From DNA to Protein Chapter 5. Ricin and your Ribosomes.
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Transcript of From DNA to Protein Chapter 5. Ricin and your Ribosomes.
DNA and RNA
DNA has one function: It permanently stores a cell’s genetic information, which is passed to offspring.
RNAs have various functions. Some serve as disposable copies of DNA’s genetic message; others are catalytic.
RNA in Protein SynthesisRNA in Protein Synthesis2 Different Kinds of RNA:2 Different Kinds of RNA:
Messenger RNA (mRNA)Messenger RNA (mRNA)Contains information transcribed from Contains information transcribed from
DNADNA
Transfer RNA (tRNA)Transfer RNA (tRNA)Delivers amino acids to ribosomesDelivers amino acids to ribosomes
Gene ExpressionGene Expression
Gene expressionGene expressionA multistep process in which genetic A multistep process in which genetic
information is converted into a information is converted into a structural or functional part of a cell or structural or functional part of a cell or bodybody
Transcription: DNA to Transcription: DNA to RNARNA
RNA polymeraseRNA polymerase assembles RNA by assembles RNA by linking RNA nucleotides into a chainlinking RNA nucleotides into a chain
Fig. 14-7, p. 220
gene
exon intron exon intron exon
DNA
transcription into RNAcap poly-A tail
mRNA 5’ 3’
snipped out snipped out
mRNA
Pre-
Post-Transcriptional Modifications
mRNA – The MessengermRNA – The Messenger
CodonCodon--A sequence of 3 mRNA A sequence of 3 mRNA nucleotides that codes for a specific nucleotides that codes for a specific amino acidamino acid The order of codons in mRNA The order of codons in mRNA
determines the order of amino acids in a determines the order of amino acids in a polypeptide chainpolypeptide chain
Common MutationsCommon Mutations
Base-pair-substitutionBase-pair-substitution DeletionDeletion or or insertioninsertion
Fig. 14-13, p. 224
THREONINE PROLINE GLUTAMATEGLUTAMATE LYSINE
THREONINE PROLINE VALINE GLUTAMATE LYSINE
THREONINE PROLINE GLYCINE ARGININE
c. Frame shift
b. Base pair substitution
a. Normal Hemoglobin chain
What Causes Mutations?What Causes Mutations?1.1. Spontaneous mutationsSpontaneous mutations
Uncorrected errors in DNA replicationUncorrected errors in DNA replication
2.2. Harmful environmental agentsHarmful environmental agentsa. UV radiationa. UV radiation
b. chemicalsb. chemicals
Inherited MutationsInherited Mutations
Mutations in Mutations in somatic cells somatic cells of of sexually reproducing species are not sexually reproducing species are not inheritedinherited
Mutations in a Mutations in a gametegamete may be may be inherited, with evolutionary inherited, with evolutionary consequencesconsequences