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Genetic Variation Flashcards

1
Q

In which direction does RNA polymerase move?

And therefore in which direction is mRNA made?

A

3’ –> 5’

mRNA made from 5’ –> 3’

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2
Q

What are the stages of the cell growth cycle?

A

G1 –> Cell prepares for cell growth

S-Phase –> DNA replicated/synthesised

G2 –> Cell prepares for division

M-Phase –> Mitosis, spindle formation and cell division

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3
Q

How is Cortisol secreted in the body?

A

Stimuli cause Corticotrophin Releasing Hormone (CRH) from the hypothalamus

This stimulates the pituitary to release AdrenoCorticoTrophic Hormone (ACTH) –> This causes the adrenals to secrete cortisol

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4
Q

Why can chemotherapy cause damage to our own cells, but not always the tumour cells?

A

Because our own cells have p53 (pro-apoptopic) and so the chemo will damage our cells enough to induce apoptosis

However the mutated tumour cells will probably not have any p53, so apoptosis will not be induced!!

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5
Q

Explain X-linked recessive Alleles?

A

The allele is on te X chromosome, so is more prevelent in females (more likely to be carriers as they have to X chromosomes)

Males only need 1 copy of the allele to be a suffer (as they only have one X-chromosome)

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6
Q

Explain the anti-inflammatory effects of glucocorticoids

A

Inhibits not the innate and adaptive immune systems

Decrease the production of inflammatory mediators (ROS, leukotrienes, complement, histamine and prostanoids)

Inhibit Th cells activation –> As well as IL-2 and clonal expansion

Decrease vasodialtion –> Preventing wbc to get to the site of infection

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7
Q

What are the 4 normal control mechanisms of the body to prevent loss of function from mutations?

A

Hetrozygosity –> 2 versions of the same gene, as there’s less chance that both will get mutated

Apoptosis –> Regulated cell death to prevent the transmission of mutated genes

Cell Cycle Control –> Checkpoints during cell division ensures thats no damaged cells become fully grown (but killed by apoptosis)

Regulation of Gene Transcription –> There is a requirement for certain activation signals for gene transcription

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8
Q

Describe the characteristics of Adult (Somatic) Stem Cells

A

They can proliferate….but not indefinitely

Multipotent/unipotent cells

Located in stem cell niches

Replace worn out/dead cells –> so important for homeostasis

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9
Q

What is the difference between Homodimers and Heterodimers?

A

Homodimers –> Cytoplasmic and nuclear loacalisation

Each subunit binds one repeat as an inverted dimer, and as a palindrome

Heterodimer –> Activated by ligands binding in the nucleus

RXR forms a dimer with either…

Vitamin D receptor (VDR) –> 3 base pair spacing

Retionic Acid receptor (RAR) –> 4bp

Tridothyronine receptor (T3R) –> 5bp

Bind direct repeat half sites

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10
Q

What will a mutation in the gene IL36RN do?

A

Cause pustular psoriasis

IL36RN usually helps regulate inflammation by suppressing cytokines like IL-1

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11
Q

Explain two reasons for Atopic Eczema?

A

A change in the Filaggrin gene that encodes for a structual protein in the skin

Genetic tendencies can cause more IgEs to be produced when exposed to certain allergens

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12
Q

What is an allele?

A

Different forms of the same gene

Can be dominant or reccesive

Can predispose to disease –> usually mutated versions (eg, CF)

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13
Q

What is the screening that is done for CF?

A

Immunoreactive Trypsinogen (IRT) - Guthrie Test –> If positive, trypsingoen will be present in the blood, due to the duct in the pancreas being blocked

Genetic Screening –> For the most common genetic mutations

Sweat Test –> Cl- above 60mM = CF likely

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14
Q

What is the difference between Cyclin/CDKs and CKIs?

A

Cyclin/CDKs –> Cell growth promoters

CKIs –> Inhibitors…..so cell cycle (growth) suppressors……there are 2 types…..

INK4/p16 –> Inhibit CDK4/6

CIP/Kip (p27) –> Inhibt all CDKs

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15
Q

Name 2 pharmacological approches for fixing the ASL in patients with CF

A

Calcium-Activated Chloride Channel (CACC) Activators

Blocking ENaC –> Amiloride

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16
Q

How does 3 person IVF work?

A

The parents embryo is fertilised with the mans sperm

The parents embryo has their nucleus removed, and inserted into a donors embryo that has healthy mitochondria (and no nuclei)

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17
Q

What are Tumour Suppressor Genes?

