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GCSE Biology > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

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1
Q

What is sexual reproduction?

A

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

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2
Q

What are gametes?

A

Reproductive cells.

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3
Q

What are the gametes in animals?

A

Sperm and egg cells.

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4
Q

What is different about gametes from normal cells in terms of chromosomes?

A

Gametes only contain half the number of chromosomes of normal. Normal cells have the full number of chromosomes

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5
Q

What’s the difference between haploid and diploid cells?

A

Haploid is half the number of chromosomes and diploid is the full number of chromosomes.

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6
Q

What happens at fertilisation?

A

A male gamete fuses with a female gamete to produce a fertilised egg, also known as a zygote. The zygote ends up with a full set of chromosomes (so it’s diploid)

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7
Q

What happens to the zygote during fertilisation?

A

It undergoes cell division by mitosis and develops into an embryo.

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8
Q

How is meiosis different to mitosis?

A

It doesn’t produce identical cells.

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9
Q

In humans, where does meiosis occur?

A

Only in the reproductive organs.

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10
Q

What are the results of meiosis?

A

You get 4 haploid daughter cells. These are gametes and each gamete has only a single set of chromosomes. The gametes are all genetically different.

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11
Q

How do cells reproduce asexually?

A

By mitosis.

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12
Q

What are the products of asexual reproduction?

A

Two diploid daughter cells that are genetically identical to each other and the parent.

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13
Q

How do cells reproduce sexually?

A

By meiosis

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14
Q

What are the advantages of asexual reproduction

A
  • Can produce lots of offspring very quickly because the reproductive cycle is so fast
  • Only one parent is needed
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15
Q

Why is producing a lot of offspring very quickly advantageous?

A

This allows organisms to colonise a new area very rapidly.

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16
Q

Why is only needing one parent advantageous?

A

organisms can reproduce whenever conditions are favourable without having to wait for a mate.

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17
Q

What is the disadvantage of reproducing asexually?

A

There’s no genetic variation between offspring in a population

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18
Q

Why is no genetic variation a disadvantage?

A

If the environment changes and conditions become unfavourable, the whole population may be affected.

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19
Q

What is the advantage of sexual reproduction?

A

It creates genetic variation within the population meaning different individuals have different characteristics.

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20
Q

Why is genetic variation advantageous?

A

If the environmental conditions change, it’s more likely that at least some of the population will have the characteristics to survive the change. Over time, this can lead to natural selection and evolution as species become better adapted to the environment.

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21
Q

What are the disadvantages of sexual reproduction?

A
  • It takes more energy than asexual reproduction so organisms produce less offspring in their lifetime.
  • Two parents are needed for sexual reproduction
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22
Q

What is DNA and what is it made up of?

A

DNA is a polymer and is made up of nucleotides

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23
Q

What is a nucleotide?

A

A repeating unit

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24
Q

What does each nucleotide consist of?

A
  • A sugar molecule
  • A phosphate molecule
  • A base
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25
Q

What does the sugar and phosphate molecule form?

A

A ‘backbone’ to the DNA strands

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26
Q

What are the 4 bases?

A

Adenine, thymine, cytosine, guanine

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27
Q

Which bases are complimentary to each other?

A

Adenine-Thymine

Cytosine-Guanine

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28
Q

What is it called when the bases are paired with each other?

A

Complimentary base pairing

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29
Q

What are the complimentary base pairs joined together by?

A

Weak hydrogen bonds.

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30
Q

What is the structure of a DNA strand described as?

A

Two strands coiled together to form a double helix.

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31
Q

What is a chromosome?

A

A long, coiled up molecule of DNA found in the nucleus of eukaryotic cells.

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32
Q

What is a gene?

A

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

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33
Q

What does all of an organisms DNA make up?

A

It’s genome

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34
Q

What does the DNA control?

A

Protein synthesis in a cell.

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35
Q

What is protein synthesis?

A

The production of proteins.

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36
Q

What are proteins made up of?

A

Amino acids

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37
Q

How do proteins get their own shape?

A

The amino acid chains fold up to give each protein a different, specific shape.

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38
Q

Why do proteins need different shapes?

A

So they can have different functions.

39
Q

What decides the order of amino acids in a protein?

A

The order of bases in a gene

40
Q

What is a base triplet?

A

A sequence of three bases in a gene that each amino acid of coded for

41
Q

What is a non-coding region of DNA?

A

A region of DNA that doesn’t code for an amino acid. Despite this, some of these regions are still involved in protein synthesis.

42
Q

What is a mutation?

A

A rare, random change to an organism’s DNA base sequence that can be inherited.

43
Q

What does a mutation in a gene produce?

A

A genetic variant.

44
Q

What’s a genetic variant?

A

A different version of the gene.

45
Q

What may happen if a genetic variant is produced?

A

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

46
Q

What could happen if a proteins shape and activity changes?

A

It could end up changing the phenotype (characteristics) of an organism.

47
Q

What’s an organisms genome?

A

All of an organisms DNA (including the non-coding region)

48
Q

Where are proteins made?

A

Cytoplasm

49
Q

What sub cellular structure makes proteins?

A

Ribosomes

50
Q

Where is DNA found?

A

Cell nucleus

51
Q

What does the cell need to do with the genetic information and what problem is there?

A

It needs to get the information from the DNA in the nucleus to the ribosomes in the cytoplasm, however the DNA is too big to move out of the nucleus.

52
Q

How is the problem of the DNA being too big solved?

A

Using a molecule called messenger RNA (mRNA)

53
Q

What is messenger RNA?

A

Like DNA it’s a polymer of nucleotides, but it’s shorter and only a single strand.

54
Q

What is RNA polymerase?

