protein synthesis Flashcards
- Describe how translation leads to the production of a polypeptide.
- mRNA attaches to a ribosome
- Ribosome reads the first codon (start codon)
- tRNA with complementary anticodon attaches to the codon on mRNA.
- The tRNA carries a specific amino acid
- A second tRNA and amino acid arrives at the ribosome and binds to the next codon.
- The two amino acids form a peptide bonds via a condensation reaction. The formation of peptide bonds require ATP.
- This process continues until stop codon is reached.
- Describe how mRNA is produced (transcription)
- DNA helicase attaches to a specific DNA sequence at the start of the gene (promoter region)
- DNA helicase breaks hydrogen bonds and the DNA “unwinds” exposing the bases
- RNA polymerase attaches to specific section of DNA called a start sequence.
- Free floating RNA nucleotides attach to the template strand DNA. A-U and G-C
- RNA polymerase joins adjacent nucleotides together creating phosphodiester bonds
- The RNA polymerase moves down the DNA molecule until it reaches a stop sequence.
- As RNA polymerase moves down the DNA strand, hydrogen bonds reform between complementary bases and strands coil back together.
- The pre-mRNA strand is spliced to remove introns and non-coding repeats. Exons are joined together forming mature mRNA.
- Mature mRNA leaves via a nuclear pore.
- Compare and contrast mRNA and tRNA.
Both are made of RNA and have nucleotides have a phosphate group, ribose sugar and the bases A, U, C and G; mRNA does not have hydrogen bonds, whereas tRNA does; mRNA does not have an amino acid binding site, whereas tRNA does; mRNA is usually longer (has more nucleotides) than tRNA; mRNAs can be different lengths, whereas tRNA are all a similar length;
mRNA has codons, whereas tRNA has anticodons;
- A polypeptide is this many amino acids long, what is the minimum number of bases needed to code for this polypeptide?
This x 3 = answer
- A gene is this many nucleotides long, what is the maximum number of amino acids it could code for?
This ÷ 3 = answer
- What is a ribosome made of?
A molecule of ribosomal RNA and a protein.
- Explain the term non-overlapping.
Each base is part of only one triplet code.
- Explain the term degenerate.
More than one triplet code (or codon) codes for each amino acid.
- Explain how the genetic code is universal.
All organisms DNA triplet code in every organism codes for the same amino acid.
- Explain the difference between transcription in prokaryotes and eukaryotes.
Eukaryotic DNA contains introns with genes whereas prokaryotes don’t; These regions are removed from the pre-mRNA in eukaryotes whereas this isn’t necessary in prokaryotes;
- Describe the genome.
The complete set of genes in a cell/organism;
- Describe the proteome.
The full range of proteins a cell is able to produce;
- Describe the role of RNA polymerase in producing mRNA
RNA polymerase joins adjacent RNA nucleotides in a condensation reaction to form a phosphodiester bond. Repeating this process produces mRNA.
- Describe the role of ribosomes in translation.
mRNA binds to ribosome; there are two codons binding sites; Allows tRNA with anticodons to bind; Catalyses formation of peptide bond between amino acids held by tRNA molecules; Moves along mRNA to the next codon;
- Describe the role of tRNA in translation.
The anticodon is complementary to codon on mRNA; each tRNA has a specific amino acid; carried to ribosome; this gives the correct sequence of amino acids along polypeptide;
