CH. 8IDENTIFYING DNA AS THE GENETIC MATERIAL

CH. 5 & 6 REVIEW•ANSWER THE FOLLOWING QUESTIONS:•1. What macromolecule group does DNA & RNA belong in?•2. What monomer do we use to assemble the macromolecule group from question #1.

CH. 5 & 6 REVIEW•ANSWER THE FOLLOWING QUESTIONS:•3. What is a nucleotide?•4. What would a nucleotide for DNA contain?•5. What would a nucleotide for RNA contain?

• Ch. 8.1 – Identifying DNA as the Genetic Material• Griffith finds a “transforming principle.” - NOTES

• Ch. 8.1 – Identifying DNA as the Genetic Material• Griffith finds a “transforming principle.”-

QUESTION & ANSWER:• 1. What was “transformed” in Griffith’s

experiment?• That the R bacteria in the presence of the dead S

bacteria became pathogenic.• 2. Explain how the results support the

experimenters conclusion.• The mice dying when they shouldn’t have means

that the S bacteria must have contained some information that was able to change the harmless bacteria t deadly bacteria.

• Ch. 8.1 – Identifying DNA as the Genetic Material• Avery Identifies DNA as the transforming principle - NOTES

• Ch. 8.1 – Identifying DNA as the Genetic Material• Avery Identifies DNA as the transforming

principle – QUESTION & ANSWERS:• 1. How did Avery and his group identify the

transforming principle?• 1st identifying the 2 components: proteins &

DNA• Used enzymes to break down the protein & the

R-bacteria were still transformed to S bacteria killing the mice.• Only when an enzyme to break down DNA did

the transformation failed to occur.

• 2. Explain how the results support their conclusions for the transforming principle.• By using the enzyme to break down DNA and

not having the transformation occur.

• Ch. 8.1 – Identifying DNA as the Genetic Material• Hershey & Chase confirm that DNA is the genetic material – NOTES

• Ch. 8.1 – Identifying DNA as the Genetic Material• Hershey & Chase confirm that DNA is the genetic material –

QUESTIONS & ANSWERS:• 1. Summarize how Hershey & Chase confirmed that DNA is the

genetic material.• A: They labeled the protein of bacteriophages with radioactive sulfur

and their DNA with radioactive phosphorus. The bacteriophages were allowed to infect bacteria.

• 2. Summarize why the bacteriophage was an excellent choice for research to determine whether genes are made of DNA or proteins?

• A: A bacteriophage consists of little more than a protein coat surrounding DNA. The protein coat is left behind when the viral DNA enters a bacterium.

• 3. Explain how the results support their conclusions.• A: That the phage’s DNA had entered the bacteria, but the protein

had not, convincing scientists that the genetic material is DNA & not protein.

•Review•1. What did Hersey & Chase know about bacteriophages that led them to use these viruses in their DNA experiments?

•ANSWER: •That bacteriophages are made up of a protein coat surrounding DNA.

• 8.2 – Structure of DNA•DNA is composed of 4 types of nucleotides (monomer):•Nucleotide composed of: •Phosphate group•5 carbon sugar•Nitrogen base

• DNA is composed of 4 types of nucleotides con’t.• Nucleotide in DNA is composed of:• Phosphate group• Deoxyribose sugar• Nitrogen base• Cytosine = C• Thymine = T• Adenine = A• Guanine = G

• Nucleotide in RNA is composed of:• Phosphate group• Ribose sugar• Nitrogen base• Cytosine = C• Uracel = U (replaces thymine)• Adenine = A• Guanine = G

• Letter abbreviations refer both to the base & to the nucleotides that contain that base

• DNA is composed of 4 types of nucleotides con’t.• CHARGAFF’S RULE:• A = T• G = C• QUESTION:•What is the only difference among the 4 DNA

nucleotides?•Which part of a DNA molecule carries the

genetic instructions that are unique for each individual; the sugar-phosphate backbone or the nitrogen-containing bases? Explain.

ANSWER TO QUESTIONS

•1. THE 4 NITROGEN BASES.•2. THE NITROGEN BASES, BECAUSE THE REMAINING PARTS OF THE NUCLEOTIDE ARE IDENTICAL.

•Watson & Crick Developed an accurate model of DNA - NOTES

•Watson & Crick Developed an accurate model of DNA – QUESTION & ANSWER:•What bases are considered pyrimidines &

purines?• Pyrimidines = T & C• Purines = A & G

•How did the Watson & Crick Model explain Chargaff’s rules?• The pyrimidine – thymine a single ringed

base pairs with a purine – adenine a double ringed base so that the double helix will be able to maintain the correct shape.

