Gene Expression And Protein Production Flashcards
Draw a DNA and RNA nucleotide
Compare DNA to RNA
What are the 3 types of RNA and what do they do
- tRNA - binds amino acid molecules dependant on the three base code it is carrying This is effectively the interpreter in the translation
- rRNA - structural or catalytic (enzyme - ribozyme) roles in ribosomes
- mRNA - carries information specifying the amino acid sequences from DNA to ribosomes
What is gene expression?
When a gene is turned into a function (protein or non coding RNA molecules that serve other functions)
Gene expression can be divided into two stages……
Transcription and translation
What is a genome?
The complete set of genes in a cell (including those in mitochondria and chloroplasts)
What is a proteome?
The full range of proteins that a cell can produce ( coded for by the cell’s DNA/ genome)
What is transcription?
Production of mRNA from DNA, in the nucleus
What is translation?
Production of polypeptides from the sequence of codons carried by mRNA, at ribosomes
Chromatin is approx:
….% DNA
….% histones
….% RNA
30
60
10
Chromosomes are very long strands of DNA compacted by being wound round molecules called ….. and then coiled up
Histones
How does transcription occur?
- Hydrogen bonds between DNA bases break
- Only one DNA strand acts as a template
- Free RNA nucleotides align next to their complementary bases on the template strand
-In RNA, uracil is used in place of thymine (pairing with adenine in DNA) - RNA polymerase joins adjacent RNA nucleotides
- This forms phosphodiester bonds via condensation reactions
- Pre-mRNA is formed and this is spliced to remove introns, forming (mature) mRNA
Gene expression is controlled at the …………. ………
Transcription stage
How does translation occur?
- mRNA attaches to a ribosome and the ribosome moves to a start codon
- tRNA brings a specific amino acid
- tRNA anticodon binds to complementary mRNA codon
- Ribosome moves along to next codon and another tRNA binds so 2 amino acids can be joined by a condensation reaction forming a peptide bond
-Using energy from hydrolysis of ATP - tRNA released after amino acid joined polypeptide
- Ribosome moves along mRNA to form the polypeptide, until a stop codon is reached
What are the two types of ribosomes that are found in cells?
Free ribosomes and bound ribosomes
What do free ribosomes do?
Free ribosomes mostly synthesize proteins that function in the cytosol
What do bound proteins do ?
Bound ribosomes make proteins of the endomembrane system and proteins that are secreted from the cell
Ribosomes are ………. And can switch from free to bound
Identical
The ribosome has three binding sites for tRNA…..
-p site
-a site
-e site
Multiple ribosomes can translate a single mRNA molecule simultaneously forming a ………..
Polyribosome
What do polyribosomes enable?
enable a cell to make many copies of a polypeptide very quickly
Transport of new proteins
Post translation
Describe the primary structure of a protein
Sequence of amino acids in a polypeptide chain, joined by peptide bonds
