14 - genetic control of protein structure and function Flashcards
Why is the genetic code described as being universal? (1)
(In all organisms/DNA,) the same triplet codes for
the same amino acid;
The genetic code uses four different DNA bases. What is the maximum number of
different DNA triplets that can be made using these four bases? (1)
64
Name the process that removes base sequences from pre-mRNA to form mRNA (1)
Splicing
Mutation 1 (at start, on exon) leads to the production of a non-functional protein. Explain why. (3)
- (Mutation) changes triplets/codons after that
point/causes frame shift; - Changes amino acid sequence (after
this)/codes for different amino acids (after this); - Affects hydrogen/ionic/sulfur bond (not peptide
bond); - Changes tertiary structure of protein (so nonfunctional);
What effect might mutation 2 (on intron) have on the protein produced?
Explain your answer. (2)
- Intron non-coding (DNA)/only exons coding;
- (So) not translated / no change in mRNA
produced / no effect (on protein) / no effect on
amino acid sequence;
For DNA, mRNA and tRNA, state whether:
Hydrogen bonds are present
Number of polynucleotide strands in molecule (2)
Hydrogen bonds:
DNA = yes, mRNA = no, tRNA = yes
DNA = 2, mRNA = 1, tRNA =1
ACAGTACTTACGATC
In the space below, give the sequence of bases on the pre-mRNA transcribed from this
strand. (1)
UGU CAU GAA UGC UAG
Name the enzyme that allows part of a gene to be transcribed. (1)
RNA polymerase
The insertion of the DNA copy in one of the host cell’s genes may cause the cell to
make a non-functional protein. Explain how. (2)
Alters base/nucleotide sequence/causes frame shift;
Different sequence of amino acids in
polypeptide/protein/primary structure;
Alters tertiary structure;
Some of the children in the trial developed cancer. How might the insertion of the DNA
have caused cancer? (2)
Affects tumour suppressor gene;
Inactivates (tumour suppressor) gene;
Rate of cell division increased/tumour cells continue to
divide
What 2 substances make up the backbone of a pre-mRNA molecule? (1)
Phosphate
Ribose
The sequence on a pre-mRNA molecule is:
AUCCGU
Give the sequence of bases on the DNA strand from which this pre-mRNA has been transcribed. (1)
TAGGCA
Give one way in which the structure of an mRNA molecule is different from the structure of a tRNA molecule. (1)
(mRNA) 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. (1)
(pre-mRNA) contains introns / mRNA contains only
exons;
Explain why the percentages of bases from the middle part of the chromosome and the end part are different. (2)
- Different genes;
- Have different (base) sequences / combinations of
(bases); - (Pre-mRNA) transcribed from different DNA/codes
for different proteins;
Hydrolysis and condensation are important in the formation of new adult proteins. Explain how (2)
1. Hydrolysis breaks proteins / hydrolyses proteins / produces amino acids (from proteins); 2. Protein synthesis involves condensation; 3. Hydrolysis of polysaccharides/lipids
Why can many different adult proteins be made using a single type of protein? (1)
Amino acids (from calliphorin) can be joined in different sequences/rearranged;
Why is the DNA that codes for complete toxin longer than mRNA used for translation? (1)
(DNA) contains introns/noncoding
bases / mRNA only
contains exons/coding bases;
The genetic code is described as being degenerate. What does this mean? (1)
One/an amino acid (can be) coded for
by more than one triplet;
Accept codon for triplet
What is a codon? (2)
- Triplet/three bases on mRNA;
2. That code for an amino acid;
What is the role of RNA polymerase during transcription? (1)
To join nucleotides together to form
mRNA/premRNA/RNA;
Explain what is meant by a palindromic sequence (1)
GGATCC same as CCTAGG in
opposite direction;
Accept reads same both
ways/same forward and back
Genetic code:
Define Messenger RNA (mRNA)
Relationship between genetic and DNA code?
Define Codon = triplet on mRNA that code for amino acid.
= transfers DNA code (as genetic code) from nucleus to cytoplasm.
Genetic code complementary to DNA code.
= triplet on mRNA that code for amino acid.
Features of genetic code:
Degenerate code?
Stop codons?
Non-overlapping?
Universal code?
Degenerate code - one amino acid can be coded for by more than one triplet.
Stop codons - do not code for amino acid, mark end of chain.
Non-overlapping - each nucleotide base only read once.
Universal code - In all organisms/DNA same triplet codes for same amino acid;
RNA structure:
How many polynucleotide chains?
1 mononucleotide unit made up of?
1 chain
Ribose, phosphate, organic base (C/G/U/A)
DNA mRNA tRNA no. chains? H bonds? Size? Shape? Backbone? T/U?
DNA mRNA tRNA
no. chains? 2 1 1
H bonds? y n y
Size? largest med smallest
Shape? double-helix single-helix clover
Backbone? deoxyribose ribose ribose
T/U? thymine uracil uracil
Transcription (3)
- DNA helicase breaks H bonds, strands separate, nucleotide bases exposed
- RNA polymerase moves along template strand, joins nucleotides together to form pre-mRNA
- Reaches stop codon and detaches
Define exons
Define introns
Splicing?
mRNA then?
Code for proteins
Do not code for proteins
Removes introns forming mRNA
mRNA leaves via nuclear pore, attaches to ribosomes in cytoplasm
Translation (5)
- Ribosome attaches to start codon of mRNA.
- tRNA with complementary anticodon pairs up with mRNA - carries 1 amino acid.
- Ribosome joins 2 tRNA at a time, 2 amino acids joined by peptide bond.
- Previous tRNA released.
- Reaches stop codon, all detach - polypeptide chain formed.
How is the quaternary structure of a protein formed? (3)
Polypeptide coiled/folded, coiled/folded further, linked together
Define mutation
Give 1 benefit of a mutation
change to the quantity or structure of the sequence of bases in DNA. (Inheritable if occur during gamete formation)
Genetic diversity - natural selection and speciation
Substitution mutation:
Define substitution mutation
Nonsense mutation? (2)
Mis-sense mutation? (2)
Silent mutation? (2)
= nucleotide replaced by nucleotide with different base
= stop codon, nonfunctional final protein
= different amino acid coded for, nonfunctional final protein.
= same amino acid coded for (degenerate code), functional final protein
Deletion mutation:
Define deletion mutation
How does a deletion mutation result in non-functional protein? (4)
Where does it have greatest effect?
= Nucleotide lost.
- Changes triplets/causes frame shift;
- Changes amino acid sequence
- Affects hydrogen/ionic/sulfur bond
- Changes tertiary structure of protein so nonfunctional
At start of DNA
Define mutagenic agent
2 examples?
= outside factor that increases natural mutation rate
High energy radiation, chemicals
Proto-oncogenes:
Define proto-oncogenes
In normal cell? (3)
Mutation causes?
In mutated cell? (3)
= stimulate/speed up cell division
Growth factors attach to receptors on membrane
‘switch on’ genes for DNA replication via relay proteins.
Normal cell division
Proto-oncogenes to develop into oncogenes
Receptors on membrane permanently activated
Genes for DNA replication permanently ‘switched on’
Excessive cell division - tumour formation
Tumour suppressor genes:
Define tumour suppressor genes
Mutation causes?
In mutated cell?
Tumour types? (2)
= inhibit/slow cell division
Inactivation
Cell division increases
Tumour formation
Malignant tumour = a harmful tumour
Benign tumour = a harmless tumour