•Nucleotides always pair in the same way.•DNA nucleotides of a single strand are

joined together by covalent bonds connecting the sugar of one nucleotide to the phosphate of the next nucleotide.•Alternating sugars & phosphates form

the sides of a double helix sort of like a twisted ladder.•DNA double helix is held together by

hydrogen bonds between the bases in the middle.

•Nucleotides always pair in the same way – QUESTIONS & ANSWERS:•What sequence of bases would pair with

the following sequence: T T A C G C G A C

•A A T G C G C T G

•8.3 – DNA Replication•Replication copies the genetic information•Watson & Crick’s experiments showed that one strand of DNA is used as a template to build the other strand•Guarantees that each strand of DNA is identical.

• Proteins carry out the process of replication• How :• DNA is unzipped at numerous places (H bonds

broken)• Free floating nucleotides pair with the exposed

bases (template strands)• DNA polymerase bonds the nucleotides together

to form the new strands that are complementary to the template strand (original strand).

• Creates 2 identical molecules of DNA.• Each DNA molecule has an original & a new

strand.• Why DNA replication is called semiconservative

replication.

• DNA Replication

•Replication is fast & accurate•Replication is fast because the DNA

strand is opened at hundreds of different points & allowing nucleotides to be added at many spots at the same time.•Proofreading is carried out at the same

time that nucleotides are added.•DNA polymerase can detect errors &

make corrections.•Pg. 238, fig. 8.9 shows this process

• 8.4 TRANSCRIPTION• RNA carries DNA’s instructions• Central Dogma• Information flows from DNA to RNA to

proteins • Transcription converts a DNA message into

an intermediate molecule, called RNA.• Translation interprets an RNA message into

a string of amino acids, called a polypeptide.• Either a single polypeptide or many

polypeptides working together make up a protein.

•RNA carries DNA’S instructions con’t.•Prokaryotic cells:•Replication, transcription, and

translation all occur in the cytoplasm at approximately the same time.

• Eukaryotic cells:•Replication, transcription, and

translation occur in different locations.•Replication & transcription – nucleus• Translation – occurs in the cytoplasm

•RNA carries DNA’s instructions con’t.•RNA acts as an intermediate link between

DNA in the nucleus & protein synthesis in the cytoplasm.•Gets used then destroyed.•RNA is single stranded, contains ribose

sugar & has uracil instead of thymine•A (DNA) = U (RNA)• T (DNA) = A (RNA)•G (DNA) = C (RNA)•C (DNA) = G (RNA)

•Transcription makes 3 types of RNA•Transcription is the process of copying a sequence of DNA to produce a complementary strand of RNA.•Part of the chromosome, called a gene, is transferred into an RNA message.•Transcription is catalyzed by RNA polymerase.

• Transcription produces 3 major types of RNA molecules•mRNA (messenger RNA) – an

intermediate message that is translated to form a protein• rRNA (ribosomal RNA) – forms part of

ribosomes, a cell’s protein factories• tRNA (transfer RNA) – brings amino acids

from the cytoplasm to a ribosome to help make the growing protein.•Pg. 241, Fig. 8.11 visualizes transcription

• Transcription vs. replication• Similarities • Happen in nucleus of eukaryotic cells• Need enzymes to begin the process• Unwind the DNA double helix• Complementary base pairing to the DNA strand• Regulated by the cell

• Differences • Replication makes sure each new cell will have one complete

set of genetic instructions & occurs only once during each round of the cell cycle.• Transcription could make hundreds or thousands of copies of

certain proteins or the rRNA or tRNA molecules needed to make proteins based on the demands of the cell, using a single stranded complementary mRNA strand.

• 8.5 TRANSLATION• Amino acids are coded by mRNA base sequences• Translation is the process that converts, or

translates, an mRNA message into a polypeptide.• Could be 1 or more polypeptides to make up

a protein• Language of nucleic acids:• DNA – uses 4 nucleotides = A, G, C, & T• RNA – uses r nucleotides = A, G, C, & U• Language of proteins uses 20 amino acids

• Triplet Code• Genetic code uses codons, which is read in groups of 3

nucleotide bases• Codon is a 3 nucleotide sequence that codes for a particular

amino acid, referred to as the reading frame.• First 2 nucleotides are usually the most important in coding for

an amino acid• Start codon – signals the start of translation and the amino

acid is methionine• 3 stop codons – signal the end of the amino acid chain.• If reading frame is changed, changes protein or even can

prevent a protein from being made.• Almost all organisms, including viruses, follows the genetic

code.• This allows scientists to insert a gene from 1 organism into

another organism to make a functional protein.

