Cell Division Mitosis The division of a nucleus

Cell Division Mitosis: The division of a nucleus of a body cell

If the nucleus is dividing, what about the “boss”? (DNA) We have 23 pairs of chromosomes in the cells of the body. That’s 46! (23 x 2) They exist in identical pairs and are joined at the centromere. (Later, we’ll discuss that chromosomes are made of genetic code…. . DNA! Check out below!)

n The Cell Cycle Interphase Mitosis Stages n n n Prophase Metaphase Anaphase The cell is growing and copying it’s chromosomes. Longest stage of the cell cycle. What happens in the nucleus 1. Chromosomes become visible. Centrioles move to opposite ends of the cell. PREPARATION 2. Chromosomes line up in the middle of the nucleus and spindle fibers attach to the centromeres of the chromosomes. MIDDLE 3. Chromosomes are pulled apart towards opposite ends of the nucleus. AWAY

--Telophase 4. The nucleus divide into two new, identical nuclei. A nuclear membrane forms around the nuclei. TWO Cytokinesis – Splitting of the cell after the cell’s nucleus undergoes Telophase…forming 2 identical daughter cells

Do plants undergo the same mitotic phases? ? Yes, but there’s 3 major differences!! 1. They do not have centrioles 2. They do not pinch apart 3. They form cell plates to divide the cell and a cell wall forms along it.

Can you label the stages of mitosis? ? n After Interphase, what are the next stages below called? ? A. Prophase A C B D B. Metaphase C. Anaphase D. Telophase

n n n Just some questions about mitosis? ? (Interphase is not pictured) What are the two structures at the opposite ends in metaphase? (picture #2) What are the structures attached to the centromere of each chromosome? After telophase (picture #4), what happens to the rest of the cell in picture #5? What is this called? What happens if the chromosomes did not exist in identical pairs and now have split and formed two nuclei that are not identical? ?

Mitosis Vs. Meiosis MITOSIS 1. Body cell’s nucleus is reproducing 2. One nucleus becomes two identical nuclei 3. 23 pairs (46 total) of chromosome in the parent cell (original) and 46 in each new daughter cell 4. One division of the nucleus 1. 2. 3. 4. MEIOSIS Sex cell’s (gamete) nucleus is reproducing One nucleus becomes four new nuclei 23 pairs (46 total) of chromosomes in parent cell and 23 in each new sex cell Two divisions of the nucleus

Sexual reproduction Vs. Asexual Reproduction Sexual Reproduction Asexual Reproduction Creation of a new organism involving two organisms. The new offspring is not identical to the parents. (DNA from 2!) Ex: 1. Internal fertilization: male sex and female sex cell unite inside the body 2. External fertilization: sex cells unite outside the body Creation of a new organism from one parent. The new offspring is identical to the parent organism. (DNA from one parent) Ex: 1. Fission 2. Regeneration 3. Budding

Asexual Reproduction n Which A. a. Budding types are illustrated below? ? B. b. fission C. c. regeneration

What is DNA? ? ? DNA is Deoxribonucleic Acid Chromosomes are made of DNA strands. They control your traits that you inherit. Rosalind Franklin Discovered DNA was in a spiral form Watson and Crick Two scientists that stated DNA was a spiral structure containing “steps” of genetic code. The colored “steps” are nitrogen base pairs, also called nucleotides. They are our code *Adenine pairs with Thymine* *Cytosine pairs with Guanine* The order of steps creates a code for a trait. The “handrails” are sugar and phosphate molecules. The base pairs link on to the sugar molecules. Watson and Crick Model

Sometimes, when replication of DNA takes place, mutation takes place. Check some examples out.

Isn’t it strange that this is our very own personal code. Next unit we study how sections of DNA, called genes, control our traits.

Quiz Time!!! 1. 3. 2. 4. 5. What are the purple structures called? ?

6. What are the “rope-like” structures that appear in the second picture? ? 7. What are the two gold colored structures that help the “rope-like” structures pull apart the chromosomes? ? 8. Picture #4 is what phase of Mitosis? ? 9. After that phase the cell and it’s cytoplasm pinches apart, what is that called? ? 10. List one difference between plant cell division and animal cell division.

Name that phase! 11. I am the phase when the nucleus splits into two, identical nuclei with the same # of chromosomes. 12. I am the phase when the double stranded chromosomes line up in the middle of the cell. 13. I am the phase when centrioles move to opposite ends of the nucleus and the chromosomes become really dark and visible. 14. I am the phase when the chromosomes are pulled apart, or away, from each other and move to opposite ends of the nucleus. 15. I am not really a stage of Mitosis, but rather a stage of a cell’s life where it is making proteins and growing. Some cells are stuck in in my stage of a cell’s life.

16. List two differences between MITOSIS and MEIOSIS. a. b. 17. Asexual reproduction is the creation of an offspring with ______ parent(s). What kinds of asexual reproduction are pictured below? ? 18. 19. 20.

21. Complete the strand below. A C