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Edexcel Biology Gcse > Changing The Genes > Flashcards

Changing The Genes Flashcards

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1
Q

Alleles

A

Different forms of the same gene

Some characteristics are controlled by a single gene, such as fur in animals and red-green colour blindness in humans. Each gene might have different forms, and these are called alleles.

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2
Q

Autosomes

definition

A

Chromosomes that control the characteristics of an organism but do not determine its sex

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3
Q

What is Beta-carotene?

A

A red-orange pigment important in the diet for maintaining health

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4
Q

Cloning

definition

A

A scientific method by which genetically identical copies are made of animals or plants

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5
Q

What are Cuttings?

A

Part of a plant stem, leaf, or root cut off and used for producing a new plant. An artificial propagation method

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6
Q

What is an Explant?

A

A small piece taken from a plant, used in plant cloning

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7
Q

What does Exponential mean?

A

A set of numbers that increase more and more rapidly

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8
Q

What is Genetic engineering?

A

A process of changing the structure of a particular gene, usually to remove defects

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9
Q

Genotype

definition

A

The alleles that an organism has for a particular characteristic, usually written as letters

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10
Q

In vitro

definition

A

In vitro experiments are done in glassware such as test tubes and Petri dishes

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11
Q

What is Insulin?

A

A hormone that regulates the level of sugar in the blood and can be produced by genetically modified bacteria

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12
Q

Mutation

definition

A

A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes

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13
Q

Plasmid

definition

A

The small circular genetic material present in bacterial cells and used in genetic engineering or genetic modification

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14
Q

Recessive

definition

A

Describes the variant of a gene for a particular characteristic which is masked or suppressed in the presence of the dominant variant. A recessive gene will remain dormant unless it is paired with another recessive gene

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15
Q

Selective breeding

definition

A

An artificial process in which organisms with desired characteristics are chosen as parents for the next generation

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16
Q

Tissue culture

definition

A

Tissue culture is the growth of tissues or cells separate from an animal or plant

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17
Q

Toxin

definition

A

A type of natural poison produced by an organism, often as a form of protection

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18
Q

Vector

A

The way in which genetic material is transferred from a donor to a recipient, eg viruses, bacterial cells or plasmids

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19
Q

Yield

definition

A

The mass of a crop produced

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20
Q

Zygote

definition

A

A fertilised egg cell

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21
Q 
define codominance
(inheritance of blood groups)
A

Some alleles are both expressed in the same phenotype, this is called codominance.

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22
Q

How are codominant alleles shown?

A

Both codominant alleles are shown with upper case letters in genetic diagrams, but the letters used are different. For example, feather colour in hens may be white, black or speckled (it has both white feathers and black feathers).

The alleles can be shown as W for white and B for black.

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23
Q

codominance

What are the 3 possible genotypes?

A

There are three possible genotypes: WW BB and BW.

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24
Q

codominance

What are the 3 possible phenotypes?

A

There are also three possible phenotypes: WW = white, BB = black, and BW = speckled.

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25
Q

Blood groups

The gene controlling human ABO blood groups has three alleles, not just two:

A
  • IA and IB are not dominant over one another

- both are dominant over IO

26
Q

Diploid human body cells have how many pairs of chromosomes, where?

A

Diploid human body cells have 23 pairs of chromosomes in the nucleus.

27
Q

22 pairs of human body chromosomes are known as what?

What is the function and name of the 23rd pair?

A

Twenty two pairs are known as autosomes, and control characteristics, but the 23rd pair carries genes that determine sex and are known as the sex chromosomes.

28
Q

A genetic diagram, like a Punnett square, shows what?

A

A genetic diagram, like a Punnett square, shows how alleles may combine in zygote. The diagram below shows how sex is inherited.

29
Q

Sex-linked disorders

A

All genetic conditions are called disorders and those that inherit them are called sufferers. Most genetic disorders, like cystic fibrosis, require two recessive alleles to be inherited (one from the mother and one from the father). So if a person inherited both recessive alleles they would be a sufferer. If a person receives only one recessive allele, their one dominant allele means they do not have symptoms of the disorder. However, they are able to pass it to their children. They are called a carrier.

If alleles for a disorder appear on the sex chromosomes they are called sex-linked. Men have one X chromosome and one Y chromosome. The Y chromosome is smaller than the X chromosome and does not possess as many genes. If a gene is contained on the part of the X chromosome that is missing from the Y chromosome, men only have one allele for that gene, rather than the usual two. If the allele on the X chromosome codes for a disorder, the man will always have the disorder because there isn’t another allele on the Y chromosome to mask the effect of the allele. This means that even conditions caused by a recessive allele will be inherited by the man because there cannot possibly be a dominant allele on the X chromosome to mask the effect of that recessive allele.

30
Q

What is the genome of an organism?

A

The genome of an organism is the entire genetic material of that organism. Each of your diploid body cells (not sperm, eggs or red blood cells) has one copy of your entire genome.

