Journal 3/7 ATCCGG Don’t forget to write the questions! No homework! Don’t forget to write the questions! Describe the structure of DNA. Draw the complementary DNA strand: ATCCGG Agenda: Structure of DNA worksheet

Journal 3/8 Don’t forget to write the questions! No homework! Don’t forget to write the questions! What two components make up the backbone of DNA? What are the 4 nitrogenous bases? Agenda: Have your DNA and eat it too! lab

With 1 partner: Build your DNA molecule as per the instructions on your handout. 1 model per pair. Label the sugar phosphate backbone, 1 adenine, thymine, cytosine, and guanine. Use masking tape & toothpicks. Answer the questions. Everyone fills in their OWN answer sheet.

Journal 3/6 Don’t forget to write the questions! No homework! Don’t forget to write the questions! Describe what you know about the structure and function of DNA. Agenda: Notes on DNA Structure of DNA worksheet

CHAPTER 10: DNA,RNA & Protein Synthesis

So - What is DNA? It’s in the nucleus of most cells in your body. A DNA molecule is a double strand of nucleotides The Double Helix shape is formed by base pairs attached to a sugar-phosphate backbone.

I. Discovery of DNA 1. Fredrick Griffith 2. Oswald Avery Many scientists had wrongly believed PROTEINS would be the molecules which contained hereditary information. Some scientists who did experiments that proved DNA had genetic information: 1. Fredrick Griffith 2. Oswald Avery 3. Hershey & Chase

James Watson & Francis Crick In 1953 DNA structure discovered Double Helix model. (2 chains of DNA) Showed how DNA could replicate. Relied on work of other scientists: Rosalind Franklin & Maurice Wilkins took X-ray photos of DNA structure ( BUT- Franklin died 1958 before Watson & Crick received Nobel Prize. 1962.)

II. DNA structure Double Helix shape is formed by base pairs attached to a sugar-phosphate backbone. The 4 “ letters” in the genetic code are the 4 nitrogenous bases inside the molecule. (A, T, G, C)

B. Parts of Nucleotides 1. 5 carbon sugar in DNA- deoxyribose (in RNA= ribose) 2. phosphate group 3. nitrogenous bases ( there are 4 different ones) Adenine Guanine Cytosine Thymine (in RNA- no thymine- Uracil is the base)

C. How Chemical Bonds hold DNA together Covalent bonds- on the “Backbone” between sugar & phosphates of 2 nucleotides Hydrogen bonds- zips down the middle- between complementary nitrogenous bases – holds A to T , G to C. www.molecularstation.com/dna/dna-structure/

Nitrogenous bases Pairing Rules: the letters: A,T,G,C These 4 letters make up the genetic alphabet Base Pairing Rules: Adenine always bonds with Thymine (AT) Guanine always bonds with Cytosine (GC)

Quick write: AAACTGCGTAA Draw the complementary strand for the following DNA molecule: AAACTGCGTAA

Answer AAACTGCGTAA TTTGACGCATT Draw the complementary strand for the following DNA molecule: AAACTGCGTAA TTTGACGCATT

Quick write: Draw the complementary strand for the following DNA molecule: CGCGAATA

ANSWER CGCGAATA GCGCTTAT Draw the complementary strand for the following DNA molecule: CGCGAATA GCGCTTAT

Must have 1 purine (a 2 ring shape) plus 1 pyriomidine (1 ring shape) in each pair or they would not “fit” inside ladder of DNA Purines (A, G) double C ring Pyrimidines (T, C) single C ring

Quickwrite How are purines and pyrimidines different?

III. DNA Replication A. Is the process by which DNA is copied in a cell before a cell divides by mitosis, meiosis or binary fission.

B. Steps in Replication 1. Separate- Helicase enzymes separate hydrogen bonds in strands & create replication fork 2. Attach- DNA polymerase enzyme -adds nucleotides 3. Release –DNA polymerase enzyme – now have 2 identical DNA strands oak.cats.ohiou.edu/.../Heredity/Heredity.htm

DNA Replication Fork: DNA synthesis occurs in 2 directions (see blue arrows) from the 5 prime end to the 3prime end on both strands, but in 1 direction overall. The leading strand is the 5 to 3 end and the lagging strand is put together with sections called Okazaki fragments.

DNA unzips & copies itself The original DNA is shown all in blue. The red strands in the daughter DNA are the ones which have been built on the original blue strands during the replication process.

