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Biology Paper 1 > DNA & Genetic Diversity > Flashcards

DNA & Genetic Diversity Flashcards

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1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

What does RNA stand for?

A

Ribonucleic acid

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3
Q

What does DNA do?

A

hold genetic info

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4
Q

What does RNA do?

A

transfer genetic information from DNA to ribosomes

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5
Q

What is DNA and RNA polymers of?

A

Nucleotides

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6
Q

What is in a nucleotide?

A

pentose
nitrogen containing organic base
phosphate group

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7
Q

What is the structure of DNA?

A

two polynucleotide strands
joined by hydrogen bonding
forming a double helix

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8
Q

What is in a DNA nucleotide?

A

pentose sugar> deoxyribose
phosphate group
nitrogen containing bases

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9
Q

What are the bases in DNA?

A

Adenine
Thymine
Guanine
Cytosine

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10
Q

What bonds join nucleotide together?

A

phosphodiester bonds
formed by condensation reactions

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11
Q

What bond joines bases together?

A

hydrogen bonds
(Maintain stable structure due to its abundance)

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12
Q

Describe the process of semi-conservative DNA replication

A
  • DNA helicase breaks hydrogen bonds & separates the two polynucleotide strands
  • strands act as a template
  • free nucleotides attach to complementary bases
  • DNA polymerase join the strands of the nucleotides
  • two new identical DNA strands (new and old)
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13
Q

What are the differences between DNA and RNA

A

pentose is Ribose in RNA

Uracin instead of Thymine

mRNA and tRNS are single strands

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14
Q

What are the properties of mRNA?

A

has linear structure

codons(base triplets)

involved in protein synthesis

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15
Q

Describe the shape of tRNA

A

clover leaf shape due to hydrogen bonds between complementary bases

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16
Q

Describe the properties of tRNA

A

anticodon ( 3 unattached tRNA nucleotide bases) on one end

binding site for amino acids on the other end

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17
Q

How is a chromosome formed?

A

from DNA and its associated protein

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18
Q

What is the shape of DNA in the nucleus of eukaryotic cells?

A

long and linear

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19
Q

What is the shape of DNA in mitochondria and chloroplasts?

A

short and circular

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20
Q

What are Chromosomes?

A

Structures formed from histones and DNA during cellular division

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21
Q

What is a gene?

A

A section of DNA base that code for specific amino acid sequence

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22
Q

What are diploid cells?

A

Have chromosomes in pairs, one inherited from one parent and one from the other

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23
Q

what is a homologous chromosome?

A

two chromosomes that carry the same genes but not the same alleles

maternal and paternal chromosome

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24
Q

What is a locus?

A

Fix position of a gene on a particular DNA molecule or chromosome

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25
Q

what is a base triplet?

A

A sequence of three nucleotide bases the code for a specific amino acid

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26
Q

what are codons?

A

based triplets in mRNA that code for an amino acid

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27
Q

what is it meant by degenerate?

A

One amino acid can be coded for by different triplets

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28
Q

what are stop codes?

A

They do not code for an amino acid, but they indicate the end of a code for specific polypeptide

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29
Q

How are codes none overlapping?

A

each base is only read once as part of a specific triplet

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30
Q

How are codes universal?

A

The same triplets code for the same amino acid in all organisms

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31
Q

What is an Intron?

A

Base sequences present in genes, but don’t code for amino acids

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32
Q

what is an Exon?

A

base sequences in genes that code for amino acids

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33
Q

What are multiple repeats?

A

some of the base sequences present between genes
it consists of the same sequence occurring again and again

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34
Q

What are some examples of non-coding DNA?

A

intron
Multiple repeats

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35
Q

What is a genome?

A

complete set of genes in a cell

36
Q

what is a proteome?

A

The full range of proteins that are cell is able to produce

37
Q

What is transcription?

A

occurs in the nucleus
involves rewriting part of the DNA into a strand of messenger RNA

38
Q

Outline transcription

A
  • The relevant DNA uncoils and strand separate
  • One of these strands act as a template
  • Individual RNA nucleotides lineup along the complementary DNA base
  • individual RNA is joined together by RNA polymerase
  • The two strands of DNA will join back together once mRNA has been produced
39
Q

what is pre-mRNA?

A

mRNA formed during transcription

40
Q

What is splicing?

A

removing introns from pre-mRNA and joining together exons to form mRNA

41
Q

Why does splicing not happen in prokaryotes?

A

prokaryotes DNA does not contain introns

42
Q

What happens during translation?

A

happenes in ribosomes
sequence of codons on the mRNA strand is used to determine the sequence of amino acids in the polypeptide

43
Q

What is genetic diversity?

A

The number of different alleles in a population

44
Q

What causes genetic diversity?

