Lecture(Protein Synthesis)

8/2/2019 Lecture(Protein Synthesis)

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Protein Synthesis


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Marvelous Mussel Adhesive

Mussel binds itself to rocks with threads

coated with the protein bysuss

Gene for bysuss has been put into yeast

Yeast synthesize the protein based on

the instructions in the mussel DNA


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Mussels Must Stick to Surfaces


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Same two steps produce all proteins:

1) DNA is transcribed to form RNA

Occurs in the nucleus RNA moves into cytoplasm

2) RNA is translated to form polypeptide

chains, which fold to form proteins

Steps from DNA to Proteins


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Three Classes of RNAsMessenger RNA

Carries protein-building instructionRibosomal RNA

Major component of ribosomes

Transfer RNA Delivers amino acids to ribosomes


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A Nucleotide Subunit of RNA

phosphate

group

sugar

(ribose)

uracil (base)

Figure 14.2

Page 228


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Base Pairing during

Transcription

DNA

DNA DNA

RNAG C A T

C G T A

G C A U

C G T A

base pairing in DNA replication base pairing in transcription


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Transcription Video http://www.youtube.com/watch?v=WsofH466l
http://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqk


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Transcription & DNA Replication Like DNA replication

Nucleotides added in 5 to 3 directionUnlike DNA replication

Only small stretch is template RNA polymerase catalyzes nucleotide addition

Product is a single strand of RNA
http://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqk


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Promoter

A base sequence in the DNA

that signals the start of a gene

For transcription to occur, RNA

polymerase must first bind to a

promoter
http://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqk


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Gene Transcriptiontranscribed DNA

winds up again

DNA to be

transcribed unwinds

mRNAtranscript

RNA polymerase

Figure 14.4c

Page 229
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Adding Nucleotides

growing RNA transcript5

35

3

direction of transcription

Figure 14.4d

Page 229
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Transcript Modificationunit of transcription in a DNA strand

exon intron

mature mRNA transcript

poly-A

tail

5

5 3

3

snipped

outsnipped

out

exon exonintron

cap

transcription into pre-mRNA

3 5

Figure 14.5Page 229
http://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqk


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Genetic Code

Set of 64 base

triplets

Codons

61 specify amino

acids3 stop translation

Figure 14.7

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tRNA Structurecodon in mRNA

anticodon

amino

acidOH

amino-acid

attachment site

Figure 14.8

Page 231
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Ribosomestunnel

small ribosomal subunit large ribosomal subunit intact ribosome

Figure 14.9b,c

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Three Stages of Translation

Initiation

Elongation

Termination
http://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqk


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Translation Video

http://www.youtube.com/watch?v=1PSwhTG
http://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=WsofH466lqkhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Initiation

Initiator tRNA binds tosmall ribosomal subunit

Small subunit/tRNAcomplex attaches tomRNA and moves alongit to an AUG start

codonLarge ribosomal subunit

joins complexFig. 14.10a-c

Page 232
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Binding Sites

binding site for mRNA

P(first

binding site

for tRNA)

A (second

binding site

for tRNA)

Figure 14.10d

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Elongation

mRNA passes through ribosomal

subunits

tRNAs deliver amino acids to the

ribosomal binding site in the order

specified by the mRNA

Peptide bonds form between the amino

acids and the polypeptide chain grows
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Elongation

Fig. 14.10e-g

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Termination

Stop codon into place

No tRNA with anticodon

Release factors bind to

the ribosome

mRNA and polypeptide

are released

new

polypeptidechain

mRNA

Fig. 14.10j-k

Page 233
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What Happens to the

New Polypeptides?

Some just enter the cytoplasm

Many enter the endoplasmic reticulum

and move through the cytomembrane

system where they are modified
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Overview

Transcription

Translation

mRNA rRNA tRNA

Mature mRNA

transcripts

ribosomal

subunits

mature

tRNA
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Gene Mutations

Base-Pair Substitutions

Insertions

Deletions
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Base-Pair Substitution

original base triplet

in a DNA strand

During replication, proofreadingenzymes make a substitution

a base substitution

within the triplet (red)

original, unmutated

sequence

a gene

mutation

possible outcomes:

or

Figure 14.11Page 234


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Frameshift Mutations

Insertion

Extra base added into gene region

Deletion

Base removed from gene region

Both shift the reading frame

Result in many wrong amino acids
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Frameshift Mutation

mRNA

parental DNA

amino acids

altered mRNA

DNA with

base insertion

altered amino-

acid sequence

arginine glycine tyrosine tryptophan asparagine

arginine glycine leucine glutamateleucine

Figure 14.12Page 234


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Transposons

DNA segments that move

spontaneously about the genome

When they insert into a gene region,

they usually inactivate that gene
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Transposons and Plants

Barbara McClintockNobel Prize 1983
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Mutation Rates

Each gene has a characteristic mutation

rate

Average rate for eukaryotes is between10-4 and 10-6 per gene per generation

Only mutations that arise in germ cells

can be passed on to next generation
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related


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Mutagens

Ionizing radiation (X rays)

Nonionizing radiation (UV)

Natural and synthetic chemicals
http://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=relatedhttp://www.youtube.com/watch?v=1PSwhTGFMxs&feature=related

Documents

Lecture(Protein Synthesis)