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Biology - Unit Two > Cell Division and Inheritance > Flashcards

Cell Division and Inheritance Flashcards

1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

How is DNA found?

A

In long molecules called chromosomes in the nucleus.

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3
Q

What kind of structure does DNA have?

A

Double helix - it is made of two separate strands that are coiled around each other in a spiral.

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4
Q

What is a gene?

A

A section of DNA. It contain the information on how to arrange amino acids to make proteins.

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5
Q

What are the two exceptions to the rule that DNA is unique?

A

Identical twins and clones

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6
Q

What is DNA fingerprinting?

A

A way of cutting up someone’s DNA and separating it into small sections to produce a unique set of bands in a gel.

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7
Q

What are two uses of DNA fingerprinting?

A
  • Paternity testing - if you have the DNA fingerprinting of a child and its potential fathers you can compare them. The candidate whose fingerprint is most like the child’s will be the father
  • Forensic science
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8
Q

Why are some people in favour of having a national database of DNA fingerprints?

A

It would speed up the process of investigating crimes.

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9
Q

Why are some people opposed to having a national database of DNA fingerprints?

A
  • Invasion of privacy
  • Worries about security
  • Tests can show false positives
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10
Q

How many copies of each chromosome does a cell usually have?

A

Two - one from the mother and one from the father.

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11
Q

How many chromosomes does a human cell have?

A

46 (23 pairs)

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12
Q

What is mitosis?

A

When a cell reproduces itself by splitting into two identical offspring.

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13
Q

When is mitosis used?

A
  • When plants and animals want to grow
  • When plants and animals need to replace cells
  • In asexual reproduction
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14
Q

What happens during mitosis?

A

1) The cell copies its DNA.
2) The chromosomes line up and have the cell fibres pull them apart to the opposite ends of the cell
3) Membranes form around each set of chromosomes to become the nuclei of two new cells
4) Lastly, the cytoplasm divides to create two new cells containing exactly the same DNA.

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15
Q

What is an allele?

A

Different versions of the same gene.

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16
Q

What happens during sexual reproduction?

A

Two gametes combine to form a new individual. Each gamete contains 23 chromosomes so the offspring ends up with 46.

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17
Q

What is meiosis?

A

Cell division in which the products have half the normal number of chromosomes.

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18
Q

What happens during meiosis?

A

1) The cell copies its DNA
2) In the first division, the chromosome pairs line up in the centre of the cell and are then pulled apart so each new cell only has one copy of each chromosome.
3) In the second division the chromosomes line up at the centre of the cell and the arms are pulled apart to either end of the cell.
4) Cell membrane forms around each set of chromosomes and so four cells are created.

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19
Q

What is differentiation?

A

The process by which a cell becomes specialised for its job. This ability is lot early on in animal cells but plants always have this ability.

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20
Q

Where are stem cells found?

A

Early human embryos and in bone marrow.

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21
Q

What can stem cells do?

A

Become any kind of cell as it has yet to undergo differentiation.

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22
Q

What is a use of bone marrow stem cells?

A

Treating anaemia. Having a bone marrow transplant gives someone the capacity to make more red blood cells to replace the faulty ones.

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23
Q

What are three uses of embryonic stem cells?

A
  • Heart muscle cells can replace damaged tissue in people with heart disease
  • Nerve cells can replace spinal tissue in people paralysed by spinal injuries
  • Insulin producing cells can replace faulty cells in those with diabetes
24
Q

Why are some people against embryonic stem cell research?

A

Each embryo is a potential human life so shouldn’t be interfered with.

25
Q

Why are some people in favour of embryonic stem cell research?

A

They argue that curing patients who are already alive is more important than the rights of embryos.

26
Q

What settlement have the for and against embryonic stem cell parties reached?

A

To only use embryos that would otherwise be thrown away from IVF labs.

27
Q

Which chromosome pair are the sex chromosomes?

