Chapter 10 DNADNA

10.1 Discovery of DNA

Griffith’s Experiments (1928)Griffith’s Experiments (1928) Griffith’s experiments showed that Griffith’s experiments showed that

hereditary material can pass from one hereditary material can pass from one bacterial cell to another.bacterial cell to another.

The transfer of genetic material to one cell The transfer of genetic material to one cell from another cell or from one organism to from another cell or from one organism to another organism is called transformation.another organism is called transformation.

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Avery’s Experiments (1940’s)

Avery’s work showed that DNA was the Avery’s work showed that DNA was the heredity material that transfers information heredity material that transfers information between bacterial cells.between bacterial cells.

Hershery-Chase Experiment•Hershey and Chase confirmed that DNA, and not protein, is the hereditary material.

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Structure of DNA10.210.2

DNA – The Blueprint of Life

•Established by James Watson and Francis Crick (1950’s)

•DNA contains the instructions for making proteins within the cell.

•Shape of a double helix

•Made up of repeating sub-units called nucleotides

DNA codes for genes

GeneGene - A segment of DNA that codes for a - A segment of DNA that codes for a protein, which in turn codes for a trait (skin protein, which in turn codes for a trait (skin tone, eye color…etc.), a gene is a stretch of tone, eye color…etc.), a gene is a stretch of DNA.DNA.

Deoxyribonucleic acid - DNA

Monomer: nucleotidesMonomer: nucleotides Each nucleotides has:Each nucleotides has:

1.1. Deoxyribose sugarDeoxyribose sugar

2.2. Phosphate groupPhosphate group

3.3. (1 of 4) nitrogen (1 of 4) nitrogen containing base containing base

The 4 Bases in DNA are:

Thymine (T)

Cytosine (C)

Guanine (G)

Adenine (A)

Nitrogen Rings PurinesPurines have have doubledouble rings of carbon- rings of carbon-

nitrogen (G, A)nitrogen (G, A) PyrimidinesPyrimidines have have singlesingle carbon-nitrogen carbon-nitrogen

rings (C, T)rings (C, T)

Complementary Base Pairing

Base Pairing RulesBase Pairing Rules

1. C and G1. C and G

2. T and A2. T and A

How do the nitrogenous bases stick together?

Hydrogen bonds!Hydrogen bonds! 3 H bonds hold G & C together3 H bonds hold G & C together 2 H bonds hold T & A together2 H bonds hold T & A together

DNA Replication 10.3

Occurs when chromosomes Occurs when chromosomes duplicate before mitosis & duplicate before mitosis & meiosismeiosis

Makes an exact copy of the Makes an exact copy of the DNADNA

H bonds between bases break H bonds between bases break and enzymes “unzip” the and enzymes “unzip” the moleculemolecule

Steps of DNA Replication (pg. 201)

1)1) Enzymes called Enzymes called helicaseshelicases separate the separate the DNA strand breaking the H bonds at the DNA strand breaking the H bonds at the replication forkreplication fork

2)2) Enzymes called Enzymes called DNA polymeraseDNA polymerase add add complementary nucleotidescomplementary nucleotides

3)3) DNA polymerase falls off when done DNA polymerase falls off when done replicating and the result is an replicating and the result is an

identical strand of DNAidentical strand of DNA

Semi-conservative replication-Each old strand of nucleotides serves as a template for each new strand.

Another View of Another View of ReplicationReplication

Mutation•A change in the nucleotide sequence of a DNA molecule.

•DNA proofreading and repair prevent many replication errors.

•Unrepaired mutations that affect genes that control cell division can cause diseases such as cancer.

Protein Synthesis10.410.4

The Central Dogma: the flow of genetic information from DNA to RNA to Protein

Protein Synthesis

2 Parts2 Parts

1. Transcription – makes a RNA molecule makes a RNA molecule complementary to a portion of DNA.complementary to a portion of DNA.

2. Translation – occurs when the sequences occurs when the sequences of bases of mRNA directs the sequence of of bases of mRNA directs the sequence of amino acids in a polypeptide.amino acids in a polypeptide.

RNA

RRiboibonnucleic ucleic AAcidcid

22ndnd type of nucleic acid type of nucleic acid

Monomer = nucleotideMonomer = nucleotide

1.1. Ribose sugarRibose sugar

2.2. 1 of 4 N bases1 of 4 N bases

3.3. Phosphate groupPhosphate group

N-bases:

A, G, C, & A, G, C, & UU Uracil replaces ThymineUracil replaces Thymine

Base pairing rules: A-U, G-CBase pairing rules: A-U, G-C

Purpose:Purpose: to transfer genetic material from to transfer genetic material from DNA (inside the nucleus) to the site of DNA (inside the nucleus) to the site of protein synthesis (in the cytoplasm)protein synthesis (in the cytoplasm)

How does RNA differ from DNA?1.1. Different sugars (deoxyribose vs. ribose)Different sugars (deoxyribose vs. ribose)

2.2. Different N-bases (thymine vs. uracil)Different N-bases (thymine vs. uracil)

3.3. Different shapes (double helix vs. single Different shapes (double helix vs. single strand)strand)

Types of RNA:

