Chapter 12: DNA & RNA What do you already know about DNA? DNA Clearly Stated

Chapter 12: DNA & RNA

What do you already know about DNA?

DNA Clearly Stated

12.1 Three important functions of DNA

1. Store genetic information – stores genes

2. Copy information – copy genes prior to cell division

3. Transmit the information – pass genetic information along to next generation

12.2 Structure of DNA• DNA = Deoxyribonucleic Acid• A nucleotide is composed of:

1. Sugar (deoxyribose)2. Phosphate group3. Nitrogenous Base

• A nucleotide is the monomer of a DNA strand (polynucleotide):

DNA polynucleotide

A

C

T

G

T

Sugar-phosphate backbone

Phosphate group

Nitrogenous base

SugarA

C

T

G

T

Phosphategroup

O

O–

OO P CH2

H3C C

C

C

CN

C

N

H

H

O

O

C

O

O

H

C H H

H

C

H

Nitrogenous base(A, G, C, or T)

Thymine (T)

Sugar(deoxyribose)

DNA nucleotide

DNA nucleotide

12.2 Structure of DNA

DNA is a double-stranded helixJames Watson and Francis Crick

• Worked out the three-dimensional structure of DNA, based on photos by Rosalind Franklin

12.2 Structure of DNA

The structure of DNA• Consists of two polynucleotide strands wrapped

around each other in a double helix (twisted ladder)

Twist

12.2 Structure of DNA

Hydrogen bonds (weak) between bases• Hold the strands together

Each base pairs with a complementary partner• A with T, and G with C

G C

T A

A T

G

G

C

C

A T

GC

T A

T A

A T

A T

G C

A T

O

O

OH–O

P

OO

–OPO

OO

P– O

– O OP

OO

O

OH

H2C

H2C

H2C

H2C

O

O

O

O

O

O

O

O

PO–

O–

O–

O–

OH

HO

O

O

O

P

P

P

O

O

O

O

O

O

O

O

T A

G C

C G

A T

CH2

CH2

CH2

CH2

Hydrogen bond

Basepair

Ribbon model Partial chemical structure Computer model

12-3 DNA Replication

When does DNA replicate?– DNA must copy before cell division (mitosis)

How does it replicate?

1. DNA is separated by helicase (enzyme)

2. Nucleotides are added according to base pairing rules, using DNA polymerase (enzyme).

A T

C G

G C

A T

T A

A T

C G

G C

A T

T A

A T

C G

G C

A T

T A

A T

C G

G C

A

T

A T

C G

AC

T

A

Parental moleculeof DNA

Both parental strands serve as templates

Two identical daughtermolecules of DNA

12-3 DNA Replication

DNA replication is semi-conservative

1. The parent strand becomes two daughter strands.

2. Each daughter strand is composed of one half the parent (old strand) and one half new.

Origin of replication

Two daughter DNA molecules

Parental strand

Daughter strand

Bubble

DNA Replication Video

Chapter 12: Protein SynthesisWhat is DNA?

– The DNA of the gene is transcribed into RNA• Which is translated into protein

• The flow of genetic information from DNA to RNA to Protein

DNA

Transcription

RNA

Protein

Translation

Chapter 13 Protein Synthesis - Overview

Central Dogma - FLOW IS FROM DNA TO RNA TO PROTEIN

Chapter 13 Protein Synthesis (Overview)

FLOW IS FROM DNA TO RNA TO PROTEIN

• Genes on DNA are expressed through proteins, which provide the molecular basis for inherited traits

• A particular gene, is a linear sequence of many nucleotides

– Specifies a protein made of amino acids

Chapter 13 Protein Synthesis (Overview)

Genes - discrete units of hereditary information comprised of a nucleotide sequence found in a DNA molecule.

Chapter 13 Protein Synthesis (Overview)

13.1 RNAThree Types of RNA

• Messenger RNA (mRNA) – carries copies of genes (DNA) to the rest of the cell.

