Download 3.PROTEIN SYNTHESIS overview

PROTEIN SYNTHESIS - An Overview
One Gene-One Polypeptide Hypothesis
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Garrod proposed that _________________________________________ (early 1900’s)
He analyzed blood and urine samples of patients with alkaptonuria- black urine
Alkapton in high concentrations turns dark when exposed to air
He proposed that some individuals have a defective alkapton metabolizing enzyme
Pedigree analysis led him to believe that the production of the enzyme was due to
_________________________________________________ (gene)
Beadle and Tatum
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Working with bread mould 33 years after Garrod, they showed that a lack of a particular
enzyme corresponded to __________________________________
They isolated 4 distinct mutant strains, each with a defective enzyme for the synthesis of the
amino acid arginine
Vernon Ingram
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Ingram found that, in sickle cell anemia RBC’s, the amino acid ___________ substitutes for
the normal amino acid in the protein
This substitution leads to a change in the shape of the red blood cell (RBC)
Ingram’s work showed that a gene specifies the _____________________of each amino acid
in a polypeptide chain
Many hereditary diseases since, such as ________________ and_________________, have
also been traced to alterations in a single gene
The Central Dogma:
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DNA is too valuable to leave the nucleus so parts of DNA are copied into a complementary
RNA message (mRNA) in a process called _______________________
The mRNA leaves the nucleus where ribosomes translate the ________________ sequence
into an amino acid sequence in a process called ____________________
RNA Vs DNA
RNA differs from DNA in many ways:
 RNA has a ribose sugar (____________________)
 RNA has ________________ instead of thymine (T)
 RNA is _____________________
 Uracil is complementary to ___________________
There are 3 major classes of RNA
 Messenger RNA ________________________________________________
 Transfer RNA (tRNA) transfers ___________________________ to the ribosome to build a
protein
 Ribosomal RNA ____________________________________________
Transcription: Overview
Can be divided into three processes:
 _________________:RNA polymerase binds to DNA near the beginning of a gene
 _____________________: RNA polymerase builds the appropriate mRNA transcript
 _____________________: RNA polymerase passes the end of a gene and recognizes a
signal to stop
Translation: Overview
This is also divided into three stages:
 Initiation: when a ribosome binds to a specific site on _________________________
 Elongation: the ribosome moves along the mRNA _____________________at a time
assembling a sequence of ____________________
 Termination: the ribosome reaches a ____________ signal on the mRNA and falls off
The Genetic Code
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The same genetic code is used for translation in every organism from bacteria to mammals
It’s universality is powerful evidence that evolution of the code happened
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_______ amino acids found in proteins are coded for by _____ different bases of RNA
3 nucleotides code for one _________________
Each triplet is called a _____________ (64 in total)
There are more codons than amino acids meaning there is _______________in the code
AUG = __________________
______ stop codons
Review
1. What did Garrod propose in the early 1900’s?
2. What did Beadle and Tatum discover 33 years after Garrod?
3. What did Ingram’s work show?
4. What two processes are involved in protein synthesis (DNA RNAProtein)?
5. Give 3 ways that RNA differs from DNA
6. Name 3 types of RNA
7. What is a triplet of nucleotides in RNA called?
8. Why do only 60 of 64 codons code for amino acids?
9. Translate this mRNA into a protein (fig. 7 p 240) 5’- GGC CAG AAA CAA GAA -3’