Chapter 12: From Gene to Protein
The genetic code is: 1. Unambiguous 2. Redundant 3. Universal
1. Each codon specifies only one amino acid 2. Several different codon may code for the same amino acid 3. Nearly all organisms on earth use the same genetic code.
What are the three stages of transcription?
1. Initiation 2. Elongation 3. Termination
What are the three major types of mutations?
1. Substitutions 2. Insertions 3. Deletions
Concept check: 1. What is meant by translation of the genetic code? 2. Do each of the 64 codons specify a different amino acid?
1. Translation converts a sequence of bases in mRNA to a sequence of amino acids in a protein. 2. No, the three stop codons do not specify for amino acids, and a single amino acid may be specified by as many as 6 different codons.
What are three types of RNA?
1. messenger RNA (mRNA) 2. Ribosomal RNA (rRNA) 3. Transfer RNA (tRNA)
What causes an insertion or deletion mutation?
A base is inserted into or deleted from a DNA sequence. This can cause a genetic FRAMESHIFT/FRAMESHIFT MUTATION messes up DONWSTREAM codons The result can be that a protein fails to function
What is a mutation?
A change in the base sequence of an organism. -change in the identity of a single base pair to -addition or deletion of a one or more chromosomes
What is a CODON?
A three base code that is read by the ribosomes. There are 64 possible codons. Each CODON encodes for a particular amino acid.
What is the difference between RNA and DNA?
DNA = double strand DNA= more stable DNA = Deoxyribose RNA = Ribose DNA = ATGC RNA= AUGC DNA = stores RNA = Expresses genetic information by directing protein manufacturing
After initiation, the ribosome recruits the needed tRNA as determined by the codons they encounter. What is this stage called?
ELONGATION
For translation, and mRNA must first bind to a ribosome. What is this first step called?
INITIATION
What is the final stage?
TERMINATION
What is TRANSLATION?
The conversion of a sequence of bases in mRNA to a sequence of amino acids in a protein. It occurs at RIBOSOMES
What is the anticodon?
The mRNA binding site. Its three base sequence can only bind to a complementary sequence in the mRNA
TEMPLATE STRAND
The one of the two DNA strands use as a template from making mRNA
Transcription Translation
Transcription= Copying the DNA sequence of a gene in mRNA Translation = mRNA code is turned into precise sequence of amino acids that become covalently linked to form proteins
What is a point mutation?
When a single base is altered.
What is a substitution mutation?
When one base is substituted for another. For example, TAA is changed to CAA. So, the mRNA codon will be changed and the wrong amino acid will be produced.
What is "WOBBLE"?
When some tRNA can recognize more than one codon, because the base at the third position can pair with more than one base Most organisms have about 40 different tRNAs rather then 61 due to WOBBLE