2.3 DNA DNA gene RNA mutation Lesson 3

What is DNA? Stands for deoxyribonucleic acid 2.1 The Cell Cycle and Cell Division Genetic material in the nucleus of cells A chemical code that contains information for an organism’s growth and function DNA helps determine nearly everything your body is and does Lesson 3

Discovering DNA In 1952, Rosalind Franklin discovered that DNA is two chains in a spiral form 2.1 The Cell Cycle and Cell Division In 1953, James Watson and Francis Crick made a model of a DNA molecule Lesson 3

DNA’s Structure A double helix or twisted ladder Sugar –phosphate backbone (sides of ladder) Sugar is deoxyribose 2.1 The Cell Cycle and Cell Division Four nitrogen bases make up the rungs Adenine (A) always pairs with Thymine (T) Cytosine (C) always pairs with Guanine (G) Lesson 3

Structure of DNA (cont.) 2.1 The Cell Cycle and Cell Division Lesson 3

Structure of DNA (cont.) Click here to see a short animation online. Click on this file Lesson 3

Copying DNA Occurs during interphase before mitosis The two sides unwind and unzip New bases pair with bases on original DNA 2.1 The Cell Cycle and Cell Division Lesson 3

Copying DNA (cont.) Lesson 3

Copying DNA (cont.) Click here to see a short animation online. Click on this file Lesson 3

Genes The instructions for making a specific protein are found in a gene which is a section of DNA on a chromosome Each chromosome contains hundreds of genes Lesson 3

Making Proteins Genes are found in the nucleus, but proteins are made on ribosomes in cytoplasm The codes for making proteins are carried to the ribosomes by RNA Lesson 3

Ribonucleic Acid (RNA) RNA is made in the nucleus from DNA RNA is a single strand RNA has the nitrogen bases A, G, C, and U (uracil) The sugar-phospate backbone contains the sugar ribose There are three types of RNA mRNA (messenger RNA) rRNA (ribosomal RNA) tRNA (transfer RNA) Lesson 3

Ribonucleic Acid (RNA) (cont.) Lesson 3

Controlling Genes Cells control genes by turning some genes off and turning other genes on Each cell uses only some of the thousands of genes that it has to make proteins For example, muscle proteins are made in muscle cells, cells in the eye produce proteins for eye color, cells in the stomach produce proteins to digest food If the incorrect proteins are produced, the organism cannot function properly Lesson 3

Mutations Sometimes mistakes happen when DNA is being copied These mistakes, called mutations, are any permanent change in the DNA sequence of a gene or chromosome Incorrect proteins are made Some mutations result in a missing or extra chromosome Lesson 3

Results of Mutations Mutations can occur in body cells (it may or may not be life threatening) or in sex cells (all the cells in the organism will be affected) Mutations can be harmful, beneficial, or have no effect on the organism Mutations add variety to a species when the organism reproduces Lesson 3

Section 3 DNA pages Click here to open and read text section on DNA. This is the handout given to you in class. This file will open in PDF format. Lesson 3

Lesson 1 Review 1.A 2.B 3.C 4.D 1. Describe how DNA makes a copy of itself. 2.Explain how the codes for proteins are carried from the nucleus to the ribosomes. 3.Apply: A strand of DNA has the bases AGTAAC. Using letters, show a matching DNA strand. 4.Use a Venn diagram, compare and contrast DNA and RNA. 5.Construct a diagram of the structure of DNA. Label the parts. 2.1 The Cell Cycle and Cell Division Lesson 3 3 Review

Lesson 1 Review 1.A 2.B 3.C 4.D What is DNA? Each side of the DNA ladder is made up of sugar-phosphate molecules, and the rungs of the ladder are made up of nitrogen bases. When DNA is copied, the new DNA has bases that are identical to those of the original DNA. 2.1 The Cell Cycle and Cell Division 3 Summary Lesson 3

Lesson 1 Review 1.A 2.B 3.C 4.D Genes The instructions for making a specific protein are found in genes in the cell nucleus. Proteins are made on ribosomes in the cytoplasm. There are three main kinds of RNA – mRNA, rRNA, and tRNA. 2.1 The Cell Cycle and Cell Division 3 Summary Lesson 3

Lesson 1 Review 1.A 2.B 3.C 4.D Mutations If DNA is not copied exactly, the resulting mutations may cause proteins to be made incorrectly. 2.1 The Cell Cycle and Cell Division 3 Summary Lesson 3

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