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Biology GCSE > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

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1
Q

What does sexual reproduction produce?

A

Genetically different cells

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2
Q

What is sexual reproduction?

A

Where genetic information from two organisms is combined to produce offspring which are genetically different

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3
Q

What happpens in fertilisation?

A

A male gamete fuses with a female gamete and forms a zygote

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4
Q

What happens to the zygote?

A

It undergoes cell division and develops into an embryo

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5
Q

Why does the embyro inherit characteristics from both parents?

A

It has recieved a mixture of chromosomes froom mum and dad

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6
Q

How is meiosis different to mitosis?

A

Meisosis only happens in the reproductive organs and doesn’t produce identical cells

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7
Q

What does meiosis produce?

A

Non-identical cells

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8
Q

What happens in the first division of meiosis?

A

DNA is duplicated

The chromosomes line up and the pairs are pulled apart and put into the new cells

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9
Q

What type of cell division does the zygote undergo?

A

Mitosis

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10
Q

What happens in the second division of meiosis?

A

The chromosomes line up again and the chromatids are pulled apart
You get four haploid daughter cells that are genetically different

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11
Q

What are the arms of the chromosomes called?

A

Chromatids

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12
Q

Why is it important genes are mixed up?

A

To introduce genetic variation

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13
Q

The haploid gamete of a plant species has 12 chromosomes
Two of these gametes fuse to make a zygote
How many chromosomes will there be in the zygote?

A

24

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14
Q

How does meiosis introduce genetic variation?

A

The products of meiosis are all genetically different, as some of the mothers chromosomes and some of the fathers go into different cells

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15
Q

How do asexual organisms reproduce?

A

Mitosis

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16
Q

How do sexual organisms reproduce?

A

Meisois and the production of genetically different haploid gametes which fuse to form a diploid cell

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17
Q

What are the advantages of asexual reproduction

A

Lots of offspring can be made quickly

Only one parent is needed

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18
Q

Whats the advantage of lot of offspring being made quickly?

A

An area can be colonised very rapidly

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19
Q

Whats the advantage of only needing one parent?

A

The organisms can produce when conditions are favourable

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20
Q

Whats the disadvantages of asexual reproduction

A

No genetic variation

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21
Q

Whats the disadvantages of having no genetic variation?

A

If there is an environment change, the whole population may be affected

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22
Q

Strawberry plants produce asexually

Discuss the advantages and disadvantages of this form of reproduction

A

There will be no genetic variation therefore if there is an environment change the whole population may be affected
However, there will be lots of offspring that can be made extremely quickly reducing the chance of extinction and also allowed an area to be colonised extremely quickly
Only one parent is needed therefore the parent can reproduce when conditions are more favourable without having to mate

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23
Q

What does each nucleotide consist of?

A

A sugar
A phosphate group
One base

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24
Q

What do the sugar and phosphate groups form?

A

A ‘backbone’ to the DNA strands

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25
Q

What are the four different bases in DNA?

A

A, T, C, G

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26
Q

What can DNA be described as?

A

Two strands of Nucleotides, that consist of a Sugar and Phosphate group with one of the four different bases attached to the sugar, coiled to form a double helix
The strands are linked by a series of complementary base pairs joined together by weak hydrogen bonds

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27
Q

How are the strands linked in DNA?

A

By a series of complementary base pairs joined together by weak hydrogen bonds

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28
Q

What are the complementary base pairs?

A

A and T

C and G

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29
Q

What are the complementary base pairs joined together by?

A

Weak hydrogen bonds

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30
Q

What are chromosomes?

A

Long, coiled up molecules of DNA

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31
Q

What is a gene?

A

A section of DNA on a chromosome that codes for a particular protein

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32
Q

What is a genome?

A

All of an organism’s DNA

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33
Q

How do you extract DNA from fruit cells?

A

Mash strawberries and put them in a beaker with detergent and salt
FIlter the mixture to get the froth and big, insoluble bits of cell out
Add some ice-cold ethanol

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34
Q

What does the detergent do?

A

Break down the cell membranes to release the DNA

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35
Q

What does the salt do?

A

Make the DNA clump together

36
Q

Why is ice-cold ethanol added?

A

The DNA is not soluble in cold ethanol

37
Q

What is formed after you extract DNA from fruit cells

A

A stringy white precipitate

38
Q

Which DNA bases pair up according to complementary base pairing?

A

A and T

C and G

39
Q

Why is it useful to use salt when extracting DNA?

A

It clumps the DNA together which makes it much easier to see and will allow it to interact with the ice-cold ethanol easier

40
Q

How are proteins made?

A

By reading the code in DNA

41
Q

What are proteins made of?

A

Chains of molecules called amino acids

42
Q

What do the amino acid chains do?

A

Fold up to give each protein a different, specific shape

43
Q

Why do proteins have different functions?

A

The amino acids fold to give a different and specific shape

44
Q

What do the non-coding regions of DNA do?

A

Nothing but some may still be involved in protein synthesis

45
Q

What is a mutation?

