Flashcards in Cellular Control Deck (29):
1
Define Gene
A length of DNA that codes for one (or more) polypeptides
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Define Polypeptide
A polymer consisting of a chain of amino acid residues joined by peptide bonds
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Define Genome
The entire DNA sequence of that organism. This consists of about 3 billion nucleotide base pairs.
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Define Protein
A large polypeptide - usually 100 or more amino acids. Some proteins consist of one polypeptide chain and some consist of more than one polypeptide chain.
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Define Transcription
The creation of a single stranded mRNA copy of the DNA coding strand.
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What is a triplet code?
It is a sequence of 3 nucleotide bases which codes of one amino acid.
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What is meant by the genetic code being a degenerate code?
All amino acids, except methionine have more than one code that codes for them.
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How does the gene sequence stop the transcription of amino acids?
Certain codes do not code for amino acid but indicate the sequence to stop so the polypeptide stops being made.
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Where are proteins assembled?
In the cytoplasm at ribosomes
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What is the first stage of protein sysnthesis?
Transcription
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What are the steps in transcription?
A strand of DNA is used as a template (the template strand).
This strand unwinds and unzips by dipping into the nucleolus where the hydrogen bonds break.
Activated RNA nucleotides bind to the exposed template strand (catalysed by the enzyme RNA polymerase).
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What are the steps in transcription?
A strand of DNA is used as a template (the template strand).
This strand unwinds and unzips by dipping into the nucleolus where the hydrogen bonds break.
Activated RNA nucleotides bind to the exposed template strand (catalysed by the enzyme RNA polymerase).
This mRNA strand is therefore a copy of the coding strand (the strand that used to be attached to the template strand).
The mRNA passes out of the nucleus through a pore in the nuclear envelope.
13
Define Translation
The assembly of polypeptides (proteins) at ribosomes.
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Define Translation
The assembly of polypeptides (proteins) at ribosomes.
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What is the primary structure of a protein?
It is the order of the amino acids in the length of the chain. This is determined by the order of bases on the mRNA.
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What is the tertiary structure of a protein?
It is the 3D structure of the protein, determined by the primary structure. This is what allowed a protein to function. It is help together by hydrogen bonds, ionic bonds and hydrophobic interations between the R groups.
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What is the tertiary structure of a protein?
It is the 3D structure of the protein, determined by the primary structure. This is what allowed a protein to function. It is help together by hydrogen bonds, ionic bonds and hydrophobic interations between the R groups.
18
Describe the structure of tRNA
Lengths of RNA (made in the nucleus) folded into a hairpin shape. It has 3 exposed bases which can bind to an amino acid, and an anticodon (with the same 3 base pair sequence) which can attach to a complementary codon temporarily.
19
Describe the assembly of a polypeptide
Molecule of mRNA binds to a ribosome.
2 codons are attached to the small subunit and exposed to the large subunit of the ribosome.
tRNA molecule with methionine attaches to the first codon (AUG).
Second tRNA molecule binds to second exposed codon.
Peptide bond forms between the adjacent amino acids catalysed by an enzyme in the small subunit.
Ribosome moves along the mRNA reading the next codon where the complimentary tRNA molecules attaches.
The first tRNA molcule is able to detach from the amino acid and pick up another amino acid.
The polypeptide keeps growing until a stop codon is read.
20
Describe the assembly of a polypeptide
Molecule of mRNA binds to a ribosome.
2 codons are attached to the small subunit and exposed to the large subunit of the ribosome.
tRNA molecule with methionine attaches to the first codon (AUG).
Second tRNA molecule binds to second exposed codon.
Peptide bond forms between the adjacent amino acids catalysed by an enzyme in the small subunit.
Ribosome moves along the mRNA reading the next codon where the complimentary tRNA molecules attaches.
The first tRNA molcule is able to detach from the amino acid and pick up another amino acid.
The polypeptide keeps growing until a stop codon is read.
21
Define Mutation
A change in the amount of, or arrangement of, the genetic material in a cell.
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Define Chromosome Mutations
Mutations which involve changes to parts of or whole chromosomes.
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Define DNA Mutations
Changes to genes due to changes in nucleotide base sequences.
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What name is gives to substances which can cause mutations? Examples?
Mutagens. These include tar (from tobacco smoke), UV light, X-rays and gamma rays.
25
What are point mutations?
A mutation where one base pair is replaced by another. Also called substitutions.
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What are insertion/deletion mutations?
Where one or more base pairs are inserted or deleted from a length of DNA. Also called frameshift.
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What are insertion/deletion mutations?
Where one or more base pairs are inserted or deleted from a length of DNA. Also called frameshift.
28
Define Allele
An alternative version of a gene. It is still at the same locus on the chromosome and codes for the same polypeptide but the alteration to the DNA base sequence may alter the protein's structure.
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