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Biology > Cellular Control > Flashcards

Cellular Control Flashcards

1
Q

What is a mutation?

A

A change in the base sequence of DNA

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2
Q

What are the 3 main types of mutation?

A
  • Substitution
  • Deletion
  • Insertion
    Of one or more nucleotides within a gene
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3
Q

What is a substitution mutation?

A

Where one (or more) bases is swapped for another

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4
Q

What is it called if only 1 nucleotide is affected?

A

A point mutation

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5
Q

What are the 3 types of point mutation?

A
  • Silent
  • Missense
  • Nonsense
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6
Q

What are silent mutations?

A

When the altered base sequence still codes for the same amino acid

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7
Q

What are missense mutations?

A

When the substituted base does code for a different amino acid in the primary protein structure and as a result, the final protein cannot function properly

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8
Q

What are nonsense mutations?

A

When the base sequence is altered in such a way that the triplet code changes from an amino acid code to a “stop” codon. This will result in a shorter protein which won’t function properly

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9
Q

What is a deletion mutation?

A

Where one (or more) nucleotides are removed from the DNA sequence

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10
Q

What is an insertion mutation?

A

Where one (or more) nucleotides are added to the DNA sequence

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11
Q

What are the consequences of mutations?

A
  • Primary protein structure is altered
  • Will twist and fold differently, altering secondary and tertiary structures
  • 3D shape and function altered
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12
Q

What is a point mutation?

A

When only 1 nucleotide is affected in the sequence

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13
Q

What types of mutation would you expect to have the greatest consequences?

A

Both insertion and deletion would alter the whole triplet code from the point of mutation onwards
= Frameshift

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14
Q

What makes a mutation neutral?

A
  • If it occurs in the introns
  • If it results in a silent mutation
  • If the altered triplet code results in a different a.a in the sequence but it’s so chemically similar to the original that it makes no difference to final protein
  • If it codes for a completely different a.a bit this a.a isn’t crucial for how the final protein works
  • If it results in a different final protein but this doesn’t affect the survival chances of the organism
    DON’T INCREASE/DECREASE CHANCES OF SURVIVAL
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15
Q

What makes a mutation beneficial?

A
  • If it has advantageous effects on organisms and increases chances of survival
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16
Q

Give an example of a beneficial mutation

A

Humans in some parts of the world can digest lactose due to a mutation

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17
Q

What makes a mutation harmful?

A
  • If it has a disadvantageous effect on an organism and reduces the chance of survival
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18
Q

Give an example of a harmful mutation

A

Cystic fibrosis

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19
Q

Give an example of how a mutation can be both beneficial and harmful

A

Eye colour

  • Blue eyes beneficial in temperature regions of the world, but not in regions where there is high light intensity
  • Have less pigmentation in iris so more light can get through to retina = better vision
  • Brown eyes better in high light intensity or can cause cateracts
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20
Q

What is a frame shift mutation?

A

A mutation caused by the insertion or deletion of a base pair/pairs in DNA, resulting in the shift of nucleotides.
This alters the reading frame of the sequence and changes every successive codon from the point of mutation

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21
Q

What leads to a frame shift mutation?

A

Insertion and deletion

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22
Q

What are the 3 effects different mutations can have?

A
  • Neutral
  • Beneficial
  • Harmful
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23
Q

What is a mutagen?

A

A chemical, physical, or biological agent that causes mutations

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24
Q

Give an example of a physical mutagen

A

Ionising radiations, such as x-rays

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25
Q

What do ionising radiations do?

A

Break one or both DNA strands

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26
Q

Give an example of a chemical mutagen

A

Deaminating agents

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27
Q

What do deaminating agents do?

A

Chemically alter bases in DNA

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28
Q

Give an example of a biological agent

A

Viruses

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29
Q

What do viruses do?

A

Viral DNA may insert itself into a genome, changing the base sequence

30
Q

Give 4 ways in which genes are regulated

A
  • Trancriptional control
  • Post-transcriptional control
  • Translational control
  • Post-translational control
31
Q

What is a promoter?

A

A section of DNA ahead of the gene which allows RNA polymerase to attach, allowing transcription of the gene to occur

32
Q

What are the 2 ways transcriptional control occurs in Eukaryotes?

A
  • Chromatin remodelling

- Histone modification

33
Q

Describe Chromatin remodelling

A
  • Heterochromatin = when DNA is tightly wrapped around histones and transcription cannot occur
  • Euchromatin = during interphase, when protein synthesis is needed, DNA is more loosely wrapped and transcription can occur as RNA polymerase can access DNA to make mRNA
    It ensures genes are “switched on” and used to make protein at the correct stage of cell cycle
34
Q

Describe histone modification

A
  • DNA coils around histones as they are + charged and DNA is - charged
  • Histones can be modified, which controls how tightly DNA wraps around
  • Addition of acetyl groups or phosphate groups reduces positive charge on histones, causing it to coil less tightly so genes can be transcribed
  • Addition of methyl groups makes the histones more hydrophobic so they bind more tightly to each other, causing DNA to coil more tightly and preventing transcription
35
Q

What groups reduce the positive charge on histones, causing DNA to coil less tightly and transcription to occur?

A

Acetyl groups or phosphate groups

36
Q

What does the addition of acetyl and phosphate groups do to DNA?

A
  • Reduces + charge on histones
  • Causes DNA to coil less tightly
  • Transcription occurs
37
Q

What does the addition of methyl groups do to DNA?