• Ribosomal RNA (rRNA) – make up the ribosomes.

• Transfer RNA (tRNA) – transfers the amino acids to the ribosomes as specified by the mRNA

12-1 Messenger (mRNA)

1. Three main differences between mRNA and DNA

• Ribose instead of deoxyribose• mRNA is single stranded• mRNA has uracil in place of thymine (U

instead of T)

12.1 TRANSCRIPTION: The process of making mRNA from DNA

– Why do you need this process?• Location of DNA?

Nucleus

• Location of Ribosome? Cytoplasm

– mRNA takes code from DNA in the nucleus to the cytoplasm

T A C T T C A A A A T C

A T G A A G T T T T A G

A U G A A G U U U U A G

Transcription

Translation

RNA

DNA

Met Lys PhePolypeptide

Startcondon

Stopcondon

Strand to be transcribed

12-3 Protein Synthesis - Translation

• Translation is defined as going from mRNA to protein– tRNA which have amino acids attached are

going to the ribosome in the cytoplasm.• What are amino acids? monomers of

proteins• Does the order of amino acids matter? Yes,

they must be in order for the protein to fold correctly.

Amino acid attachment site

– How does the correct tRNA (with amino acid attached) bind to the mRNA? The tRNA contains an anticodon which matches up with the mRNA sequence (codon).

– Translation at Ribosome

Amino acid attachment site

Hydrogen bond

RNA polynucleotide chain

AnticodonAnticodon

Amino acid attachment site

Transfer RNA (tRNA) molecules serve as interpreters during translation

tRNAmolecules

mRNA Small subunit

Growingpolypeptide

Largesubunit

Animation

1. Take the DNA and transcribe it into mRNAExample: TAC ATA CTA GCG ACT

mRNA:

2. Take the mRNA sequence and decode it using the codon chart.

AUG UAUGAU CGC UGA

AUG = METUAU = TYRGAU = ASPCGC = ARG

Figure out the exact sequence of amino acids needed

13.3 Mutations• Mutations – heritable changes in genetic information (changes to the

DNA sequence)

• Two types - gene and chromosomal mutations

• Mutations can be caused by chemical or physical agents (mutagens)– Chemical – pesticides, tobacco smoke, environmental pollutants

– Physical – X-rays and ultraviolet light

13.3 Mutations• Gene mutations

– Point Mutation: mutations that affect a single nucleotide

– Frameshift mutation: shift the reading frame of the genetic message.

• Can change the entire protein so it doesn’t work

• Gene Mutations Explained

13.3 Mutations

13.3 Chromosomal Mutations• Chromosomal mutation: mutation

that changes the number or structure of chromosomes.

13.3 Chromosomal Mutations• Types of chromosomal mutations:

– Deletion: The loss of all or part of a chromosome

– Duplication: A segment is repeated

– Inversion: part of the chromosome is reverse from its usual direction.

– Translocation: one chromosome breaks off an attaches to another chromosome.

1. Each person, Construct the DNA Strand Below2. Then, construct the complimentary strand to make a complete DNA molecule3. Ignore the color scheme below. Use:

Cytosine = Blue Deoxyribose Sugar = Black PentagonThymine = Green Phosphate = White TubesAdenine = Orange Ribose Sugar = Purple PentagonGuanine = Yellow tRNA = Purple PlasticUracil = Purple Amino Acid = Black Plastic

4. When you have constructed the complementary strand join the two strands together with Hydrogen bonds

DNA Modeling

1. Each group will construct an mRNA strand from the DNA strand below2. Then, take your mRNA strand outside the nucleus to the ribosome3. Use the codons of mRNA and anticodons of tRNA to manufacture proteins4. Use the following model pieces:

Cytosine = Blue Deoxyribose Sugar = Black PentagonThymine = Green Phosphate = White TubesAdenine = Orange Ribose Sugar = Purple PentagonGuanine = Yellow tRNA = Purple PlasticUracil = Purple Amino Acid = Black Plastic

Peptide Bonds (between AAs) – Grey Tubes

5. When you have constructed the complementary strand join the two strands together with Hydrogen bonds

Transcription and Translation Modeling

Making a DNA Molecule

• Must Contain– Deoxyribose Sugar – Pentagon shape– Phosphate Group – Circle– At least 6 base pairs (complimentary base pair

must be interlocking)– Label all parts of the DNA– Question: How could the structure of a DNA

molecule allow it to carry information and replicate (make copies of itself).

