DNA Deoxyribonucleic acid•Hereditary material found in the nucleus of cells •Codes for proteins

•Consist of repeating units called nucleotides Nucleotides have 3 parts

Base pairs: A&T and G&C

= phosphate= 5 carbon sugar (deoxyribose)

= nitrogenous base 4 Types = adenine, thymine, guanine, cytosine

Mnemonic – George the CAT

What is the DNA??

A Passion for DNA Video Clip

Watson and Crick ModelWaston and Crick developed a model of the DNA molecule

• A DNA molecule consists of two complimentary chains of nucleotides• There is a “ladder type” organization twisted into a double helix• The sides of the DNA ladder are made up of alternating phosphate and deoxyribose sugar• Each rung is composed of nitrogenous bases held together by relatively weak hydrogen bonds

Bases are paired according to the following rules:A-T

(Adenine-Thymine)C-G

(Cytosine-Guanine)

If the sequence on one strand is: A A T T C C G GThen the complimentary strand is: T T A A G G C C

Notice that the bases are paired following the rules.Adenine is always with ThymineCytosine is always with Guanine

DNA ReplicationOccurs during interphase before mitosis and meiosis

How DNA Replication Works

1. Double stranded DNA unwinds and “unzips” along weak hydrogen bonds between the nitrogenous base pairs with help from enzymes.

2. Free nucleotides in the nucleus attach to both sides of the opened strand of DNA forming 2 double strands of DNA (1 old strand and 1 new strand per double strand)

3. Each new strand is identical to each other and the original DNA molecule.

EXAMPLE:Original Strand:A A T T C C G G A T C GT T A A G G C C T A G C

Unzipped DNA:

A A T T C C G G A T C G

T T A A G G C C T A G CNew Nucleotides Added:

A A T T C C G G A T C G

T T A A G G C C T A G C

T A A G G C C T A G C

A T T C C G G A T C G

2 New DNA molecules:Semi-conservative replication – one new strand and one old strand

A A T T C C G G A T C GT T A A G G C C T A G C

A A T T C C G G A T C GT T A A G G C C T A G C

OLD – YellowNEW - Blue

Mutations:• Gene mutations involve a random change in the nature of DNA • Bases are added or deleted in the DNA sequence or substituted (example: T for C)• May be visible in phenotype (appearance) example: sickle cell hemoglobin

SICKLECELL

NORMALCELL

WARM-UP: Pick up and complete the warm-up from the black metal

basket1. WHAT IS DNA? 2. WHERE IS DNA LOCATED?3. WHAT ARE THE BASES IN DNA? *BE READY TO SHARE YOUR ANSWERS*

Gene Control of Cellular Activities:Modern definition of a gene:

Sequence of nucleotides in a DNA molecule necessary to synthesize a polypeptide/protein.Control of cellular activities involves both DNA and RNARNA – Ribonucleic AcidDiffers from DNA in 3 ways:

Single Stranded Double Stranded Ribose Sugar Deoxyribose Sugar

Uracil Thymine

RNA DNAvs

3 Types of RNA:• Messenger RNA – mRNA• Transfer RNA – tRNA• Ribosomal RNA – rRNA

Type of RNA Type of Codon Function

mRNA codon, 3 bases, UAC Copies DNA and carries genetic messages to the

ribosomes

tRNA anticodon, AUG Transfers amino acids to mRNA at the ribosomes

rRNA --------- Forms with the ribosomes where proteins are

synthesized

A genetic code contains the information for the sequence of amino acids in a particular protein. This code is present in mRNA molecules, which are complimentary to DNA.RNA code is in triplet code called codon. A codon is based on various sequences of 3 bases in a mRNA moleculeDNA serves as the template for synthesis of mRNA fromfree RNA nucleotides in the nucleus.DNA -----> RNA is called transcription – mRNA forms a complimentary copy of DNA in the nucleus

A A T C G A = DNAU U A G C U = RNA 1 codon = 1 amino

acid

DNA REPLICATION REVIEW

Protein Synthesis:

DNA ProteinmRNA tRNAtranscription

nucleus

translation

cytoplasm carry amino acids

1. Transcription = copying the genetic code from DNA to mRNA

2. Translation = mRNA moves from the nucleus to the cytoplasm where they meet up with the ribosomes.

Ribosomes = rRNA and proteinSpecific tRNA molecules pick up an transfer amino acids found in the cytoplasm to the ribosomes

DNA TRANSCRIPTION

• tRNA is the anticodon that matches with a specific codon on mRNA.Particular polypeptide chains (protein chains with three ormore amino acids) are formed as amino acids, are carriedby the tRNA, and are bonded together at the ribosomesin a sequence determined by the mRNA.

Example mRNA codon A A U C C G U U C

tRNAanticodon

U U A G G C A A Ga.a a.a a.a

New polypeptideforming

Serine Alanine Glycine Proline Valine

polypeptide – protein chain

mRNA & tRNA

DNA TRANSLATION

Central Dogma of Science

DNADNA Transcription RNARNA

ProteinProteinTran

slation

TraitTraitExpression