31
Q

The mapping of the whole human genome has great importance for medicine. In order to exploit its secrets, it is vital that the human genome is fully understood. It enables us to:

A
  • search for genes linked to different types of disease
  • understand inherited disorders and their treatment
  • trace human migration patterns from the past
32
Q

What is selective breeding?

A

Selective breeding or artificial selection is when humans breed plants and animals for particular genetic characteristics. Humans have bred food crops from wild plants and domesticated animals for thousands of years.

33
Q

Main steps in selective breeding

Selective breeding takes place over many generations. These are the main steps for both plants and animals:

A

1) Decide which characteristics are important enough to select.
2) Choose parents that show these characteristics from a mixed population. They are bred together.
3) Choose the best offspring with the desired characteristics to produce the next generation.
4) Repeat the process continuously over many generations, until all offspring show the desired characteristics.

34
Q

Characteristics can be chosen for usefulness or appearance.

Desired characteristics in plants:

A
  • disease resistance in food crops
  • wheat plants that produce lots of grain
  • large or unusual flowers
35
Q

Characteristics can be chosen for usefulness or appearance.

Desired characteristics in animals:

A
  • animals that produce lots of milk or meat
  • chickens that lay large eggs
  • domestic dogs that have a gentle nature
36
Q

Reasons the new varieties produced by selective breeding are good.

A

The new varieties may be economically important. For example, they may provide more or better quality food, or allow farmers to feed more people.

37
Q

Problems with selective breeding

A

Because of selective breeding, future generations of selectively bred plants and animals will all share very similar genes which will reduce variation. Genes and their different alleles within a population are known as its gene pool. Inbreeding can lead to a reduced gene pool, making it more difficult to produce new varieties in the future. This also makes organisms prone to certain diseases or inherited defects.

38
Q

Benefits of selective breeding include:

A
  • new varieties may be economically important, by producing more or better quality food
  • animals can be selected that cannot cause harm, for example cattle without horns
39
Q

Risks of selective breeding include:

A
  • reduced genetic variation can lead to attack by specific insects or disease, which could be extremely destructive
  • rare disease genes can be unknowingly selected as part of a positive trait, leading to problems with specific organisms, eg a high percentage of Dalmatian dogs are deaf
  • creation of physical problems in specific organisms, eg large dogs can have faulty hips due to not being formed correctly
40
Q

Cloning in plants

overview

A

Clones are genetically identical individuals. The cloning of plants has many important commercial implications. It allows a variety of a plant with desirable characteristics to be produced cheaply, quickly and on a large scale. Cloning often follows genetic engineering. It allows many copies of the new organism to be produced.

Cloning expensive food crops has been carried out for many years, and causes the public fewer ethical and moral concerns than animal cloning.

41
Q

Cuttings

Cloning in plants

A

The simplest way to clone a plant involves taking a cutting. This is an old but simple technique, used by gardeners. A branch from the parent plant is cut off, its lower leaves are removed, and the stem is planted in damp compost. Plant hormones are often used to encourage new roots to develop. The cutting is usually covered in a clear plastic bag to keep it moist and warm. After a few weeks, new roots develop and a new plant grows.

42
Q

Tissue culture

Cloning in plants

A

Another way of cloning plants is by tissue culture. It works with small pieces of plants, called explants. These are grown in vitro using sterile agar jelly that contains plant hormones and nutrients. This makes tissue culture more expensive and difficult to do than taking cuttings. This is an important way to preserve rare plant species or grow commercially in larger nurseries.

43
Q

The process of cloning plants by tissue culture

A

1) Tissue sample scraped from parent plant
2) Tissue sample placed in agar growth medium containing nutrients and auxins
3) Samples develop into tiny plantlets
4) Plantlets planted into compost

44
Q

The process of cloning animals by embryo transplant
in cows for best milk production
(cloning in animals)

A

1) Sperm is taken from a bull from a high yield dairy herd
2) Cow is artificially inseminated with sperm
3) Zygotes develop into embryos in cow and then removed from the uterus
4) Embryos are split into several smaller cells before they become specialised, each of which can grow into a new calf
5) Identical embryos are transplanted into host mothers

45
Q

What is the most basic technique of animal cloning?

A

Embryo transplants

46
Q

Cloning in animals

The method for adult cell cloning is:

A

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

47
Q

Current uses of genetic engineering

Human insulin in bacteria

A

Diabetes is a disorder in which the body’s blood glucose levels remain too high because glucose is not effectively removed from the blood. It can be treated by injecting insulin. The injected insulin acts just as natural insulin and causes glucose to be taken up by the liver and other tissues, which results in cells receiving the glucose they need, and blood glucose levels stay normal.

Bacterial cells have been genetically modified to produce substances such as human insulin.