A

The enzyme involved in joining together RNA nucleotides to make mRNA.

55
Q

What is the first stage of transcription?

A

RNA polymerase binds to a region of non-coding DNA in front of a gene.

56
Q

What is the second stage of transcription?

A

The two DNA strands unzip and the RNA polymerase moves along one of the strands of DNA

57
Q

What is the third stage of transcription?

A

It uses the coding DNA in the gene as a template to make the mRNA. Base pairing between the DNA and RNA ensures that the mRNA is complementary to the gene.

58
Q

What is the fourth and final stage of transcription?

A

Once made, the mRNA molecule moves out of the nucleus and joins with a ribosome.

59
Q

What is the first stage of translation?

A

Amino acids are brought to the ribosomes by another RNA molecule called transfer RNA (tRNA)

60
Q

What is the second stage of translation?

A

The order in which the amino acids are brought to the ribosome matches the order of the base triplets (codons)

61
Q

What is the third stage of translation?

A

Part of the tRNA’s structure is called an anticodon - it is complementary to the codon for the amino acid. The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order.

62
Q

What is the fourth and final stage of translation?

A

The amino acids are joined together by the ribosome. This makes a polypeptide (protein)

63
Q

What happens if a mutation occurs in the non-coding region of the DNA that the RNA polymerase has to bind to?

A

It could affect the ability of the polymerase to bind to it. It might make it easier to bind to or harder.

64
Q

What does how well RNA polymerase can bind to this region of DNA affect?

A

How much mRNA is transcribed and therefore how much protein is produced. Depending on the function of the protein, the phenotype of an organism may be affected by how much of it is made.

65
Q

Who was Gregor Mendel?

A

An Austrian monk who trained in mathematics and natural history.

66
Q

What did Mendel not of his garden plot in the mid 19th century?

A

He noted how characteristics in plants were passed on from one generation to the next.

67
Q

Describe Mendels experiment on the height of peas.

A

In an experiment, Mendel crossed two pea plants of different heights - a tall pea plant and a dwarf pea plant. The offspring produced were all tall pea plants. He then bred two of the tall offspring together. He found that when the offspring from the first cross were crossed with each other, three tall offspring were produced for every one dwarf offspring overall.

68
Q

What were Mendels three conclusions about hereditary in plants?

A

1) Characteristics in a plant are determined by “hereditary units”
2) Hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
3) Hereditary units can be dominant or recessive - if an individual has both the dominant and the recessive gene, the dominant characteristic will be expressed.

69
Q

What are hereditary units known as today?

A

Genes

70
Q

What are alleles?

A

Different versions of a gene.

71
Q

How many alleles for every gene are there in your body?

A

2

72
Q

What is the difference between homozygous and heterozygous?

A

Homozygous is when an and organisms has two of the same alleles for a particular gene and heterozygous is when an organism has two different alleles for a particular gene.

73
Q

What is your genotype?

A

The combination of alleles you have.

74
Q

What do you alleles determine?

A

Your phenotype

75
Q

What is monohybrid inheritance?

A

The inheritance of a single characteristic

76
Q

What is the 23rd pair of chromosomes labelled in the human body cell?

A

XX or XY

77
Q

What makes a characteristic sex-linked?

A

If the allele that codes for it is located on a sex chromosome (X or Y)

78
Q

Why does the Y chromosome carry fewer genes than the X chromosome?

A

It’s smaller

79
Q

What is the effect of men only having one X chromosome?

A

They often only have one allele for sex-linked genes meaning the characteristic of this allele is shown, even if it’s recessive.

80
Q

What is a sex-linked genetic disorder?

A

Disorders caused by faulty alleles located on the sex chromosomes.

81
Q

Which two blood groups are co-dominant with each other?

A

A and B

82
Q

What does co-dominant mean in terms of blood groups?

A

When an individual has both of these alleles (genotype A and B) then they’ll have blood type AB.

83
Q

Which blood type is recessive?

A

O

84
Q

Which blood type is universal recipient, what does this mean and why?

A

Type AB - this means they can receive blood from any of the blood types because type AB avoids incompatibility reactions when a person with AB blood receives blood from another ABO group.

85
Q

What blood type is universal donor what does this mean and why?

A

Type O - this means they can donate blood to any blood type because type O blood is compatible with any blood recipients type.

86
Q

How is genetic variation within a species caused?

A

Organisms having different alleles which can lead to differences in phenotypes. Can be caused by new alleles arising through mutations. Sexual reproduction also causes variation since it results in alleles being combined in lots of different ways in offspring.

87
Q

What is environmental variation also known as?

A

Acquired characteristics.

88
Q

What are acquired characteristics?

A

Characteristics that organism acquire during their lifetimes.

89
Q

What is a neutral mutation?

A

A mutation that doesn’t have an effect on an organisms phenotype

90
Q

What was the Human Genome project?

A

The idea was to find every single human gene. It officially started in 1990 and a complete map of the human genome, including the locations of around 20,500 genes was completed in 2003.

91
Q

What would the benefits be if doctors knew which genes predisposed people to which diseases?

A

We could all get individually tailored advice on the best diet and lifestyle to avoid our likely problems. Doctors could also check us regularly to ensure early treatment if we do develop the diseases we’re susceptible to.

92
Q

How could the Human Genome Project help us to develop new and better medicines?

A

S scientists can design new drugs that are specifically tailored to people with a particular genetic variation. They can also determine how well an existing drug will work for an individual.

93
Q

What would be the drawbacks of the advantages of the Human Genome Project?

A
  • Increased stress - if you knew you were susceptible to a serious disease
  • People with genetic problems could come under pressure to not have kids
  • Discrimination by employers of insurers if susceptible to serious diseases.

GCSE Biology (9 decks)

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