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Unit 5 > Gene Expression > Flashcards

Gene Expression Flashcards

1
Q

What are the three kinds of change to the base sequence that cause a mutation?

A

Insertion, Deletion and Substitution

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2
Q

What is base substitution?

A

A mutation which switches out a single base for another which alters a single amino acid, not the whole protein May not even have an effect if the substituted base is the third in a codon

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3
Q

What is an insertion?

A

Where a base is inserted, causing a reading frame shift, affecting the rest of the protein

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4
Q

What is a deletion?

A

Where an original base is removed, causing a reading frame shift affecting the rest of the protein

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5
Q

What are the three kinds of mutation?

A

Non-sense, mis-sense and silent

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6
Q

What is a silent mutation?

A

A mutation which results in no change to the amino acid sequence

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7
Q

What is a non-sense mutation?

A

A mutation which results in the formation of a stop codon

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8
Q

What is a mis-sense mutation?

A

A mutation which changes the amino acid(s) being coded for potentially resulting in a non-functional protein or not being made at all

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9
Q

What causes mutations?

A

Exposure to mutagens

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10
Q

What are mutagens?

A

Ionising radiation or certain chemicals like carcinogens

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11
Q

What is a malignant tumour?

A
  • More mutations than Benign
  • Can invade other tissues so it is hard to determine boundary of tumour
  • Fast Growing, Cells recruit formation of blood vessels
  • Can invade other tissues by metastasis
  • Cancer Forming
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12
Q

What is a benign tumour?

A
  • mutations in one or two controlling cells
  • localised populations of cells, distinct demarcation
  • Growth rate matches death rate
  • Cannot invade other tissues
  • Non-cancerous
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13
Q

What two genes cause cancer if mutated?

A
  • Proto-oncogenes

- Tumour suppressing genes

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14
Q

How does a mutation in a proto-oncogene cause cancer?

A

Proto-oncogenes encode proteins which stimulate cell division when activated. If it is mutated the gene becomes an ‘oncogene’ which makes too much permanently activated protein so cell division occurs constantly which can cause cancer

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15
Q

How does a mutation in a tumour suppressing gene cause cancer?

A

Tumour suppressing genes encode proteins which inhibit cell division when activated. when the gene is mutated the protein is not synthesised so cell devision is unchecked.

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16
Q

Is the mutation that turns a proto-oncogene into an oncogene dominant or recessive?

A

Dominant

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17
Q

Is the cancer causing mutation of the tumour suppressing gene dominant or recessive?

A

Recessive.

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18
Q

What are the 5 points at which gene expression can be controlled?

A
  • Transcription
  • Post transcriptional modification
  • Longevity of mRNA
  • Translation
  • Post translational modification
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19
Q

How is gene expression controlled during DNA Transcription?

A

Transcription factors determine which genes are expressed

20
Q

How is gene expression controlled during Post-transcriptional modification?

A

different Splicing means different mRNA so different proteins coded for

21
Q

How is gene expression controlled by the longevity of mRNA?

A

If mRNA does not last very long, less of it can be translated into proteins. The longer it lasts the more protein will be made from it

22
Q

How is gene expression controlled during DNA Translation?

A

Ribosomes control how much protein is translated

23
Q

How is gene expression controlled during post translational modification?

A

The activity of the protein can be altered by other enzymes

24
Q

How do transcription factors control DNA Transcription?

A

Transcription Factors bind to the promoter region to influence the binding of the RNA Polymerase enzyme. Some Transcription Factors activate transcription from here while others inhibit it.

25
Q

How do steroid hormones such as oestrogen control protein synthesis?

A
  • Osetrogen diffuses across the cell membrane into the cytoplasm
  • Oestrogen binds to a receptor protein to form a hormone receptor complex, which becomes a transcription factor
  • The active transcription factor diffuses into the nucleus through a nuclear pore
  • The transcription factor binds to a specific base sequence on a DNA promoter, upstream of RNA Polymerase and then binds to it, stimulating protein synthesis
26
Q

Through what named process can the longevity of mRNA be directly affected?

A

RNA Interference (RNAi)

27
Q

What molecule is the control of mRNA breakdown carried out by?

A

Small interfering RNA (siRNA)

28
Q

How is siRNA made?

A

Single stranded RNA is transcribed and then folds back on itself by complementary base pairing to form double stranded RNA (dsRNA). The dsRNA is then seperated into two single stranded siRNA molecules by the enzyme ‘dicer’.

29
Q

How is RISC made?

A

siRNA binds to a ‘Slicer’ enzyme.

30
Q

How does RNAi work?

A

the RISC molecule binds to mRNA molecules by complementary base pairing. The binding causes RISC to cleave the mRNA into two pieces which can then no longer be used in translation so it is broken down by nuclease enzymes.

31
Q

How can RNAi be practically applied for scientific/medical purposes?

A
  • GMO; silencing undesirable genes
  • Identifying functions of genes by silencing them and observing the effect
  • Treating human patients by silencing essential viral or cancer causing genes.
32
Q

What are Stem cells?

A

Undifferentiated cells which are immortal (Can divide infinitely) and potent (can differentiate into specialised cell types)

33
Q

Where are the 3 sources of stem cells for research?

A
  • Embryo stem cells from spare blastocysts from IVF (totipotent)
  • Adult stem cells (multipotent)
  • induced Pluripotent stem cells
34
Q

What does multipotent mean?

A

Can only differentiate into their own family of cells (e.g. blood cells, muscle cells)

35
Q

What does totipotent mean?

A

Can differentiate into any kind of cell

36
Q

what are induced pluripotent stem cells?

A

iPSCs are normal specialised adult cells which have been genetically reprogrammed to become undifferentiated, pluripotent stem cells.

37
Q

Where are stem cells found in plants?

A

Meristem tissue

38
Q

What do meristem cells contain?

A

totipotent stem cells, small vacuoles, undeveloped chloroplasts called proplastids, and thin cell walls.

39
Q

What are the numerous forms of vegetative propagation?

A

that which occurs in:

  • bulbs
  • corms
  • rhizomes
  • stolons
  • runners
  • tubers
  • tap roots
  • tillers
40
Q

What is vegetative propagation?

A

The natural method of asexual reproduction in plants where the new plant grows from meristem tissue in a vegetative part of the plant.

41
Q

How are plants cloned through cuttings?

A

Cuttings of a plant are replanted in wet soil, growing a new plant.

42
Q

What is micropropagation in plants?

A

More efficient modern plant cloning.

  • small tissue sample of plant (explant) is grown on agar
  • individual cells are seperated and left to grow into a mass of undifferentiated cells called calluses
  • plant growth regulators are added then the calluses will grow into whole plantlets
43
Q

Why is the genetic code described as being universal?

A

the same triplet codes for the same amino acid in all organisms

44
Q

Name the process that removes base sequences from pre-mRNA to form mRNA

A

Splicing

45
Q

What is a transcription factor? (3 marks) from mark scheme, tried to make it some what more pleasant to read, didn’t do a very good job :)

A

Protein or moecule that moves from cytoplasm
to DNA;
That binds to specific gene/genes/ to specific
part of/site on DNA/ binds to promoter/RNA
polymerase
Which leads to/blocks (pre)mRNA production /
allows/blocks binding of RNA polymerase (to
DNA)/allows RNA polymerase to work

46
Q

Name the type of enzyme used to produce the cDNA

A

reverse transcriptase

Unit 5 (9 decks)

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