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Biology Year 2 > Chapter 20 - Gene Expression > Flashcards

Chapter 20 - Gene Expression Flashcards

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1
Q

What is a mutation

A

A change to the nucleotide sequence of DNA

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2
Q

How does a mutation occur

A

It is a spontaneous mistake made during replication of DNA (interphase)

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3
Q

What are the 3 causes of mutations

A

Base analogs
Radiation
Change DNA bases

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4
Q

What is meant by a substitution mutation

A

When one base is swapped for another

  • Could be no change as DNA is degenerate
  • Could cause single amino acid change
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5
Q

What is meant by an addition mutation

A

When an extra base is added

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6
Q

What is meant by a deletion mutation

A

A base is removed

- Causes frame shift so all triplets are affected

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7
Q

What is meant by an inversion mutation

A

A sequence of basis is removed

  • Could be no change or could change a few triplets
  • Can’t cause frame shift
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8
Q

What is meant by a duplication mutation

A

When one or more bases are repeated

- Can be more than once

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9
Q

What is meant by a translocation mutation

A

When a sequence of DNA is moved from one part of genome to another

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10
Q

Why may a mutation cause no change to the amino acid sequence

A

DNA is degenerate

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11
Q

What is caused if a mutation causes a change to a single amino acid

A
  • Changes one DNA triplet
  • Change the translation of one amino acid
  • Change the primary structure of the protein
  • Change the hydrogen and ionic bonding
  • Change in tertiary structure
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12
Q

What is caused if a mutation causes a change to the sequence of amino acids

A
  • Frameshift changes the sequence of all the following DNA triplets
  • Changes all the following amino acids in sequence
  • Changes the primary structure
  • Changes the hydrogen/ionic bonding
  • Changes tertiary structure
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13
Q

What are stem cells

A

Cells that can differentiate to become different types of cells
They can divide for all of the organisms lifetime

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14
Q

What is meant by totipotent stem cells

A

Cells that have the ability to differentiate into any type of specialised cell

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15
Q

What are examples of totipotent stem cells

A

Embryonic cells

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16
Q

What is meant by pluripotent stem cells

A

Cells that can differentiate into many types of specialised cell
Both embryos and adult cells can, but only specialised cells they can’t differentiate into are placental cells

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17
Q

What is meant by multipotent stem cells

A

Cells that can differentiate into a few types of specialised cells

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18
Q

What is an example of a multipotent stem cell

A

Bone marrow

Differentiate into red and white blood cells

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19
Q

What is meant by a unipotent stem cell

A

A cell that can differentiate into one type of specialised cell

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20
Q

What is an example of a unipotent stem cell

A

Heart unipotent cells that differentiate into cardiomycetes

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21
Q

How can cells differentiate into specialised cells

A
  • All cells contain 100% of an organisms DNA
  • Conditions within the cell control which genes are expressed in proteins
  • By changing internal environment of the cell, the expression of certain genes is affected
  • Cells then become specialised
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22
Q

What are the 3 ways that stem cells can be obtained

A
  • Induced pluripotent stem cells
  • Embryonic stem cells
  • Adult stem cells
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23
Q

What is an induced pluripotent stem cell (iPS cells)

A

Treating a unipotent stem cell with transcription factors that make them pluripotent

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24
Q

Explain how iPS cells are obtained

A
  • Modified virus used as a vector
  • Virus inserts transcription factor genes from pluripotent cells into the DNA of unipotent stem cells
  • Transcription factors are expressed
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25
Q

Explain how embryonic stem cells are obtained

A
  • Embryos are made in a lab by IVF
  • Pluripotent stem cells are removed after a few days
  • Embryo is destroyed
  • Pluripotent stem cells can differentiate with all types of body cells
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26
Q

Explain how adult stem cells are obtained

A
  • Taken from adults during an operation (eg bone marrow)

- Adults stem cells are multipotent so are less useful for medicine as they can’t make every type of cell

27
Q

Why are stem cells useful for medicine

A

They can differentiate to form any type of specialised cell, so can be used to replace faulty or damaged cells

28
Q

What are examples of how stem cells can be used in medicine

A
  • Bone marrow transplant

- Growing new organs

29
Q

Explain how a bone marrow transplant is useful

A
  • Bone marrow contains multipotent stem cells that can differentiate into white and red blood cells
  • If someone’s has faulty bone marrow this can’t be done
  • Replace bone marrow from a donor
  • Able to produce healthy cells
30
Q

How can stem cells be used to grow new organs

A
  • iPS cells produced
  • iPS organs can be
  • Organs have the same antibodies so aren’t rejected
31
Q

What are the three main advantages of stem cells for medicine

A

Save lives
Improve quality of life
Prevents suffering

32
Q

What are some ethical issues with stem cells

A
  • May be taken from IVF embryos which could develop into a foetus if implanted
  • A fertilised zygote has a right to life (although unfertilised eggs have been stimulated to prevent this issue)
  • Adults stem cells aren’t pluripotent
33
Q

What is meant by transcription factors

A

Proteins that control the rate of protein synthesis by switching some genes on and other genes off

34
Q

What is meant by a promotor region

A

A short sequence of DNA at the start of a gene (DNA/RNA polymerase attaches to this)

