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GCSE Biology - Edexcel > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

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1
Q

Which structures are found inside the nucleus?

A

chromsomes

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2
Q

Which substance forms a long strand in each chromosome?

A

DNA

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3
Q

How do body cells make copies of themselves?

A

cell division, mitosis

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4
Q

How many chromosomes are there in a human body cell nucleus?

A

46

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5
Q

What happens in fertilisation?

A

two gametes fuse

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6
Q

What is the name of the cell formed in fertilisation?

A

zygote, fertilised egg cell

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7
Q

Which term means producing more of the same kind of organism?

A

reproduction

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8
Q

What is the name of the human male gamete?

A

sperm cell

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9
Q

The DNA strand in a chromosome contains sections that carry instructions for characteristics. What are these sections called?

A

genes

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10
Q

What molecule forms the genome of an organism?

A

DNA

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11
Q

Where are genes found?

A

[in sections of DNA] on chromosomes

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12
Q

What does a gene carry the instructions for?

A

making a protein

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13
Q

A protein is made by linking together smaller molecules. What are these smaller molecules called?

A

amino acids

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14
Q

What is any molecule made of repeating units called?

A

a polymer

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15
Q

A human cell contains 46 strands of DNA. Is it diploid or haploid?

A

diploid

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16
Q

Are the cells produced by meiosis haploid or diploid?

A

haploid

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17
Q

Are the cells produced by mitosis haploid or diploid?

A

diploid

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18
Q

What shape is DNA?

A

a double helix

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19
Q

What is a chromosome made out of?

A

DNA and proteins [to package the DNA]

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20
Q

What shape is a DNA molecule?

A

double helix

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21
Q

What part of a DNA strand contains the instructions for a protein?

A

gene

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22
Q

What are the letters of the bases that form the DNA code?

A

A,C,T and G

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23
Q

How do these bases pair up in DNA?

A

A with T, C with G

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24
Q

Apart from bases, what other parts are needed in a DNA molecule?

A

phosphate group, sugar

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25
Q

What is one phosphate group, one sugar and one base called?

A

nucleotide

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26
Q

Why is DNA a polymer?

A

It is made of many nucleotides joined in a chain.

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27
Q

Give an example of a protein.

A

any example. E.g. an enzyme

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28
Q

How is the active site of an enzyme formed?

A

by folding of protein/polypeptide/amino acid chains

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29
Q

Why are proteins polymers?

A

They are made of many amino acids joined in a chain.

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30
Q

Triple only- What molecule is produced in transcription?

A

mRNA or messenger RNA

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31
Q

Triple only- What base does mRNA contain that DNA does not?

A

uracil

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32
Q

Triple only-What is the name of the enzyme that allows transcription to occur?

A

RNA polymerase

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33
Q

Triple only-The mRNA nucleotides fit together with the nucleotides on the DNA template strand. What word describes bases that fit together?

A

complementary

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34
Q

Triple only- Where does transcription occur in a cell?

A

nucleus

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35
Q

Triple only-Where does translation occur in a cell?

A

cytoplasm

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36
Q

Triple only-What has to bind to an mRNA molecule for translation to occur?

A

ribosome

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37
Q

Triple only-What molecule carries amino acids to the mRNA in the ribosome?

A

tRNA

38
Q

Triple only- What has to happen to the polypeptide for an enzyme in order for it to become a functional enzyme?

A

It has to fold

39
Q

How many bases does a codon contain?

A

three

40
Q

Triple only-What does each codon contain the code for?

A

the addition of a particular amino acid to the polypeptide chain

41
Q

Triple only-What is the name of the process in which the genetic code is used to make a polypeptide?

A

translation

42
Q

A change in the bases of a gene creates a genetic variant. What is this sort of change called?

A

mutation

43
Q

Triple only-What does translation produce?

A

a polypeptide

44
Q

Triple only- Why might a mutation in a codon not cause a change in the polypeptide produced?

A

It does not affect the amino acid that is coded for.

45
Q

Triple only- Why can a difference of a single amino acid change how a protein functions?

A

It can interfere with the way the polypeptide chain(s) fold(s).

46
Q

Triple only- What has to bind to an mRNA molecule for translation to occur?

A

ribosome

47
Q

Triple only- Why might a mutation in the non-coding region before a gene cause an increase in the production of a certain protein?

A

The mutation causes RNA polymerase to bind better.

48
Q

What is an organism’s phenotype?

A

its observed characteristics

49
Q

What are different versions of the same gene called?

A

alleles

50
Q

What sort of variation do alleles cause in organisms?

A

genetic variation

51
Q

When we consider one gene, what word is used to say that both alleles are the same?

A

homozygous

52
Q

If a dominant allele has the letter A, how would you show that an organism is heterozygous?

A

Aa

53
Q

What word describes the characteristics caused by the alleles of a gene?

A

phenotype

54
Q

What word describes the alleles of a gene found in an organism?

A

genotype

55
Q

What word describes an allele that only has an effect if an organism has two copies?

