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DNA LAB: Extract your DNA

DNA KNOWLEDGE!

DNA? Where is it located?

What is the shape?

What has DNA?

Deoxyribonucleic Acid

Nucleus

Living OrganismsDouble Helix

DISCOVERING DNA IS THE GENETIC MATERIAL

20th century – Major challenge: What arethe molecules of inheritance? T. H. Morgan’s group showed that genes are

located on chromosomes The 2 components of chromosomes—DNA and

protein—became candidates for the genetic material

1928 - Frederick Griffith discovered of the genetic role of DNA by working with two strains of a bacterium, one pathogenic and one harmless.

ADDITIONAL EVIDENCE THAT DNA IS THE GENETIC MATERIAL

It was known that DNA is a polymer of nucleotides, each consisting of a nitrogenous base, a sugar, and a phosphate group

In 1950, Erwin Chargaff reported that DNA composition varies from one species to the next

phosphate group

deoxyribose (sugar)

nitrogen-containingbase

FINDING THE STRUCTURE OF DNA New Challenge: What is the structure

of DNA? Maurice Wilkins and Rosalind Franklin

(King’s College) were using a technique called X-ray crystallography to study structure

Franklin produced a pictureof the DNA molecule using this technique (photo 51)

THE DISCOVERY OF DNA STRUCTURE 1953 – Watson and Crick (Cambridge

University) saw Photo 51 and discovered the structure of DNA. Double Helix – long twisted zipper

Segment with James Watson

LAB!! The double helix of a chromosome is so thin that it

only be detected through innovative, high-tech procedures.

Chromosomal DNA from a single cell is not visible to the naked eye.

However, when chromosomal DNA is extracted from multiple cells, the DNA can be seen.

We will collect cheek cells. Then, we will lyse the cell membranes by adding a

detergent. (This allows the DNA to be freed.) DNA is soluble in water, but much less soluble in

alcohol. Thus, alcohol will be slowly added, and DNA will precipitate to the sports drink/alcohol interface, and you will be able to see your own DNA!

DISCOVERING THE STRUCTURE OF DNA Read Molecular structure of Nucleic

Acids

BUILDING BLOCK/MONOMER DNA is made of nucleotides of

Deoxyribose (sugar) PO4 (phosphate group) Nitrogen bases

1. adenine—A 2. guanine—G 3. thymine—T 4. cytosine—C

phosphate group

deoxyribose (sugar)

nitrogen-containingbase

NITROGENOUS BASES

Double ring PURINESAdenine (A)Guanine (G)

Single ring PYRIMIDINESThymine (T)Cytosine (C) T or C

A or G

hydrogen bond

covalent bond

BASE PAIRING RULES A bonds to T with 2 hydrogen bonds

G bonds to C with 3 hydrogen bonds

REPLICATION DNA makes a copy of DNA Where? In the nucleus Semiconservative Replication

Parental strands separate and serve as templates

New DNA have one parent strand and one new strand

STEPS TO REPLICATION Step 1 – DNA helicase breaks the H+

bonds between the nitrogen bases (un-zipping DNA)

Step 2 – Free floating nucleotides in the cell bond to the complementary bases on the original strands

Step 3 – An enzyme secures the two strands together,forming two new chains

DNA replication animation

Replication occurs in 3’ to 5’ direction. DNA polymerase adds the nucleotides Two strands:

Leading Strand Lagging Strand –

Okazaki fragments

DNA replication animation

PRACTICE!!

CGATATATTCCCGAG

ATTCAGTTCAGACCC

ACGTTATACGCTAAC

CENTRAL DOGMA

Central DogmaDNA RNA PROTEIN

TRANSCRIPTION DNA RNA Where? In the nucleus

animation

RNA DIFFERS FROM DNA1. RNA has a sugar ribose

DNA has a sugar deoxyribose2. RNA contains the base uracil (U)

DNA has thymine (T)3. RNA molecule is single-stranded

DNA is double-stranded

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FOR YOU TO TRY…TRANSCRIPTION

CGATATATTCCCGAG

ATTCAGTTCAGACCC

ACGTTATACGCTAAC

THREE TYPES OF RNA Messenger RNA (mRNA) -

carries genetic information

Ribosomal RNA (rRNA) - makes the ribosomes

Transfer RNA (tRNA) - transfers amino acids to the ribosomes where proteins are made

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.

MESSENGER RNA (MRNA)

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A U G G G C U C C A U C G G C G C A U A AmRNA

startcodon

codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1

mRNA has a code (codon) for tRNA

TRANSLATION RNA protein Where? In cytoplasm. The chain of amino acids linked

together is a specific protein.

animation

FOR YOU TO TRY… TRANSLATIONMAKE AMINO ACIDS

GCUAUAUAAGGGCUC

UAAGUCAAGUCUGGG

UGCAAUAUGCGAUUG

TRANSFER RNA (TRNA)

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amino acidattachment site

A A G

anticodon

Phenylalanine

amino acid

FOR YOU TO TRY… MAKE ANTICODONS

GCUAUAUAAGGGCUC

UAAGUCAAGUCUGGG

UGCAAUAUGCGAUUG

FOR YOU TO TRY Given the following DNA sequence

CGATATATTCCCGAG 1. What is the complimentary DNA?

2. What is the mRNA strand (codon)?

3. What amino acids are created?

4. What is the tRNA (anticodon)?

WHAT IF THERE IS A MISTAKE? MUTATION-error

Substitutions Insertions Deletions Frameshift Translocation Inversion

Not all are harmful Read Happy Birthday Double

Helix

SUBSTITUTION

INSERTION

CCA TAT CAT GGC CCA TAT GCA TGG C

DELETION

FRAMESHIFT MUTATIONS HAPPEN BECAUSE OF INSERTIONS OR DELETIONS

Original: The fat cat ate the wee rat.

Frame Shift (“a” added): The fat caa tet hew eer at.

TRANSLOCATION

CCC GCG ATT TAT CCC TAT ATT GCG

INVERSION