35
Q

Explain and draw how a transcription factor acts as an activator

A
  • Transcription factor moves from cytoplasm to nucleus
  • Binds to promotor region
  • Helps RNA polymerase to bind to DNA
  • Gene is transcribed
36
Q

Explain and draw how a transcription factor acts as a repressor

A
  • Transcription factor moves from the cytoplasm into the nucleus
  • Binds to promotor region
  • Prevent RNA polymerase binding to DNA
  • Gene is not transcribed
37
Q

What is the rate of mitosis controlled by

A

The expression of tumour suppressor genes and Proto-oncogenes

38
Q

What is meant by apoptosis

A

Programmed cell death (basically the opposite to mitosis)

39
Q

What do tumour suppressor genes do

A

Make proteins that slow down the rate of mitosis or speed up the rate of apoptosis

40
Q

Explain how a tumour May develop (tumour suppressor genes)

A
  • Mutation to tumour suppressor Gene

- Proteins May be non-functional

41
Q

Explain how the protein can be non-functional

A
  • Change to base sequence of gene
  • Change to DNA
  • Change to triplet codon
  • Change to mRNA codon
  • Change to amino acid
  • Change to primary structure
  • Change bonding
  • Change tertiary structure
42
Q

Explain how a tumour May develop (Porto-oncogenes)

A
  • Make proteins that increase the rate of mitosis
  • If a Proto-oncogene mutates it is called an oncogene
  • Oncogenes can be over expressed
  • Increased rate of mitosis
43
Q

What is meant by epigenetics

A

Changes to gene expression due to environmental factors (so no change in base sequence of DNA)

44
Q

How does epigenetic control gene expression

A

Environmental factors prevent transcription

45
Q

How is epigenetics useful

A

It helps organisms respond to changes in their environment

Can be inherited between generations due to control of gene expression

46
Q

What is an example of epigenetics

A

Pregnant mice exposed to a famine

Offspring are better adapted to low calories

47
Q

Explain methylation of DNA

A
  • Methyl can attach to DNA at CpG sites (cytosine and guanine next to each other in DNA)
  • Methylated CpG sites prevent transcription enzymes such as RNA polymerase attaching
  • Transcription is prevented

More methylation = Terminates transcription

48
Q

What are histones

A

Proteins that supercoil DNA into chromatin

50
Q

Explain acetylation of histones

A
  • Acetyl groups make histones spread out so DNA is less tightly coiled
  • Allows transcriptional enzyme to attach
  • Gene is expressed
  • Enzymes remove acetyl groups
  • Preventing transcription

Less acetylation = Terminates transcription

51
Q

What is RNA interference (RNAi)

A

Controlling gene expression by preventing translation

52
Q

Explain what small interfering RNA does (SiRNA)

A
  • Short and double stranded section combines with proteins to form SiRNA-protein complex
  • SiRNA becomes single stranded
  • SiRNA has complementary base sequence to the target mRNA
  • SiRNA-protein complex breaks down mRNA into pieces
  • Prevent transcription
  • mRNA pieces are recycled
53
Q

Explain how hypomethylation can cause cancer

A
  • Hypomethylation
  • Proto-oncogenes expresses more
  • More proteins transcribed
  • Uncontrolled cell division causing a tumour
54
Q

Explain how hypermethylation

A
  • Hypermethylation
  • Tumour suppressor genes (less)
  • Proteins not transcribed
  • Uncontrolled cell division causing a tumour
55
Q

What are 5 ways that tumour cells can be identified

A
  • More cells dividing (mitosis)
  • Nuclei are often large and odd shaped, and there may be more than one per cell
  • Cell shape is often irregular
  • Loss of normal cell function
  • Disorganised cell organelles
56
Q

What are the 2 types of tumour

A

Benign

Malignant

57
Q

Describe benign tumours

A
  • Non cancerous
  • Grow slowly
  • Harmless
  • Can become malignant
58
Q

Describe malignant tumours

A
  • Cancerous
  • Grow quickly
  • Harmful (destroy tissues)
  • Can spread through blood or lymphatic systems of broken up
59
Q

Describe the relationship between oestrogen and breast cancer

A
  • High levels of oestrogen can cause some types
  • Oestrogen can bind to proteins to form a transcription factor called oestrogen-oestrogen receptor complex
  • Increases rate of cell division so increase DNA replication
  • Increase chance of mutations and therefore cancer
60
Q

What is meant by genome

A

The complete set of genetic material that an organism has (genes and non-coding DNA)

61
Q

What is meant by proteome

A

The complete set of proteins that an organism can make

62
Q

What is meant by phylogeny

A

Evolutionary relatedness

63
Q

What are the uses of the genome project

A
  • Understand evolutionary relatedness

- Can help in medicine as it can increase understanding of antigens to develop new vaccines

64
Q

Explain what MicroRNA does

A
  • MicroRNA combines with a protein
  • Forms MicroRNA-protein complex
  • Binds to mRNA by complementary base pairing
  • Less specific than SiRNA so works on more than one mRNA
  • Prevents translation by stopping the ribosome attaching
  • mRNA can be stored and used later or recycled

Biology Year 2 (10 decks)

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