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OCR A level biology > Cellular Control > Flashcards

Cellular Control Flashcards

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1
Q

Define mutation

A

A change in the sequence of bases in DNA

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2
Q

What is a point mutation?

A

A change in a single nucleotide base

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3
Q

What is a frameshift mutation?

A

The addition or deletion of a nucleotide moves/shifts the reading frame of the sequences of bases, altering every successive codon from the point of mutation

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4
Q

What are the 5 types of point mutation?

A
  • Substitution
  • Deletion
  • Insertion
  • Duplication
  • Inversion
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5
Q

What is a silent mutation?

A

A mutation which results in the same protein being produced

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6
Q

Why can silent mutations occur?

A

The genetic code is degenerate, so the mutated codon may still code for the correct amino acid

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7
Q

What is a missense mutation?

A

When one or more amino acids are added to the primary structure of the protein

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8
Q

What effect can a missense mutation have on the phenotype of an organism?

A

The effect can be neutral, beneficial, or harmful

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9
Q

What is a nonsense mutation?

A

The result of frameshift mutations, a shorter unfinished protein is often produced

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10
Q

What kind of effect does a nonsense mutation have on phenotype?

A

A harmful effect

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11
Q

What is a chromosomal mutation?

A

A mutation leading to the addition or deletion of a portion of a chromosome

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12
Q

Why can a change in the sequence of nucleotides affect the function of a protein?

A
  • 3 nucleotides code for an amino acid
  • Change in nucleotides can change the amino acid coded for
  • Different amino acids have different R groups
  • Different R groups alter 3D shape of protein
  • Different shape may affect the protein’s function
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13
Q

How can mutations have a beneficial effect?

A

A mutation causes a protein with a useful effect to be produced

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14
Q

How can mutations have a harmful effect?

A

The proteins coded for are no longer synthesised or non-functional proteins are synthesised

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15
Q

What are the 3 types of mutagens?

A
  • Physical
  • Chemical
  • Biological
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16
Q

What is a mutagen?

A

Something which induces mutations in DNA

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17
Q

Give an example of a physical mutagen

A

Ionising radiation

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18
Q

Give an example of a biological mutagen

A

Some viruses

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19
Q

Give an example of a chemical mutagen

A

Deaminating agents

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20
Q

What are the 4 types of chromosomal mutation?

A
  • Deletion
  • Duplication
  • Translocation
  • Inversion
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21
Q

What happens in a translocation chromosomal mutation?

A

A section of one chromosome breaks off and joins another non-homologous chromosome

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22
Q

Give 2 examples of the harmful effects of point mutations

A
  • Sickle cell anaemia
  • Cystic Fibrosis
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23
Q

What is gene expression?

A

The process by which instructions in DNA are converted into a functional product

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24
Q

What is chromatin remodelling?

A

The control of whether or not a gene is contained within heterochromatin or euchromatin

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25
Q

What is heterochromatin?

A

The form of chromatin in which DNA is tightly wound around histones

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26
Q

What is the effect of heterochromatin on transcription?

A

RNA polymerase cannot reach the genes so transcription does not occur

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27
Q

What are the 3 types of transcriptional control in eukaryotes?

A
  • Chromatin remodelling
  • Histone modification
  • Transcription factors
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28
Q

What transciptional control occurs in prokaryotes?

A

Operons

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29
Q

What is Euchromatin?

A

The form of chromatin in which DNA is loosely wound around histones

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30
Q

What is the effect of euchromatin on transcription?

A

The gene can be accessed by RNA polymerase so transcription can occur

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31
Q

What is the effect of methylation on transcription?

A

Causes the histones to become more hydrophobic so they bind together more tightly. This prevents transcription by preventing RNA polymerase binding

32
Q

What is histone modification?

A

The alteration of histones by the addition of a methyl or acetyl group

33
Q

What is the effect of acetylation on transcription?

A

Causes the histone proteins to become more negatively charged so DNA is bound less tightly. This allows transcription as it allows RNA polymerase to bind

34
Q

What is epigenetics?

A

The study of changes in organisms caused by modification of gene expression rather then alteration of the genetic code

35
Q

What is an operon?

A

A group of genes under the control of the same regulatory mechanism which are expressed at the same time

36
Q

What are structural genes?

A

Genes which code for proteins not involved in DNA regulation (e.g. enzymes)

37
Q

What does the lac Z gene code for?

A

ß galactosidase

38
Q

What does the lac y gene code for?

A

Lactose permease

39
Q

What is the effect of lactose permease?

A

Allows the bacteria to take up lactose

40
Q

What is the function of ß galactosidase?

