DNA: The Molecule of Life

Alan D. MoralesBiology

Introduction Genetic code: the program of the

cell that is passed from one generation to another; tells cells what to do and how to do it Must be able to:

1. duplicate itself quickly and accurately 2. be decoded and put into effect

Discovery of DNA Griffith: 1928--discovered transformation of

bacteria Avery: 1944-discovered that DNA was the

transforming factor Hershey and Chase: 1952-studied whether

viruses that infect bacteria inject protein or DNA

PA Levine- Discovered the nitrogenous bases, deoxyribose, and phosphate group.

Franklin and Wilkins: DNA has a helical structure

What is DNA? Deoxyribose Nucleic Acid Chargraff

A=T, G=C James Watson and Francis

Crick Model of DNA

Double stranded structure Bases inside

DNA-Deoxyribose Nucleic Acid

What is DNA Made of? 5-carbon sugar

(Deoxyribose) Phosphate Nitrogenous Base

Adenine (A) Guanine (G) Thymine (T) Cytosine (C)

What are the Structures of the bases? Purines

Adenine

Guanine

What are the structures of the bases? Pyrimidines

Thymine

Cytosine

A View of base pairing A:T

2 hydrogen bonds

A View of Base Pairing G:C

3 hydrogen bonds

What is important about base pairs? Can predict sequence of one

strand based on the sequence of the other.

Replication and Transcription Repair of damaged DNA

Linking it all together:

A, G, C or T

What makes DNA Different from RNA?

Forms sugar Phosphate Backbone

Where is DNA in the cell? Prokaryotic cell: Cytoplasm Eukaryotic cell: in the

chromosomes

DNA-Chromosome Formation http://www.cleanvideosearch.com/

media/action/yt/watch?videoId=4PKjF7OumYo

DNA Replication: Why?

When cells divides, each new cell needs it’s own copy of DNA.

Where? Nucleus in Eukaryotes. Cytosol in Prokaryotes

When? S phase of Interphase

What causes? DNA Polymerase

DNA Replication

DNA Replication DNA Helicase cause DNA to unwind and

unzip SSB: Single strand binding protein keeps

DNA separated RNA Primase add a short segment on

each end DNA Polymerase causes addition of new

nucleotides 3’ to 5’ direction Leading and Lagging strand Matching on Base pairing

DNA Replication Okazaki fragment

is small segment of lagging strand of DNA formed during replication

DNA Ligase connect the Okazaki fragments

Comparing DNA Replication in Eukaryotes and Prokaryotes cells Eukaryotes cells unwind in multiple

areas Prokaryotes cells unwind only in

area of replication

DNA Replication Lab DNA Replication Video

RNA Transcription

Transcription DNA RNA What is the difference between DNA

and RNA? Sugar: Ribose Strands: 1 Instead of thymine

=Uracil A, U, C, G

Types of RNA mRNA-messenger RNA

Take message from DNA out of nucleus to ribosomes

tRNA-transfer RNA Transfer code to protein

rRNA-ribosomal RNA Assist with making protein

Transcription Where?

Nucleus in Eukaryotes Cytosol in Prokaryotes

What? DNA copied/written by mRNA

When? When protein is needed

Transcription How?

RNA polymerase Base-pairing

A-U and G-C Only one strand

RNA Synthesis Animation

Transcription

Transcription Lab

Translation Language of RNA

instructions A, U, G, C

Codon: three consecutive nucleotides that forms a specific single amino acid from mRNA. 1 codon=3 nucleotides

Anticodon-3 consecutive nucleotides that from tRNA

Codon tRNA Molecule

Example: UCGCACGGU UCG-CAC-GGU Serine-Histidine-Glycine

UCG=Serine CAC=Histidine GGU=Glycine

Start Codon AUG

Stop Codon UAA, UAG, UGA

Amino Acids-Proteins Amino acids are

attached to tRNA Amino acids joined

together into long chains to make proteins

Protein properties are determined by order of amino acid.

20 different amino acids

The Genetic Code

Translation What?

mRNA with tRNA & rRNA Protein Where?

Cytosol When?

When proteins are needed Why?

Proteins are vital for cells

Translation How?

Ribosomal Subunits mRNA, tRNA, & rRNA

Stages of Translation Initiation: AUG starts process Elongation: Amino acids attach to each

other Termination: ends with stop codon

Translation Animation

Quick Lab1. What is the difference between DNA and RNA? 2. Replicate the following DNA Molecule: (hint: in DNA

Replication you will match it to another DNA molecule): GACAAGTCCACAATC

3. Transcribe the following DNA Molecule (hint: in Transcription you will match it to mRNA molecule): GACAAGTCCACAATC

Genetic Code

Quick Lab Answers1. What is the difference between DNA and

RNA?1. Sugar: Ribose2. Strands: 13. Instead of thymine

2. Replication of DNA Molecule: CTGTTCAGGTGTTAG

3. Transcribe into mRNA molecule: CUGUUCAGGUGUUAG

Protein Synthesis Review Replicate the following DNA

molecule DNA: GACTTACCGGGA DNA: CTGAATGGCCCT

Transcribe the following DNA molecule DNA: GACTTACCGGGA mRNA: CUGAAUGGCCCU

Protein Synthesis Review Translate the

following RNA molecule into a protein mRNA:

CUGAAUGGCCCU tRNA:

GACUUACCGGGA GAC-UUA-CCG-GGA Aspartic Acid-Leucine-Proline-

Glycine

Pop Quiz1. Translate following

mRNA molecule: GACAAGUCCACAAUC 1. tRNA strand:2. Amino Acid:

Pop Quiz Answers1. Translate from mRNA molecule to

amino acid sequence via tRNA1. tRNA strand: CUG-UUC-AGG-UGU-UAG2. Amino Acid: Leucine-Phenylalanine-Arginine-

Cysteine-Stop

Genes and Protein Genes contain information to

assembly Protein Proteins carry out the instructions

of the genes One gene-One enzyme

Beadle-Tatum

Gene Regulation Ability of an organism to control

which genes are transcribed in response to the environment

Gene Regulation Prokaryote Cells

Operon-Segment of DNA that contains genes for the protein in specific metabolic pathway

Eukaryote Cells Regulate protein synthesis using

various transcription factors, nucleosomes structures and RNA interferences

Why is this important? Mutations Genetic

Engineering Gene Splicing

Cloning

Mutations Mutation-change in the DNA

sequence that affect genetic information

Types of Mutations Point Mutation Chromosomal Mutation

Mutations Point Mutation-

one nucleotide has changed

Mutations Chromosomal

Mutation changes in the

number or structure of the chromosome

Body cell vs. Sex cell Mutations Somatic cell

Mostly neutral mutation

Are not passed on to offspring

Sex Cell Mutations are

passed on to offspring

The End