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GCSE Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

What does DNA stand for?

A

DeoxyriboNucleic Acid

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2
Q

What does DNA determine?

A

What inherited characteristics you have

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3
Q

How many chromosomes does a human cell nucleus contain?

A

23 pairs

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4
Q

What do chromosomes carry?

A

Genes

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5
Q

What do genes do?

A

Control the development of a characteristic e.g. Hair colour

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6
Q

What is a gene?

A

A section of DNA

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7
Q

What are alleles?

A

Different versions of the same gene, which give different characteristics

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8
Q

What is mitosis?

A

Mitosis is when a cell reproduces itself by splitting to form two identical offspring

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9
Q

Why is mitosis needed?

A
  1. To grow
  2. Replace worn out cells
  3. Repair damaged tissue
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10
Q

Describe what happens in mitosis

A

When the cell gets the signal to divide, it doubles all its chromosomes. The chromosomes line up at centre of the cell and cell fibres pull them apart. Membranes form around each of the sets of chromosomes. Lastly, the cytoplasm divides, leaving two cells with identical DNA.

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10
Q

What is meiosis?

A

Meiosis produces cells which have half the normal number of chromosomes

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12
Q

Describe what happens during meiosis

A

The cell duplicates its DNA. In the first division, the chromosome pairs line up in the centre of the cell. The pairs are then pulled apart, so each new cell only has one copy of each chromosome. In the second division the chromosomes line up again in the centre of the cell and are pulled apart.

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13
Q

What is meiosis for?

A

Producing gametes

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14
Q

What is special about cells that are undifferentiated and what are they called?

A

They can develop into different types of cell. They are called stem cells

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15
Q

Where are stem cells found?

A

Early human embryos

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16
Q

Where are stem cells found in adults?

A

Bone marrow

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17
Q

How can blood diseases be treated using stem cells?

A

Bone marrow transplants. Bone marrow contains stem cells than can turn into new blood cells to replace the faulty old ones

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18
Q

What can embryonic stem cells be used for?

A

Could be used to replace faulty cells in sick people - you could make beating heart muscle cells for people with heart disease.

19
Q

What is therapeutic cloning?

A

An embryo would be produced with the same genes as the patient,so any cells produced from this embryo would not be rejected by the patients body

20
Q

How is cancer caused?

A

By cells dividing out of control

21
Q

How is a tumour formed?

A

When cells start to divide in an abnormal and uncontrolled way.

22
Q

What are the two types of tumour?

A

Benign and malignant

23
Q

What is benign tumour?

A

Where the tumour grows until there’s no more room. The cells stay where they are and don’t invade other tissues. It normally isn’t dangerous

24
Q

What is a malignant tumour?

A

This is where the tumour grows and can spread to healthy tissue. Some malignant tumour cells can get into the bloodstream and circulate around the body. Here, the malignant cells invade healthy tissues and form secondary tumours. They are dangerous and can be fatal

25
Q

Give two ways that tumours can be formed

A

Chemicals and radiation

26
Q

How do chemicals cause tumours?

A

Chemical carcinogens are chemicals that can cause cancer. The chemicals interfere with normal cell functions, causing cells to divide uncontrollably and form a tumour

27
Q

How does ionising radiation cause cancer?

A

Ionising radiation breaks molecules up into ions. These ions interfere in the normal reactions going on inside the cell. They can cause the cell to start dividing abnormally, producing a tumour.

28
Q

What is a homozygous cell?

A

When the two alleles are the same

29
Q

What is a heterozygous cell?

A

When the two alleles are different

30
Q

Define genotype

A

The alleles you have

31
Q

Define phenotype

A

The characteristics you have

32
Q

What is cystic fibrosis caused by?

A

A recessive allele

33
Q

What is polydactyl caused by?

A

A dominant allele

34
Q

What is sickle-cell anaemia caused by?

A

A recessive allele

35
Q

What happens in embryo transplants?

A
  1. Sperm cells are taken from a prize bull and egg cells are taken from a from a prized cow
  2. The sperm are used to artificially fertilise an egg cell. The embryo that develops is then split many times before any cells become specialised
  3. These clones are then implanted into lots of other cows where they grow into baby calves
36
Q

What happens in adult cell cloning?

A
  • take an unfertilised egg cell and remove its nucleus. A complete set of chromosomes is from an adult body cell is inserted to the empty egg cell
  • the egg cell is stimulated by an electric shock - this makes it divide, just like a normal embryo
  • when the embryo is a ball of cells, it is implanted into a surrogate mother to grow into a clone of the original adult body cell
37
Q

Give negative issues surrounding cloning

A
  1. You get a reduced gene pool. This means that there are fewer different alleles in the population so if a new disease appears they might all be wiped out
  2. Cloned animals might not be as healthy as normal ones e.g Dolly the sheep had arthritis
  3. Some people worry that humans might be cloned in the future
38
Q

Give 2 positive issues surrounding cloning?

A
  1. The study of animal clones could lead to greater understanding of the development of the embryo, and of ageing and age-related disorders.
  2. Cloning could help to preserve endangered species
39
Q

Describe what happens during genetic engineering?

A
  1. A useful gene cut from one organisms chromosome using enzymes
  2. This gene is inserted into a vector - usually a virus or a bacterial plasmid
  3. The vector is then used to insert the gene into a different organism, or into the chromosome of the different organism. The DNA is used to make a protein
40
Q

What are GM crops?

A

Crops that have had their genes modified

41
Q

Why are crops genetically modified?

A

To make them resistant to viruses, insect attacks or herbicides

42
Q

Give 3 pros of GM crops?

A
  1. GM Crops can increase the yield of a crop, making more food
  2. People in developing countries often lack nutrients in their diets. GM crops could be engineered to contain the nutrient that’s missing
    3 GM crops are already being grown elsewhere in the world often without any problems
43
Q

Give three disadvantages with GM crops?

A
  1. Some people say that growing GM crops will affect the number of weeds and flowers that live around the crops - reducing farmland biodiversity
  2. People are worried they might develop allergies to the food
  3. Transplanted genes may get out into the environment. E.g. Superweeeds could be created

GCSE Biology (12 decks)

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