1

WARM-UPIf the DNA sequence is ---

AAA TAT CCG TAG CAA ATG Write the mRNA sequence, tRNA anticodon

sequence, and the six amino acids.

DNA: AAA TAT CCG TAG CAA ATG

mRNA:tRNA:Amino acids:

ReviewChromosomes v. Genes v. DNA

• Chromosomes contain genetic information

• Genes are sections of chromosomes

• Segments of genes are called DNA

3

DNA and RNA are examples of what major

macromolecule?

Nucleic Acids

What are the other 3 macromolecules?

-Lipids-Carbohydrates-Proteins

4

What does DNA stand for?

Deoxy-ribo-nucleic acid • DNA DNA is often called the blueprint

of life

• DNA contains the instructions for what traits (eye/hair color, etc.) are inherited from generation to generation

• Where is it found? Nucleus

5

DNA StructureDNA Structure• Composed of sub-units called Nucleotides• Nucleotides can be broken down into 3 parts

1. Phosphate Group

2. Deoxyribose Sugar (5 carbon sugar)

3. Nitrogenous Base

•Cytosine (C)•Guanine (G)•Adenine (A)•Thymine (T) 2. Deoxyribose Sugar

1. Phosphate

3. Nitrogenous Base

(A, T, G, C)

6

The Shape of DNAThe Shape of DNA• The basic shape is

like a twisted ladder or zipper.– This is called a

double helix, which means it is double stranded

NitrogenousNitrogenousBase (Base (C,G, A or TC,G, A or T))

““Rungs of ladder”Rungs of ladder”

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

7

One Strand of DNAOne Strand of DNA

• One strand of DNA is a polymer of nucleotides.

• One strand of DNA has many millions of nucleotides.

nucleotide

phosphate

deoxyribose

bases

8

NucleotidesNucleotides

C C

C

OPhosphate

O

CC

O -P OO

O

O -P OO

O

O -P OO

O One deoxyribose together with its

phosphate and base make a nucleotide.

Nitrogenous base

Deoxyribose

9

DNADNA

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

10

Double Stranded DNADouble Stranded DNA

• Remember, DNA has 2 strands that fit together like a zipper.

• The teeth are the nitrogenous bases but why do they stick together?

11

Chargaff’s RuleChargaff’s Rule• They stick together because of They stick together because of

hydrogen bonds of the hydrogen bonds of the nitrogenous basesnitrogenous bases

• AdenineAdenine always pairs with ThymineThymine– A T

• Cytosine Cytosine always pairs with GuanineGuanine– C G

G C

T A

12

DNA by the NumbersDNA by the Numbers

• Each cell has about 2 m of DNA.

• The average human has 75 trillion cells.

• The average human has enough DNA to go from the earth to the sun more than 400 times.

• DNA has a diameter of only 0.000000002 m.

The earth is 150 billion mor 93 million miles from the sun.

13

What about RNA?Stands for: Ribo-nucleic

acid • Structure similar to DNA but different

– Nucleotides divided into 3 parts1. Phosphate Group2. Ribose Sugar3. Nitrogenous Base

– Adenine (A)– Uracil (U) (Replaces Thymine)– Guanine (G)– Cytosine (C)

– Single stranded

14

How are DNA and RNA related?

• DNA codes for RNA, which guides protein synthesis – The reading and expression of

genes is from DNA to RNA to protein

– DNA -> RNA -> Protein = Central Dogma of Biology

15

DNA StructureDNA Structure•Rosalind Franklin took

diffraction x-ray photographs of DNA crystals

• In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays

16

DNA NucleotideDNA Nucleotide

O=P-O O

PhosphatePhosphate GroupGroup

NNitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)

CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

O

17

Pentose SugarPentose Sugar• Carbons are numbered

clockwise 1’ to 5’CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

18

Antiparallel Antiparallel StrandsStrands

• One strand of DNA goes from 5’ to 3’ (sugars)

