Review last week
DNA Structure Nucleotides have: A sugar molecule A phosphate molecule A nitrogenous base molecule
DNA Structure Each nucleotide has one of four different nitrogenous bases Adenine (A), Thymine (T), Cytosine (C), Guanine (G) Which bases pair together? A with T (vice versa) C with G (vice versa)
The Genetic Code DNA has a _______-character code, which form _______________(i.e. GGC) Each 3 letter word codes for the production of one of 20 different amino acids
Definition These are a short section of DNA that contains instructions to make a specific protein GENES
The Cell Cycle
The Cell Cycle At any moment, there are millions of cells going through cell division But what about the trillions of cells that aren’t? What are they doing? They are in some phase of the Cell Cycle
The Cell Cycle
The Cell Cycle The cell cycle is a sequence of events in the cell from one cell division to another. The growing and working phase of the cell is called interphase
The Cell Cycle A cell is in interphase for 90% of the total time of the cell cycle. During interphase a cell will: Make copies of each organelle Make copies of chromosomes (DNA) Each chromosome and its copies = sister chromatids
Cell Division
Cell Division What needs to happen in order for cells to divide? DNA needs to copy itself (chromosomes) Chromosomes Thread-like structures containing DNA
Cell division There are two types of cell division: Mitosis Meiosis
Mitosis One cell splits into two identical daughter cells
What is mitosis for? Mitosis is used to produce new body cells (eg. for growth and repair). Simple plants and animals can also use mitosis to reproduce This is called Asexual reproduction
What happens before mitosis? 1. The chromosomes get thicker
What happens before mitosis? 2. The chromosomes are replicated and can now be seen as x-shapes
What happens in mitosis? 3. The nuclear membrane disappears. The chromosomes line up on the spindle. The chromosomes are pulled to opposite ends of the cell
What happens in mitosis? 4. Each new cell is IDENTICAL to the original and has THE SAME number of chromosomes
Mitosis The stages of mitosis are: Prophase Metaphase Anaphase Telophase *Each stage has specific details about what is happening to the cell during mitosis
Cytokinesis Cytokinesis is the second process of cell division It divides the cytoplasm into two daughter cells
Question 1 If a cell with 28 chromosomes divides into 2 new cells, how many chromosomes will each new cell have? 28 chromosomes
Question 2 True or False . . . The cells produced in mitosis are genetically identical TRUE