The Nucleus Controls the Functions of Life Section 4.1 Biology Unit CHAPTER 4 The Nucleus Controls the Functions of Life Section 4.1

The Nucleus and DNA We know that the nucleus is the control centre of the cell. The nucleus directs every single activity that the cell carries out. The nucleus tells the cell how to grow, how to make proteins, how to repair itself and when to divide. Have you ever stopped and wondered how something so incredibly small can command so much power and authority over our lives? Essential Questions What is DNA? What does DNA look like? What is the role of DNA in the everyday function of your cells? How does a cell produce proteins?

Cell Parts and Organelles Cells are equipped with many structures that allow the cell to perform a variety of functions. Animal Cell See page 122

The Nucleus Structure: The dense dark part at the centre of the cell Function: The control centre of the cell. Controls all of the cell’s activities.

DNA Function What is DNA? The nucleus of every cell in your body contains DNA.  Deoxyribonucleic Acid DNA is the molecule that has the master set of instructions for: how cells function what cells they will become how they will grow, repair themselves, and divide when they will die The puropose of the DNA is to store information/instructions on how to make PROTEINS. See page 126

DNA Structure The Structure of DNA DNA looks like a twisted ladder called a double helix. Two strands wrap around each other in a spiral shape.

DNA Structure DNA is made up of 3 parts/components. This whole structure is called a NUCLEOTIDE

DNA Structure The sides of the DNA ladder are made of repeating sugar and phosphate molecules The steps of the ladder are made of four nitrogen bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) The bases join in a specific way A always joins with T G always joins with C

DNA Structure Mutation See page 126

Chromosomes Structure: DNA and associated proteins Chromatin = uncoiled Chromosomes = tightly coiled Function: The template for making all proteins

DNA in the Nucleus Most of the time DNA is in the form of chromatin Chromatin coils tightly into X-shaped chromosomes Every organism has a specific number of chromosomes Human cells have 46 chromosomes arranged in 23 pairs The 23rd pair determines the sex of an individual: XX for females and XY for males See pages 127 - 128

Genes Genes are small segments of DNA located on a chromosome Genes store the information needed to produce proteins Each chromosome can carry thousands of genes All your body cells have the same genes, but only specific genes are “read” in each cell to produce specific proteins Specialized proteins called enzymes and hormones carry out important specific functions in the body See pages 129 - 130

Summary Can you… State what items are found the nucleus? Explain why is DNA important? Explain how DNA is structured? Describe what a gene is? Explain how DNA, genes, and proteins are related?