How DNA codes for proteins

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  • Created by: Steff06
  • Created on: 22-04-16 18:51
What is a gene?
A length of DNA that codes for 1 or more polypeptides.
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What are polypeptides?
Polymers consisting of a chain of amino acids joined by peptide bonds.
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What is a genome?
Entire DNA sequence of an organism.
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What is the definition of a protein?
1 or more polypeptide chains.
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What does each gene occupy on a chromosone?
A specific locus
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What are examples of the polypeptides that genes code for?
Structural proteins such as collagen and keratin, haemoglobin, actin and myosin in muscle cells, enzymes.
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What is the purpose of the genetic code?
To provide instructions for the construction of a polypeptide or protein.
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What are the characteristics of the genetic code?
It is a triplet code, it is a degenerate code, some codes indicate stop and it is widespread.
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What is a triplet code?
A sequence of 3 nucleotide bases which code for an amino acid.
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What does degenerate mean?
All amino acids apart from methionine have more than 1 code.
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What effect do codes indicating stop have?
They will end the polypeptide chain.
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How does the nucleotide sequence code for amino acid sequence in a polypeptide?
Genes are on chromosomes in nucleus. Proteins assembled at ribosomes in cytoplasm. mRNA produced as copy of genetic code which passes through pore in nuclear envelope to cytoplasm.
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What is the 1st stage of protein synthesis?
Transcription
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What happens first in transcription?
The gene to be transcribe unzips and unwinds.
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How does the gene unzip/unwind?
DNA that makes up the gene dips into the nucleolus.
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What then happens?
Hydrogen bonds between complementary base pairs break.
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What do these hydrogen bonds then bind with?
Hydrogen bonds bind with activated RNA nucleotides to their complementary bases.
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Which bases are complementary to each other?
A and U, C and G, A and T
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Where do these base pairs bind?
On the template strand.
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What is this binding catalysed by?
The enzyme RNA polymerase.
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What is then released?
2 extra phosphates which release energy for bonding nucleotides.
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What is the mRNA produced?
Complementary to nucleotide base sequence on the template strand of the DNA and is a copy of the base sequence on the coding strand of the length of DNA.
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How is mRNA released and where does it go to?
Released from DNA, passes out of nucleus through a pore in the nuclear envelope to a ribosome.
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What is transcription?
The creation of a single-stranded mRNA copy of the DNA coding strand.
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Other cards in this set

Card 2

Front

What are polypeptides?

Back

Polymers consisting of a chain of amino acids joined by peptide bonds.

Card 3

Front

What is a genome?

Back

Preview of the front of card 3

Card 4

Front

What is the definition of a protein?

Back

Preview of the front of card 4

Card 5

Front

What does each gene occupy on a chromosone?

Back

Preview of the front of card 5
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