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A-Level Biology - OCR A > 6.1.1 Cellular Control > Flashcards

6.1.1 Cellular Control Flashcards

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1
Q

What is a mutation?

A

A random change to the amount or structure (sequence of bases) of genetic material (DNA)

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2
Q

When do mutations occur?

A

During DNA replication before cell division in stomatic cells.

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3
Q

What are stomatic cells?

A

Body cells

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4
Q

Is gene mutation random?

A

Yes - it happens spontainiouesly

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5
Q

Are mutations passed onto offspring?

A

Mutations that occur in body cells are not passed on. e.g. aging and cancer.
Only mutations that occur in gamete formation are passed on.

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6
Q

What can increase the chances of gene mutations?

A

Chemicals such as tar in tobacco smoke.
Ionising radiation such as UV light, X-rays and gamma rays.

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7
Q

What are things that cause mutations called?

A

Mutagenic

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8
Q

What types of mutations are there?

A

Point Mutations.
Chromosome Mutations.

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9
Q

What are point mutations?

A

Changes in the sequence of a gene:
Changes a base pair during replicaton

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10
Q

What are the types of point mutations?

A

Silent mutations.
Missense mutations.
Nonsense mutations.

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11
Q

What is a silent mutation?

A

One base changes but due to degenerative code there is no change to the amino acid being coded for.

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12
Q

What is a missense mutation?

A

One base changes which changes thee amino acid that the triplet codes for - changing the amino acid being coded for and so the AA sequence of the protein

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13
Q

What is a nonsense mutation?

A

One base is changed so that the triplet codes for a STOP code. This means that the polypeptide chain is truncated and remains incomplete - can mean that the protein doesn’t function properly.

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14
Q

What are insertion mutations?

A

An additional nucleotide base pair is added (inserted) into the chain

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15
Q

What are deletion mutations?

A

A base pair is deleted from the chain

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16
Q

What effect do InDel mutations cause?

A

frameshift-
move the 3 base codon so the whole polypeptide sequence changes. Causes issues as all sequential amino acids are affected - leading to the protein being unable of carrying out its function.

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17
Q

What are Chromosomal Mutations?

A

Mutations that cause a change to the structure of a chromosome or the number of chromosomes within a nuclius.

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18
Q

When do chromosomal mutations occur?

A

During DNA replication where the chromosomes may not separate during anaphase (miosis and mitosis)

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19
Q

What is a gene?

A

A section of DNA that codes for a particular protein

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20
Q

What is an operon?

A

Multiple genes within DNA that are under control of a single promotor in order to produce mRNA. Consists of structural genes and control sites.

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21
Q

What is the structural gene?

A

The part of the operon that contains the genetic code for the gene

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22
Q

What is the control site?

A

The operator and promotor region of DNA

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23
Q

What is the promotor?

A

A short sequence of DNA where RNA polymerase can bind to begin transcription.

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24
Q

What is the operator?

A

Short portion of DNA where an active repressor can bind to prevent RNA pol from binding and transcription taking place.

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25
Q

What is the regulatory gene?

A

Gene that codes for the repressor protein

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26
Q

What is a repressor protein?

A

A protein that acts as a transcription factor that controls when transcription can take place.

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27
Q

What is a transcription factor?

A

Something that controls when transcription can take place. They can increase and decrease the transcription of genes.
They effectively turn a gene on and off by controlling the rate of transcription.

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28
Q

What is an example of a transcription factor?

A

Glucose - a transcription factor for the production of insulin

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29
Q

What are active transcription factors?

A

Those that increase the rate of transcription

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30
Q

What are repressor transmission factors?

A

Those which decrease the rate of transcription

31
Q

What effects the binding of a transcription factor?

A

The shape of the transcription factor determines whether it can bind to the DNA or not. The shape can be changed by the binding of another molecule - like hormones or sugars. This means the amount of a molecule in an environment can control the rate of protein synthesis.

32
Q

How are transcription factors different in Eukaryotes and Prokaryotes

A

In Eukaryotes transcription factors bind to the DNA sites near the start of the gene to be transcribed - whereas they bind to the operon in Prokaryotes

33
Q

What is Ecoli?

A

A type of bacteria

34
Q

What is Ecoli’s primary respiratory substrate?

A

Glucose

35
Q

If glucose isn’t available, what is used as the respiratory substrate?

A

Lactose

36
Q

What is needed in order to use lactose as a respiratory substrate in Ecoli?

A

Enzymes:
Lactose permiase - Allows lactose into the Cell.
B-galactosidase - hydrolyses the lactose to glucose and galactose

37
Q

What prevents the transcription of the enzymes in Ecoli?

A

The lac repressor (LacI)

38
Q

What happens in Ecoli to produce the enzymes?

A

Once glucose is used up, if lacte is present, a molecule of lactose will bind to the LacI repressor protein - changing its shape so it can no longer bind to the operator.
RNA polymerase cn then bind to the promotor region and beguin transcription - producing mRNA.
The mRNA is then translated by a ribosome to form B-galactosidase (from lac Z) and lactose permease (from lac Y)

39
Q

At what levels can genes be regulated?

