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Biology- B2 > B2.7 Cell division and inheritance > Flashcards

B2.7 Cell division and inheritance Flashcards

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1
Q

What do body cells divide by?

A

mitosis

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2
Q

What do chromosomes contain?

A

genetic information

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3
Q

Describe what happens when a body cell divides by mitosis

A

copies of genetic material are made.

then the cell divides once to form 2 genetically identical body cells

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4
Q

When does mitosis occur?

A

during growth or to produce replacement cells

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5
Q

What are sex cells called?

A

gametes

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6
Q

How many sets of chromosomes do body cells have?

A

2

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7
Q

How many sets of chromosomes do gametes have

A

1

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8
Q

How many pairs of chromosomes does a human body cell have?

A

23

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9
Q

Why do gametes only have 1 set of chromosomes (one copy of each chromosome)?

A

So when the sperm and egg fuse, you will get 46 chromosomes again.

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10
Q

What are the reproductive organs?

A

testes and ovaries

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11
Q

Which cells divide by meiosis to form gametes?

A

cells in reproductive organs -testes and ovaries

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12
Q

What is meiosis?

A

A type of cell division which produces cells which have half the normal number of chromosomes (gametes)

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13
Q

Describe what happens when a cell divides to to form gametes (meiosis)

A

Copies of the genetic information are made.

Then the cell divides twice to form 4 gametes, each with a single set of chromosomes.

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14
Q

What happens when gametes join at fertilisation?

A

a single body cell with new pairs of chromosomes is formed. A new individual then develops by this cell repeatedly dividing by mitosis

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15
Q

What are genetic diagrams?

A

biological models which can be used to predict the outcomes of crosses

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16
Q

Most type of animal cells differentiate at an early stage whereas many plant cells retain the ability to….

A

differentiate throughout life.

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17
Q

What are stem cells?

A

cells from adult bone marrow and human embryos which can be made to differentiate into many different types of cells. eg nerve cells

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18
Q

Human stem cells have the ability to differentiate into…

A

any kind of human cell

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19
Q

What may treatment with stem cells be able to do?

A

help conditions such as paralysis

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20
Q

What are some advantages of using embryonic stem cells?

A
  • Have the ability to develop into any kind of human cell unlike stem cells in adult bone marrow
  • cure diseases and saving lives
  • embryos used in research are only unwanted ones, which would probably just be destroyed
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21
Q

What are some disadvantages of using embryonic stem cells?

A
  • Killing potential human life
  • Embryo can not give consent
  • Some believe should use other sources of stem cells
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22
Q

What are the cells of offspring produced by asexual reproduction produced by?

A

mitosis from the parent cells - they contain the same alleles as the parents so there’s so variation

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23
Q

Why does sexual reproduction give a rise to variation?

A

Fertilisation occurs

which leads to the mixing of genetic information

one copy of each allele comes from each parent

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24
Q

What are the sex chromosomes in females?

A

XX

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25
Q

What are the sex chromosomes in males?

A

XY

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26
Q

What is an allele?

A

a different form of the same gene

27
Q

What is a dominant allele?

A

expresses if just one copy of the allele is present

28
Q

What is a recessive allele?

A

An allele that controls the development of characteristics only if the dominant allele is not present

29
Q

What does DNA stand for?

A

deoxyribo nucleic acid

30
Q

What structure does DNA have?

A

a double helix structure

31
Q

What are chromosomes made up of?

A

large molecules of DNA

32
Q

Each gene code for a particular combination of amino acids which makes a…

A

specific protein

33
Q

What is DNA finger printing used to do?

A

identify individuals

34
Q

Some disorders are…

A

inherited

35
Q

Describe the genetic disorder - polydactyly

A

having extra fingers or toes- caused by a dominant allele of a gene and can therefore be passed on if only one parent has the disorder

36
Q

Describe the genetic disorder- Cystic fibrosis

A

-a disorder of cell membranes

must be inherited from both parents. The parents may be carriers of the disorder without actually having the disorder themselves. It can be caused by a recessive allele of a gene and can therefore be passed on by parents, neither of whom has the disorder.

37
Q

Where are chromosomes found?

A

in body cells in the nucleus

38
Q

Why may embryos be screened?

A

To check for alleles that cause genetic disorders

39
Q

Give some reasons why people may be against embryo screening

A
  • expensive
  • implies that people with genetic problems are ‘undesirable’ which could increase prejudice
  • May become a point where everyone wants to screen their embryos so they can pick the most desirable one ‘designer babies’
  • rejected embryos are destroyed
  • embryos have a right to life
40
Q

Give some reasons why people are for embryo screening

A
  • It will help stop people suffering
  • There are laws to stop it going too far
  • Treating disorders costs the government a lot of money so it reduces healthcare costs
41
Q

Describe the work of Mendel

A

Mendel cross bred pea plants.

Discovered:

  • characteristics in plants are determined by ‘hereditary units’
  • hereditary units can be dominant or recessive
  • hereditary units are passed on from both parents, one unit from each parent
42
Q

Why was the importance of Mendel’s discovery not recognised until after his death?

A

Nobody knew anything about genes or DNA

Mendel was not a well respected scientist

43
Q

What does it mean if an organism is homozygous?

A

it has 2 alleles for a particular gene the same. (eg AA)

44
Q

What does it mean if an organism is heterozygous?

A

2 alleles for a particular gene are different (eg Aa)

45
Q

What is a dominant allele shown by?

A

a capital letter

46
Q

What is a recessive allele shown by?

A

a small letter

47
Q

What does genotype mean?

A

combination of alleles you have (eg Bb)

48
Q

What does phenotype mean?

A

The characteristic you have (eg tall)

49
Q

From a family tree diagram, how can you tell if a disease is recessive (is not dominant)

A

if someone in the family carry the allele but are not sufferers

50
Q

Explain why offspring produced by sexual reproduction will look similar to its parents

A

because genes are passed from parents

51
Q

Explain why off spring produced by sexual reproduction will not be identical to either of its parents?

A

Chromosomes are from 2 parents

Environmental factors

may have been a mutation

52
Q

What is affected by cystic fibrosis?

A

cell membranes

53
Q

What is a gene?

A

a small section of DNA that codes for a particular combination of amino acids that make a specific protein

53
Q

What is the principle behind DNA finger printing?

A

every individual apart from identical twins has different DNA

54
Q

Why is it easier to clone plants than animals?

A

Most plant cells retain the ability to differentiate throughout life whereas most animal cells become specialised during the formation of an embryo

55
Q

Is polydactyl dominant or recessive?

A

dominant

56
Q

is cystic fibrosis dominant or recessive?

A

recessive

57
Q

What are the features of polydactyl?

A

extra fingers or toes

58
Q

What happens to the genetic material before the cell divides?

A

it replicates

59
Q

Why is it important that a sperm cell has 23 chromosomes?

A

as a sperm cell fuses with an egg cell

fertilised egg cell now has 46 chromosomes- the full number

60
Q

give advantages of using stem cells from adult skin cells instead of from embryo cells

A
  • no risk of damage to the embryo
  • adult can give consent for the removal of cells
  • skin cells are more accessible
61
Q

Explain why stem cells can be used to treat conditions such as paralysis?

A

because stem cells can be made to differentiate into nerve cells

62
Q

What are some differences between mitosis and meiosis

A

mitosis one cell division, meiosis 2 cell division

cells produced by mitosis have 2 sets of chromosomes. cells produced by meioses have one set of chromosomes

Biology- B2 (8 decks)

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