DNA and RNA

• Genetics • List the conclusions and how each of these scientist got there:

– Griffith– Avery– Hershey and Chase

• Why did Hershey and Chase grow viruses in cultures that contained both radioactive phosphorus and radioactive sulfur? What might have happened if they only used one?

• How did Watson and Crick’s model explain why there are equal amounts of thymine and adenine in DNA?

Frederick Griffith 1928

TransformationTransformation - process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

Oswald Avery 1944

• World knows a molecule carries the genetic information.

• Doesn’t know if the molecule is a: protein, lipid, carbohydrate, RNA, or DNA

• Avery performs Griffith’s experiment again with a twist.

Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.

Hershey-Chase Experiment 1952

• Good scientists are naturally skeptical.

• Hershey-Chase are testing to see if DNA is the molecule that carries genetic information.

• BacteriophageBacteriophage - virus that infects bacteria

Hershey-Chase Experiment

DNA Structure

• Nucleotide - monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base

Sugar-Phosphate Backbone and Chargaff’s Rule

• Simply states: If I have a certain number of Cytosines I will have about the ______ number of Guanines. Same with A’s and T’s.

Rosalind Franklin 1950 X-Ray Diffraction

• Clues from the X-Ray– Coiled

(forming Helix)

– Double-stranded

– Nitrogeneous bases are in the center

Watson & Crick

• Francis Crick – British physicist

• James Watson – American Biologist– Building a 3D model of DNA– Franklin’s X-Ray opened their eyes to the

Double Helix

• Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other.

Double Helix

Homework StudyGuide12-1 and 12-2

1. List the conclusions and how each of these scientist got there:– Griffith– Avery– Hershey and Chase

2. How did Watson and Crick’s model explain why there are equal amounts of thymine and adenine in DNA?

3. Why did Hershey and Chase grow viruses in cultures that contained both radioactive phosphorus and radioactive sulfur? What might have happened if they only used one?

DNA, DNA replication, and protein synthesis

• Homework – study for quest on Friday– Bio 10 Quest Thursday

– Homework for break • Complete Protein Synthesis Lab• Complete Bio SAT II diagnostic test

– Use any resources available to you!!!

Prokaryote DNA• Prokaryotes

– No Nucleus– Most have one circular chromosomeone circular chromosome located in

the cytoplasm with some plasmids as well– E.Coli (1.6μm diameter)– 4,639,221 base pairs 1.6mm long – Like packing 300m of rope in your backpack

Eukaryotes and DNA

• 1000 time more base pairs than bacterial DNA

• Smallest human chromosome has 30million base pairs of DNA

• How do eukaryotes fit all that DNA in its nucleus?

DNA to Chromosomes

• Vocab– Chromatin - granular material

(uncondensed) within the nucleus; consists of DNA tightly coiled around proteins

– Chromosomes – condensed chromatin

– Histone - globular protein molecule around which DNA is tightly coiled in chromatin

DNA Replication

• During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template, or model, for the new strand.

Read 12-3

• Crossword Puzzle

1. Enzymes unwind DNA

2. Enzymes split “unzip” double helix

3. The enzyme, DNA DNA polymerase,polymerase, finds and attaches the corresponding N-base

4. Each “old” stand serves as a template and is matched up with a new stand of DNA

5. New helixes wind back up.

DNA Replication

A – C – T – T – G – G – A – C

T – G – A – A – C – C – T - G

Homework 12-3 Studyguide

RNA and

Protein Synthesis

• Codon - three-nucleotide sequence on messenger RNA that codes for a single amino acid

• Anticodon - group of three bases on a tRNA molecule that are complementary to an mRNA codon

Protein SynthesisTwo Main Parts

• Transcription– Formation of a single

strand of messenger RNA from DNA in the nucleus

• Translation– Occurs on ribosomes– Cell uses the

information on mRNA to assemble amino acids in the proper order to form specific proteins

Transcription1. Occurs in nucleus

2. Enzymes unwind DNA

3. Enzymes split “unzip” double helix

4. RNA Polymerase binds to promoter sequence on DNA

5. RNA Polymerase transcribes a single strand of mRNA

mRNA Editingbefore going to transcription

• Intron - intervening sequence of DNA; does not code for a protein (not used)

• Exon - expressed sequence of DNA; codes for a protein (used)

Translation

Translation

Genes and Proteins

• Most genes only have instructions for assembling proteins.

• If that’s the case what do proteins have to do with eye color, hair color or height?

Homework

• 12-4 in Guided Reading Workbook

Mutations

• Mutation - change in a DNA sequence that affects genetic information

• Two Main Types:

– Gene Mutation• Mutation that causes a change in a single gene

– Chromosomal Mutation• Mutation that causes a change in an entire

chromosome

Gene Mutations• Point Mutation

(substitution)– mutation that affects a

single nucleotide, usually by substituting one nucleotide for another

• Frameshift Mutation (insertion or deletion)– mutation that shifts the

“reading” frame of the genetic message by inserting or deleting a nucleotide

Chromosomal Mutations

• Chromosomal mutations involve changes in whole chromosomes.

1. What is meant by term base pairing? How is base pairing involved in DNA replication?

2. When a DNA molecule is replicated, how do the new molecules relate to the original molecule?

3. What is a codon?anticodon? How do they relate?4. Explain why controlling proteins in an organism

controls the organism’s traits.5. Name two major types of mutations. What do they

have in common? How are they different? Give an example of each.

6. The word transcribe means “to write out”, and the word translate means “to express in another language.” Review the meanings of transcription and translation in genetics. How do the technical meanings of these words relate to meanings of the words in ordinary language?