A

Genes that exert negative effects on cell growth (eg, p53)

So mutations in these will cause an increase in cell growth!!

Usually recessive, so less likely to have full mutations

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18
Q

Explain how the differentation of embryonic stem cells occurs

A

ESCs will form embryoid bodies once they have stopped renewing (around 6 days)

These bodies have three germ layers (endoderm/mesoderm/ectoderm)

After another 10 days, with differentation factors, the specific cell is formed (for example a cardiomyocyte for the heart)

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19
Q

Explain siRNA mediated RNA interference

A

Short dsRNA (siRNA) binds to a specific part of an mRNA coding region –> Causing mRNA cleavage

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20
Q

What’s the difference between Heterochromatin and Euchromatin?

A

Heterochromatin –> Densely packed (condensed) and deacetylated….so not actively transcribed

Euchromatin –> Beads on a string apprearance and acetylated….so actively transcribed!

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21
Q

What are the 2 types of families of proteins involved in the cell growth cycle?

And where abouts are these used?

A

Cyclins –> Transcription dependent

Cyclin-Dependent Kinases –> Activation dependent

Usually by phosphorylation

22
Q

What is a Single Nucelotide Polymorphism (SNP)?

And what criteria needs to be filled for something to be called an SNP?

A

A varation in a DNA sequence by a single nucleotide, at the same position, in the genome between members of the same species

The variation must occur in at least 1% of the population

23
Q

Generically speaking…. if a molecule involved in cell growth starts with a p (eg, pRb/P53/P16) what do they do?

A

They inhibit cell growth (suppress it)

So mutations in these will cause an increase in cell growth

24
Q

Where are endogenous steroids made?

And what different types are made here?

