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Biology : Transcription and Translation

Terms in this set (16)

Starting with mRNA, describe how the process of translation leads to the production of a polypeptide.
mRNA attaches to ribosome;
codon on mRNA;
binds to an anti-codon on tRNA;
each tRNA brings a specific amino acid;
sequence of codons / bases on mRNA determines order of amino acids;
formation of peptide bonds / amino acids joined by condensation
reactions;
Messenger RNA (mRNA) is used during translation to form polypeptides.
Describe how mRNA is produced in the nucleus of a cell.
1. Helicase;
2. Breaks hydrogen bonds;
3. Only one DNA strand acts as template;
4. RNA nucleotides attracted to exposed bases;
5. (Attraction) according to base pairing rule;
6. RNA polymerase joins (RNA) nucleotides together;
7. Pre-mRNA spliced to remove introns;
Describe the structure of proteins.
1. Polymer of amino acids;
2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding of polypeptide chain due to hydrogen bonding;
Accept alpha helix / pleated sheet
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
7. Quaternary structure is two or more polypeptide chains;
Describe how proteins are digested in the human gut.
1. Hydrolysis of peptide bonds;
2. Endopeptidases break polypeptides into smaller peptide chains;
3. Exopeptidases remove terminal amino acids;
4. Dipeptidases hydrolyse / break down dipeptides into amino acids;
Explain how the structure of DNA is related to its functions.
) 1. Sugar-phosphate (backbone) / double stranded / helix so provides strength / stability / protects bases / protects hydrogen bonds;
Must be a direct link / obvious to get the mark
Neutral: reference to histones
2. Long / large molecule so can store lots of information;
3. Helix / coiled so compact;
Accept: can store in a small amount of space for 'compact'
4. Base sequence allows information to be stored / base sequence codes for amino acids / protein;
Accept: base sequence allows transcription
5. Double stranded so replication can occur semi-conservatively / strands can act as templates / complementary base pairing / A-T and G-C so accurate replication / identical copies can be made;
6. (Weak) hydrogen bonds for replication / unzipping / strand separation / many hydrogen bonds so stable / strong;
The genetic code is described as being degenerate. What does this mean?
One / an amino acid (can be) coded for by more than one triplet;
What is a codon?
1. Triplet / three bases on mRNA;
2. That code for an amino acid;
What is the role of RNA polymerase during transcription?
To join nucleotides together to form mRNA / premRNA / RNA;
mRNA can be converted to cDNA.
Name the enzyme used in this process.
Reverse transcriptase;
Differences between the structure of mRNA and tRNA
mRNA has no base-pairing, tRNA has base-pairing / mRNA linear, tRNA cloverleaf shape;
mRNA has no binding site for amino acids, tRNA has; mRNA different for each gene / many kinds, only few / 20 / 64 kinds of tRNA;
accept mRNA longer / larger / more nucleotides than tRNA
Name the process that removes base sequences from pre-mRNA to form mRNA.
Splicing;
A mutation which deletes single bases leads to the production of a non-functional protein.
Explain why.
1. (Mutation) changes triplets / codons after that point / causes frame shift;
2. Changes amino acid sequence (after this) / codes for different amino acids (after this);
3. Affects hydrogen / ionic / sulfur bond (not peptide bond);
4. Changes tertiary structure of protein (so non-functional);
A mutation substitutes a single base. What effect might this mutation have on the protein produced?
Explain your answer.
1. Intron non-coding (DNA) / only exons coding;
2. (So) not translated / no change in mRNA produced / no effect (on protein) / no effect on amino acid sequence;
OR
3. Prevents / changes splicing;
4. (So) faulty mRNA formed;
Accept exons not joined together / introns not removed
5. Get different amino acid sequence;
Explain how a change in the DNA base sequence for a protein may result in a change in the structure of the protein.
Change in amino acid / s / primary structure;
Change in hydrogen / ionic / disulfide bonds;
Alters tertiary structure;
Give one way in which the structure of an mRNA molecule is different from the structure of a tRNA molecule.
Does not contain hydrogen bonds / base pairs / contains
codons / does not contain anticodon / straight / not folded / no
amino acid binding site / longer;
Explain the difference between pre-mRNA and mRNA.
(pre-mRNA) contains introns / mRNA contains only exons;
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