Chapter 7, Part 1:The Blueprint of Life, from DNA to Protein

2 Minute Brainstorm• Put these terms in order as they occur:–RNA– Transcription–DNA–Protein– Translation

DNA RNA ProteinTranscription Translation

Question 1: What is DNA Made Up Of (Subunits)?

1. Why deoxy?

2. What are the bases?

Sugar

Hydroxyl groups have what charge? Phosphate have what charge?

Negative

≠ Supercoil

(Fix this by eliminating

O!)REPEL!

Question 2: How do the subunits link together?

Sugar

2. What happens to the phosphates and why?

1. How are the subunits linked together?

5’ PO4 to 3’ OH

Only 1 gets incorporated and the release of energy by breaking the bonds helps give “fuel” to form the phosphodiester backbone

LABEL THE CARBONS!

Question 3: How do the strands link together?

Sugar

1. How are the bases paired together? H?

2. What are the orientation of the strands?

LABEL THE CARBONS!

Antiparallel!

Question

Given the amount of Adenine in a DNA sample is 37%, what is the amount of cytosine?

A. 37%B. 13%C. 74%D. 50%

Individual and Group Work (5 mins)

• Work by yourself for 2 minutes and fill out the work sheet

• Then compare your answers with your partner

5’

5’

3’

3’

Sugar

Phosphate

1234

5 T

A

C

G

2

2

3

3

Why do prokaryotes replicate DNA?

“Bidirectional”

Why?

TIME IS PRECIOUS!

Bacteria Have Circular DNA! Do Eukaryotes? NO!

How Is Replication Initiated?• Must have

Origin of Replication (ori)

• Region of specific base pairs “code”

• No ori=no replication!

• ~20 initiator proteins bind to ori-facilitate melting

A-T Rich! WHY?

Takes less energy to separate 2 H bonds than 3!

DNA Is Open at the Ori…Now What?

2.

3.

Why doesn’t DNA Polymerase just start synthesizing?NEEDS A PRIMER!!! RNA Primase has to do its job 1st

Synthesis Occurs In Leading and Lagging Strands

4.

5.

WHY?

WHY?

Has primer, replication and unwinding is going in the correct direction for continuous synthesis: opening up so can lay down more 3’

Can only lay down short tracks…opening in the 5’ direction

Filling In the Gaps

5.

6.

Question• Identify the leading and lagging strand

Supercoiling Can Be A Problem…DNA Gyrase to the Rescue!

How do we solve the problem?

DNA Gyrase

http://www.youtube.com/watch?v=3QWA-

tFdGN8(1:21)

How Do We End DNA Replication?• Just like initiation of replication, termination

is governed by a termination site• In this site, a protein binds and prevents

helicase activity

Just Like Eukaryotes, Bacteria DNA Replication is Semiconservative

How are genes encoded in DNA actually expressed?

• 2 steps:– Transcription (DNARNA)• Is the language mostly the same? Yes • Think transcribe: “re-write”

– Translation (RNAprotein)• Is the language mostly the same? No• Think translate/decipher: to express in another

language

Question 1: What Is RNA Made Up Of (Subunits)?

1. Why the hydroxyl group?Hydroxyl groups have what charge? Phosphate have what charge?

NegativeREPEL!

2. What are the bases?

≠ Supercoil (why it is

single stranded!)

Question 2: What Are The Types of RNA and Their Purpose?

tRNA

rRNA

mRNA

*Important in translation

*Important in translation

*Holds encryptedinformation

How Is Transcription Initiated?

• RNA Polymerase recognizes a specific sequence in the DNA (promoter)

• Sigma factor is the portion of the polymerase that recognizes the promoter

• Promoters are upstream of the genes they control• Binding causes DNA to melt

Promoters Can Be In Both Directions!

• The direction of the promoter dictates the template strand• How can you figure out the template strand? • First, what direction does the RNA Polymerase go? 5’ to 3’• Then, the template (-) strand will be the opposite!

Elongation of the Transcript

• RNA Polymerase moves along the DNA, melting it, and adding nucleotides at the 3’ end

• Base pairing: A=U, G=C• Once RNA Polymerase has cleared the promoter,

another molecule of the enzyme can bind and start again!

How Do We End Transcription?

• Just like initiation of transcription, termination is governed by a termination site

• In this site, the RNA polymerase stalls and releases

Homework & Muddiest Point

Homework Due At the Start of Class (Friday!)No late, no make-ups!

Hand-In Questions!