A

The 23rd pair

28
Q

What sex chromosomes do males have?

A

XY

29
Q

What sex chromosomes do females have?

A

XX

30
Q

What are the chances of each sperm cell getting an X or a Y chromosome?

A

50% either way

31
Q

How do you draw a Punnett Square?

A

1) Draw a two-by-two grid
2) Put the chromosomes from one parent along the top and the chromosomes from the other parents along the side.
3) Then fill in each square with the letter from the top and the letter from the side.

32
Q

Who was Gregor Mendel?

A

An Austrian monk who noted how characteristics in plants were passed on. He is now known as the father of modern genetics.

33
Q

What plant did Mendel work with?

A

Pea plants

34
Q

What happened when Mendel bred a tall pea plant and a short pea plant?

A

The offspring were all tall pea plants.

35
Q

What happened when Mendel bred two of the tall pea plants from his earlier experiment?

A

The offspring where three talk plants and one short plant.

36
Q

What conclusion did Mendel reach?

A

1) Characteristics are determined by hereditary units.
2) Hereditary units are passed on by both parents.
3) Hereditary units are recessive or dominant.

37
Q

What does a capital letter on a Punnett Square represent?

A

A dominant hereditary unit.

38
Q

What does a lower case letter on a Punnett Square represent?

A

A recessive hereditary unit.

39
Q

What do we now know hereditary units to be?

A

Alleles

40
Q

What does homozygous mean?

A

When an organism has two of the same alleles for a particular gene.

41
Q

What does heterozygous mean?

A

When an organism has two different alleles for a particular gene.

42
Q

What does genotype mean?

A

What alleles an organism has.

43
Q

What does phenotype mean?

A

The characteristic an organism has as a result of the alleles it has.

44
Q

What are genetic disorders?

A

Disorders that are caused by abnormal genes or chromosomes.

45
Q

What is cystic fibrosis?

A

A genetic disorder of cell membranes. It results in the body producing thick mucus in the air passages and the pancreas.

46
Q

Is the allele for cystic fibrosis dominant or recessive?

A

Recessive

47
Q

What proportion of people carry the cystic fibrosis gene?

A

1 in 25

48
Q

What is a carrier?

A

A person who carries a recessive allele without being affected by it. It is possible for them to pass this allele on to their offspring.

49
Q

If both parents are cystic fibrosis carriers, what is the percentage chance that their offspring has cystic fibrosis?

A

25%

50
Q

What is polydactyly?

A

A genetic disorder where a baby is born with extra fingers or toes. It isn’t life threatening just inconvenient.

51
Q

Is polydactyly caused by a dominant or recessive allele?

A

Dominant

52
Q

If a polydactyly sufferer breeds with somebody who is unaffected, what is the likelihood of the offspring having polydactyly?

A

50%

53
Q

What is a method of detecting genetic disorders?

A

Embryonic screening.

54
Q

What is PGD?

A

Pre-implantation Genetic Diagnosis is when doctors check the embryos during IVF to make sure that they only put healthy embryos into the uterus.

55
Q

What is CVS?

A

Chorionic Villus Sampling is carried out between 10 and 13 weeks of pregnancy. A sample of cells is taken from the placenta and analysed. If the cells are found to have a genetic disorder, the parents can decide whether or not to terminate the pregnancy.

56
Q

What are the arguments in favour of embryonic screening?

A
  • It helps to stop people suffering from some genetic disorders
  • Screening embryos could reduce health costs
  • During IVF some embryos are destroyed anyway
  • If an embryo is diagnosed using CVS, the parents don’t have to choose abortion
57
Q

What are the arguments against embryonic screening?

A
  • Fears that people will begin to screen embryos for trivial things like hair colour
  • Implies that disabled people are undesirable
  • After PGD, the unwanted embryos are destroyed so are not given the chance to develop into humans
  • There’s a link between CVS and miscarriage

Biology - Unit Two (8 decks)

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