From DNA to From DNA to ProteinProtein

Chapter 5Chapter 5

Ricin and your Ricin and your RibosomesRibosomes

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.

DNA template

mRNA

protein stop Gly Glu

Amino acid Amino acid Amino acid

Transcription

Translation

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

DNA template

mRNA

Transcription

Transcription: DNA to RNA

Base-Pairing in DNA Synthesis and Transcription

Fig. 14-5a, p. 218

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

Genetic Information

• From DNA to mRNA to amino acid sequence

codon

TranslationTranslation

2 subunits Ribosomesmade of rRNA & proteins

Codons of the Genetic Codons of the Genetic CodeCode

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