The Cell Cycle & Mitosis Do Now: Take out the 8-1 review homework (period 7, take out the back of the earlier worksheet also) Complete the FAKE pop quiz without using your notes or the text – it’s NOT a quiz… but it could have been! We will go over it in 10 minutes sharp!

New Procedure For Do Nows Beginning tomorrow, you will be absolutely required to copy the Do Now for each day into your notebook. Keep it separate from the rest of your notes and notebook, because I will collect it on the last day of the week. Keep all of the do nows for each week together. At the beginning of the week, title your do nows with your name, the week of the school year (week 22 right now) It will count as a mini quiz grade (10 points, quiz = 25)

New Do Now Format The Do Now will now include the learning objectives for the day – so we all know EXACTLY what you are going to learn that day. It will still include an activity or question which you will also write beneath the learning objective. Make sure you include the date!

Example – Today’s Do Now 1.30 Objective: Be able to describe what happens during each stage of the cell cycle, and draw a picture of what the chromosomes in a cell look like during that stage. Do Now Task: complete a fake pop quiz

What your Weekly Do Now List Should Look Like John D. Student Period X Do Nows, week 22 1.30: Objective: Be able to describe what happens during each stage of the cell cycle, and draw a picture of what the chromosomes in a cell look like during that stage. Do Now Task: complete a fake pop quiz

If You are Absent… You are required to get any do nows you missed for the day online or from another student. If you are absent when I collect do nows, they should be ready to be turned in when I see you next. It’s ok if the day you missed isn’t there the day you return.

Diploid vs. Haploid Most of the cells in your body (and in all mammals) are DIPLOID, meaning they have 2 copies of all of your DNA

Haploid Cells Some cells (like animal reproductive cells – sperm and eggs, aka gametes) have only 1 copy of each chromosome. They are haploid.

The Cell Cycle The cell cycle is like a cell’s life cycle. G0

G1 S G2 M Foldables Make cell cycle and mitosis foldable notes! Follow verbal instructions carefully Cell cycle steps on top flap (G1, S, G2, M) Details / sketches on the inside. View when closed: G1 S G2 M

On the Inside of Your Foldable View when open Details about cell cycle stages go in this row A picture of a cell in this stage goes in this row Leave the bottom two rows blank today

The Cell Cycle Copy the descriptions into the top row. For “M” write “Cell divides”

G1 – The first growth stage G1 is the stage when a new cell grows and carries out its normal functions Some cells will exit the cell cycle and stop dividing during after G1. Those non-dividing cells are said to be in G0.

Chromosomes During G1 NOTE: these examples are for cells that have a diploid (2n) number = 4. In other words, there are 2 types of chromosomes, and 2 copies of each type, for a total of 4 During G0, G1, S, and G2, a cell’s chromosomes are unwound and are not actually visible. The picture shows what they would look like if they were visible during G1. NOTICE: The chromosomes during G1 have only 1 chromatid!

What Your Foldable Should Look Like Right Now View when open Growth and normal metabolic roles. Cells can stop dividing and go to G0 2n = 4

“S” is For Synthesis (of DNA) During the S, or synthesis phase of the cell cycle, all of a cell’s DNA is copied When complete, each chromosome has 2 chromatids NOTE: 2n = 4. There are still 2 different types of chromosomes, and 2 of each type. The cell is still diploid, and the chromosome number has not changed. The number of chromatids per chromosome has now gone from 1 to 2.

G2 – The Second Growth Phase In G2, the cell grows and prepares to divide. The chromosomes look exactly as they did at the end of the S phase.

“M” is for Mitosis Mitosis is the process of separating the chromosomes during cell division. It occurs in several stages we will see tomorrow.

Chromosomes During Mitosis During mitosis, each chromosome divides, so that one chromatid from each chromosome goes to each daughter cell No nucleus: it disintegrates at the beginning of mitosis. NOTE: 2n = 4 Now, each new cell will have 2 types of chromosomes, and 2 copies of each, so 2n STILL = 4 Now, each chromosome returns to having only 1 single chromatid.

Your Completed Foldable Notes View when open Growth and normal metabolic roles. Cells can stop dividing and go to G0 DNA is copied. When done, all chromosomes have 2 chromatids. Growth and preparation for mitosis Each chromosome separates during cell division. 2n = 4 2n = 4 4n = 8 2n = 4

The BIG Idea MITOSIS DOES NOT CHANGE THE CHROMOSOME NUMBER OF A CELL Ever, at all, even a little The only thing that changes is the number of chromatids each chromosome has. This is the same homologous pair of chromosomes, when each has only 1 chromatid. This is one homologous pair of chromosomes, each has 2 chromatids

Homework Read pp. 148-149 Answer SR #1, 2 on p. 151