Bio yay!

Describe the possible causes and consequences of a substitution mutation in DNA

Substitution mutations are caused by mutagens/radiation and they occur when randomly a base is replaced by another. Due to the degeneracy of the genetic code, an altered codon can still code for the same AA, resulting in same-sense mutation with no consequences to the protein. Also, mutations in gametes can pass onto offspring. If theres no same-sense mutation though and the changed base codes for another AA, the polypeptide may become non-functioning

Distinguish between cell division by mitosis and by meiosis in eukaryote cells

Mitosis results in 2 genetically identical daughter cells from only one division. Meiosis has 2 divisions though and will cause 4 genetically varied daughter cells. Mitosis occurs for growth/repair and meiosis occurs for producing gamete cells. Mitosis daugher cells are diploid and meiosis is haploid.

Explain how gene expression can be regulated during transcription to determine an organism’s phenotype

Transcription factors can bind to enhancers to increase the rate of transcription/promote whereas when binded to silencers it reduces the rate of transcription/represses. Epigentic modifications such as methylation can change gene expression like when the methylation of cytosine bases within a promoter region it can repress transcription of that gene + methylation of histone proteins can cause transcription to be activated or repressed → this all together regulates the production of proteins from that gene.

Steroid hormones can also act as chemical signals which activate receptors that promote transcription.

Compare and contrast simple vs facilitated diffusion

both move down their conc gradients and hence dont utilize ATP/passive. Simple diffusion uses no proteins and is non-specific, facilitated diffusion requires proteins and is highly-specific

protein structure thing + what is the secondary structure

quaternary

alpha-helix: the diagram X is coiled, alpha-helices are held together by weak hydrogen bonds

role of tRNA in haemoglobin synthesis

tRNA carries specific amino acids that are brought to the ribosome during translation. each tRNA molecule holds complementary anticodes (due to complementary base pairing) to the codons of the mRNA strand transcribed from the haemoglobin gene. The tRNA moves from A to P to E sites all whilst the next mRNA codon is exposed and a tRNA with the complementary anticodon binds to the unoccupied “A” site whilst its amino acid is linked to the polypeptide (haemoglobin) chain via peptide bonds by the ribosome.

why doesnt the biological species concept (BSC) apply to bacteria

they’re asexually reproducing and the BSC focuses on seeing whether the organisms can reproduce fertile offspring

How does nodes of ranvier & myelin sheet increase the rate of action potential along a neuron (2)

In the myelin sheet which insulates the axon, it allows saltatory conduction which is when the action potential jumps between nodes of ranvier which allows the impulse/action potential to move much faster

Describe the effects of neonicitinoids on synaptic transmission in insects (3)

Will bind irreversibly to the acetylcholine receptors as the acetylcholinesterase cannot break it down. As the receptors are blocked, acetylcholine is unable to bind which stops impulses from being transmitted across synapses → leads to paralysis/death

How crispr cas9 allows changing mutations

Involves using the natural self defense bacteria which has evolved which has evolved to cut the DNA strands at a specific point as determined by a guide RNA attached to an enzyme (Cas9)