A

recessive

56
Q

A genotype is written QQ. What does this tell you?

A

It is homozygous for the dominant allele.

57
Q

What is a probability?

A

the chance of an event occurring

58
Q

If the occurrence of an event has a probability of 1, what does this mean?

A

It is certain to occur.

59
Q

Triple only- What is monohybrid inheritance?

A

inheritance of alleles of one gene

60
Q

Triple only- In monohybrid inheritance, what is the theoretical probability of parents who are both heterozygous for a gene producing an offspring that is also heterozygous for the gene?

A

probability 50 per cent or half

61
Q

Triple only- In monohybrid inheritance, what is the theoretical ratio of dominant to recessive phenotypes produced by parents who are both heterozygous for the characteristic?

A

03:01

62
Q

Triple only- What letters are used to describe the different human blood groups?

A

A, B, O

63
Q

How can we show the possible inheritance of alleles by offspring from their parents?

A

genetic diagram, Punnett square

64
Q

Which type of diagram is used to show the inheritance of a characteristic through different generations in a family?

A

family pedigree

65
Q

If the genotype for one gene of a rabbit is Bb, where B is the allele for brown coat and b the allele for black coat, what is the rabbit’s phenotype?

A

brown

66
Q

What are the possible allele combinations of offspring from heterozygous parents who are both Aa for a gene?

A

AA, Aa and aa

67
Q

A human egg cell that contains an X sex chromosome is fertilised by a sperm cell containing a Y sex chromosome. What will be the sex of the baby that develops?

A

male

68
Q

What is the theoretical probability of a couple having a baby boy?

A

probability 50 per cent or half

69
Q

Who devised the laws of inheritance and why wasn’t his methods accepted at the time?

A

Mendel
Published in a little-known journal

70
Q

What is a type of mutation when bases swap positions?

A

Substitution.

71
Q

What is the dominant eye colour?

A

Brown

72
Q

How many base pairs in a human genome?
How many base pairs in DNA?

A

3 billion
4

73
Q

What molecules are used to copy DNA in protein synthesis?

A

Enzymes

74
Q

What occurs during transcription?

A

A mRNA copy of a section of a DNA strand is made.

75
Q

Problems with selective breeding?

A

Reduced variation

76
Q

What are the sex chromosomes pair and what are they for male and female?

A

The sex chromosomes are the 23rd pair.
XX = female
XY = male

77
Q

What are alleles?

A

Forms of the same gene.

78
Q

What is the phenotype of the genotype I^B I^O?

A

Phenotype B for the blood group.

79
Q

What percentage of offspring have blue eyes from a cross between two homozygous dominant parents?

A

0% B is the dominant allele for brown eyes. bb will only get you blue eyes.

80
Q

What percentage of offspring have blue eyes from a cross between two heterozygous parents?

A

25% B is the dominant allele for brown eyes. bb will only get you blue eyes.

81
Q

What is the two types of variation?

A

Environmental
Genetic

82
Q

What does variation mean?

A

A greater chance that some offspring will be better suited to new conditions and so will be more likely to survive and reproduce.

83
Q

What does meiosis produce?

A

Gametes
4 haploid daughter cells which is how gametes are produced.

84
Q

How to get DNA? DNA extraction?

A
  1. Peel the skin from half a kiwi fruit and mash it up.
  2. Mix a teaspoon of salt and small volume of washing up liquid into the fruit.
  3. Gently heat this mixture at about 60°C for five minutes.
  4. Filter the mixture and retain only the filtrate (the filtered liquid).
  5. Cool using an ice bath and gently pour chilled ethanol onto the top of the filtrate.
85
Q

What are the benefits about the human genome project?

A

Can indicate their risk of developing diseases that are caused by different alleles of genes and what medicines can be used to treat the person effectively.

86
Q

What is discontinuous variation?

A

Where the the data can only take a limited set of values. Bar chart, the bars don’t touch.

87
Q

What is continuous variation?

A

Where the data can be any value in a range. Bar charts, the bars touch.

88
Q

What is codominance?

A

When both alleles for a gene affect the phenotype, we say they are codominant.

89
Q

The sequence of Meiosis?

A
90
Q

The steps of Transcription?

A
  1. RNA polymerase attaches to a start codon in the DNA
  2. mRNA is transcripted base by base
  3. RNA is similar to a DNA complementary strand, except A bonds to U(uracil) and RNA is single stranded
  4. mRNA strand escapes the nucleus through tiny pores
91
Q

The steps of Translation?

A
  1. mRNA escapes out tiny pores in the nucleus to the cytoplasm
  2. A ribosome attaches to the mRNA
  3. Complementary tRNA with an anticodon and a specific amino acid attaches to an mRNA codon
  4. Ribosomes causes peptide bonds to form between amino acids.tRNA is released
  5. At the stop codon, ribosomes are released
  6. The protein chain is released and folds to form a polypeptide(protein)

GCSE Biology - Edexcel (9 decks)

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