"semi-conservative replication" Each of the daughter molecules is made of half of the original DNA plus a new strand. “Semi-conservative replication" means half of the original DNA is conserved (kept) in each of the daughter molecules.

DNA replication practice: If a DNA strand had the following nucleotide sequence what would the sequence of the complementary daughter strand be? 5'-ATGCGGCTAGAATATTCCA-3' TACGCCGATCTTATAAGGT

C. Errors DNA replication is very accurate. Errors occur ~ 1 in 1 billion paired nucleotides. “Proofreading” enzyme checks for “spelling” errors. *If a mistake does occur- new DNA is different: Mutation- a change in the nucleotide sequence of a DNA molecule. Caused by chemicals, radiation,UV rays. Mutations can be favorable - or harmful. (examples- sickle cell, cancer)

IV Protein Synthesis Flow of Information (DNA to RNA to Proteins) Before protein can be synthesized, the instructions in DNA must first be copied to another type of nucleic acid called messenger RNA. Then -a group of 3 nucleic acids codes for an amino acid & it is built at the ribosomal RNA with help from the transfer RNA

RNA differs from DNA in the following ways: RNA is single stranded while DNA is double stranded. RNA has a sugar called ribose while DNA has a sugar called deoxyribose. RNA has the nitrogenous base uracil while DNA has the base thymine.

B. 3 types RNA: 1. messenger RNA(mRNA) – is the “list” of amino acids needed to build the protein 2. transfer RNA (tRNA) – is the “hook” –picks up amino acids needed to build a protein. 3. ribosomal RNA (rRNA) -is the “place” building occurs

Messenger RNA, or mRNA. Transfer RNA or tRNA. Ribosomal RNA or rRNA carries the code for building a protein from the nucleus to the ribosomes in the cytoplasm. It acts as a messenger. IT’S THE “LIST” Transfer RNA or tRNA. picks up specific amino acids in the cytoplasm & brings them into position on ribosome where they are joined together in specific order to make a specific protein. IT’S THE “HOOK” Ribosomal RNA or rRNA place for protein synthesis. IT”S THE “PLACE”

C. Steps in Transcription-making RNA 1. Attach enzyme: RNA polymerase (enzyme)– binds to promoter area on DNA 2. Add: Nucleotides added & joined by the enzyme (RNA polymerase) Stop: Termination signal -stop- RNA polymerase releases both DNA & new RNA molecules

Transcription: making RNA from DNA http://www.phschool.com/science/biology_place/biocoach/transcription/tcproc.html

TRANSCRIPTION practice: Which nitrogen base CAN’T you use during transcription ? _____________ Use the DNA code provided below to copy an m-RNA: 1. ACTGGATAC ________________ 2. ACGGATCGTGCCTA ______________________

D. Proteins Review of protein structure -recall that proteins are made of amino acid monomers (building blocks) joined together with peptide bonds -there are 20 different amino acids, the order they are joined determines the structure & function of the proteins. -proteins can be very large, complicated molecules

mRNA codons for specific amino acids Each 3 nucleotide sequence (letters) in mRNA encodes for 1 specific amino acid, or a “start” or “stop” signal. Each 3 nucleotide group is called a codon. The genetic code- means the rules that relate how a particular sequence of nitrogenous bases corresponds to a particular amino acid. (3 letters = 1 amino acid)

teachline.ls.huji.ac.il/72693/weekly2.html

E. Steps in Translation (Making Proteins from RNA) Initiation- tRNA & mRNA join together. (The codon is on the mRNA, the “anticodon” is on tRNA) The tRNA has an amino acid attached to it) Elongation- continued as ribosome moves the distance of 1 codon on mRNA Protein- is built with new tRNAs attaching each amino acid as it reads the codons on the mRNA. Termination- ribosome reaches “stop” codon on the mRNA Disassembly – each piece is free. (see sequence page 208-209 in textbook)

How a protein is translated: http://kentsimmons.uwinnipeg.ca/cm1504/proteinsynth.htm

mRNA, tRNA & ribosomal RNA all work together to add amino acids to a polypeptide (a protein) http://www.frontiers-in-genetics.org/page.php?id=protein-synthesis_en

http://kentsimmons.uwinnipeg.ca/cm1504/proteinsynth.htm

Remember: Replication- copying DNA from DNA Transcription- making RNA from DNA Translation- making proteins