A

Enables the bacteria to hydrolyse lactose into glucose and galactose

41
Q

Why do bacteria not produce enzymes for lactose metabolism all the time?

A

This would require energy, so it would be a waste

42
Q

What type of protein does a regulatory gene code for?

A

Repressor protein

43
Q

Describe what occurs in a bacterial cell when lactose is not present

A
  • Regulatory gene codes for repressor protein
  • Repressor protein binds to the operator, which prevents RNA polymerase from binding to the promoter region
  • RNA polymerase cannot bind so the lac genes are not transcribed
44
Q

Describe how the presence of lactose affect the lac operon

A
  • Lactose binds to the repressor protein and causes a confirmational change in shape of the repressor
  • This prevents the repressor from binding
  • RNA polymerase can now bind to the operator so the lac genes are transcribed
45
Q

What is an exon?

A

A section of DNA or RNA which codes for a protein

46
Q

What is an intron?

A

A section of non-coding DNA or RNA

47
Q

What is RNA processing?

A

The process by which introns are removed from pre-mRNA

48
Q

What are transcription factors?

A

Proteins or short ncRNA which regulate whether RNA polymerase can bind to DNA

49
Q

What are the two types of trancription factors?

A

Repressors or activators

50
Q

How can transcription factors act as activators?

A
  • Transcription factor binds to a specificbinding site on DNA
  • The binding of the transcription factor encourages the binding of RNA polymerase
  • RNA polymerase binds to the gene so the gene is transcribed
51
Q

What are the 3 types of post-transcriptional control?

A
  • RNA processing
  • RNA editing
  • Small interfering RNA
52
Q

What occurs in RNA processing?

A
  • Entire DNA sequence is transcribed, a cap is added to the 5’ end and a poly A tail is added to the 3’ end
  • Introns are removed by splicing resulting in functional RNA which can now be transcribed
53
Q

What is RNA editing?

A

A codon within a gene is changed on mRNA, consequently different proteins can be synthesized from the same gene

54
Q

What is small interfering RNA?

A

Short pieces of double stranded RNA which cut up mRNA before it can be translated

55
Q

What are the 2 types of translational control?

A
  • mRNA degradation
  • Activation and binding of inhibition factors
56
Q

What is the role of inhibition factors in translational control?

A

Proteins which bind to mRNA and prevents it from attaching to ribosomes

57
Q

What are the 4 types of post translational control?

A
  • Addition of non-protein groups
  • Modification of amino acids
  • Folding/shortening of protein
  • Modification by cAMP
58
Q

Define body plan

A

A set of morphological features common to many animals

59
Q

What is morphogenesis?

A

The development of form and structure in an organism during its growth from embryo to adult

60
Q

What are homeotic genes?

A

Regulatory genes that determine where anatomical structures (e.g arms and legs) will develop in an organism during morphogenesis

61
Q
A
62
Q

What is a homeobox?

A

A section of homeotic genes

63
Q

How many base pairs long is a homeobox?

A

180

64
Q

What are homeobox genes?

A

Genes responsible for the development of body plans

65
Q

What is a homeodomain?

A

A conserved motif of 60 amino acids found in all homeobox proteins

66
Q

Why are homeobox genes highly conserved between plants, animals, and fungi?

A
  • It is very important in the development of an organism
  • Any changes would result in an organism unlikely to survive
67
Q

What are HOX genes?

A

A distinct family of homeobox genes responsible for the correct positioning of body parts

68
Q

Which kingdom are HOX genes present in?

A

Animalia

69
Q

Which organism is often used to study development?

A

Drosphila (fruit fly)

70
Q

Why are drosphila a suitable organism for studying development?

A
  • small genome
  • cheap
  • easy to breed and keep
  • short life cycle
71
Q

Why are drosphila a good model for development in humans?

A
  • similar/shared genes
  • similar cells and metabolism
  • shared ancestry
72
Q

What is apoptosis?

A

Programmed cell death, following a well-defined sequence of events ‘built-in’ to the cell

73
Q

Outline the steps in apoptosis

A
  • cells shrink in size
  • nucleus condenses
  • Organelles break down and become enclosed in blebs (extensions of cell membrane)
  • blebs are engulfed by phagocytes
74
Q

What are the roles of apoptosis in growth and development?

A
  • shapes body parts by removing unwanted cells e.g. hands
  • formation of synapses
  • menstruation (apotosis removes cells which hold the lining of the womb in place)
  • metamorphsis e.g. tadpoles to frogs
75
Q
A

OCR A level biology (44 decks)

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