1.What are the three components of this DNA nucleotide? 2. What is the function of DNA in the cell?

Section 11.1 Summary – pages Although the environment influences how an organism develops, the genetic information that is held in the molecules of DNA ultimately determines an organism’s traits. DNA achieves its control by holding the instructions on how to make all different kinds of proteins. DNA

Section 11.1 Summary – pages All actions, such as eating, running, and even thinking, depend on proteins called enzymes. So what? Why are proteins important???? DNA You are composed of proteins- your skin contains proteins….organs, muscles, bones…..

Section 11.1 Summary – pages Enzymes are proteins that control the chemical reactions needed for life. Why is this important??? What do enzymes do?

Section 11.1 Summary – pages DNA is a polymer made of repeating subunits called nucleotides. Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base. Phosphate group Sugar Nitrogenous base What is DNA made of?

Section 11.1 Summary – pages The phosphate group is composed of one atom of phosphorus surrounded by four oxygen atoms. The simple sugar in DNA, called deoxyribose, gives DNA its name—deoxyribonucleic acid. What is DNA made of? Sugar Phosphate group

Section 11.1 Summary – pages A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen. What is DNA made of? Nitrogenous base

Section 11.1 Summary – pages In DNA, there are four possible nitrogenous bases: Adenine (A)Guanine (G)Thymine (T)Cytosine (C) What is DNA made of?

Section 11.1 Summary – pages Thus, in DNA there are four possible nucleotides, each containing one of these four bases. What is DNA made of?

Section 11.1 Summary – pages The phosphate groups and sugar molecules form the backbone of the chain DNA STURCTURE The nitrogenous bases stick out like the teeth of a zipper. Nucleotide

Section 11.1 Summary – pages The phosphate groups and sugar molecules form the backbone DNA STURCTURE The nitrogenous bases stick out like ladder rungs in the middle Nucleotide “Legs of ladder” Phosphate & Sugar Backbone Nitrogenous Base (A,T,G or C) “Rungs of ladder”

Section 11.1 Summary – pages In DNA, adenine always pairs with thymine, A --- T and guanine always pairs with cytosine. G --- C DNA STRUCTURE These paired bases are called complementary base pairs.

Section 11.1 Summary – pages When something is twisted like a spring, the shape is called a “helix”. Because DNA is composed of two strands twisted together, its shape is called double helix. DNA STRUCTURE

Section 11.1 Summary – pages Chromosome The sequence of nucleotides forms the unique genetic information of an organism. The closer the relationship is between two organisms, the more similar their DNA nucleotide sequences will be. DNA STRUCTURE

Section 11.1 Summary – pages Scientists use nucleotide sequences to determine evolutionary relationships among organisms, to determine whether two people are related, and to identify bodies of crime victims. DNA STRUCTURE

Section 11.1 Summary – pages Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes. The DNA in the chromosomes is copied in a process called DNA replication. Without DNA replication, new cells would have only half the DNA of their parents. DNA REPLICATION

Replication of DNA

ReplicationFork Parental DNA Molecule 3’ 5’ 3’ 5’ DNA Template New DNA Parental DNA

Section 11.1 Summary – pages DNA is copied during interphase prior to mitosis and meiosis. It is important that the new copies are exactly like the original molecules. DNA REPLICATION

Proofreading New DNA Enzymes proofread and correct these mistakesEnzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errorsThe new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors

Talk to the people next to you about what a DNA nucleotide is and what it is made of. 2.What is a DNA nucleotide made of? 3.How many nucleotides are in the pic below?

Talk to the people next to you about when DNA replication takes place. 4. When does DNA replication occur?

Talk to the people next to you and make sure you understand complementary base pairs in DNA. 1.What is the complementary strand for: ATCGGATCG

Talk to the people next to you about what DNA replication starts and ends with. 5. What is the end result of DNA replication?

Section 1 Check Question 1 Which of the following is NOT a component of DNA? D. proteins C. nitrogenous bases B. phosphate groups A. simple sugars The answer is D.

Section 1 Check Question 2 Which of the following correctly comprises a complimentary base pair? D. cytosine – thymine C. guanine – adenine B. thymine – guanine A. adenine – thymine The answer is A.

Question 3 Which DNA strand can base pair with the DNA strand shown here (Top of pic to bottom)? D. T-C-C-A-G C. T-G-C-A-G B. T-G-C-A-T A. T-A-C-G-T

To return to the chapter summary click escape or close this document. The answer is B, T-G-C-A-T. In DNA, adenine pairs with thymine and cytosine pairs with guanine. T G C A T