A

The Adrenal Cortex

Mineralcorticoids –> Aldosterone

Glucocorticoids –> Cortisol

25
What is a promoter?
A DNA sequence that determines the site of transcription initiation for an RNA polymerase /Transcription factors
26
What is the link between **LL37** and Psoriasis?
LL37 is an endogenous antimicrobial thats needed to prtect the body when skin is broken In psoriasis LL37 is overexpressed, allowing more to bind/activate dendritic cells --\> Acts as an autoantigen This triggers an immune response, which causes cytokines like IL-17 to be produced
27
What is **NFkB**?
Nuclear Factor of Kappa (light chain) in B cells Causes the activation of inflammatory genes Inhibited by IKb which binds across the Rel domain
28
What are the characteristcs of **embryonic stem cells**?
They will continue to proliferate almost indefintely They will form tumours in immunocompromised rats They are pluripotent
29
**Alkaline phosphotase** surface expression is exclusive to what type of stem cell?
Pluripotent embryonic stem cells
30
How does the CRISPR/Cas system work in bacteira to prevent viral infection?
Viral DNA is cleaved by the Cas complex, producing short spacer regions. These are then inserted into the CRISPR region of the bacterias genome. The CRISPR is then transcribed and then pairs with TracrRNA to produce a dsRNA that is cleaved by endonuclease III. This produces (crRNA-tracrRNA) dsRNA sequances. This binds to Cas9. This searches for matching DNA from viruses that matches the spacer regions. If found, it is destroyed.
31
What's the difference between **miRNA** and **siRNA**? And their effects?
**miRNA** --\> 21 nucleotides long Target the 3' end of mRNA, causing a prevention of translation **siRNA** --\> 21 nucleotides long and double stranded Cleaves mRNA in the coding region Both interfere using the protein **AGO 2**
32
Explain what **oncogenes** are? And what can they can cause?
They are mutated forms of normal genes needed for growth They are usually dominant, so only one mutation is needed Point mutations in RAS cause **ligand independence** (activation without a ligand) due to constitutive activation of **EGFR** (Epidermal Growth Factor Receptor) and **overexpression of genes**
33
When are bone-marrow transplants done? And what are the types?
For people whose bone marrow is destroyed during the treatment of myelomas and lymphomas **Autologus** --\> Self transplant (most common due to lack of rejection) **Allogenic** --\> Non-self transplant
34
What is the **principal cause of mortality** in people with Cystic Fibrosis?
Malnutrition due to pancreatic insufficiency So the pancreas cannot produce the digestive enzymes needed --\> so food is not digested properly Therefore they need Pancreatin (**Creon**) --\> Amylase, Lipase and Protease
35
How do **glucocorticoids** work?
Bind to intracellular receptors (as GCs are lipophillic) Bind to their specific receptor inside of the cell, once the receptor has been activated. It is normally held in an inactivated state by the heat shock protein (HSP90) The complex then translocates to the nucleus to act as a transcription factor. They **must bind as dimers** to show biological activity This can cause the repression of anti-inflammatory genes (**by controlling gene transcription**)
36
Explain a few ways that **antisense/siRNA/gRNA** can be transported into the body
These are large and -vly charged molecules, so can be hard to get into the body **Packaging of Vesicles** --\> They are packed inside of a +vly charged vesicle (done via negative transfection) **Addition of delivery agents** --\> Conjugation of cholesterol/peptides with antisense **Electroporation** --\> Electricity is used to punch holes in the membrane, allowing the molecules to get into them **Viral Carrier** --\> Lentiviruses can integrate the molecules into the target DNA
37
How does Antisense work?
A single strand of DNA/RNA that is complemetory to the mRNA (15-30 nucleotides long) binds This causes RNase H to split the mRNA into 2, causing it to degrade
38
Define.. **Functional Genomics** **Pharmacogenetics** **Pharmacogenomics**
**Functional Genomics** --\> Genomic science in whole cell or in vivo situations **Pharmacogenetics** --\> The influence of an individuals genetic profile on medicine efficacy and safety **Pharmacogenomics** --\> Using genetic information in the discovery of new medicines and targets
39
What mutations cause **CF** and **Sickle Cell Anaemia**
**CF** --\> 3 nucleotide deletion of phenylalanine in the CFTR (cystic fibrosis transmembrane conductance regulator) channel **Sickle Cell Anaemia** --\> An SNP (A --\> T) of the (B)-globin gene
40
Define what a **Stem Cell** is, and the different types
**Stem Cell** --\> Unspecialised cells that can proliferate and differrentiated into many other cell types - Adult (somatic) / Embryonic (ESC) / Induced pluripotent (iPC) **Totipotent** --\> Can form all tissues needed for an organism, including the placenta (eg, a fertalised egg) **Pluripotent** --\> Can form all cells needed for a human, just not the placenta **Multipotent** --\> Can only form a limited number of cell types (eg, most adult stem cells) **Unipotent** --\> Can only form one type of cell
41
What is a **Simple Sequence Repeat** (SSR)?
A tandam repeat of between 2-8 base sequences Eg, TGTGTG Each person will inherit a different number of these SSRs, which creates a biological fingerprint
42
Explain the **effects of losing the CFTR channel** in terms of the Air-Surface Liquid (ASL) And how can these effects be dampened?
Usually there is a large layer of mucus (ASL), caused by Cl- ions that are moved by the CFTR channel However when we remove the CFTR channel, we lost lots of Cl-.... causing a much thinner layer of mucus (ASL), which is dehydrated and sticky.... which makes it harder fo cilia to clear pathogens Can be partially fixed using hypertonic saline
43
When will a mutation affect the function of a protein?
When the mutation occurs in the **coding region** of the gene
44
Name 3 new drugs that are being used to treat specific mutations of CF?
**Ataluren** --\> For class I mutations (force through a premature stop codon) **Lumacaftor** --\> For class II (acts as a chaperone in channel processing) --\> Must be with Ivacoftor **Ivacoftor** --\> For class III (acts as a potentiator)
45
What are the characteristic features of the lung damage done in patients with CF?
Strucutual changes --\> Bronchial wall thickening, and lung collapses **Mucus plugging** **Chronic infections** Epithelial Damage **Massive neutrophil infiltration of the airways** --\> frustrated phagocytosis caused by an inability to clear infections (so neutrophils die)
46
What is **AP-1**?
Regulates cell growth as well as **early response** genes Made up of a dimer of **Fos** (needs to be transcribed) and **Jun** (needs to be phosphorylated)
47
What is stem cell differentation driven by?
**Growth factors** and other extracellular mediators
48
Name the two main things that can move through damaged skin?
**Allergens** --\> Bypass the innate system and directly activate B cells (which create IgE) **Bacteria** --\> Activate the innate and then adaptive immune systems
49
What are **translocation mutations**?
Where there are crossovers of chromosomes during cell division An example is the translocation of bcl-2 which comes under the control of the Ig promotor (as a result of the translocation) Therefore lots of bcl-2 is produced, and as it is an anti-apoptopic protein, it causes a decreased ability of cells to die by apoptosis
50
What **type of inheritance** is associated with both **huntingtons disease and hypercholesteremia**?
Autosomal Dominant
51
Name a few examples of diseases that are caused by **X-linked Recessive alleles**?
Haemophillia Colour Blindness Muscular Dystrophy

PA20320 (7 decks)

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