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
Explain how embryonic stem cells are obtained
- 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
26
Explain how adult stem cells are obtained
- 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
Why are stem cells useful for medicine
They can differentiate to form any type of specialised cell, so can be used to replace faulty or damaged cells
28
What are examples of how stem cells can be used in medicine
- Bone marrow transplant | - Growing new organs
29
Explain how a bone marrow transplant is useful
- 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
How can stem cells be used to grow new organs
- iPS cells produced - iPS organs can be - Organs have the same antibodies so aren’t rejected
31
What are the three main advantages of stem cells for medicine
Save lives Improve quality of life Prevents suffering
32
What are some ethical issues with stem cells
- 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
What is meant by transcription factors
Proteins that control the rate of protein synthesis by switching some genes on and other genes off
34
What is meant by a promotor region
A short sequence of DNA at the start of a gene (DNA/RNA polymerase attaches to this)
35
Explain and draw how a transcription factor acts as an activator
- Transcription factor moves from cytoplasm to nucleus - Binds to promotor region - Helps RNA polymerase to bind to DNA - Gene is transcribed
36
Explain and draw how a transcription factor acts as a repressor
- Transcription factor moves from the cytoplasm into the nucleus - Binds to promotor region - Prevent RNA polymerase binding to DNA - Gene is not transcribed
37
What is the rate of mitosis controlled by
The expression of tumour suppressor genes and Proto-oncogenes
38
What is meant by apoptosis
Programmed cell death (basically the opposite to mitosis)
39
What do tumour suppressor genes do
Make proteins that slow down the rate of mitosis or speed up the rate of apoptosis
40
Explain how a tumour May develop (tumour suppressor genes)
- Mutation to tumour suppressor Gene | - Proteins May be non-functional
41
Explain how the protein can be non-functional
- 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
Explain how a tumour May develop (Porto-oncogenes)
- 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
What is meant by epigenetics
Changes to gene expression due to environmental factors (so no change in base sequence of DNA)
44
How does epigenetic control gene expression
Environmental factors prevent transcription
45
How is epigenetics useful
It helps organisms respond to changes in their environment | Can be inherited between generations due to control of gene expression
46
What is an example of epigenetics
Pregnant mice exposed to a famine | Offspring are better adapted to low calories
47
Explain methylation of DNA
- 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
What are histones
Proteins that supercoil DNA into chromatin
50
Explain acetylation of histones
- 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
What is RNA interference (RNAi)
Controlling gene expression by preventing translation
52
Explain what small interfering RNA does (SiRNA)
- 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
Explain how hypomethylation can cause cancer
- Hypomethylation - Proto-oncogenes expresses more - More proteins transcribed - Uncontrolled cell division causing a tumour
54
Explain how hypermethylation
- Hypermethylation - Tumour suppressor genes (less) - Proteins not transcribed - Uncontrolled cell division causing a tumour
55
What are 5 ways that tumour cells can be identified
- 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
What are the 2 types of tumour
Benign | Malignant
57
Describe benign tumours
- Non cancerous - Grow slowly - Harmless - Can become malignant
58
Describe malignant tumours
- Cancerous - Grow quickly - Harmful (destroy tissues) - Can spread through blood or lymphatic systems of broken up
59
Describe the relationship between oestrogen and breast cancer
- 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
What is meant by genome
The complete set of genetic material that an organism has (genes and non-coding DNA)
61
What is meant by proteome
The complete set of proteins that an organism can make
62
What is meant by phylogeny
Evolutionary relatedness
63
What are the uses of the genome project
- Understand evolutionary relatedness | - Can help in medicine as it can increase understanding of antigens to develop new vaccines
64
Explain what MicroRNA does
- 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
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