Backbone

Phage attachesto bacterial cell.

Phage injects DNA. Phage DNA directs hostcell to make more phageDNA and protein parts.New phages assemble.

Cell lyses and releases new phages.

HIV Images – NPR Story Toddler

DNA – Structure Questions

1.What pair of scientists are largely credited for discovering the shape of the DNA molecule?

2.Name the scientist whose photographs helped solve the mystery of DNA’s structure

3.DNA is in the shape of a _______ _______.

4.What are the sides of the DNA molecule made of? (2 things)

5.What are the rungs of the ladder made of?

6.What is the monomer of DNA?

7.What holds nitrogenous bases together?

DNA – early scientists

• Scientist/Experiments– What did Griffith call the phenomenon he

observed in the mouse experiment?– What did Hershey and Chase mark the

bacteriophage with? What parts were marked?– How did marking the bacteriophage assist in

determining DNA was the transforming factor?

Bryson Reading – Discovery of DNA

Section 1.a. Why is it surprising that the scientists working

in England even discovered the structure of DNA?

b. When did Watson start college and when did he get his Ph.D.?

Section 2.a. Why was understanding the shape of DNA so

important?b. What did Watson remark about that is surprising

in his autobiography?

Bryson Reading – Discovery of DNA

Section 3.a. How did Watson depict Rosie Franklin in his book

The Double Helix?b. What did Rosie Franklin have that at the time was

the best in the field? c. What method was Franklin using to capture DNASection 4.a. How were women treated at Kings College?b. What did Franklin do to throw her colleagues off the

trail?c. How did Watson and Crick eventually see Franklin’s

photos?

Central Dogma Questions1.The flow of genetic information is from ______ to ______

to ______.

2.Why does DNA send a “messenger” out into the cytoplasm?

3.The manufacture of mRNA from DNA is called _____________.

4.What cellular organelle uses the DNA codes to manufacture proteins?

5.How is DNA ultimately associated with our phenotype or outward appearance?

Homework Chapter 13 Sections 13.3 and 13.4

Section 13.3 Mutations 372-376 a. Explain the difference between the three types of “point”

mutations?

a. How do point mutations differ from chromosomal mutations?

a. Explain how mutations could be harmful or beneficial

Section 13.4 Gene Regulation and Expression 377-383a. Describe how prokaryotes turn lac genes on and off (mention:

promoters, operators, lactose, repressor, and RNA polymersase)?

a. How do eukaryotes regulate genes during transcription?

a. What do homeotic genes like homeobox and hox genes have to do with development? What is the difference between homeobox and hox genes?

Twist

Drawing a DNA Molecule

• Must Contain– Deoxyribose Sugar – Pentagon shape– Phosphate Group – Circle– At least 6 base pairs (complimentary base pair

must be interlocking)– Label all parts of the DNA– Question: How does the structure of a DNA

molecule allow it to carry information and replicate.

– Worth 20 Points

Backbone

Please complete the following:– The complementary DNA strand for:

• GACTGAGGA– The mRNA strand for:

• GACTGAGGA– Translate the mRNA sequence to amino acids:

• CCAUUUACG – Translate the mRNA codons to tRNA anticodons:

• CCAUUUACG

Extra Credit:

Biology 1 pts each:

1. What is one part of the cell theory?

2. What are the single units of a polymer called?

Non Bio 2 pts:

Title and artist of these lyrics

3. Aww, he got the velcro!

MutationsFANTASY REALITY

MutationsFANTASY REALITY