48
Q

Current uses of genetic engineering

Genetically modified crops

A

Current genetically modified crops include those that are resistant to insect attack or are herbicide resistant, this produces increased yields. Herbicide resistant crops allow them to tolerate herbicide, but the weeds are killed by it, therefore less herbicide is needed.

49
Q

Current uses of genetic engineering

Golden rice

A

Scientists have added a gene to wild rice that makes it produce beta carotene. This changes the colour of the wild rice to a golden colour. Beta carotene is needed by humans in order to make vitamin A which is essential for good vision.

The advantage of golden rice is that it can be used in areas where vitamin A deficiency is common, so it can help prevent blindness. In many countries golden rice is not being grown commercially over fears associated with genetically modified crops.

50
Q

Current uses of genetic engineering

Ethics

A

There are ethical issues involved in genetic modification, as well as concerns about the possible health risks of genetically modified food. For example, a genetically modified food might contain a substance that causes an allergic reaction in some people, or higher levels of a toxin naturally found in the food. Others think it is ethically wrong to create new life forms, or to move genes between different species.

51
Q

Current uses of genetic engineering

Future uses

A

In the future, researchers are hoping to use genetic engineering to be able to overcome some inherited disorders, such as cystic fibrosis and Huntington’s disease amongst others.

52
Q

The main steps of genetic engineering:

A

1) Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are a short section of unpaired bases
2) A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.
3) The vector and the isolated gene are joined together by ligase enzyme.
4) The vector inserts the gene into required cells.
5) The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.

53
Q

Benefits of genetic engineering:

A
  • Genetic engineering is a 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 resistance from Bacillus thuringiensis can be inserted into the plants. The plant produces toxins, which would discourage insects from eating the crop.
  • Sterile insects could be created, such as mosquitoes. They would breed with fertile mosquitos, but be unable to reproduce. This would reduce the number of offspring and may help with spread of diseases, such as malaria, dengue fever and the Zika virus.
54
Q

Risks of genetic engineering:

A
  • Transfer of the selected gene into other species. What benefits one plant may harm another.
  • Some people believe it is not ethical to interfere with nature in this way. Also, genetically engineered crop seeds are often more expensive and so people in developing countries cannot afford them.
  • Genetically engineered crops could be harmful, for example toxins from the crops have been detected in some people’s blood.
  • Genetically engineered crops could cause allergic reactions in people.
  • Pollen produced by the plants could be toxic and harm insects that transfer it between plants.
55
Q

(Agricultural solutions to the demands of a growing population)
Selective breeding
This process has occurred for thousands of years. Farmers have naturally known to breed large bulls with large cows to get large calves. This is the process of selective breeding:

A

1) Decide which characteristics are important enough to select.
2) Choose parents that show these characteristics from a mixed population. They are bred together.
3) Choose the best offspring with the desired characteristics to produce the next generation.
4) Repeat the process continuously over many generations, until all offspring show the desired characteristics.

56
Q

(Agricultural solutions to the demands of a growing population)
Genetic modification
Genetic modification is a more recent technology than the process of selective breeding. It involves moving a gene for a desirable characteristic from one organism to another. This is the process of genetic modification:

A

1) Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are short strands of unpaired bases.
2) A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.
3) The vector and the isolated gene are joined together by ligase enzyme.
4) The vector inserts the gene into required cells.
5) The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.

57
Q

(Agricultural solutions to the demands of a growing population)
Intensive farming
Intensive farming is a series of techniques that maximise the yield of animal or plant crops. Give examples of intensive farming (Actions, treatments, Explanation and side effects.)

A
  • Action: Remove competing plants from the crop growing area
    Treatment: Herbicide spray
    Explanation: Allows more energy to be transferred to the crop
    Side effect: Reduces biodiversity. May have harmful effect on health.
  • Action: Remove animals that feed on the crop
    Treatment: Pesticide spray
    Explanation: Prevents energy being transferred from the crop to consumers
    Side effect: Reduces biodiversity. May poison helpful organisms.
  • Action: Keep animals indoors
    Treatment: ‘Battery’ farming
    Explanation: Reduces energy transferred to environment so more energy available for growth
    Side effect: Increased risk of disease. Lower quality product. Ethical concerns.
58
Q

Biological control

Agricultural solutions to the demands of a growing population

A

Biological control is an alternative to using pesticides. By releasing a natural predator into the crop growing area, the number of pests can be reduced. This can have unforeseen consequences as the numbers of different organisms in the food web are changed. There have been examples of the predator becoming a more serious pest than the original problem.

59
Q

Why are more men red green colour-blind?

A

Men are more likely to be colour-blind because it is a sex-linked disorder.

60
Q

How many base pairs are in the human genome?

A

There are over three billion base pairs in the human genome.

61
Q

What molecules are used to cut DNA in genetic modification?

A

Restriction enzymes are used to cut DNA in genetic modification.

Edexcel Biology Gcse (36 decks)

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