there are fewer different alleles in a population.
•If a population are all closely related and a new disease, they could all be wiped out- there may be no allele in the population giving resistance to the disease.
Not as healthy:
•It’s possible that cloned animals might not be as healthy as normal ones- e.g. Dolly the sheep had arthritis, which tends to occur in older sheep (but the jury’s still out on if this was due to cloning).
•Humans might be cloned in the future. If it was allowed, any success may follow many unsuccessful attempts- e.g. children born severely disabled.

45
Q

What are the advantages of genetic engineering?

A
  • Cures genetic diseases.

* Improves quality of plants.

46
Q

What are the disadvantages of genetic engineering?

A
  • Designer babies can be created.
  • It does not always work.
  • Un-natural.
  • There are religious morals/it is un-ethical.
  • Long-term effects are unknown- changing a person’s genes might accidentally create unplanned problems which could be inherited by future generations.
47
Q

What are the reasons for cloning?

A
  • Cures diseases.
  • It is not tested on animals.
  • Kill a human or a bundle of cells?
  • More understanding of the body.
48
Q

What are the reasons against cloning?

A
  • Diversity of genes are effected.
  • Procreation sex act.
  • Some cells can mutate.
  • Bodies may reject the transplant.
  • Animal testing is the same a human testing.
  • Negative side effects.
49
Q

What are stem cells?

A
  • A class of undifferentiated cells that are able to differentiate into specialised cell types.
  • From two main sources: embryos and adult tissue.
  • These can grow into any type of cell found in the body.
50
Q

What are the advantages of genetically modified crops?

A
  • GM crops can increase the yield of a crop, making more food
  • People living in developing nations often can lack nutrients in their diets. GM crops could be engineered to contain the nutrients that’s missing. For example, they’re testing ‘golden rice’ that contains beta-carotene- lack of this substance causes blindness.
  • GM crops are already being grown elsewhere in the world (not the UK) often without any problems.
51
Q

What are the disadvantages of using genetic engineering in GM crops?

A
  • Long-term, unpredicted effects of consuming GM plants on human health.
  • Genes for pesticide resistance may spread from GM plants to their wild relatives, creating pesticide resistant weeds.
  • People may want to manipulate the genes of their future children.
52
Q

How many chromosomes does a human gamete contain?

A
  • 23 chromosomes- half the number of chromosomes in a normal cell (instead of having two of each chromosome, a gamete has just one of each).
  • The egg and the sperm cell then fuse together (fertilisation) to form a cell with the full number of chromosomes.
53
Q

Looking at the similarities and differences between organisms, it allows us to classify them into groups. For example…?

A
  • Plants make their own food (by photosynthesis) and are fixed in the ground.
  • Animals move about the place and can’t make their own food.
  • Microorganisms are different to plant and animals e.g. bacteria are single-celled.
54
Q

What are the developed characteristics genetic engineering uses enzymes to cut and paste genes?

A
  • Genetic modified (GM) crops have had their genes modified e.g. to make them resistant to viruses, insects or herbicides (chemicals used to kill weeds).
  • Sheep have been genetically engineered to produce substances, like drugs, in their milk that can be used to treat human diseases.
  • Genetic disorders like cystic fibrosis are caused by faulty genes. Scientists are trying to treat these disorders by inserting working genes into sufferers. This called gene therapy.
55
Q

What are the cons of genetically modified crops?

A
  • Not everyone is convinced that GM crops are safe. People are worries they may develop allergies to the food- although there’s probably no more risk for this than for eating usual foods.
  • Some people say that growing GM crops will effect the number of weeds and flowers (and so the population of insects) that live in and around the crops- reducing farmland biodiversity.
  • A big concern is that transplanted genes may get out into the natural environment. For example the herbicide resistance gene may be picked up by weeds, creating a new ‘super weed’ variety.
56
Q

What are the reasons against cloning?

A
  • Diversity of genes are effected.
  • Procreation sex act.
  • Some cells can mutate.
  • Bodies may reject the transplant.
  • Animal testing is the same as human testing.
  • Negative side effects.
57
Q

What are the advantages of trying to preserve endangered species?

A
  • To maintain biodiversity.
  • Animals may be economically useful in the future.
  • To maintain food chains and ecosystems.
58
Q

When does genetic modification occur when it is used on animals?

A

•At early stage of development, before cells become specialised.

59
Q

What does DNA stand for?

A

•Deoxyribonucleic acid.

Biology 1 (9 decks)

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