A
  • gene & chromosome mutations
  • meiosos
  • random fusion of gametes during fertilisation
45
Q

What is gene mutation?

A

changes in the sequence of nucleotide bases

new alleles of genes are produced

46
Q

What are mutagenic agents?

A

increase the rate of mutation
(x-rays, benzene)

47
Q

What are the different ways a mutation can occur?

A

substitution
addition
Deletion
Duplication
Inversion
Translocation

48
Q

What is substitution?

A

the replacement of one or more bases by a one or more different base

49
Q

What does substitution result in?

A
  • a new triplet coding for a different amino acid, this may result in a non functional protein
  • one different amino acid changes but a functional protein is still produced
  • same amino acid may be coded for due to degeneracy, so polypeptide remains unchanged
50
Q

What is deletion?

A

removal of one or more bases

resulting in frame shift

51
Q

What is a frame shift?

A

alteration in all triplets from the point of mutation
the protein formed is nearly always non functional

52
Q

What is addition?

A

addind one or more bases
results in frame shift

53
Q

What is duplication?

A

when one or more bases are repeated
results in frame shift

54
Q

What is inversion?

A

where a sequence of bases is reversed

55
Q

What is translocation(mutation)?

A

where a sequence of bases is moved from one location to another

56
Q

What is an allele?

A

different forms of genes that code for different types of the same characteristic

arise due to mutations of a gene

57
Q

What is mitosis?

A

produces cells that are genetically identical

two daughter cells

58
Q

What are the stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

59
Q

What happens during interphase?

A

cell prepares for nuclear division
- DNA is doubled
- Increase in protein synthesis
- cell organelles are replicated

60
Q

What happenes in prophase?

A

each chromosome shortens then thickens(condensation)

nuclear membrane breaks down

61
Q

What happens during metaphase?

A

centrioles from a spindle across the cell, this spindle consist of protein microtubules

Each chromosome moves to the equator of the spindle and attaches to it by its centromere

62
Q

What happens during anaphase?

A

The centromere splits and sister chromatids separate

sister chromatids are pulled to opposite poles of the cell by the spindle microtubules

63
Q

what happens during telophase?

A

chromatids are at opposite poles and begin to uncoil

Nuclear membrane reforms

The two cells or genetically identical to each other and the original parent cell

64
Q

What happens during Cytokinesis?

A

The cytoplasm splits in two

Two new cells form as the cell surface membrane (plant cell: cell wall) forms

65
Q

What is cancer?

A

A group of diseases caused by uncontrolled growth and rapid cell division

Results from damage to genes that regulate mitosis s and cell cycle

66
Q

What is a tumour?

A

A group of abnormal cells

67
Q

how do drugs help with cancer?

A

They can inhibit the enzymes, (DNA helicase or DNA polymerase) or inhibit the formation of the spindle

68
Q

What is meiosis?

A

nuclear division that produces cells that are genetically different

four non identical daughter cells

69
Q

What type of gametes are produced during meiosis?

A

Haploid

diploid number will be restored at fertilisation

70
Q

What happenes during meiosis?

A

two nuclear divisions

71
Q

What happens during late interphase in meiosis?

A

DNA replication
Buildup of ATP
Protein synthesis and replication of organelles

72
Q

what happens in meiosis I?

A

The first division separates the membranes of each homologous pair

73
Q

what happens in meiosis II?

A

Chromatids are separated from each chromosome

74
Q

What is independent segregation of homologous chromosomes?

A

In meiosis, chromosomes pair then separate so one from each pair enters the gamete

75
Q

how do you calculate the possible number of varied combinations?

A

2^n

n= number of pairs

76
Q

What is crossing over?

A

The two members of each homologous pair lie side-by-side forming a bivalent

The chromatids of the homologous chromosomes then interwine

77
Q

What is the name of the place where crossing over occurs?

A

Chiasma

78
Q

What does does crossing over lead to?

A

exchange of alleles of the same gene

this can produce new combinations of alleles called recombinants

79
Q

Why is the number of recombinants low?

A

beacuse crossing over is rare

80
Q

What is chromosome non-disjunction?

A

when a homologous pair of chromosomes do not separate on the first meiotic division

both members of a homologous pair o to the same side during anaphase I

81
Q

What is the result of chromosome non-disjunction?

A

gametes will have one extra/less chromosome than normal

82
Q

What is genetic diversity?

A

the number of different alleles of genes in a population

83
Q

How do new alleles come about?

A

random mutations

84
Q

What is directional selection?

A

when there is a change in the environment in which the alleles of an extreme type are selected for

85
Q

What is stabilising selection?

A

(nothings changing)
an average phenotype is selected for and extremes of the phenotype are selected against

Biology Paper 1 (8 decks)

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