Gene Expression Flashcards
What does gene expression involve?
Transcription and Translation of DNA expressing only a fraction of the genes in a cell
What is the structure of RNA?
It is single stranded, it has Uracil instead of Thymine and has ribose sugar instead of deoxyribose
What are the three types of RNA that gene expression consists of?
mRNA, tRNA and rRNA
What does mRNA do?
It carries a copy of the DNA code from the nucleus to the ribosome
What is mRNA made of?
It is made of a series of base triplets known as codons which code for a specific amino acid
What does tRNA do?
Folds due to the complementary base pairing and carries a specific amino acid to the ribosome
What is tRNA made of?
It has an exposed triplet of bases known as anticodons on one side and an attachment site for a specific amino acid at the other
What does rRNA do?
Forms the ribosome with proteins
What is Transcription?
This is the synthesis of mRNA from a section of DNA
What does RNA polymerase do during transcription?
RNA polymerase moves along the DNA strand unwinding and breaking the hydrogen bonds between the bases adding new RNA nucleotides following RNA base pairing rules
Polymerase can only add new nucleotides to the 3’ end of the new mRNA strand
The resultant mRNA breaks of and is the primary transcript
What is RNA splicing?
This is where the regions of the transcript known as introns (non-coding) and exons (coding). Introns are cut out and exons joined together (order of exons unchanged), now known as the mature transcript
What is Translation?
This is the synthesis of the polypeptide from mRNA at the ribosome
What happens during Translation?
It begins at a start codon and ends at a stop codon. Each tRNA picks up its specific amino acid
Each anticodon on tRNA is complementary to a codon on the mRNA and bonds by complementary base pairing translating the genetic code into a sequence of amino acids
As each amino acid is brought to the tRNA, peptide bonds join the amino acids together and the tRNA molecule leaves to pick up another amino acid
What is One Gene, Many Proteins?
This consists of alternative RNA splicing. This is where different segments of mRNA may be treated as exons and introns, same primary transcript can produce several mature transcripts
What are Polypeptides?
Amino acids are linked by peptide bonds to from Polypeptides which fold to form a 3D shape held together by hydrogen bonds and interactions between individual amino acids
