Protein Synthesis Flashcards
What is transcription?
The process of an RNA sequence being produced from a DNA template. Only occurs along one of the two strands of DNA
What is the RNA polymerase?
It is an enzyme that binds to a site on the DNA at the start of the gene that is being transcribed. it unwinds the DNA and positions the RNA nucleotides on the template strand with bases complementary to those of the template
What is the sense strand vs the antisense strand?
The template strand is the antisense strand and the sense strand is the one not being used. Therefore, the RNA strand will be identical to the sense strand
The Role of Hydrogen Bonding and Complementary Base Pairing in Transcription
DNA molecules consist of two antiparallel polynucleotide chains that spiral around an imaginary axis to form a double helix - anti-parallel = the two strands run in opposite directions.
The sugar-phosphate backbone is on the outside, the bases are on the inside.
The strand is held together by hydrogen bonds between the bases
A purine molecule (A and G) is always paired with a pyrimidine molecule (T and C): a purine must always base-pair with a pyramidine
Stability of DNA during transcription
The strands are only separated for a short time as RNA polymerase moves along the
sense strand gene, so the bases are only vulnerable to chemical changes that would cause mutation for a short time.
Stability of the DNA template is essential since they may be transcribed many times
If mutations were common, then the frequently used templates would accumulate mutations and the RNA copies would be made with errors, leading to dysfunction of proteins made during translation
What is gene expression?
The process where information carried by a gene has observable effects on an organism
The sequence of the bases in genes does not determine the observable characteristics in an organism
The function of most genes is to specify the sequence of amino acids in a particular polypeptide
What is a transcriptome?
A full range of RNA types made in a cell.
* Within an individual, different cells or tissue types have different transcriptomes
* Over time, the transcriptome changes as the cell activity changes
What is translation?
Translation is the process of protein synthesis, which occurs in the cytoplasm, in which the genetic information encoded in mRNA is translated into a sequence of amino acids in a polypeptide chain
Where does translation happen?
The cytoplasm
Codon vs Anticodon
The codon is the sequence of three nucleotides on the mRNA strand. The anti codon is the sequence of three nucleotides on the tRNA strand.
What happens in the ribosome during translation?
Ribosomes are complex structures consisting of a small and a large subunit. The small subunit has a
amino acid binding site for mRNA and the large subunit has three binding sites for tRNA. The large subunit also has a catalytic site that makes peptide bonds between amino acids, to assemble the polypeptide
What is the start codon?
AUG Methionine
What are the stop codons?
UAA, UAG, UGA
What is silent mutation?
The change in base sequence has had no effect on the amino acid produced
What is missense mutation?
The change in base sequence has caused one different amino acid to be produced (e.g. sickle cell)