1.1. Messenger RNA (mRNA):Messenger RNA (mRNA): Carries genetic info from the nucleus to the Carries genetic info from the nucleus to the

cytoplasmcytoplasm

2.2. Transfer RNA (tRNA):Transfer RNA (tRNA): Carries specific amino acids to the ribosome to Carries specific amino acids to the ribosome to

build the proteinbuild the protein

3.3. Ribosomal RNA (rRNA):Ribosomal RNA (rRNA): Major component of the ribosome organelleMajor component of the ribosome organelle Site of protein synthesisSite of protein synthesis Most abundant type of RNAMost abundant type of RNA

3 Types of RNA

Notebook Quiz1. Outline the flow of genetic material in cells.2. List the 3 parts of a nucleotide.3. What role does helicase and DNA polymerase play in

DNA replication?4. a. Write the complementary strand of DNA to the DNA

template below…b. Write the complementary strand of RNA to the DNA

template below…G A T T A C A T C C G A C T A C

5. What is the purpose of RNA?6. List 2 differences between DNA and RNA (be specific).

How is RNA made?

TranscriptionTranscription The process by which RNA is copied The process by which RNA is copied

from DNA in the nucleusfrom DNA in the nucleus

Steps of Transcription:

1.1. RNA polymeraseRNA polymerase binds to the binds to the promoterpromoter section of DNAsection of DNA

2.2. DNA unwinds and separatesDNA unwinds and separates

3.3. RNA polymerase adds nucleotides RNA polymerase adds nucleotides complimentary to the complimentary to the DNA templateDNA template strand strand

4.4. Process ends once RNA polymerase reaches Process ends once RNA polymerase reaches the the termination signaltermination signal on the DNA on the DNA

Definitions:

RNA polymerase: RNA polymerase: enzyme use to make an enzyme use to make an RNA polymer from DNARNA polymer from DNA

Promoter: Promoter: Starting point on DNAStarting point on DNA DNA template:DNA template: Strand of DNA that RNA is Strand of DNA that RNA is

complementary to (create from)complementary to (create from) Termination signal: Termination signal: Ending point on DNAEnding point on DNA

Products of Transcription:

mRNA, tRNA, & rRNAmRNA, tRNA, & rRNA

All products move out of the nucleus and All products move out of the nucleus and go into the cytoplasm to be used in protein go into the cytoplasm to be used in protein synthesissynthesis

DNA RNA mRNAtRNArRNA

Protein Synthesis: The making of proteins at the ribosomeThe making of proteins at the ribosome The amount and kind of proteins produced in a The amount and kind of proteins produced in a

cell determine its structure & functioncell determine its structure & functionProteins carry out the genetic instruction in DNA

Protein Review:

Monomer = amino acidsMonomer = amino acids 20 different types20 different types

Linked together byLinked together by peptide bonds

Sequence of amino acids determines the Sequence of amino acids determines the proteins structure and functionproteins structure and function

The Genetic Code:

The correlation between The correlation between nucleotide nucleotide sequence (DNA or RNA) and sequence (DNA or RNA) and amino acidamino acid sequence (protein)sequence (protein)

Codons: Codons: combination of 3 mRNA combination of 3 mRNA nucleotides that code for a specific amino nucleotides that code for a specific amino acidacid

Types of codons: 64 codons code for 20 amino acids64 codons code for 20 amino acids

Thus more than one codon codes for an AAThus more than one codon codes for an AA

Start codon: (AUG) starts the process of : (AUG) starts the process of translationtranslation

Stop codons: (UAA, UAG, UGA) ends the : (UAA, UAG, UGA) ends the process of translationprocess of translation

Circular Genetic Code

Translation:

The process of assembling The process of assembling polypeptides (proteins) from polypeptides (proteins) from nucleotide sequence in mRNAnucleotide sequence in mRNA

““Translating” from one Translating” from one language (nucleotides) into language (nucleotides) into another language (amino acids)another language (amino acids)

Steps of Translation

1.1. Initiation: Initiation: mRNA binds to the ribosome and the mRNA binds to the ribosome and the tRNA carrying methionine binds to the tRNA carrying methionine binds to the start start codoncodon

2.2. Elongation: Elongation: as mRNA codons move through as mRNA codons move through the ribosome, tRNA’s add specific amino acids the ribosome, tRNA’s add specific amino acids to the growing polypeptide chainto the growing polypeptide chain

3.3. Termination and Disassebly: Termination and Disassebly: the process the process continues until a continues until a stop codon is reached and the is reached and the newly made protein is releasednewly made protein is released

So what is the Central Dogma?

The flow from The flow from DNADNA to to RNARNA to to ProteinProtein

Notebook Quiz1)1) What type of RNA is pictured here? What is its What type of RNA is pictured here? What is its

function?function?

2)2) List the 4 bases in RNA?List the 4 bases in RNA?

3)3) What is the function of mRNA?What is the function of mRNA?

4)4) Define translation. Define translation.

5)5) Where are proteins assembled in the cell?Where are proteins assembled in the cell?

6)6) Describe the flow of genetic material in the cell. Describe the flow of genetic material in the cell. In other words, how do cells make proteins? In other words, how do cells make proteins?

#1) T A C C G G A T G C C A G A T C A A A T C#1) T A C C G G A T G C C A G A T C A A A T C