Review 1. Describe how chromosomes and DNA are related. 2. The DNA molecule is shaped like a twisted ladder. (a) What are the sides of the ladder made of? (b) What are the rungs made of? (c) Name each of the molecules that make up the rungs. 3. Describe how the DNA molecule replicates. 4. Which base joins with each base listed below? (a) cytosine (b) thymine (c) adenine (d) guanine Answers… 1. Chromosomes are made up of DNA. 2. (a) The sides of the “ladder” are made of phosphate and sugar joined together. (b) The rungs are made of nitrogenous bases. (c) The nitrogenous bases are adenine, thymine, cytosine, and guanine. 3. To replicate, a DNA molecule splits and new bases are added onto each of the open sides to make two identical DNA molecules. 4. (a) cytosine pairs with guanine (b) thymine pairs with adenine (c) adenine pairs with thymine (d) guanine pairs with cytosine Marks Science 9 Biology Marks 3 tests 30% 3 major assignments 30% Daily assessment and quizzes 20% Notebook 10% Participation 10% How genes make proteins Science 9 Biology lesson #4 What you need to learn • that members of the same species have the same number genes but different traits. • the difference between DNA and RNA • that amino acids are the building blocks of proteins • some common proteins and their functions • how ribosomes make proteins using RNA and amino acids Genes are stored on DNA • A gene is a short section of DNA that contains the instructions to make a specific protein. The Genome • All of an organism’s genes (its entire DNA) is called the genome. • The human genome = 23 pairs of chromosomes • almost every cell in the body has those chromosomes Genes to Proteins (Protein synthesis) 1. A gene segment of DNA separates and an RNA molecule is constructed from one half of the DNA. RNA is very similar to DNA except it has only one strand (DNA is double strand) 2. The RNA strand travels from the nucleus to the cytoplasm. 3. The ribosome “reads” the instructions on the RNA and assembles the protein out of amino acids floating in the cytoplasm. Traits • All members of the same species have the same number and types of genes. They are responsible for making hair, nails, eyes, and every other human characteristic. • Within a species, there are different versions of the same gene. The different versions produce slightly different variations, or traits, for each characteristic. Review Questions 1. Describe how DNA and genes are related. 2. How is the genetic code transferred from the nucleus into the cytoplasm? 3. How is RNA different from DNA? 4. Place the following events of protein synthesis in the correct order. (a) Ribosomes manufacture protein. (b) RNA is formed from a gene.(c) Part of a DNA molecule “unzips.” (d) RNA carries the genetic code into thecytoplasm. (e) Amino acids attach to ribosomes. 1 2 3 4 Answers 1. Describe how DNA and genes are related. 2. How is the genetic code transferred from the nucleus into the cytoplasm? 3. How is RNA different from DNA? 4. Place the following events of protein synthesis in the correct order. (a) Ribosomes manufacture protein. (b) RNA is formed from a gene.(c) Part of a DNA molecule “unzips.” (d) RNA carries the genetic code into thecytoplasm. (e) Amino acids attach to ribosomes.