Ms. Hughes

Why Cells Reproduce Multicellular organisms grow larger by producing more cells. New cells are needed to keep organisms healthy and replace old worn out cells. 3 main reasons for cells to reproduce

Cell Size Larger cells require more nutrients than smaller cells. Smaller cells are easier to maintain than larger cells. Recall surface area-to-volume ratio

Cell maintenance More proteins are required to keep a larger cell up and running. Smaller cells require less protiens. If a cell gets larger DNA cannot be copied quickly enough for that cell to continue dividing. DNA limits a cell’s size.

Making New Cells “Daughter” cells have a higher surface area-to-volume ratio than it’s parent does. Because larger cells are more difficult to maintain, cells divide when they grow to a certain size.

chromosomes Define: Genes Chromosomes Complete doodle definitions for these terms.

Prokaryotic Chromosomes Single circular molecule of DNA Thousands of genes on this molecule Condensed like a rubber band coiling back onto itself.

Eukaryotic Chromosomes Linear chromosomes Much more genes than prokaryotes. Eukaryotic DNA is packaged into highly condensed chromosome structures with the help of many proteins DNA and chromosomes make up chromatin.

Forms of chromatin 1. Histones ( a protein) allow DNA to wrap around them like a spool of thread. 2. Once DNA has wrapped around the histone this is now called a nucleosome. 3. Nucleosomes line up together to form a chord.

Packaging During Cell Division For most of its life the cell’s DNA remains in this chord of nucleosomes. During cellular division the chord condenses even farther to ensure that the DNA is not damaged and is copied properly during cellular replication and division.

Chromosome structure Define and do a doodle def for Chromosome Chromatid Sister chromatid centromere

Preparing for cell division All cells come from pre-existing cells DNA is copied before cell is replicated and divides All newly-formed cells require DNA, so before a cell divides a copy of DNA is made for each daughter cell

Prokaryotes The cell grows larger The DNA strand is doubled like a rubber band. The cell is pinched in the middle like a balloon animal.

Eukaryotes Eukaryotic cellular reproduction is much more complicated because they contain more DNA, organelles and are more complex themselves.

Activity Recap: how are these related??? Chromosome Chromatid DNA Genes Histones nucleosome

Homework Create a comic strip, rap or dance about chromosomes and their relationship to DNA and it’s packaging.

Mitosis Mitosis is the division of a cell’s nucleus. There are several steps that must be complete before this can happen however.

Eukaryotic Cell Cycle Cell cycle: is a sequence of cellular growth and division during the life of a cell. The life of a eukaryotic cell cycles through phases of growth, DNA replication, preparation for cell division, and division of the nucleus and cytoplasm.

Interphase Composed of three separate phases: G1, S, and G2 During interphase the cell is not dividing. The cell is growing and preparing to divide. Some cells divide often and others do not.

1, 2, 3 pair share Assign 1, 2, 3 and paraphrase each step 1 – G1 2 – S 3 – G2

Cell Division Mitosis Cytokinesis Complete doodle definitions for these words.

Activity Read aloud each of the steps for the stages of mitosis and create comic strip on the board. Pages

Cytokinesis During cytokinesis, the cell membrane grows into the center of the cell and divides it into two daughter cells of equal size. Each daughter cell has about half of the parent’s cytoplasm and organelles.

Animal cell vs. plant cell cytokinesis. Cell plate formation page 232

Activity Using yarn replicate the phases of mitosis on a piece of construction paper with the yarn as chromosomes. You must also thoroughly explain what is happening in each of the four phases in your OWN words. Draw, label and explain the other phases of the cell cycle on the back of your construction paper.

Home Work Compare each phase of the cell cycle to a part in the life cycle of a human. Ex: interphase can be childhood with G1 as an infant. But you must explain why!!

Controls Cell growth and division depend on protein signals and other environmental signals. Available nutrients Size of cells Etc.

Checkpoints Doodle defs for the 3 checkpoints G1 – S – G2

Cancer Read aloud and paraphrase (This will be done to work on your comprehension skills) Loss of control Development Treatment Prevention

Activity Create a memory game Write definitions for the check points and phases of the cell cycle on index cards. Write the actual term on another index card Place all cards facing down Match cards until all cards are matched.

Homework Create a board game in which the cell experiences the cell cycle. All phases and check points must be covered.