Topics

• DNA organization, structure, & function

• Replication

• RNA

• Protein Synthesis– Transcription– Translation

DNA Function

• genetic information– how to build, operate, and repair cell– Specifically how and when to make proteins

• passed from one cell generation to the next; – From one cell to the next within an individual– passed from parent to child

DNA Organization• DNA molecule = genes + “non-coding DNA)

• gene =protein instructions• non-coding = when to activate gene/make a protein

chromosome

~3% of DNA

“coding”

“chromosome” ~97% of DNA

genes Non-coding

• Double helix• Two strands twisted together like a corkscrew

DNA Structure• long chains of nucleotides• Nucleotide = sugar + phosphate + nitrogenous base

• Sugar = deoxyribose (5C)• 4 Different Bases: A, T, G, C• Bases = pyrimidines (1 ring) or purines (2 rings)

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DNA Structure Cont.:Double Helix

• double stranded– sugar-phosphate backbone=covalent– base-base=hydrogen

• Twisted=helix

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covalent bond

hydrogen bond

‘f’-five; ‘f’ phosphate; 5’ end

DNA Structure Cont.:Complementary Base Pairing

• 4 different bases

• Complementary pairing– C—G– A—T

Functional Characteristics of DNA: IMPORTANT!!

• Information = order of the bases/base sequence

– ATTGCGCA means something different then:– ATTGCGGA

• Complementary base pairing • Allows DNA to be copied over and over and the

information stays the same.

DNA Replication

• Happens as part of cell cycle

• In preparation for cell division

• Duplicates all the DNA: 1 copy 2 copies

• One copy for each cell

• Semiconservative

• In nucleus of cell

• NOT! NOT! NOT! PART OF PROTEIN SYNTHESIS!!!!!!!

Base Paring and Replication

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1 copy of all DNA

2 copy of All DNA

Replication of DNA

1 copy of DNA

1 copy of DNA

• Mitosis divides/separate the two copies of identical chromosomes

• Cytokinesis divides up the cytoplasm contents

Parent/mother celldaughter cells: each one identical copy of all the DNA: genetically identical to the mother cell

DNA Replication

• DNA helicase “unzips” the DNA

• New nucleotides are added/paired with the existing strands

• DNA polymerase binds the new nucleotides together creating the P-S backbone

• Result is two identical DNA molecules (i.e., the base sequence is the same)

Protein Synthesis: making proteins from DNA

1. Transcription= DNA mRNA (in nucleus)

2. Translation = mRNA Protein (in cytoplasm @ ribosome)

mRNA• Single stranded chains of nucleotides• Sugar = ribose• Bases and Pairing

– G, C, A, U replaces T– G-C– T-A or A-U

• Codons = 3-base groups– One codon is a “start” codon

– Three codons are “stop codons”– Each codon corresponds to a specific amino acid (except stops)

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Transcription

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Template strand

Coding strand

RNA Polymerase

Transcription

Transcription:from DNA mRNA

– promoter = how much transcription

• RNA Polymerase unzips gene and moves down DNA– Complimentary RNA nucleotides bind DNA– RNA nucleotides bind together (via RNA poly)– at end of gene mRNA detaches and RNA poly detaches

• DNA zips up when transcription is done

• mRNA is made and leaves nucleus and enters cytoplasm

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tRNA

• Single stranded piece of RNA• Carried and delivers amino acids• Anticodon binds w/ mRNA codon

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Mutations, DNA, and Protiens

• Mutation = change in DNA base sequence

• change in protien change in structure and/or function

Change DNA sequence

Change mRNA sequence

Change codons

Change amino acid sequence

Change protein Change protein function or make

non-functional

Mutations, DNA, and Protiens

• Mutation = change in DNA base sequence

Mutation = Δ in DNA sequence Δ in RNA sequence/codons Δ in amino acid sequence Δ in protein

– change in protein change in structure and/or function

Restriction Enzymes:

• Discovered in bacteria• Cut DNA at specific locations

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Genetic Expression: from DNA to cell function/structure

DNA mRNA Proteins cell function/structure

•structure

•transport

•contraction

•receptors

•cell ID

•hormones/signaling

This is the big picture: The instructions on DNA make proteins when the cell receives a signal and then those proteins are synthesized and used as enzymes, transport proteins, receptors, hormones or as building materials for the cell so that the cell can carry out its functions

Protein Synthesis and the Genetic Code

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DNA template strand