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Proteins are made by decoding the Information in DNA. Proteins are not built directly from DNA. A molecule called RNA – ribonucleic acid is used to decode the instructions in DNA,. RNA Structure. Like DNA, RNA is a nucleic acid. RNA is a nucleic acid made up of repeating nucleotides. - PowerPoint PPT Presentation
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Proteins are made by decoding the Information in DNA
Proteins are not built directly from DNA
A molecule called RNA – ribonucleic acid is used to decode the instructions in DNA,
RNA Structure
Like DNA, RNA is a nucleic acid.
RNA is a nucleic acid made up of repeating nucleotides
RNA differs from DNAin three different ways.
The sugar in RNA is ribose
RNA is single- stranded
RNA contains the base uracil instead of thymine.
Like thymine, uracil can form bonds with adenine
TranscriptionThe instructions for making a protein are transferred from a gene (DNA) to RNA
Transcription = DNA → RNA
Segment of DNA unwinds
DNA unzips
RNA is produced one nucleotide at a time by matching base pairs with the nucleotides in DNA.
After the synthesis is complete, the RNA separates from the DNA and the DNA recoils into its helix.
The RNA strand leaves the nucleus and goes into cytoplasm
In what part of the cell does transcription take place?
RNA makes proteins.
Where are proteins made in the cell?
Forms of RNA
Messenger RNA - mRNA
mRNA carries the information to the cytoplasm where the ribosomes can make it into protein.
– "Blueprint" for protein synthesis that is transcribed from one strand of the DNA (gene) and which is translated at the
ribosome into a polypeptide sequence.
Ribosomes take RNA coded information and "translate" that information into chains of amino acids called pollypeptides
A protein is made up of one or more polypeptide chains.
Ribosomal rRNA
• a structural component of the ribosome.
tRNA molecule that converts nucleic acid sequence to protein sequence
tRNA - transfer RNA • It acts as an adaptor to carry the amino acid
elements of a protein to the appropriate place as coded for by the mRNA.
Small, single-stranded RNA molecules that bind to amino acids and deliver them to the proper codon on messenger RNA.
Messenger RNA (mRNA) is the blueprint for construction of a protein.
Ribosomal RNA (rRNA) is the construction site where the protein is made.
Transfer RNA (tRNA) is the truck delivering the proper amino acid to the site at the right time.
Translation
The ribosome reads the mRNA sequence and translates it (or decodes it) into an amino acid sequence in a polypeptide.
Polypeptides are chains of amino acids.
Proteins are made up of one or more polypeptide molecules.
So….the building block of proteins are ___________________.
There are 20 essential amino acids that make up proteins.
The instructions in DNA specify the order in which the amino acids are put together.
RNA – contains 4 different nucleotides.(Language – 4 letters)
How can a code with only 4 letters carry instructions for 20 amino acids?
# of letters # of words
1 4
2 16
3 64
The genetic code could signify 64 different words
The group of 3 nucleotides in mRNA that specifies an amino acid is known as a codon.
Think of codons as the words of the genetic message.
Example: The following sequence of nucleotides in mRNA
• AAACACGGU
Would be read as 3 codons
AAA- CAC-GGU
And each codon represents a different _____.
G
First Second Third
U C A G
U
UUUPhenylalanine
UCUSerine
UAUTyrosine
UGUCysteine U
UUCPhenylalanine
UCCSerine
UACTyrosine
UGCCysteine C
UUALeucine
UCASerine
UAASTOP
UGASTOP A
UUGLeucine
UCGSerine
UAGSTOP
UGGTryptophan G
C
CUULeucine
CCUProline
CAUHistidine
CGUArginine U
CUCLeucine
CCCProline
CACHistidine
CGCArginine C
CUALeucine
CCAProline
CAAGlutamine
CGAArginine A
CUGLeucine
CCGProline
CAGGlutamine
CGGArginine G
A
AUUIsoleucine
ACUThreonine
AAUAsparagine
AGUSerine U
AUCIsoleucine
ACCThreonine
AACAsparagine
AGCSerine C
AUAIsoleucine>
ACAThreonine
AAALysine
AGAArginine A
AUGMethionine
ACGThreonine
AAGLysine
AGGArginine G
GUUValine
GCUAlanine
GAUAspartic acid
GGUGlycine U
GUCValine
ValineAlanine
GACAspartic acid
GGCGlycine C
GUAValine
GCAAlanine
GAAGlutamic acid
GGAGlycine A
GUGValine
GCGAlanine
GAGGlutamic acid
GGGGlycine G
Page figure
Shows all 64 possible codons of the genetic code.
Notice: More than one codon can specify the same amino acid.
How do tRNAs recognize to which codon to bring an amino acid?
The tRNA has an anticodon that is complementary to the codon on the mRNA. Each tRNA only binds the appropriate amino acid for its anticodon
amino acids are carried by the molecules of tRNA.
The ribosomes “read” the codons in mRNA allowing tRNA molecules to bring the proper amino acid. (the anti-codon on tRNA bonds to the proper codon on mRNA)