• The other strand is opposite in direction going 3’ to 5’ (sugars)

19

Nitrogenous Nitrogenous BasesBases

• Double ring Double ring PURINESPURINESAdenine (A)Adenine (A)Guanine (G)Guanine (G)

• Single ring Single ring PYRIMIDINESPYRIMIDINES

Thymine (T)Thymine (T)Cytosine (C)Cytosine (C) T or C

A or G

20

Base-PairingsBase-Pairings•Purines only pair with

Pyrimidines•Three hydrogen bonds

required to bond Guanine & Cytosine

CG

3 H-bonds

21

T A

•Two hydrogen bonds are required to bond Adenine & Thymine

22

DNA DNA ReplicatiReplicati

onon

23

3 Questions about DNA Replication

1. What is DNA Replication? the process where DNA make a copy of itself

2. Why does DNA need to copy? Simple: Cells divide for an organism to grow or reproduce, every new cell needs a copy of its DNA or instructions to know how to be a cell.

24

3. When does DNA 3. When does DNA replication occur? replication occur? – It occurs right before the It occurs right before the

cell dividescell divides– During the During the S Phase S Phase of of

interphase of the cell cycleinterphase of the cell cycle

3 Questions about DNA Replication

25

Synthesis Phase (S Synthesis Phase (S phase)phase)

• S Phase during interphase of the cell cycle

Mitosis-prophase-metaphase-anaphase-telophase

G1 G2

Sphase

interphase

DNA replication takesDNA replication takesplace in the place in the S phaseS phase..

26

DNA Replication is DNA Replication is Semiconservative Semiconservative

• TheThe two strands of the parental molecule separate, and each acts as a template for a new complementary strand

• In other words: In other words: when DNA makes a copy, one half of when DNA makes a copy, one half of the OLD strand is always kept in the NEW strand. the OLD strand is always kept in the NEW strand. – This helps reduce the number of COPY errors.This helps reduce the number of COPY errors.

• New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA

Parental DNA

DNA Template

New DNA

27

Semiconservative Replication

28

Question:Question:

•What would be the complementary DNA strand for the following DNA sequence?

DNA 5’-CGTATG-3’DNA 5’-CGTATG-3’

29

Answer:Answer:

DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’

DNA 3’-CGCATAC-5’DNA 3’-CGCATAC-5’

31

1. What is the complimentary mRNA sequence to DNA sequence A-T-T-G-C-A?

A. T-A-A-C-G-T C. U-A-A-C-G-T B. U-A-A-C-G-U D. T-A-A-G-C-U

2. What causes the two sides of the double helix of DNA to stay joined together?

A. joining of phosphate molecules C. joining of base pairs

B. joining of sugar molecules D. joining of RNA3. What the three main parts of a nucleotide of DNA? (Choose all that

Apply) A. phosphate group C. deoxyribose sugar B. ribose sugar D. nitrogenous base

4. The process whereby DNA unzips and makes a strand of mRNA is called?

A. replication C. translation B. transcription D. complementation

5. When does DNA replication occur? A. During transcription C. During translation B. During mitosis D. During the S phase of interphase

6. Determine the amino acids sequence from this mRNA sequence: AUG CCC GGA UUA UAG (Use amino acid chart on board)

A. Met Pro Gly Leu Stop C. Met Leu Pro Gly Stop B. Stop Leu Pro Gly Met D. Met Pro Cys Gly Stop

Lesson Closure

3 things you learned in class 3 things you learned in class todaytoday

2 questions you have about the 2 questions you have about the lessonlesson

1 real-life connection1 real-life connection

33

MIND MAPSCreate a map using all of the following terms

Be sure to link them together

DNA RNANucleotide ThymineTranscription chromosomeTranslation nucleic acidUracil deoxyribose sugarRibose sugar mRNAAmino acid UnzippingNucleus ProteinDouble Helix