Protein Synthesis Flashcards
Function of mRNA
Carries genetic information/ a copy of DNA/ the order of bases from the nucleus to the cytoplasm for protein synthesis
What is transcription?
Transcription is the synthesis of mRNA from a section of DNA
Describe transcription
Starts from region of DNA called the promoter, RNA polymerase binds at the promoter region
RNA polymerase breaks weak hydrogen bonds between bases and unwinds DNA
RNA polymerase adds nucleotides (Uracil instead of thymine) using complementary base pairing from 3’ to 5’ and joins them to form the primary mRNA transcript
When the terminator is reached the RNA polymerase is released
Why is the primary mRNA transcript modified?
Not all the regions in a eukaryotic gene are required to produce the final protein
What are introns?
Non-coding regions of the primary mRNA transcript that are not needed to make protein
What are exons?
Coding regions of the primary mRNA transcript that are needed to make protein
Describe RNA splicing
The introns are removed from the primary mRNA transcript
The remaining exons are spliced together to form a continuous sequence
This leaves the mature mRNA transcript which leaves the nucleus to travel to the cytoplasm
Steps of Protein synthesis
Transcription creates primary mRNA transcript
RNA splicing creates the mature mRNA transcript
Mature mRNA transcript leaves the nucleus to travel to the cytoplasm
Translation occurs at the ribosome to form a protein
Post translational modification
What is tRNA?
Transfer RNA
Held together by hydrogen bonds
Carries amino acids on anticodon to appropriate codon at the ribosome to form a poly peptide (amino acid chain)
Describe translation
At the ribosome rRNA reads the incoming mRNA three at a time
When start codon is reached, the ribosome starts attaching tRNA bases (one for every three bases) to the mRNA (tRNA description)
Amino acids are joined together by peptide bonds
tRNA disengages and goes to find another amino acid
This is repeated until a stop codon is reached, the ribosome disassociates and the poly peptide is released
Function of rRNA
Ribosomal RNA
Reads incoming mRNA
Links amino acids using peptide bonds
How can the same gene be used to make several different proteins?
Alternative RNA splicing
Post translational modification (cleavage and addition of other molecules)
Describe cleavage
When a single polypeptide chain is cleaved by enzyme to make it active
Describe addition of other molecules as a type of post translational modification
Carbohydrate and phosphate groups can be added to proteins
Describe alternative RNA splicing
When the primary mRNA transcript undergoes splicing different parts can be treated as introns and exons so different mature mRNA transcripts are made allowing different proteins to be formed
