gene expression and neurones

define mutation

a change in the DNA base sequence

What are the 6 types of mutations?

substitution, inversion, translocation (these 3 don’t cause a frame shift but may change the AA produced) deletion, addition, duplication

what’s a mutagenic agent and how do they work?

increase the rate of a mutation which results in a different AA sequence by either:

• acting as a base

• altering bases

• changing the DNA structure

What are stem cells? what are the 4 types?

Unspecialised cells that have the ability to become any other type of cell

• totipotent (embryonic cells and can become ANY cell,) pluripotent, multipotent, unipotent

what are induced pluripotent cells

adult cells reprogrammed using transcription factors to make pluripotent cells.

what are transcription factors

molecules that bind to DNA (in the promoter region) that initiate transcription by allowing RNA polymerase to bind to them

what’s epigenetics?

how environmental influences alter genetic inheritance. involves heritable changes in gene function WITHOUT changing the DNA BASE SEQ.

how does acetlyation affect gene expression/ transcription

acetyl groups added to histones. histones forced apart which makes it easier for RNA polymerase to bind an activate transcription

• remove acetyl groups = decreased transcription

how does methylation affect gene expression/transcription.

methyl groups attach to cytosine bases. silences genes because T.F and RNA polymerase can’t bind/move along DNA strand and activate transcription

what does siRNA do?

stands for short interfering RNA. silences genes by destroying target/preventing transcription

• (ds)RNA hydrolysed into smaller (ss) siRNA which binds to complementary mRNA (becoming dsRNA) and forms a group of proteins called RISC which breaks down mRNA so that they can’t be translated to form functional proteins

what do the 3 types of neurone do

• sensory: carries impulse from receptors to CNS

• relay: relays impulse from sensory neurone to motor neurone

• motor: carries impulse to effector organ

what is resting potential and how is it maintained?

• -70mv

• outside membrane is more +ve than inside. this difference in charge = membrane is polarised.

• Na+ pumped out but can’t diffuse back in which creates electrochemical gradient due to more +ve ions outside

• k+ pumped in but some diffuses back out which keeps outside membrane more +ve

Describe the process of an action potential?

1. begins at resting potential. stimulus excites neoprene so Na+ diffuses in. at threshold of -55mv more Na+ channels open and more Na+ diffuses in (depolarisation)

2. at p.d 30mv. Na+ channels close and k+ channels open. K+ diffuses in and down gradient. (repolarisation)

3. K+ channels slow to close, too many K+ diffuse out so p.d now more negative than resting potential (hyper polarisation)

4. channels rest Na+ pump returns membrane back to resting potential

what does the refractory period do?

ion channels recover and can’t open which acts as a time delay between action potentials

what three things affect the speed of an impulse?

1. myelination

2. axon diameter

3. temperature

describe the process of synaptic transmission

1. presentation neoprene contains NT in vesicles

2. a.p causes NF to be released from vesicles into synaptic cleft

3. NT diffuses across to post synaptic membrane and bind to specific receptors. triggers a.p and causes muscle contraction

4. NT removed from cleft, broken down or reuptaken

what does excitatory and inhibitory mean?

excitatory: depolarises posty synaptic membrane so an action potential is more likely to fire

inhibitory: hyperpolarises post synaptic membrane which prevents action potential from firing

what happens at a neuromuscular junction?

• NT acetylcholine (ACh) binds to cholinergic receptors called nicotine cholinergic receptors.

• post synaptic membrane has lots of folds that form clefts which store an enzyme that breaks down ACh called AChE

• ACh is always excitatory = a.p will always trigger muscle response

describe the structure of the mitochondria?

• matrix contains enzymes for oxidative phosphorylation

• inner, inter and outer membrane

• ribosomes

• DNA for mitochondria to replicate

describe the process of glycolysis

1. glucose phosphorylated to form glucose phosphate (and 1ADP)

2. ATP used to add another phosphate and form expose biphophate (and 1ADP)

3. heckles bi. split into 2 molecules of triose phosphate

4. tri.phos. oxidised so loses H+ which forms 2 red NAD

5. 2 pyruvate formed

describe the process of the link reaction?

1. private decarboxylated (Co2 removed)

2. pyruvate oxidised to form acetate and NAD is reduced to form red. NAD

3. acetate combined with coenzyme A to form Acetyl CoA

4. occurs twice per glucose molecule