Cellular Control
What effect would the acetylation of histones have on transcription?
Increased transcription
What value is stated as the threshold potential for the generation of an action potential?
-55 mV
What technique allows us to make genome-wise comparisons?
DNA sequencing
The complete set of DNA in an organism
Genome
What bond is formed in a condensation reaction between two nucloetides?
Phosphodiester bond
What are the three main ways of controlling gene expression at the transcriptional level in eukaryotes?
2. Chromatin remodelling
3. Epigenetics and histone modification
What is the difference between temporal and spatial summation?
-Temporal summation is where repeated firing by a presynaptic neurone leads to continuous neurotransmitter release that increases the chances of postsynaptic firing
-Spatial summation is where multiple presynaptic neurons converge on a single postsynaptic neurone or effector cell and the combined input of neurotransmitters triggers postsynaptic firing
Why is the proteome larger than the genome?
Alternative splicing and post translational modification of proteins means that there are more final protein products than protein coding genes
The rapid propagation of action potentials along myelinated axons, where the impulse "jumps" between Nodes of Ranvier
Saltatory conduction
What is the equation needed to calculate the respiratory quotient?
RQ=CO2 produced/O2 consumed
What three factors affect the rate of translation?
1. mRNA degradation rates
2. Inhibitory proteins
3. Initiation factors
What three factors affect the speed of transmission of action potentials, and how?
1. Myelination - myelination allows saltatory conduction and increases speed
2. Axon diameter - larger diameter means lower resistance so increased speed
3. Temperature - higer temperature accelerates diffusion of ions so increased speed
Give three uses of DNA profiling
1. Forensics
2. DNA profiling (identifying risk for disease/determining familial relationships)
3. Species conservation (preventing inbreeding)
A change to the sequence of nucleotides in a DNA molecule
Mutation
What chemical is produced by plants in response to attack by pathogens?
Callose
-Homeobox sequences encode the homeodomain, the part of a protein that binds to DNA
-The homeodomain operates as a transcription factor
-It binds to DNA, switching developmental genes on or off
-This modifies the transcription of proteins necessary for the development of body plans
Describe how the resting potential is established and maintained in a myelinated neurone
-Sodium potassium pumps actively transport three sodium ions out of the neurone for every two potassium ions they move in
-Potassium ion channels allow the diffusion of potassium ions out of the neurone down its concentration gradient
-Sodium ion channels are closed, preventing the movement of sodium ions into the neurones
-As a result, the extracellular space outside the axon accumulates more positive ions, making the axon cytoplasm more negatively charged in comparison, causing the membrane to be polarised at its resting potential of -70mV
What are the five steps required for the genetic engineering of an organism?
1. Identification of the DNA fragment or gene
2. Isolation of the desired DNA fragment
3. Multiplication of the DNA fragment
4. Transfer into the organism using a vector
5. Identification of the cells with the new DNA fragment and subsequent cloning
Diploid cells that make up the body of an organism
Somatic cells
What is the expected ratio of genotypes in a dihybrid cross for the offspring of two heterozygous parents
9:3:3:1
Outline the regulation of the lac operon by glucose, discussing what happens when only lactose is present and when both lactose and glucose are present
-Glucose is the preferred energy source for E. coli. The presence of glucose indirectly inhibits the lac operon via a signalling molecule, cAMP
-When only lactose is present, cAMP levels increase and cAMP binds to its receptor protein which upregulates the transcription of the lac operon, thus optimising lactose metabolism
-When both glucose and lactose are present, glucose reduces cAMP levels so CRP-cAMP complex cannot form and the lac operon's transcription is downregulated. Lactose metabolism enzymes are therefore not produced
What are the six phases involved in the generation of an action potential (in order)?
1. Resting potential - membrane polarised at -70 mV
2. Stimulus - voltage gated Na+ channels open, Na+ ions move into the axon
3. Depolarisation - if threshold potential of -55 mV reached, more Na+ channels open causing influx of Na+
4. Repolarisation - at +30 mV, Na+ channels close and K+ channels open
5. Hyperpolarisation - an excess of K+ leaves the axon, dropping the PD below -70 mV
6. Refractory period - ion pumps and channels work to restore the membrane back to the resting potential
Describe the process of translation
-mRNA leaves the nucleus via a nuclear pore and attaches to a ribosome
-the anticodon of tRNA molecules bind to the complementary codon on mRNA
-each tRNA molecule brings with it a specific amino acid
-two tRNA molecules fit onto the ribosome at any one time, and a peptide bond forms between the amino acids carried by those tRNA molecules
-Once the bond is formed, the tRNA molecule leave the ribosome and new ones enter until a 'stop' codon on the mRNA molecule is reached
-The amino acid chain then forms the final polypeptide
Chemical messengers stored in synaptic vesicles within the presynaptic neuron that are released upon the arrival of an action potential
Neurotransmitters
What does it mean for DNA replication to be 'semiconservative'?
Each new daughter DNA molecule consists of one original (parental) strand and one newly synthesized strand