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Biology Unit 5 > 14 - genetic control of protein structure and function > Flashcards

14 - genetic control of protein structure and function Flashcards

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1
Q

Why is the genetic code described as being universal? (1)

A

(In all organisms/DNA,) the same triplet codes for

the same amino acid;

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2
Q

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)

A

64

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3
Q

Name the process that removes base sequences from pre-mRNA to form mRNA (1)

A

Splicing

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4
Q 
Mutation 1 (at start, on exon) leads to the production of a non-functional protein.
Explain why. (3)
A
  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 nonfunctional);
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5
Q

What effect might mutation 2 (on intron) have on the protein produced?
Explain your answer. (2)

A
  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;
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6
Q

For DNA, mRNA and tRNA, state whether:
Hydrogen bonds are present
Number of polynucleotide strands in molecule (2)

A

Hydrogen bonds:
DNA = yes, mRNA = no, tRNA = yes
DNA = 2, mRNA = 1, tRNA =1

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7
Q

ACAGTACTTACGATC
In the space below, give the sequence of bases on the pre-mRNA transcribed from this
strand. (1)

A

UGU CAU GAA UGC UAG

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8
Q

Name the enzyme that allows part of a gene to be transcribed. (1)

A

RNA polymerase

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9
Q

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)

A

Alters base/nucleotide sequence/causes frame shift;
Different sequence of amino acids in
polypeptide/protein/primary structure;
Alters tertiary structure;

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10
Q

Some of the children in the trial developed cancer. How might the insertion of the DNA
have caused cancer? (2)

A

Affects tumour suppressor gene;
Inactivates (tumour suppressor) gene;
Rate of cell division increased/tumour cells continue to
divide

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11
Q

What 2 substances make up the backbone of a pre-mRNA molecule? (1)

A

Phosphate

Ribose

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12
Q

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)

A

TAGGCA

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13
Q

Give one way in which the structure of an mRNA molecule is different from the structure of a tRNA molecule. (1)

A

(mRNA) Does not contain hydrogen bonds/base pairs
/contains codons / does not contain anticodon /
straight/not folded / no amino acid binding
site/longer;

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14
Q

Explain the difference between pre-mRNA and mRNA. (1)

A

(pre-mRNA) contains introns / mRNA contains only

exons;

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15
Q

Explain why the percentages of bases from the middle part of the chromosome and the end part are different. (2)

A
  1. Different genes;
  2. Have different (base) sequences / combinations of
    (bases);
  3. (Pre-mRNA) transcribed from different DNA/codes
    for different proteins;
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16
Q

Hydrolysis and condensation are important in the formation of new adult proteins. Explain how (2)

A 
1. Hydrolysis breaks proteins / hydrolyses proteins / produces
amino acids (from proteins);
2. Protein synthesis involves condensation;
3. Hydrolysis of polysaccharides/lipids
17
Q

Why can many different adult proteins be made using a single type of protein? (1)

A 
Amino acids (from calliphorin) can be joined in different
sequences/rearranged;
18
Q

Why is the DNA that codes for complete toxin longer than mRNA used for translation? (1)

A

(DNA) contains introns/noncoding
bases / mRNA only
contains exons/coding bases;

19
Q

The genetic code is described as being degenerate. What does this mean? (1)

A

One/an amino acid (can be) coded for
by more than one triplet;

Accept codon for triplet

20
Q

What is a codon? (2)

A
  1. Triplet/three bases on mRNA;

2. That code for an amino acid;

21
Q

What is the role of RNA polymerase during transcription? (1)

A

To join nucleotides together to form

mRNA/premRNA/RNA;

22
Q

Explain what is meant by a palindromic sequence (1)

A

GGATCC same as CCTAGG in
opposite direction;

Accept reads same both
ways/same forward and back

23
Q

Genetic code:

Define Messenger RNA (mRNA)
Relationship between genetic and DNA code?
Define Codon = triplet on mRNA that code for amino acid.

A

= transfers DNA code (as genetic code) from nucleus to cytoplasm.
Genetic code complementary to DNA code.
= triplet on mRNA that code for amino acid.

24
Q

Features of genetic code:

Degenerate code?
Stop codons?
Non-overlapping?
Universal code?

A

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;

25
Q

RNA structure:

How many polynucleotide chains?
1 mononucleotide unit made up of?

A

1 chain

Ribose, phosphate, organic base (C/G/U/A)

26
Q 
DNA             mRNA           tRNA
no. chains?                             
H bonds?
Size?
Shape?
Backbone?
T/U?
A

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

27
Q

Transcription (3)

A
  1. DNA helicase breaks H bonds, strands separate, nucleotide bases exposed
  2. RNA polymerase moves along template strand, joins nucleotides together to form pre-mRNA
  3. Reaches stop codon and detaches
28
Q

Define exons
Define introns
Splicing?
mRNA then?

A

Code for proteins
Do not code for proteins
Removes introns forming mRNA
mRNA leaves via nuclear pore, attaches to ribosomes in cytoplasm

29
Q

Translation (5)

A
  1. Ribosome attaches to start codon of mRNA.
  2. tRNA with complementary anticodon pairs up with mRNA - carries 1 amino acid.
  3. Ribosome joins 2 tRNA at a time, 2 amino acids joined by peptide bond.
  4. Previous tRNA released.
  5. Reaches stop codon, all detach - polypeptide chain formed.
30
Q

How is the quaternary structure of a protein formed? (3)

A

Polypeptide coiled/folded, coiled/folded further, linked together

31
Q

Define mutation

Give 1 benefit of a mutation

A

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

32
Q

Substitution mutation:

Define substitution mutation

Nonsense mutation? (2)
Mis-sense mutation? (2)
Silent mutation? (2)

A

= 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

33
Q

Deletion mutation:

Define deletion mutation

How does a deletion mutation result in non-functional protein? (4)

Where does it have greatest effect?

A

= Nucleotide lost.

  1. Changes triplets/causes frame shift;
  2. Changes amino acid sequence
  3. Affects hydrogen/ionic/sulfur bond
  4. Changes tertiary structure of protein so nonfunctional

At start of DNA

34
Q

Define mutagenic agent

2 examples?

A

= outside factor that increases natural mutation rate

High energy radiation, chemicals

35
Q

Proto-oncogenes:

Define proto-oncogenes

In normal cell? (3)

Mutation causes?

In mutated cell? (3)

A

= 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

36
Q

Tumour suppressor genes:

Define tumour suppressor genes

Mutation causes?

In mutated cell?

Tumour types? (2)

A

= inhibit/slow cell division

Inactivation

Cell division increases
Tumour formation

Malignant tumour = a harmful tumour
Benign tumour = a harmless tumour

Biology Unit 5 (9 decks)

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