DNADeoxyribonucleic Acid

Nature vs. Nurture?

DNA

We know traits are inherited but how are

they inherited?

ChargaffChargaff’’s Rules Rule

Chargaff’s Rule

X-ray EvidenceX-ray Evidence

• 1952 Rosalind Franklin took an x-ray diffraction to take picture of DNA shape

• Picture gave clues to structure of DNA

Watson & CrickWatson & Crick

• Watson & Watson & Crick made a Crick made a model of DNA model of DNA structurestructure

• Won Nobel Won Nobel PrizePrize

Watson and Crick’s model of DNA was a double helix

The Components & Structure The Components & Structure of DNAof DNA

NucleotideNucleotide1. 5-carbon sugar 1. 5-carbon sugar

deoxyribosedeoxyribose2. phosphate 2. phosphate groupgroup3. nitrogenous 3. nitrogenous basebase

i. Adeninei. Adenineii. Thymineii. Thymineiii. Guanineiii. Guanineiv. Cytosineiv. Cytosine

Nucleotides are monomers!Nucleotides are monomers!

• Nucleotides are Nucleotides are linked in a strandlinked in a strand

• The sides of the The sides of the ““ladderladder”” are are phosphates and the phosphates and the sugar sugar deoxyribosedeoxyribose

- Sugar & phosphate form backbone- The bases form the “steps” of ladder, held together by Hydrogen bonds

• C-G = 3 hydrogen bonds• A-T = 2 hydrogen bonds

How is DNA Packaged? How is DNA Packaged? • DNA DNA is wrapped around proteins is wrapped around proteins called called histoneshistones forming beads forming beads• These beads pack together, forming These beads pack together, forming nucleosomesnucleosomes. . •These coil to make These coil to make chromatinchromatin•When the chromatin (stringy DNA) coils it make a When the chromatin (stringy DNA) coils it make a chromosomechromosome

DNA ReplicationDNA Replication

• Think about DNAThink about DNA’’s s structurestructure

• Perfect for use of Perfect for use of replication!replication!

• Each original side Each original side is a is a Template Template

Parent StrandOr Template

Daughter strand

Before a cell divides, it duplicates its Before a cell divides, it duplicates its DNA in a process called DNA in a process called replicationreplication. .

•This makes sure each cell will have a This makes sure each cell will have a complete set of DNAcomplete set of DNA

How is it done?!How is it done?!

1. DNA is unwound1. DNA is unwound2.2. DNA helicaseDNA helicase enzyme unzips the weak enzyme unzips the weak hydrogen bonds between base pairshydrogen bonds between base pairs3.3. DNA polymeraseDNA polymerase enzyme matches up enzyme matches up nucleotides to complement the other nucleotides to complement the other

sideside4. Strands checked for error4. Strands checked for error

““Semi-conservativeSemi-conservative””- why?- why?

Replicate your own DNA • 1. Take piece of paper and fold is

vertically • NOW REPLICATE

Label 1.Template/ Parent Strand 2.Hydrogen Bonds 3.Complementary Base Pairing 4.DNA Helicase 5.DNA Polymerase 6.Daughter Strands

Central Dogma

• DNA RNA Protein

• DNA gives the instructions for RNA which gives the instructions to make proteins

Central Dogma

What is a gene? • Part of the DNA

(letters/bases) that code for a particular protein

Genotype vs. Phenotype

• Genotype, genetic makeup, is the sequence of bases in the DNA

• Phenotype, traits, due to proteins

Proteins we learned! Structural •Keratin ( hair, skin and nails )•Muscles Reactions •Enzymes (lactase)Signal •Insulin, human growth hormone Hemoglobin- carriers oxygen in your red blood cells

RNA vs DNA

• RNA• Ribonucleic Acid • Ribose Sugar• A,C,G,U

– U = Uracil • Single Stranded

Transcription1. RNA copies the

message from DNA - Called messenger RNA ( mRNA)

2. Complementary base pair ( NO T!! In RNA)

3. Only copies a gene of the DNA

4. mRNA Leaves the Nucleus

Transcription • Enzyme that build RNA

strand • RNA polymerase

RNA Splicing Introns stay in the nucleus Exons join (splice) together and exit – final mRNA

Translation mRNA to Protein 1. mRNA goes to the Ribosome

– Each 3 letters of the mRNA is called a codon

2. Each mRNA codon bonds to a tRNA (transfer RNA) anticodon

– Complementary Base paring rules

3. tRNA carries the amino acid which builds the polypeptide (protein) 4. Begins with mRNA start codon AUG and ends with mRNA STOP Codon

Introduction Worksheet

• http://learn.genetics.utah.edu/content/begin/dna/transcribe/

• Transcribe and Translate a Gene

SHOW REAL TIME

• Great Simple Video!!

Mutations

http://www.dnalc.org/resources/3d/17-sickle-cell.html

1 base change in 438-base sequence. Change in DNA, change in RNA, change in Amino Acid Hemoglobin protein does not work properly to carry oxygen.

Tay Sachs

Cracking the Code:17:00-20:00

Inherited genetic mutation •Mutation in a gene that codes for an enzyme protein that breaks down fatty acids in the brain

Mutation

• Change in the nucleotide Sequence ( letters/bases) of a gene

1.Base Substitution (can be bad or silent) 2. Base Addition/ Deletion- worse

- Frameshift mutation= alter group of 3

Affects the function of the PROTEIN

ADDITION

• THE CAT ATE THE RAT• THE ACA TAT ETH ERA T

Mutagens cause Mutations

• Xray, UV light, smoking chemicals, pesticides

• Sometimes GOOD? How so?

Example of Inherited DNA Mutations: Diseases

Mutations