Objective(s): I can define genes and describe their functions. I can define mutations.

What is a gene? Mutation? https://youtu.be/ubq4eu_TDFc Answer the last question in the video Mutation?

A gene is a specific segment of DNA that provides instructions for an inherited trait. Each gene has a starting point and an ending point. DNA is read in one direction, just as you read words from left to right. Genes are responsible for the inherited traits of an organism. Organisms that reproduce sexually have two versions of the same gene for every trait—one version from each parent.

What does DNA look like? Genes are segments of DNA that relate to a certain trait. The code in the nucleotide order has information about which proteins the cells should build. The types of proteins that your body makes help determine your traits. Copyright © Houghton Mifflin Harcourt Publishing Company 4

Replication and Mutation Unit 2 Lesson 6 DNA Structure and Function Replication and Mutation How are copies of DNA made? The cell makes copies of DNA molecules through a process known as replication. During replication, the two strands of DNA separate. The bases on each side of the molecule are used as a pattern for a new strand. Copyright © Houghton Mifflin Harcourt Publishing Company 6

How are copies of DNA made? Unit 2 Lesson 6 DNA Structure and Function How are copies of DNA made? As bases on the original molecule are exposed, complementary nucleotides are added. When replication is complete, there are two identical DNA molecules. Copyright © Houghton Mifflin Harcourt Publishing Company 7

How are copies of DNA made? Unit 2 Lesson 6 DNA Structure and Function How are copies of DNA made? Describe what is happening in the diagram. Copyright © Houghton Mifflin Harcourt Publishing Company 8

When are copies of DNA made? Unit 2 Lesson 6 DNA Structure and Function When are copies of DNA made? Before a cell divides, it copies its DNA. Our cells can replicate DNA in just a few hours, because replication begins in many places along a DNA strand. Many groups of proteins are working to replicate your DNA at the same time. Copyright © Houghton Mifflin Harcourt Publishing Company 9

Complete the DNA sequence by adding complementary bases to the DNA strand. You may use colors or write letters to represent the nucleotide bases. https://www.hmhco.com/content/science/sciencedimensions/na/gr6-8/ese_modd_9780544882270_/book_pages/#cards--6l1_0810_ese_ee1_geneticchangetime/

Figure it out !

Mutations Definition A change in the base-pair sequence of a gene is called a mutation. Cause 1: Most mutations occur when a cell copies its DNA for cell division. As the DNA is copied, base pairs may be added, removed, or substituted.

Effect of a mutation These chance mutations may be beneficial, neutral, or harmful to organisms. For example, a mutation that results in longer fangs may be beneficial if it helps the bush viper grab prey.

Effect of a mutation and diseases In individuals with sickle cell disease, abnormal hemoglobins, oxygen-carrying proteins, develop because of a single amino acid substitution. These abnormal hemoglobins crystallize, deforming the red blood cells and leading to clogs in tiny blood vessels

Cause 2 Mutations can also occur when DNA is exposed to mutagens, substances that cause genetic mutations. Examples of mutagens include UV radiation and the chemicals in cigarette smoke.

Explain and Elaborate (SEP, CCC) Activity # 1: Think, Pair, and Share Discuss with your elbow partners the questions on page 77 in their textbooks.

Activity # 2: work in pairs to solve Exercise # 3-page 79

Types of mutation 1

Types of mutation 2

Types of mutation 3

Unit 2 Lesson 6 DNA Structure and Function What are mutations? Mutations are changes in the number, type, or order of bases on a piece of DNA. There are three main kinds of mutations: deletions, insertions, and substitutions. Copyright © Houghton Mifflin Harcourt Publishing Company 23

What are mutations? In a deletion mutation, a base is left out. Unit 2 Lesson 6 DNA Structure and Function What are mutations? In a deletion mutation, a base is left out. In an insertion mutation, an extra base is added. The most common mutation, substitution, happens when one base replaces another. Copyright © Houghton Mifflin Harcourt Publishing Company 24

Unit 2 Lesson 6 DNA Structure and Function What are mutations? Which type of mutation is shown in each row? (The first row is the original sequence.) Copyright © Houghton Mifflin Harcourt Publishing Company 25

Unit 2 Lesson 6 DNA Structure and Function What are mutations? Mutations can happen by random error, and also by damage to the DNA molecule by physical or chemical agents called mutagens. Cells make proteins that can fix errors in DNA, but sometimes the mistake is not corrected. The mistake then becomes part of the genetic code. Copyright © Houghton Mifflin Harcourt Publishing Company 26

Unit 2 Lesson 6 DNA Structure and Function What are mutations? A genetic disorder results from mutations that harm the normal function of the cell. Some genetic disorders are inherited, or passed on from parent to offspring. Other disorders result from mutations during a person’s lifetime. Most cancers fall in this category. Copyright © Houghton Mifflin Harcourt Publishing Company 27

Protein Factory What is the role of DNA and RNA in building proteins? Unit 2 Lesson 6 DNA Structure and Function Protein Factory What is the role of DNA and RNA in building proteins? Some of the information in the DNA is copied to a separate molecule called RNA, or ribonucleic acid. RNA is used to build proteins. Copyright © Houghton Mifflin Harcourt Publishing Company 28

What is the role of DNA and RNA in building proteins? Unit 2 Lesson 6 DNA Structure and Function What is the role of DNA and RNA in building proteins? Like DNA, RNA has a sugar-phosphate backbone and the bases adenine (A), guanine (G), and cytosine (C). Instead of thymine (T), RNA contains uracil (U). Three types of RNA have special roles in making proteins. Copyright © Houghton Mifflin Harcourt Publishing Company 29

What is the role of DNA and RNA in building proteins? Unit 2 Lesson 6 DNA Structure and Function What is the role of DNA and RNA in building proteins? When a cell needs to make a protein, it makes an RNA copy of a section of the DNA. This is called transcription. In transcription, DNA is used as a template to make a complementary strand of messenger RNA (mRNA). The information in the mRNA is then used to build proteins. This is called translation. Copyright © Houghton Mifflin Harcourt Publishing Company 30

What is the role of DNA and RNA in building proteins? Unit 2 Lesson 6 DNA Structure and Function What is the role of DNA and RNA in building proteins? In translation, the mRNA passes through a protein assembly line within a ribosome. Copyright © Houghton Mifflin Harcourt Publishing Company 31

What is the role of DNA and RNA in building proteins? Unit 2 Lesson 6 DNA Structure and Function What is the role of DNA and RNA in building proteins? A ribosome is a cell organelle made of ribosomal RNA (rRNA) and protein. As mRNA passes through, transfer RNA (tRNA) delivers amino acids to the ribosomes. The order of the bases codes for which amino acid is attached. The amino acids are joined together to form a protein. Copyright © Houghton Mifflin Harcourt Publishing Company 32