Molecular Biology Flashcards
What is the central dogma of molecular biology (macromolecules involved and their function)
theory stating- genetic information flows only in one direction, DNA to RNA to protein
DNA- the information
RNA- the messenger
Protein- the worker
Initiation of transcription
Transcription factors bind to the TATA box of the promoter region
RNA pol II binds which forms transcriptional initiation complex with transcription factors
Two DNA strands seperate and the RNA Pol starts MRNA synthesis
what is being synthesises during transcription
DNA dependent RNA synthesis in the 5’-3’ direction
what happens during elongation of transcription
RNA Pol-II uses the template strand that runs in the 3’-5’ direction as a template and inserts the complementary RNA nucleotides in the 5’-3’ direction.
what part of a gene is transcribed from DNA to RNA
5UTR , coding sequence and the 3’ UTR
what part of a gene is translated from RNA into protein?
Only the coding sequence
Function of the promoter region
DNA segment recognised by the RNA polymerase to initiaite transcription, particularly important ijn the TATA region
How are mutations in the non coding regions harmful?
They disrupt the normal gene expression
Function of the 5’ G cap
prevent mRA degradation, promote intron excision and act as a binding site for small ribosomal subunits
Function of the 3’ poly-A tail
prevents mRNA degradation and helps the export of mRNA from the nucleus into the cytoplasm
where does transcription take place
in the nucleus
where does translation take place
in the cytoplasm
how many amino acids are there?
20
what codon specifies for start
AUG
what codons specifiy to stop?
UAA , UAG and UGA
what are the features that make tRNA an adaptor molecule?
It has a region that can bind an amino acid and a region that can interact with mRNA
how does a tRNA become charged?
An enzyme recognises a specific amino acid and the correct tRNA for this amino acid and joins them together therefore charging the tRNA
order of tunnels from left to right, and which does the exit tunnel extend from?
E, P, A. exit tunnel extends from the P tunnel
describe initiation of translation
small ribsomal subunit binds to the mRNA through specific initiation tRNA, these identify the 5’ G cap and attach to the mRNA
the small ribosomal subunit/ initiator tRNA complex moves along the mRNA to find the AUG ( start codon)
the large ribosomal subunit attaches
describe elongation of translation
charged tRNA with an anticodon complementary to the site A codon lands in A site.
2 things occur at the same time, the amino acid from the first enzyme is transferred to the second enzyme. The ribosome moves along the mRNA codon so the amino acids are going through the exit tunnel ( p site)
the last part of elongation is to get the enzyme out of the E site.
A new charged tRNA with an anticodon complemenatry to the next site A codon enters ribosome at the A site and repeats itself
describe the termination process of translation
eventually the ribosome meets one of the stop codons (UGA, UAG, UAA).
siteA accepts a release factory enzyme and frees the polypeptide chain of amino acids
Ribosome units break off and dissociate and can be used again.
what is mendels first law
law of segregation- genes segregate at meiosis so that each gamete contains only one of the two possed by the parent
what is mendels second law
law of independent assortment, alleles of different genes assort independently during gamete formation
when does segragation of chromosomes occur?
during anaphase I and anaphase II of meiosis
what is incomplete dominance
when no allele is phenotypically dominant over another, results in a blended phenotype. heterozygous= blended phenotype
what is codominance
both phenotypes exist side by side within an organsim eg blood type AB
what are polygenetic traits and how are they represented in the population
phenotype controlled by many different genes that have an additive effect- eg height and weight.
example is skin colour that is coded by 3 genes where each has an allele for colour or no colour
polygenetic traits have a normal distributoon in a population
how does the environment effect phenotype
effects phenotype, eg hydrangers pink in alkaline, blue in acidic soil
the environment smooths differences among phenotypes.
eg 50% effect wouldn’t know the genotype and a combination of phenotype and environment create a normal distribution.
why would we want to estimate the genotype frequencies in a population?
to predict how many individuals will inherit a genetic disease
to estimate the proportion of individuals who are carrires of a genetic disease
what are the 7 ways that allele frequency can change
bottleneck effect
founder effect
random genetic drift
natural selection
mutation
migration
non random mating (assortative mating and inbreeding)
what is a cline with an example
gradual geographic change in genetic or phenotypic composition
eg the cyanide production in clover- increasing from warm to cooler temperatures
what is stablising selection
when medium/ normal individuals are favoured
doesnt change the mean but it reduces variation
what is directional selection
extreme individuals are favoured (eg large or small)
this causes the mean to shift to to one extreme
what is disruptive selection
this is when both large and small individuals are favoured
favouring the two extremes means that two peaks form
how does frequency dependent selection work
natural selection remains in equal proportion as there is a fluctuation in which species are favoured.
rare trait does better, more individuals copy that trait