• GENETIC CODE

• Genetic Code

• DETERMINE WHAT AMINO ACID SEQUENCES ARE CREATED FROM THE FOLLOWING STRINGS OF NUCLEOTIDES

•1) A U G A C C A A C A G C•A) methionine(start), threonine, asparagine, serine

•2) A U G C C C C A A U G A•A) methionine(start), proline, glutamine, stop

•Amino acids are linked to become a protein•Review:•mRNA is a short lived molecule that

carries instructions from DNA in the nucleus to the cytoplasm•mRNA message is read in groups of 3

nucleotides called codons•How it translates the codon into an amino

acid requires the use of rRNA & tRNA molecules

• Amino acids are linked to become a protein• Ribosomes are made of a combination of rRNA & proteins &

they catalyze the reaction that forms the bonds between amino acids.• Ribosomes have a large & small subunit that fit together & pull

the mRNA strand through.• Small unit holds the mRNA strand & the large subunit holds

onto the growing protein• tRNA carries amino acids from the cytoplasm to the ribosome• Has an L shape to the tRNA molecule, one end of the L is

attached to the specific amino acid & the other end of the L, is called the anticodon, which recognizes a specific codon.• Anticodon is a set of 3 nucleotides that is complementary

to an mRNA codon.

• PG. 246, Fig. 8.16 Translation• Read pg. 247

• 8.6 – GENE EXPRESSION & REGULATION• mRNA processing• Important part of gene regulation in eukaryotic cells

is RNA processing.• mRNA that is produced by transcription needs to be

edited• Exons are nucleotide segments that code for parts

of the protein.• Introns are nucleotide segments that are located

between the exons• Introns are removed from mRNA before it leaves

the nucleus.• Exons are joined back together

• TRANSLATION

• 8.7 MUTATIONS• Some mutations affect a single gene & others affect the entire

chromosome• Mutation is a change in an organism’s DNA• Types of gene mutations:• Point mutation – a mutation in which one nucleotide is

substituted for another.• DNA polymerase could find & correct mistake, if not may

permanently change an organism’s DNA• Frameshift mutation – involves the insertion or deletion of a

nucleotide in the DNA sequence• Affects the polypeptide more than a point mutation

(substitution)• Causes the reading frame from point of insertion or

deletion to change the remaining amino acids

•MUTATIONS•ORIGINAL NUCLEOTIDE SEQUENCE:•A U G C C G U U A A C G C G A U C C G G •READS:•MUTATED NUCLEOTIDE SEQUENCE:•A U G C A C G U U A A C G C G A U C C G G •READS:

• Types of chromosomal mutations:• Gene duplication:• During crossing over chromosomes do not align & the

chromosomal segments are different sizes. The chromosome receiving the larger segment would have part of the chromosome that is duplicated.

• Gene deletion:• During crossing over chromosomes do not align & the

chromosomal segments are different sizes. The chromosome receiving the smaller segment would have part of the chromosome that is deleted.

• Translocation: • A piece of one chromosome moves to a non-

homologous chromosome.

• Mutations may or may not affect phenotype. • Phenotype – Collection of all of an organism’s physical

characteristics. • Ex: black hair, blue eyes, attached ear lobes.

• Chromosomal mutations• Usually have big affect on organisms• Ex: may break a gene causing it not to function • Ex: may create a new hybrid gene with a new function• Ex: may cause a gene to be more or less active

• Gene mutations – could have a bad affect, no affect, or create a beneficial mutation• Could change the active site for an enzyme & now it cannot

accept the substrate• Could affect how protein folds & possibly destroying the

protein’s function• Could create a premature stop, making protein nonfunctional

• Impact on offspring• Mutations can happen in body cells & in germ cells.• Body cell mutations only affect that individual• Germ cell mutations may be passed to offspring • Can be source of genetic variations, which is the basis

of natural selection.• Will affect the phenotype of offspring• Could be harmful & the offspring do not develop

properly or could die before reproducing• Could be mutations not well suited to environment

& the alleles will be removed from the population• Could be a mutation that is well suited to

environment & the alleles will be increased in the population

• http://staff.tuhsd.k12.az.us/gfoster/standard/bmut.htm

•Mutations can be caused by several factors•Mutagens – agents in the environment

that can change DNA.• Speed up the rate of replication errors•Break DNA strands•Cause cancer• Types of mutagens:•UV light• Industrial chemicals