3/10/16

1

DNA

Essential Question. Answer in your journal

notebook/

• What impact does DNA play in agriculture, science, and society as a whole?

3/10/16

2

Benchmark SC.912.N.1.3, SC912.L16.9 Explain how & why the genetic code is universal & common to all organisms

EOC Study Items: 1.  Describe a bacteriophage. 2.  Identify and describe the structure & function

of DNA. 3.  Explain the basic process of DNA replication 4.  Explain the basic process of transcription &

translation 5.  Types of genetic mutations 6.  mRNA codon chart Pg 244

WARM-UP

3/10/16

3

Why are proteins important? 1.  Proteins make up

the structural components of a cell

2.  Direct most of the cells chemical activity

3.  Body movement 4.  Defense against

germs (antibodies) 5.  Biochemical

reactions (enzymes)

DNA (Deoxyribonucleic Acid)

3/10/16

4

Friedrich Miescher

Montage showing (from left to right) Friedrich Miescher, Tübingen castle, a vial containing DNA

isolated by Miescher, his original publication describing his discovery of DNA and his laboratory

in Tübingen castle.

• 1869 • Swiss physician • Discovered DNA • Studied pus-ridden bandages • Isolated nuclei called “nuclein”

A HISTORY OF DNA

•  Discovery of the DNA double helix

A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)

B. Rosalind Franklin - X-ray photo of DNA. (1952)

C. Watson and Crick - described the DNA’s structure molecule from

Franklin’s X-ray. (1953)

SEE p. 231-232

3/10/16

5

Fredrick Griffith – microbiologist was investigating two forms of the bacterium that causes pneumonia. What material changed harmless R bacteria into disease-causing S bacteria? Griffith called this mystery material the “transforming principle.”

Alfred Hershey and Martha Chase •  American biologists •  Studied viruses that

infect bacteria called “bacteriophage”

•  Takes over a bacterium’s genetic machinery and directs it to make more viruses.

•  DNA molecule surrounded by a protein coat

3/10/16

6

Bacteriophage

•  DNA molecule surrounded by a protein coat

•  Experiment concluded that the phages’ DNA had entered the bacteria, but the protein had not.

Hersey-Chase Experiment

3/10/16

7

Genetic material of cells…

•  GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT

•  Called NUCLEIC ACIDS (DNA/RNA)

•  DNA is made up of repeating molecules called NUCLEOTIDES (monomer)

DNA Nucleotide (3 Parts)

O O=P-O O

Phosphate Group

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

CH2

O

C1 C4

C3 C2

5

Sugar (deoxyribose)

Single or double rings

3/10/16

8

Watson & Crick proposed… • DNA had specific pairing between the

4 nitrogen bases:

ADENINE – THYMINE

CYTOSINE - GUANINE

• DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”

DNA Double Helix

Nitrogenous Base (A,T,G or C)

“Rungs of ladder”

“Legs of ladder”

Phosphate & Sugar Backbone

3/10/16

9

DNA Double Helix

P

P

P

O

O

O

1

2 3

4

5

5

3

3

5

P

P

P O

O

O

1

2 3

4

5

5

3

5

3

G C

T A

strong

weak

Nitrogenous Bases

•  PURINES 1. Adenine (A)

2. Guanine (G)

•  PYRIMIDINES 3. Thymine (T)

4. Cytosine (C) T or C

A or G

3/10/16

10

Chargaff’s Rule •  Adenine must pair with Thymine

•  Guanine must pair with Cytosine

•  Their amounts in a given DNA molecule will be about the same.

G C T A

BASE-PAIRINGS

C G

H-bonds

T A

3/10/16

11

Genetic Diversity… •  Different

arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

The Code of Life… •  The “code” of the chromosome is the

SPECIFIC ORDER that bases occur.

A T C G T A T G C G G…

3/10/16

12

DNA is wrapped tightly around histones and coiled tightly to form

chromosomes

LET’S REVIEW DNA… 1.  List the conclusions Griffith & Avery,

Hershey & Chase drew from their experiments.

2.  Summarize the relationship between genes & DNA.

3.  Describe the overall structure of the DNA molecule.

4.  What are the 4 kinds of bases?

3/10/16

13

LET’S REVIEW DNA… 1.  List the conclusions Griffith & Avery, Hershey

& Chase drew from their experiments. Genetic material is made of DNA

2.  Summarize the relationship between genes & DNA. Genes are segments on DNA

3.  Describe the overall structure of the DNA molecule. Stores genetic information, Double helix, 2 spirals or DNA strands twisted, phosphate group, sugar, nitrogen bases

4.  What are the 4 kinds of bases? ADENINE – THYMINE CYTOSINE - GUANINE

What is DNA?

3/10/16

14

DNA Replication •  DNA must be copied

•  The DNA molecule produces 2

IDENTICAL new complementary strands following the rules of base pairing:

A-T, G-C

• Each strand of the original DNA serves as a template for the new strand See p. 235

Interesting fact!

3/10/16

15

DNA Replication •  Semiconservative

Model:

1. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.

. Parental DNA DNA Template

New DNA

1. Why is replication necessary? 2. When does replication occur? 3. Describe how replication works. 4.  Use the complementary rule to

create the complementary strand:

A---? G---? C---? T---? A---? G---? A---? G---? C---? A---? G---? T---?

Replication Quiz

3/10/16

16

1. Why is replication necessary? So both new cells will have the correct DNA 2. When does replication occur? During interphase (S phase). 3. Describe how replication works. Enzymes unzip DNA and complementary

nucleotides join each original strand. 4. Use the complementary rule to create the complementary strand:

A---T G---C C---G T---A A---T G---C A---T G---C C---G A---T G---C T---A

Replication Quiz

(1961) Watson & Crick proposed… •  …DNA controlled cell function by

serving as a template for PROTEIN structure.

•  3 Nucleotides = a triplet or CODON (which code for a specific AMINO ACID)

See p.303

•  AMINO ACIDS are the building blocks of proteins.

3/10/16

17

DNA Transcription •  DNA can “unzip”

itself and RNA nucleotides match up to the DNA strand.

•  Both DNA & RNA are formed from NUCLEOTIDES and are called NUCLEIC acids.

See p.301

AMAZING DNA FACTS… •  DNA from a single human

cell extends in a single thread for almost 2 meters long!!!

•  It contains information equal to some 600,000 printed pages of 500 words each!!! (a library of about 1,000 books)

3/10/16

18

DNA Translation •  The cell uses

information from “messenger” RNA to produce proteins

See p.304-305

We will discuss details

of this on a later date

Transcription/Translation Quiz 1.  Why is transcription necessary? 2.  Describe transcription. 3.  Why is translation necessary? 4.  Describe translation. 5.  What are the main differences

between DNA and RNA. 6.  Using the chart on page 303,

identify the amino acids coded for by these codons: UGGCAGUGC

3/10/16

19

1. Why is transcription necessary? Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.

2. Describe transcription. RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.

3. Why is translation necessary? Translation assures that the right amino acids are joined together by peptides to form the correct protein.

4. Describe translation. The cell uses information from MRNA to produce proteins.

5. What are the main differences between DNA and RNA. DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.

6.  Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGC tryptophan-glutamine-cysteine