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
Describe the secondary structure of a protein
● Folding (repeating patterns) of polypeptide chain eg. alpha helix / beta pleated sheets
● Due to hydrogen bonding between amino acids
● Between NH (group of one amino acid) and C=O (group)
Describe the tertiary structure of a protein
● 3D folding of polypeptide chain
● Due to interactions between amino acid R groups
(dependent on sequence of amino acids)
● Forming hydrogen bonds, ionic bonds and disulfide bridges
Describe the quaternary structure of a protein
● More than one polypeptide chain
● Formed by interactions between polypeptides
(hydrogen bonds, ionic bonds, disulfide bridges)
What is DNA
-DNA is a long double stranded helical molecule composed of multiple nucleotide sequences
-it stores your genetic information
-acts as a template for the protein synthesis
What are histones?
-proteins that are packed with DNA in the nucleus
-help condense DNA into chromatin
What does the DNA double helix contain?
-it consists of two complementary DNA strands held together by hydrogen bonds between the base pairs
What is a codon?
-a sequence of three bases in the DNA molecule that codes for a single amino acid
What are introns and exons?
-introns-> regions of DNA molecules that do not code for proteins
-exons-> regions of DNA molecules that code for proteins
What is a genome?
-the complex set of hereditary info in an individual
-contains genes and non coding segments
-2% of genome is composed of genes (code proteins)
-the remaining is non coding parts ( regulatory functions)
What is the function of RNA polymerase ?
responsible for copying DNA sequence into RNA sequence, during transcription
What is a mutation?
Change in DNA sequence
What is a single point mutation and give an example?
-changing one purine or pyrimidine
-it may change the amino acid that the nucleotides code for
-e.g. sickle cell anaemia
What is an anticodon ?
-A sequence of 3 nucleotides
-complementary to the codon in mRNA sequence
-found at one end of tRNA
What is an enzyme that catalyses the formation of peptide bonds?
Peptidyl transferase
Name 4 gene regulations
-transcription control
-control of RNA transport
- protein turnover control
-translation control
