Unit 7 (A)-DNA Structure Learning Targets I can describe the role that Wilkins, Franklin, Watson, and Crick had in the discovery of the structure of DNA. – Chargaff’s rule and complementary base-paring – Franklin’s X-ray photograph of DNA and the double helix – Watson and Crick and their 3-D model piecing together the puzzle of DNA’s structure I can describe the structure of DNA. – DNA is a double-stranded molecule. – Each strand of DNA is a polymer consisting of nucleotide monomers. – Each strand is composed of covalently bonded sugar and phosphate molecules and are connected by complementary base pairs (A-T and C-G) like rungs on a ladder. The ladder twists to form a double helix. – A DNA nucleotide is made up of 3 parts (sugar, phosphate, nitrogen base) and is identified by the base it contains: adenine (A), guanine (G), cytosine (C) or thymine (T).

Number of A’s = Number of T’s Number of G’s = Number of C’s Bases pair with each other and Form complementary base pairs. X-shaped pattern in X-ray photo Indicates Double Helix shape. DNA is double helix with bases Paired on the inside. A pairs with T and G pairs with C. Base pairs held together by Hydrogen bonds.

DNA Ladder Model Learning Check: I can identify… □ nucleotide □ nitrogenous base □ deoxyribose sugar □phosphate group □polynucleotide □ double helix □ antiparallel □ sugar- phosphate backbone □ hydrogen bonds □ complementary base pair

Learning Check A. Can you… □ (1) describe the twisted ladder model of DNA? - What makes up each side of the ladder? - What makes up the rungs of the ladder? □ (2) identify which part of DNA is held together by very strong, covalent bonds that do not come apart easily? □ (3) identify which part of DNA is held together by weaker hydrogen bonds that can be broken and pulled apart? □ (4) explain Chargaff’s rule and how it is connected to the idea of complementary base-pairing? □ (5) describe what technology Wilkins and Franklin used to study DNA? □ (6) describe the discovery Franklin made that was the key to unlocking the structure of DNA? □ (7) describe what the X-shape pattern in the X-ray photo of DNA told Watson and Crick?

Warm-up: (On the lined piece of paper where you keep all of your warm-ups) Question: Who are the following scientists? Watson Crick Wilkins Franklin

Unit 7 (B)- DNA Replication Learning Targets I can describe why DNA is important to the function of the cell. Before a cell divides, the instructions are duplicated so that each of the two new cells gets all the necessary information for carrying on life functions. Cells pass on their genetic code by replicating their DNA. I can describe how the structure of DNA is suited for efficient replication and transfer of the genetic information stored in the sequence of nucleotides. I can list the steps needed for DNA replication. – Enzymes unwind and unzip the double helix by breaking the base pairs connecting the double helix. – Each strand and the unpaired bases serves as a template for building a new DNA molecule – Free nucleotides are bonded to the unpaired bases on the template forming a complementary strand. – The final product of replication is two identical DNA molecules.

One duplex is unzipped and copied to produced two duplexes of DNA. Helicase Enzyme Unzips helix Enzyme Helps to copy DNA

Original parental strands provide a template for the production of the new daughter strands.

This type of replication is called semi- conservative because after replication each of the DNA duplexes has kept 1 strand the same and has 1 new strand.

DNA Replication

Learning Check B. Can you… □ (8) describe the steps involved in DNA replication? - What do enzymes need to do first to the DNA double helix? - What is added to each template strand? - What is the final product of DNA replication? □ (9) describe how complementary base pairing is used in replication of DNA? - If the template strand is GCGCGCATTA, then what will the complementary strand be?

Unit 7 (C). Protein Synthesis Learning Targets I can explain how the information stored in DNA is used to instruct the construction of proteins in a cell. I can explain how these protein products are the workers in the cell and are responsible for helping build up and maintaining an organism. (Proteins do work in the cell, proteins signal cells, proteins make up different structures in an organism, proteins help control chemical reactions in the body, proteins help transport materials in to and out of a cell.) I can explain the multi-step process a cell uses to make proteins. First, the DNA code must be transcribed (copied) to messenger RNA (mRNA). Then, the mRNA carries the code from the nucleus to the ribosomes in the cytoplasm. At the ribosome, amino acids are linked together to form specific proteins. The amino acid sequence is determined by the sequence of nucleotides in the mRNA (and ultimately the DNA). I can explain how the structure of RNA is different from DNA. RNA is a single-stranded polymer made up of any combination of four nucleotide monomers linked together. A RNA nucleotide is identified by the base it contains: adenine (A), guanine (G), and cytosine (C) or uracil (U). I can explain why an mRNA copy of DNA is needed to provide a temporary copy of the information in DNA. DNA contains the information for ALL the proteins needed in the cell. The cell itself is efficient and will only make proteins that it currently needs. Multiple mRNA copies get made of the instructions to make 1 protein. Those instructions get sent out to the multiple ribosome (assembly workers) in the cytoplasm. There the ribosomes use the copy of the instructions to make protein. The mRNA copy gets degraded in the cytoplasm when the workers are finished with it.

Warm-up: How is a cell like a factory? What are the instructions for making proteins stored? What are the building blocks of proteins? Where are proteins built in the cell?

So DNA contains the info needed to make products in the cell…how does that affect the organism? DNA determines the amount of melanin in our skin. DNA determines the amount of melanin in our eyes. DNA determines the type of proteins in our hair and our hair texture.

Building blocks DNA mRNA Protein Genetic info in DNA needs to be copied and decoded in order to build the protein product.

Genetic Code is used to determine which amino acids the nucleotide sequence codes for. There are 20 common amino acids and only 4 different possible bases. Combination of 3 bases codes for a particular amino acid. This is called a CODON. Codon= base 1 -base 2 - base 3

DNA and RNA Structure Can you spot the 3 differences? RNA has…

Overview of Protein Synthesis -mRNA copy leaves the nucleus and is decoded at the ribosome to make the protein product I can identify how the following are involved in protein synthesis □nucleus □ DNA □messenger RNA (mRNA) □cytoplasm □ribosome □start codon □transfer RNA (tRNA) □Amino acid □anticodon □codon

Learning Check C. Can you… □ (10) describe why proteins are important. □ (11) identify where the instructions to make proteins comes from. □ (12) describe how mRNA is involved in the process of making proteins. - Where is mRNA made? - What information is contained in the mRNA? - Where does the mRNA take the information? - If the DNA sequence is GGTTAAC, then what would the sequence of the mRNA copy be? □ (13) describe how proteins are constructed. - Where are proteins made? Which cell structure is needed? - Which building blocks are used to make proteins? - How does the sequence of nucleotides code for a particular amino acid? □ (14) describe how tRNA helps make proteins. □ (15) summarize how information flow from DNA to mRNA to protein. - What is transcription? - What is translation?

Unit 7 D-Mutations I can explain how mutations in the DNA bases can alter genes. Inserting, deleting, or substituting different nucleotides can cause mutations in the DNA that can be passed on to every to every cell that develops from it. These mutations can be harmful, helpful, or have no effect at all.

A point mutation occurs when 1 single nucleotide in DNA is changed.

An insertion or deletion can shift how the entire sequence is decoded. Normal DNA DNA with insertion DNA with a deletion

RNA vs. DNA Differences – RNA is only 1 stranded – RNA has ribose sugar instead of deoxyribose sugar – RNA has Us instead of Ts – RNA Has more jobs than DNA Messenger RNA Transfer RNA Similarities – Both are nucleic acids – Both are made up of nucleotides – Both have sugar- phosphate backbones – both have nitrogen bases