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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
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