Chapter 6 CMB RNA & Protein Synthesis Flashcards
What are chromosomes made up of?
DNA + histone proteins
Segments of DNA code for a protein
Protein in turn, relates to a trait (eye colour, enzymes, hormones..)
How are proteins synthesized from DNA?
- DNA is transcribed into mRNA (messenger RNA)
- mRNA leaves the nucleus and travels to the cytoplasm
- The mRNA sequence is then translated into amino acids in the ribosomes
- Amino acids form a peptide chain - a protein
What is the Central dogma?
DNA (replication) > RNA (transcription) > Proteins (translation)
State the 3 types of RNA
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
Role of messenger RNA (mRNA)
Bring information and acts as a template for a new protein to produce.
Role of ribosomal RNA (rRNA)
Site where protein synthesis occurs
Role of transfer RNA (tRNA)
Bring amino acids to the ribosomal subunits, where protein synthesis takes place
What is the process of making mRNA called?
Transcription
What are the main ingredients needed for mRNA synthesis? 5
- DNA template (one of the strands of DNA)
- RNA polymerase – to synthesize mRNA
- rNTP’s - bases for the mRNA (A,U,C,G)
- Transcription factors – required to carry the RNA polymerase and complete the mRNA synthesis
- ATP – required to begin the mRNA synthesis
What happens during transcription of DNA
A strand of RNA complementary to the DNA is formed; the mRNA
State the 4 steps of transcription
- Enzyme RNA polymerase binds tightly to a promoter.
- RNA polymerase opens up the DNA helix.
- The enzyme adds new RNA nucleotides that are complementary to the template DNA.
- mRNA is made.
What are the 3 processing steps of newly synthesized primary mRNA?
- Capping
- Addition of poly A tail
- Splicing
Why is processing needed?
Processing is necessary as it stabilizes the mRNA.
Only mRNAs with cap and tail remain active in the cell.
What happens after processing?
-After processing, it is now known as the mature mRNA
-Leave the nucleus into the cytoplasm where it gets associated with the ribosomes.
What is splicing?
- Excision and rejoining process of RNA.
- The removal of introns.
What are exons?
Exons are called coding sequences and code for proteins
What are introns and why are they removed during processing?
Introns are called non-coding sequences and do not code for proteins. Hence, they have to be removed.
What are the main ingredients for translation? 7
- mRNA
- Transfer RNA (tRNA)
- Ribosomes
- Amino acids
- Start codon (AUG)
- Stop codon (UAG/UAA/UGA)
- Release factors (scissors)
What is start codon & stop codon?
Start codon (AUG) – place where translation begins
Stop codon (UAG/UAA/UGA) – place where translation ends
What are release factors?
When ribosome approaches the stop codon these factors come and contact with the A site of the ribosomes and stop the process.
What happens during translation? 3 steps.
- Initiation
- Elongation
- Termination
What happens during initiation in translation?
- Small ribosomal subunit attaches to the mRNA close to the start codon (AUG).
- Anticodon of the initiator tRNA-methionine complex pairs with this codon.
- Large ribosomal subunit joins to the small subunit
What happens during elongation?
Two tRNAs can be at a ribosome at one time. The tRNA at the P site passes its peptides to the tRNA at the A site. The tRNA at the P sites leaves. The ribosome move forward (translocation), and the tRNA-peptide complex is now at the P site. A new tRNA-amino acid complex comes to the A site.
What happens during termination?
When stop codon (UAA, UAG & UGA) appears at the A site of a ribosome, termination occurs.
A protein called release factor binds to the stop codon and cleaves the polypeptide from the last tRNA.
