Biology unit 5

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What is a codon?
A group of three bases that codes for one amino acid
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What is meant by degenerate?
More than one codon for each amino acid
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What is mRNA?
Carries the message that codes for a particular protein from the nucleus to the cytoplasm, contains one gene only.
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what is tRNA?
Matches amino acids to their codon
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what is rRNA?
rRNA with proteins forms ribosomes, the site of mRNA translation and protein synthesis.
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What is the promoter?
A special sequence of bases that marks the start of each gene on DNA
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What is the template strand?
The copied DNA strand (original strand)
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How are the new nucleotides in transcription joined together?
By strong covalent phosphodiester bonds by the enzyme RNA polymerase
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how long is an mRNA molecule?
the length of one gene
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How does mRNA leave the nucleus?
Diffuses out through a nuclear pore into the cytoplasm and attaches to a ribosome for translation
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what is post transcriptional modification?
the removal of introns from mRNA so it can translated into a protein
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what is pre-mRNA?
intial mRNA that is transcribed, an exact copy of the gene on DNA (contains exons and introns)
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what is splicing?
when introns are cut out and exons joined together, some is done by RNA itself or snurps
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What is an initiation codon?
Nucleotides AUG on mRNA where ribosome attaches in translation, ribosome encloses two codons.
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what is met-tRNA?
the first tRNA molecule with an amino acid attached that diffuses into the ribosome
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what are ribozymes function?
To catalyse the cutting of the amino acid and tRNA bond and the formation of the peptide bond between amino acids
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what is post-translational modification?
Modification of protein by enzymes, include chain cutting and addition of groups
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How do mutations occur?
changes in bases during DNA replication
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What is substitution mutation?
changing of one amino acid
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what is a nonsense mutation?
Mutation leads to premature stop codon.
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What are mutagens?
Chemicals that increase rate of mutation
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What are proto-oncogenes role?
encode proteins that stimulate cell division, when activated by growth signals.
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What is a oncogene?
Mutated proto, overly active making cell division unchecked.
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What do mutated tumour supressor genes do?
stop making protein that inhibits cell division. mutation is recessive.
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Other cards in this set

Card 2


What is meant by degenerate?


More than one codon for each amino acid

Card 3


What is mRNA?


Preview of the front of card 3

Card 4


what is tRNA?


Preview of the front of card 4

Card 5


what is rRNA?


Preview of the front of card 5
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