Topic 3 - Gene Expression Flashcards
What regulation controls gene expression?
Transcription and Translation
Structure of RNA
Single stranded, with nucleotides
Bases in RNA and who they’re paired with
Uracil with Adenine, Guanine with Cytosine
Difference in nucleotides between RNA and DNA structure
The bases (uracil instead of thymine), the sugar (ribose instead of deoxyribose)
What’s the function of mRNA
Carries a copy of the DNA code from the nucleus to the ribosome
What’s the function of rRNA
Along with proteins, it forms the ribosome
What’s the function of tRNA
Carries a specific amino acid
Primary Transcript of DNA into mRNA
A copy of information is made in the nucleus from a DNA molecule on to a RNA molecules called mRNA
First stage of Transcription of DNA Into mRNA
RNA polymerase moves along DNA unwinding a section of the double helix
What happens to the sugar phosphate bonds during transcription
They form between adjacent RNA nucleotides
What is required for transcription?
ATP and RNA polymerase
Complementary Base Pairing takes place during Transcription. What does this mean?
Free nucleotides pair with DNA bases, guanine and cytosine, uracil and adenine
What happens in RNA splicing? (To the introns)
The introns of the primary transcript of mRNA are non- coding and are removed
What happens in RNA Splicing? (To the Exons)
They are coding regions and are joined together to form mature transcript
How is gene expression influenced?
By intra and extra - cellular environmental factors
A Polypeptide Chain
A short chain of 6 - 8 amino acids joined together
What is mRNA translated into and where is it translated?
It’s translated into a polypeptide chain at a ribosome
Why does tRNA fold during transcription?
Due to base pairing to form a triplet anticodon site and an attachment site for a specific amino acid
What is mRNA transcribed from?
DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm
Introns
Non-coding regions of genes
Exons
Coding regions of genes
What do triplet codons on mRNA and anticodons translate?
They translate the genetic code into a sequence of amino acids
Start codon
The first three bases on a mRNA strand (i.e the first codon)
Stop Codon
The last codon
What happens when the translation reaches the stop codon?
The ribosome releases the newly synthesised polypeptide chain
ATP in Translation
It provides energy for the process
What will the sequence of the codons in the mRNA strand determine?
The amino acids in the polypeptide that will be synthesised
How do anticodons on tRNA relate to the codons on mRNA?
They are complementary to each other
Hydrogen bonds form between..
Bases
Peptide bonds form between..
Amino acids
Where does transcription take place?
The nucleus
Where does translation take place?
Ribosome
What happens to a protein after translation?
The protein is modified
How is the protein modified after translation?
The cutting and joining of polypeptide chains or by the addition of a carbohydrate or a phosphate group to the final protein molecule
Structural similarities with mRNA and tRNA
Both contain the bases A,U,C and G
Structural differences with mRNA and tRNA
tRNA is folded, when mRNA is not. tRNA has base pairing, mRNA doesn’t. mRNA is single-stranded and tRNA is double-stranded
Transcription
Copying of the DNA code onto the mRNA
Translation
Converting the information given on the mRNA into a sequence of amino acids
Triplet
Sequence of bases specifying one amino acid
Codon
Triplet of bases on mRNA
Anti-Codon
Triplet of bases on tRNA
