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MPW 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. Different amino acids now coded for.

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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 a mutation alters triplet(s) in such a way that they code for different type(s) of amino acid(s) than previously

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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

when a new triplet generated by a mutation does not encode any amino acid, but instead (once transcribed to mRNA) it will function as a stop (termination) codon during translation.

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

Gene expression is the term used to describe whether a gene is transcribed and translated to produce a functional protein

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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

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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 with a metabolic function (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
  1. The regulator gene, as is always the case, is transcribed and translated to produce the lac repressor protein. [The regulator gene is separate from the operon itself, but is found in a separate region of the E. coli cell’s circular DNA molecule.]
  2. The lac repressor protein has a binding site with complementary shape to the operator region of the lac operon and hence binds with the operator.
  3. This binding of the repressor protein to the operator sequence distorts the DNA in that vicinity and thus prevents the enzyme RNA polymerase binding to the promoter region.
  4. Since RNA polymerase cannot attach to the promoter sequence, transcription of the structural genes in the lac operon is not activated.
  5. The genes are not transcribed, no mRNA is produced and hence there can be no translation to synthesise the proteins required for lactose metabolism.
  6. Resources including ATP, RNA nucleotides and amino acids are conserved. It would be a waste of materials and energy for the cell to make proteins relating to lactose metabolism when no lactose is available.
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
76
Q

Control at the transcriptional level:

A

lac operon system in E. coli, and the use of transcription factors in eukaryotes

77
Q

Control at post‐transcriptional level

A

editing of primary mRNA and the removal of introns to produce mature mRNA

78
Q

Control at the post‐translational level

A

the activation of proteins via the binding of cyclic AMP.

MPW biology (26 decks)

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