A

Transcription.
Post-transcription.
Translation.
Post translation.

40
Q

How are genes regulated during transcription?

A

Genes can be turned on and off by repressor proteins produced by the regulatory gene.

41
Q

What is an intron?

A

The non-coding part of a DNA strand.

42
Q

What is an extron?

A

The coding regions of DNA.

43
Q

How can genes be regulated post-transcription?

A

Within the DNA there are non-coding regions called introns that separate the coding regions called exons.
During transcription, both introns and extrons are transcribed to produce primary RNA.
Introns are then removed from the mRNA strand by splisosome enzyme in a process called splicing. The exons are then joined together to produce the final mRNA.

44
Q

How can genes be regulated in translation?

A

Prevent Translation (repressor)
Promote Translation (activators)

45
Q

How can genes be regulated post-translation?

A

By epigenetics

46
Q

How is oestrogen part of cell signaling?

A

The hormone (oestrogen) binds to a receptor on the plasma membrane of the target cell.
This activates a transmembrane protein (e.g. a glycoprotein) which undergoes a conformational change - this activates a G protein.
Adenyl Cyclase is then activated by the G protein.
Adenyl cyclase catalyses the conversion of ATP into cAMP (Cyclic AMP).
cAMP activates the protein Kinase A.
This acts as a transcription factor taking information from cAMP to turn the transcription on.

47
Q

What is homeosis?

A

When one part of a developing embryo becomes anomalously transformed into another

48
Q

What is a homeobox sequence?

A

A large group of ancient genes responcible for morphogenisis (the anatomical shape - where things are) of an organism.

49
Q

What do homeobox genes ensure?

A

All structures develop in the correct location, according to the organisms body plan.

50
Q

What is the homeobox sequence made of?

A

a stretch of 180 DNA base pairs (excluding introns).

51
Q

What does highly conserved mean?

A

The homeobox sequence hasn’t changed throughout the evolution of descendent species.

52
Q

What does the homeobox sequence code for?

A

Homeodomain Sequence

53
Q

What is the homeodomain sequence?

A

A sequence of 60 amino acids within a protein.

54
Q

What does the homeodomain sequence do?

A

Produces a part of a protein that can fold into a particular shape and bind to DNA to regulate the transcription of adjacent genes. The proteins are transcription factors and act within the cells nuclius.

55
Q

What shape does the homeodomain-containing protein fold into?

A

HTH.
consists of two a-helices (H) connected by a turn (T).
Helix - Turn - Helix

56
Q

Where does the HTH bind to?

A

Bonds with the DNA sequence TAAT - which is an enhancer region for the gene to be transcribed.

57
Q

What are Hox Genes?

A

A subset of homeobox genes that specify specific regions within the body plan. They are only found in animals.

58
Q

What is a bilaterian?

A

An organism with the same body plan as humans.
A longitudinal axis with a top and bottom, and two sides - left and right.

59
Q

Where are Hox Genes found?

A

Clusters on one chromosome.
Humans have 4 clusters

60
Q

How many genes are there in each Hox cluster?

A

up to 10

61
Q

What do Hox Genes do?

A

Regulate the development of embryos along the anterior-posterior axis (head to tail). They control which body parts go where.

62
Q

What are Hox genes regulated by?

A

Maternal genes.
Gap genes.
Pair rule genes.
Polarity genes.

63
Q

How do maternal genes regulate Hox Genes?

A

Regulates the anterior-posterior axis (top and bottom). Maternally supplied mRNA from the egg cytoplasm.

64
Q

How do Gap Genes regulate Hox genes?

A

They define the different areas. e.g. head, abdomen, thorax

65
Q

How do pair-rule genes regulate Hox genes?

A

They refine the segments.

66
Q

How do polarity genes regulate Hox genes?

A

Refine how far the segments go

67
Q

What are the types of cell death?

A

Apoptosis.
Necrosis.

68
Q

What is apoptosis?

A

Controlled and programmed cell death

69
Q

What is necrosis?

A

inappropriate, unplanned and accidental cell death

70
Q

When do cells undergo necrosis?

A

When they are starved or poisoned.
e.g. blockages in arteries cause cardiac cells to die - these deaths are necrosis as they are unplanned.

71
Q

What happens during necrosis?

A

Cells swell and burst - this damages surrounding cells.

72
Q

When do cells undergo apoptisis?

A

Controlled by both intrinsic (in cell) and extrinsic (outside the cell) factors.
DNA has sustained too many injuries - e.g. radiation damage.
Cell is infected by a virus.
Cells need to be removed so that a body part can grow.
The cell is old and the Hayflick limit is reached.

73
Q

What happens during apoptisos?

A

A neat and tidy death. It Involves dismantling organelles and proteins while the cell shrinks to a few vesicles that get cleared by other cells. Enzymes break down the cytoskeleton and make the cell shrink.

A-Level Biology - OCR A (16 decks)

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