Genetic Information DNA – RNA to Protein Unit 4 Genetic Expression.
2 Genetic Code and RNA
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Transcript of 2 Genetic Code and RNA
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5.6 The sequence ofbases in the DNA
determines thestructure of proteins,
including enzymes.
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Specification
The genetic code as base triplets in mRNA
which code for specific amino acids.
The genetic code is universal, non-overlapping
and degenerate. The structure of molecules of messenger RNA
(mRNA) and transfer RNA (tRNA).
Candidates should be able to compare thestructure and composition of DNA, mRNA and
tRNA.
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The Genetic Code
A sequence of three bases, called a triplet, codes
for a specific amino acid.
Amino acid 1 Amino acid 2 Amino acid 3 Amino acid 4
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The order in which
the triplets appeardetermines the
sequence in which
the amino acids are
combined to make
the polypeptide
chain
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1st
Base
2nd
Base
3rd
Base
T C A G
T
Phenylalanine Serine Tyrosine Cysteine T
Phenylalanine Serine Tyrosine Cysteine C
Leucine Serine Stop Stop A
Leucine Serine Stop Tryptophan G
C
Leucine Proline Histidine Arginine T
Leucine Proline Histidine Arginine C
Leucine Proline Glutamine Arginine A
Leucine Proline Glutamine Arginine G
A
Isoleucine Threonine Asparagine Serine T
Isoleucine Threonine Asparagine Serine C
Isoleucine Threonine Lysine Arginine A
Methionine
(Start)1
Threonine Lysine Arginine G
G
Valine Alanine Aspartate Glycine T
Valine Alanine Aspartate Glycine C
Valine Alanine Glutamate Glycine A
Valine Alanine Glutamate Glycine G
http://www.soc-bdr.org/rds/authors/unit_tables_conversions_and_genetic_dictionaries/e5202/index_en.htmlhttp://www.soc-bdr.org/rds/authors/unit_tables_conversions_and_genetic_dictionaries/e5202/index_en.html -
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The code is
Universal all living things share the same
four organic bases
Degenerate one amino acid can be
coded for by more than one triplet
Non-overlapping the triplets are all
sequential and it matters where you start
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Guess the
nucleic
acid?
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Compare:
RNA
Uracil pairs with Adenine
Ribose sugar
Usually single stranded
Not arranged in a helix
Relatively short
DNA
Thymine pairs with adenine
Deoxyribose sugar
Double stranded
Arranged in a double helix
Much longer
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Function of RNA
It transmits genetic information stored in DNA:
Transcription: it expresses the genetic
information as mRNA
Translation: it transports amino acids to the
ribosome in protein synthesis (tRNA)
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Messenger RNA
mRNA
a template for
protein
synthesis made in the
nucleus when
free RNA
nucleotides
match up with
DNA template
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Transfer RNA
tRNA
The RNA molecule is
formed into a
secondary structurelike a cloverleaf
Transfers amino acids
to the ribosome
during protein
synthesis.
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tRNA molecule
The amino acidcollected by the
tRNA molecule is
determined by the
arrangement ofbases at the
anticodonAnticodon
Amino acid attaches here
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Base sequences
DNA triplet mRNA codon tRNA - anticodon(phenylalanine)
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Ribosomal RNA
rRNA
Combines with protein to
form ribosomes
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Describe how proteins are
synthesised using the DNA code
enzymes break weak hydrogen bonds betweenthe bases
one strand of DNA acts as a template
to form a molecule of mRNA by the process of complimentary base pairing
(C=G, T=A, A=U, G=C)
free nucleotides are found in the nucleoplasm
mRNA molecule leaves nucleus via nuclearpores
travels to ribosomes in cytoplasm
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ribosome attaches to mRNA at a start code
a tRNA molecule with a complimentary
anticodon will bind to the appropriate codon onthe mRNA
this tRNA molecule will bring a particular aminoacid to the ribosome
sequence of amino acids is determined by thesequence of bases in DNA chain
peptide bonds form between amino acids
a polypeptide chain is formed this is transported to the endoplasmic reticulum(ER) to be folded into a protein