A

A rare, random change to an organisms DNA base sequence

46
Q

How does a mutation affect the organism?

A

The variant may code for a different sequence of amino acids which may change the shape of the final protein and so its activity

47
Q

Explain how a gene can code for a particular protein?

A

The order of bases in a gene determines the order of the amino acids
Each gene contains a different order of bases, which the gene can code for a particular protein

48
Q

Explain how a genetic variant can result in a protein with a very low activity?

A

A genetic variant could alter the sequence of amino acids coded for by a gene which could affect the shape of the protein, decreasing its activity

49
Q

What are the two stages of protein synthesis?

A

Transcription and Translation

50
Q

What happens in the transcription of proteins?

A

RNA polymerase binds to a region of non-coding DNA in front of a gene
The two DNA strands unzip and the RNA polymerase moves along one of the strands of the DNA
It uses the coding DNA in the gene as a template to make the mRNA

51
Q

What is RNA polymerase?

A

An enzyme involved in joining together RNA nucleotides to make mRNA

52
Q

Why can’t DNA move out of the cell nucleus?

A

It is too large

53
Q

What is mRNA

A

Messsenger RNA which is a polymer of nucleotides expect it’s shorter and only a single strand

54
Q

What happens in the translation of proteins?

A

Amino acids are brought to the ribosome by tRNA

The order of the amino acids matches the mRNA and joins together to make a polypeptide

55
Q

What are base triplets in mRNA called?

A

Codons

56
Q

What is an anticodon?

A

Complementary to the codon for the amino acid

57
Q

Why does non-coding DNA affect the binding of RNA polymerase?

A

RNA polymerase must bind to a non-coding DNA

If a mutation happens in this region it could affect the ability of RNA (easier or harder)

58
Q

How does the ability to bind to the non-coding DNA affect protein synthesis?

A

How much mRNA is transcribed and therefore how much is produced
The potential phenotype of the orgaism (depending on the function of the protein)

59
Q

Describe how a gene is transcribed to form mRNA?

A

RNA polymerase binds to a noncoding region of the DNA and the two DNA strands unzip and the RNA polymerase moves along one of the strands to the coding region in which it copies the gene as a template using complementary base pairs

60
Q

What did Mendel do for his first experiment?

A

He bred a tall pea plant with a small pea plant, the offspring were all tall pea plants
He then bred the offspring together where he found a 3:1 of tall:dwarf plants

61
Q

What did Mendel show through his experiment?

A

The height characteristic in pea plants were determined by separately inherited units passed on from each parent

62
Q

Suggest why the importance of Mendel’s work wasn’t realised straight away?

A

Scientists then didnt have the background knowledge to understand his findings

63
Q

What is a homozygous?

A

An organism that has two alleles for a particular gene that are the same

64
Q

What is a heterozygous?

A

An organism that has two different alleles for a particular gene

65
Q

What is the genotype?

A

The specific alleles the organism has

66
Q

What is the phenotype?

A

The characteritic the genotype represents

67
Q

What sex chromosomes do males have?

A

XY

68
Q

What sex chromosomes do females have?

A

XX

69
Q

What does sex determination depend on in humans?

A

The sperm (male)

70
Q

What chromosomes do eggs always possess?

A

X

71
Q

When is a characteristic sex-linked?

A

If the allele that codes for it is located on a sex chromosome

72
Q

Give examples of sex-linked disorders?

A

Colour blindness

Haemophillia

73
Q

Haemophillia is caused by a recessive allele located on the X chromosome. A couple are having a baby
The mother is a carrier of haemophillia
The father does not have the disorder
What is the probability the son will have haemophillia?

A

25%

74
Q

Haemophillia is caused by a recessive allele located on the X chromosome. A couple are having a baby
The mother is a carrier of haemophillia
The father does not have the disorder
What is the probability the daughter will have haemophillia?

A

0%

75
Q

How many blood types do humans have?

A

O, A, B and AB

76
Q

What blood genes are codominant?

A

IA and IB

77
Q

Why are IA and IB codominant?

A

One allele isn’t dominant over the other one (there is no recessive)
Both genotypes when together show both phenotypes

78
Q

Explain how a mother with A and a father with B can have a child with O?

A

Both parents may have O as a recessive, therefore, although unlikely, both gametes that produce the zygote may have O as the gene so the offspring will have O blood

79
Q

What types of variation are possible?

A

Genetic and environmental

80
Q

How is genetic variation caused?

A

By organisms having different alleles which can lead to differences in phenotype

81
Q

How does sexual reproduction lead to variation?

A

Sexual reproduction offers many different combinations of offspring due to meisosis producing 4 genetically different gametes

82
Q

How does the environment affect variation?

A

Organisms will acquire characteristics to combat environmental changes

83
Q

What is most variation often involved with?

A

A mix of genetic and environmental factors

84
Q

Give an example of a mix of genetic and environmental factors?

A

A plants max height is determined by its genes, however, how far it actually grows depends on the environment

85
Q

What are neutral mutations?

A

Mutations that show no phenotype (effect) on an organism

Biology GCSE (9 decks)

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