Chapter 8

From DNA to RNA to Proteins2 Types of nucleic acids

And Protein

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DNA- Life’s CodeDNA -> RNA -> Protein

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Identifying DNA as the genetic material

Frederick Griffith – Experimented with two forms of bacteria that cause pneumonia on miceoSmooth (S harmful) and Rough (R non harmful)oDemonstrated Transformation

His conclusion: some factor changed the bacteriao “Transforming Principal”

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Identifying DNA as the genetic material

Oswald Avery – Was puzzled by Griffith’s discovery and worked for 10 years to find the answer. o Directly observed transformation of R bacteria (harmless)

into S bacteria (harmful)o Proteins do not contain phosphorous – tests showed

phosphorus presento Performed chemical tests which indicated there was no

protein present, and DNA was present. Concluded that DNA is the transforming principal

o DNA = Genetic material

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Identifying DNA as the genetic material

Hershey and Chase- supported the conclusion - DNA is the source of genetic information o Bacteriophage – a virus that infects and replicates within

bacteria.o Used bacteriophage infected with radioactive phosphorus

atoms on DNA. • Radioactivity found in bacteria

o Used bacteriophage infected with radioactive sulfur atoms on protein.

• No radioactivity found in bacteria

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2 Types of Nucleic AcidsDNA and RNA

DNA DNA stands for Deoxyribo Nucleic Acid DNA is genetic material that determines inherited

characteristics/traits The job of DNA is to code for proteins in the body.

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DNA Structure What is the monomer that makes up DNA?

o DNA is made up of long chains of Nucleotides. o Nucleotides- make up genes that code for a specific trait.

What makes up a Nucleotide?o 1. Deoxyribose sugar ( )o 2. Phosphate ( )o 3. Nitrogen Base

• Adenine (A)• Guanine (G)• Cytosine (C)• Thymine (T)

phosphate group

deoxyribose (sugar)

Nitrogencontainingbase

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Structure of DNA

Double Helix – Spiral laddero Discovered by Watson and Crick in the 1950’s with the

help of Rosalind Franklin’s x-ray crystallography pictureso Double stranded

Complementary base paring – the nitrogen bases on one side of the ladder ALWAYS pair up with the same nitrogen base on the other side of the ladder. o Discovered by Chargaffo The pairs are held together

with hydrogen bonds A T G C

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Review How many different types of nucleotides are there? How

do they differ?

What is the monomer of DNA?

What does DNA stand for?

DNA’s shape can be described as a ______________?

What makes up the sides of DNA?

What makes up the rungs?

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DNA Replication Remember: DNA is always copied during cell

reproductiono Mitosis

This takes place during the S phase of Interphase

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Steps to DNA Replication

1. The DNA molecule is split down the middle (at the nitrogen bases) by helicase, breaking the hydrogen bonds. o Similar to a zipper

2. The nitrogen bases on each side of the molecule are used as a pattern for a new strand.

nucleotide

The DNA molecule unzips in both directions.

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3. Complementary bases are added to each individual strand by DNA polymerase (enzyme).

Steps to DNA Replication

DNA polymerase

new strand nucleotide

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4. Each new cell can now get a complete copy of all the DNA. o One of the original strand, one new strand

original strand new strand

Two molecules of DNA

Steps to DNA Replication

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Practice Base-Paring Original strand: ATTCCG Complementary strand :

Original strand: GCTAAG Complementary strand:

Original strand: CTACCA Complementary strand :

Original: o Strand A: GACCTAo Strand B:

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Review What is the purpose of replication?

How does DNA serve as its own template?

DNA polymerase

new strand nucleotide

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Central Dogma DNA RNA Protein

Transcription

DNA RNA

TranslationRNA Protein

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DNA makes RNA RNA is the 2nd type of Nucleic Acid RNA is made of nucleotides, just like DNA

o 1. Ribose is the sugaro 2. Phosphateo 3. Nitrogen Bases

• Adenine (A)• Guanine (G)• Cytosine (C)• Uracil (U): NOT Thymine (T)

o Single Strandedo When RNA is assembled based off of DNA’s pattern, this is

called Transcription

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Transcription Occurs in the nucleus 1. DNA is again unzipped by helicase.

DNA

DNA is too large to get out of the nucleus, RNA carries DNA’s message out of the nucleus to a ribosome.Ribosome – where the protein will be made.

start site

nucleotides

transcription complex

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2. RNA Polymerase adds complementary RNA nucleotideso This makes mRNAo mRNA = messenger = carries the messageo The DNA helix winds again as the gene is transcribed.

Transcription

DNA

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3. The mRNA strand detaches from the DNA once the gene is transcribed.o mRNA leaves the nucleus.

Transcription

RNA

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RNA complimentary base pairingduring Transcription

DNA strand = AATTTGCGCGGCT mRNA strand =

DNA strand = TATGCGCACTG mRNA strand =

DNA strand = CGATCAGCCTAT mRNA strand =

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Transcription

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3 Types of RNA

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Translation RNA to Protein Translation converts mRNA messages into

Polypeptideso String of amino acids held together by a peptide bond

A codon is a sequence of three nucleotides that codes for an amino acid.

Examples:o AUG= Methionineo CUU= Leucine

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The Genetic Code The genetic code matches the mRNA codon with

the amino acid or action AUG= Start/ Methionine UAA, UGA or UAG= Stop

Codon GCA = Codon AAG = Codon CUG = Codon CGA =

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Translation mRNA carries the DNA instructions for making protein mRNA goes into the cytoplasm mRNA attaches to a ribosome to be “read”

o Ribosomal RNA (rRNA) Appropriate amino acids are strung together to build a

polypeptide chain by reading codons. Amino acids are attached to Transfer RNA (tRNA)

o tRNA is complementary to mRNAo mRNA strand - ACCo tRNA strand = o mRNA strand - GUCo tRNA strand =

Polypeptide chain = protein

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TranslationAn anticodon is a set of three nucleotides that is complementary to an mRNA codon.An anticodon is carried by a tRNA.

Ribosomes consist of two subunits.-1. The large subunit has three binding sites for tRNA.-2. The small subunit binds to mRNA.

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Translation

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Translation

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Review What are the three parts to the Central Dogma?

How is RNA similar to DNA?

How is RNA different from DNA?

What are the 3 types of RNA?

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Mutations There are two types of mutationsoSex cell mutations: affect the offspring

oBody cell mutations: affect the individual only

Lethal mutations vs. beneficial mutationsoMost mutations are good

DNA Polymerase can usually detect errors

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Causes of Mutations Mistakes in base paring during DNA Replication

o Cause of many genetic disorderso Insertions and deletions

Chemicals: like tobaccoo Can lead to cancer because it changes the

genes that regulate mitosis

Radiation: including UV (sun) and X-rayo Can lead to cancer because it changes the

genes that regulate mitosis

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Point Mutations 1. Substitution – also known as a point mutation

o Point where one nitrogen base is substituted for anothero Sickle Cell Anemia: substitute A for T

mutatedbase

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Frame Shift Mutations 2. Deletions and insertions

o When a nitrogen base is deleted or addedo Also known as - Frame shift mutations- because it moves

the codon up or down

o Changes the sequence of amino acids