DNA, RNA and Protein

1
DNA, RNA and Protein

• How the Information in DNA Is Used to Build a
  Protein

2
Information Flow From DNA
Gene sequence of DNA that codes for a protein
DNA
(ongoing parts of cell metabolism)
RNA
Protein
3
DNA and RNA Structure
Nucleotide phosphate sugar
nitrogen-containing base
4
DNA and RNA Structure
OH
OH
OH
H
5
Nucleotide Chain

• Nucleotides are joined together by dehydration
  synthesis

The phosphate of one nucleotide is joined to
sugar of next nucleotide, forming a
sugar-phosphate backbone
6
DNA Structure
3 end
A
5 endhas free phosphate

• Two nucleotide chains
• In opposite orientations
• Held together by hydrogen bonds
• Twisted into a helix

C
G pairs with C
A
T
G
A
3 endhas free sugar
5 end
A pairs with T
7
Applying Your Knowledge

• In the DNA double helix, which base is paired
  with adenine?
• Adenine
• Cytosine
• Guanine
• Thymine
• Uracil

8
DNA Replication

• DNA chains separate
• Each chain is used as a pattern to produce a
  new chain
• Each new DNA helix contains one old and one
  new chain

9
DNA Replication
DNA replication requires 1. Enzymes, including
DNA polymerase that adds nucleotides in a
5?3 direction. 2. nucleotides 3. energy
5A G C T 3
A 5
G
C
3 T
G
C
T 3
5 A
3T C G A 5
10
Enzymes Involvedin DNA Replication
11
Directionality of DNA Replication
12
Applying Your Knowledge

• Two new chains
• Two old chains
• One old and one new chain
• One helix has two new chains and one has two old
  chains
• None of these is correct.

• After DNA replication, what is the composition of
  the new double-helical molecules?

13
Building Your DNA Model
Join the phosphate of one nucleotide to the sugar
of the next one
One chain can have bases in any order, the other
chain must be complementary
Your completed model will have two DNA chains,
each with 9 nucleotides.
14
Transcription Production of RNA Using
DNA as a Template

• DNA chains separate
• ONE DNA chain is used as a pattern to produce
  an RNA chain
• RNA chain is released and the DNA chains
  reform the double-helix

In DNA In RNA A U T
A G C C G
15
Transcription
Transcription requires 1. Enzymes,
including RNA polymerase that adds
nucleotides in a 5?3 direction. 2.
nucleotides 3. energy
3---TACAAAGAGACT---5 5---ATG TTTCTC
TGA---3
5---AUGUUUCUCUGA---3 mRNA
16
Applying Your Knowledge

• What is the sequence of an RNA molecule
  transcribed from a DNA template strand that reads
  3-ATG-5?
• 5-TAC-3
• 5-CAU-3
• 5-AUG-3
• 5-UAC-3
• 3-TAC-5

17
Products of Transcription

• Messenger RNA
• Contains the code words for the sequence of
  amino acids in a specific protein
• CODON group of three nucleotides acting as a
  code word for an amino acid

18
Interrupted Genes
Eukaryotic Genes have interruptions within
regions coding for protein intron
interrupting sequence exon portion of coding
region
19
mRNA Processing
DNA
Primary transcript RNA
Add 5 cap
Add 3 poly-A tail
Remove Introns Splice Exons together
Mature mRNA leaves for cytoplasm
20
Products of Transcription

• Transfer RNA
• Translates the message by bringing a specific
  amino acid into the correct position on the
  growing protein chain
• Has ANTICODON a group of three nucleotides on
  a tRNA that recognizes a mRNA codon
• Has amino acid attachment site

21
Genetic Code
Chart is written as a CODON dictionary, reading
5?3
22
Products of Transcription

• Ribosomal RNA
• One of the structural components of the
  ribosome
• Ribosome organelle where protein synthesis
  occurs
• Has sites to bind both mRNA and tRNA

23
Applying Your Knowledge

• Which molecule contains the information for
  assembling the amino acids in the correct order
  in the protein?
• rRNA
• tRNA
• mRNA
• All of these
• None of these

24
Building Your DNA Model
Choose one DNA chain as the template for RNA
Read the template from 3?5 to produce the mRNA
from 5?3
Your completed messenger RNA will have 9
nucleotides.
25
Translation
At the ribosome, codons in mRNA are recognized by
tRNA anticodons to place amino acids in the
specific sequence specified by the DNA.
Three Stages of Translation Initiation-
assemble components to start process
Elongation- add amino acids in repeated cycles
Termination- release protein product

26
Translation

• Initiation
• mRNA binds to ribosome
• First tRNA binds to mRNA

met
UAC
5---AUGUUUCUCUGA---3 mRNA
27
Translation

• Elongation
• Next tRNA binds to mRNA

met
phe
UAC
AAA
5---AUGUUUCUCUGA---3 mRNA
28
Translation

• Elongation
• Amino acids are joined
• First tRNA is released

met
phe
UAC
AAA
5---AUGUUUCUCUGA---3 mRNA
29
Translation

• Elongation
• Ribosome moves by one codon

met
phe
UAC
AAA
5---AUGUUUCUCUGA---3 mRNA
30
Translation

• Elongation (second cycle)
• Next tRNA binds to mRNA

met
phe
leu
UAC
AAA
GAG
5---AUGUUUCUCUGA---3 mRNA
31
Translation

• Elongation (second cycle)
• Amino acids are joined
• Second tRNA is released

met
phe
leu
UAC
GAG
5---AUGUUUCUCUGA---3 mRNA
AAA
32
Translation

• Elongation (second cycle)
• Ribosome moves by one codon

met
phe
leu
UAC
GAG
5---AUGUUUCUCUGA---3 mRNA
AAA
33
Translation

• Termination
• Termination factor binds to stop codon

met
phe
leu
UAC
T
GAG
5---AUGUUUCUCUGA---3 mRNA
AAA
34
Translation

• Termination
• Protein chain is released
• Other components separate

met
phe
leu
UAC
T
GAG
AAA
5---AUGUUUCUCUGA---3 mRNA
35
Applying Your Knowledge

• If the mRNA sequence for codons 5, 6, and 7 of a
  protein is 5-AAG-AUU-GGA-3, what is the amino
  acid sequence in the protein?
• Gly-ile-lys
• Arg-leu-glu
• Glu-leu-arg
• Asn-met-gly
• Lys-ile-gly

36
Building Your DNA Model
Attach 3 bases to the tRNA to form the anticodon
Read the CODON from 5?3 to find the name of the
amino acid
Serine
Your completed model will have 3 tRNAs, one for
each codon in mRNA. Show the name of the amino
acid carried by each tRNA.
37
Summary of Completed DNA Model

• One DNA double helix, two chains of 9 nucleotides
  each
• one chain can have any sequence
• second chain must be complementary
• One chain of mRNA, 9 nucleotides long
• must be complementary to one of the two DNA
  chains (DNA template is 3?5, mRNA is 5?3)
• Three tRNAs with appropriate amino acids attached
• tRNA anticodons must match mRNA codons