A
  • Makes histones more hydrophobic
  • Bind more tightly to each other so DNA could more tightly
  • Prevents transcription
38
Q

What is epigenetics?

A

A term used to describe the control of gene expression by the modification of DNA

39
Q

How does post transcriptional control occur?

A
  • mRNA is “edited” after transcription
  • Mature mRNA = functional mRNA
  • Introns are removed from primary mRNA strands (splicing)
  • Exons are joined in nucleus, forming mature mRNA
  • A “cap” is added to the 5’ end of mRNA and a “tail” to the 3’ end
  • These both stabilise the mRNA so it doesn’t break down in cytoplasm
40
Q

What is splicing?

A

Where introns are removed from primary mRNA strands and exons are joined in nucleus to form mature mRNA

41
Q

What factors can regulate when translation starts and stops?

A
  • How long the mRNA lasts in cytoplasm: some strands persist longer, which means more translation and more protein made
  • Inhibitory proteins: can bind to mRNA and stop it attaching to ribosomes, so inhibit translation
  • Initiation factors: help binding of mRNA to ribosomes, so promote translation and protein synthesis
42
Q

How does post-translational control occur?

A

Involves the final modifications to proteins, including:

  • Addition of non-protein groups, e.g. carbs/lipid/phosphate groups
  • Folding + shortening of protein into final shape
  • Activation of proteins by cAMP
43
Q

What is cAMP?

A

A messenger molecule in cells, involved in activation of enzymes. It can result in a change to 3D shape of protein

44
Q

Give an example of an enzymes activated by cAMP?

A

Protein Kinase (PKA)

45
Q

What is PKA?

A

An enzyme made up of 4 subunits

46
Q

Describe how the enzyme protein kinase (PKA) is activated?

A
  • When cAMP isn’t bound, the 4 subunits of PKA are bound together and inactive
  • When cAMP binds, it causes a change in the enzyme’s 3D structure, releasing the active subunits, PKA is now activated
  • Once activated, it can then activate other proteins/enzymes within the cell
47
Q

What happens to the 4 subunits in PKA when cAMP isn’t bound?

A

The are bound together an inactive

48
Q

What happens to the 4 subunits in PKA when cAMP binds?

A

It causes a change in the enzyme’s 3D structure, releasing the active subunits, PKA is now activated

49
Q

What happens when PKA is activated?

A

It can activate other proteins/enzymes within the cell

50
Q

What are hox genes?

A

Subset of homeobox genes, found only in animals. They are responsible for the correct positioning of body parts

51
Q

What are homeobox genes?

A

Regulatory genes responsible for the development of body plans

52
Q

What is a homeobox?

A

A section of DNA, 180 b.p long, coding for a part of the protein 60 a.a long that is highly conserved in plants, animals and fungi

53
Q

What is a homeodomain?

A

A highly conserved 60‐amino‐acid protein domain that is encoded by the homeobox and is found in organisms as diverse as mammals, insects, plants and yeast

54
Q

Where are hox genes found?

A

In clusters on particular chromosomes (hox clusters)

55
Q

How many hox clusters do mammals have on their chromosomes?

A

4 clusters

56
Q

How do homeobox genes determine body plans?

A
  • Polarity of embryo (“head” & “tail” ends)
  • Polarity of each “segment” of organism
  • Which structures develop from each segment (e.g. arms & legs)
57
Q

How many primary tissue layers do diploblastic animals have?

A

2

58
Q

How many primary tissue layers do triploblastic animals have?

A

3

59
Q

What type of animals have 2 primary tissue layers?

A

Diploblastic

60
Q

What type of animals have 3 primary tissue layers?

A

Triploblastic animals

61
Q

What organisms have radial symmetry?

A

Diploblastic animals (e.g. jellyfish)

62
Q

What is radial symmetry?

A

No left or right sides, only top and bottom

63
Q

What organisms have bilateral symmetry?

A

Most animals

64
Q

What is bilateral symmetry?

A

They have both left and right sides and a head and tail

65
Q

What organisms have asymmetry?

A

Sponges

66
Q

What is asymmetry?

A

No lines of symmetry/equality

67
Q

Why have homeobox genes changed very little over time?

A
  • They are crucial to body plans of organisms
  • Any mutations to these genes would result in organisms that cannot function properly, so don’t survive
  • The process of natural selection has eliminated most organisms with mutated homeobox genes (highly conserved)
68
Q

Why is mitosis important for the development of body form?

A

It ensures each new daughter cell contains the full genome and is a clone

69
Q

What is apoptosis?

A

Programmed cell death

70
Q

Describe the 6 steps in apoptosis

A

1- Enzymes (lysosomes) break down cell cytoskeleton
2- Cytoplasm becomes dense; organelles tightly packed
3- Plasma membrane changes and blebs form
4- Chromatin condenses, nuclear envelope breaks
5- DNA breaks into fragments
6- Cell breaks into vesicles, ingested by phagocytic cells, so cell debris doesn’t damage other cells/tissues

71
Q

Give 3 internal stimuli that controls apoptosis

A

1- DNA damage
2- Hormones
3- Cytokines (cell signals) from the immune system

72
Q

Give 4 external stimuli that controls apoptosis

A

1- Infections by pathogens
2- Changes in temp
3- Changes in light intensity
4- Stress

Biology (19 decks)

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