Cell Cycle and Cell Division Ms. Miller

Essential Question What are the phases of the cell cycle?

Objective Students will be able to: Explain how a cell duplicates itself

What is the cell cycle? Cell cycle is the regular sequence of growth and division that cells undergo.

Growing is a complex business We know that living things grow. How do things grow?

Three types of Cell Division

Binary is the type of cell division occurring in bacteria

Meiosis A special kind of cell division –Related to sex cells

Mitosis Plants and animal cells with a nucleus (Eukaryotic cells) undergo mitosis

How Do We Grow? It may be hard to believe but in your distant past you were a small, single cell created by the fusion of two special cells: one from your father - the sperm - and the other from your mother - the egg. These cells fused together, fertilization happened, and a unique person was created: you!

Growing is a complex business A baby will grow into a child and then an adult.

Growing is a complex business A new plant also start as a single cell! –A plant will get taller and produce new leaves and flowers.

Cell Division When cells are dividing, they grow in size for a bit and then split in two. The cells must make copies of their chromosomes (the information storing part of the cell) before they split.

The Great Divide Activity Use I.N. pg. ____ Purpose: to see how fast the number of cells increase when cells divide repeatedly. Material: - A thin sheet of paper Data table pencil to record your results Divide# of cells

What to Do: 1.Begin with a sheet of paper to represent the original cell 2.Fold the sheet of paper in half. Each section represents one daughter cell. 3.Prepare a table to record the number of “cells” 4.Fold the paper in half again. Record the number of cells in your table. 5.Repeat step 4 as many times as you can

Conclusion 1.How many times could you fold the paper? 2.How many sections did you make? 3.Did you see a pattern? Explain 4.How is paper-folding model like cell division? Explain 5.Starting with one cell, how many cell division are needed to produce more than one thousand new cells?

Background Multicellular organisms use cell cycle for growth, cell repair, and cell replacement. In the human body, for example, an estimated 25 million cell divisions occur every second in order to replace cells that have completed their normal life cycles.

Growing is a complex business

Cell Cycle (Mitosis) There are 2 stages in all multicellular cell cycle: 1 st stage: Interphase 2 nd stage: Mitotic phase

Remember The cells must make copies of their chromosomes (the information storing part of the cell) before they split. –This phase is called interphase

DNA - The Double Helix Backgrounf In the beginning of the 1950s, biologists knew that DNA carried the hereditary message. But how? The DNA molecule looks like a spiral ladder where the rungs are formed by base molecules, which occur in pairs. These sequences of base pairs represent the genetic information.

Structure of DNA DNA (deoxyribonucleic acid): the molecule that encodes genetic information. The DNA molecule is shaped like a twisted ladder –In order to understand why DNA adopts such a characteristic shape, a strong background in general and organic chemistry is required.

DNA - DNA stands for deoxyribonucleic acid. - It is the chemical that makes up your chromosomes - It has a double helix shape. - There are sugars and phosphates located in DNA. - The nitrogen base pairs are Adenine, Thymine, Guanine, and Cytosine

Structure of DNA

Cell Cycle What are the 2 main stages in all plant and animal cells cycle: 1 st stage: 2 nd stage:

Stage 1: Interphase In this phase the cell grows, makes a copy of its DNA, and prepares to divide. –It produces structures that it will use to divide. The process in which the cell makes a copy of the DNA is called replication.

This cell is shown, as this is how all cells look during Interphase; before mitosis

Stage 2: Mitotic Phase This phase is divided into 2 stages: Mitosis and Cytokinesis

Mitosis It is the stage in which the cell’s nucleus divides into two new nuclei (not nucleus yet) –One copy of the DNA is distributed into each of the two daughter cells Mitosis can be broken into four phases: –prophase –metaphase –anaphase –telophase

Mitosis: Prophase To begin mitosis, the nuclear membrane breaks down, while the chromosomes shorten and thicken (here, a chromosome is two chromatids, bound at a point called the centromere, making an "X" shape). The other structures important for mitosis are also forming (i.e. the centrioles).

Mitosis: Prophase

Mitosis: Metaphase The chromosomes are lined up along the cell's equator.

Mitosis: Metaphase

Mitosis: Anaphase The newly formed chromosomes! The cell stretches out as the opposite ends are pushed apart

Mitosis: Anaphase

Mitosis: Telophase The chromosome have finished their migration to the poles and the mitotic structures breakdown. The plasma membrane of the cell pinches down along the equator creating two separate cells –(similar to twisting a long balloon and forcing it to pinch in the middle). –At this time, the chromosomes become indistinct (as they are during Interphase), the nuclear membrane forms again and the nucleolus reappears. And it everything starts all over again, and again, …

Mitosis: Telophase

Cytokinesis The final stage! In this final stage: –The cytoplasm divides. –The organelles are distributed into each of the two new cells When this stage ended, two identical cells, or daughter cells have formed.

Cytokinesis

The Two Stages

Recognize the following What stage is shown in each of the following pictures?

Why is it important for Replication to occur?

Replication of DNA Ensures that each daughter cell will have the genetic information it needs to carry out its activities

Infer what would happen if cell division occurred without DNA replication occurring first. How would this affect the daughter cells?

How would this affect the daughter cells? If cell division occurred without DNA replication occurring first, each daughter cell would have half of the DNA of the parent cell and would be unable to direct all cell activities. The cells probably would not survive

What happens during cytokinesis?

Answers 1. The cytoplasm divides, distributing the organelles into each of the two new cells.

Mitosis Song sites.googlegroups.com/site/cyberscienceschool/CyberScienceSchool- MitosisSong.htm?attachauth=ANoY7cohUR5vLQZFZpzI8YUb2imV4g09HlY2Dn1NnCb4pcFEdQQZt2128JIGaB62 6F5FDyeBsLgXLwE6vINZt2gtQHtHCiUdgQib-I3L6LB51Zw_ykh0FwM7HCn5zkUjhqtUkcuDY27aIEMJ- w6H_9ZVR1afcwiGeaCSDXB40XTGPpoBUMpxhPzTUwMg_Iip_Nadi- o060OX4RCC0hA4hp6RZHgPlfEgb4APobURwDBjFx-J6l-3gB4%3D&attredirects=0http:// a s- sites.googlegroups.com/site/cyberscienceschool/CyberScienceSchool- MitosisSong.htm?attachauth=ANoY7cohUR5vLQZFZpzI8YUb2imV4g09HlY2Dn1NnCb4pcFEdQQZt2128JIGaB62 6F5FDyeBsLgXLwE6vINZt2gtQHtHCiUdgQib-I3L6LB51Zw_ykh0FwM7HCn5zkUjhqtUkcuDY27aIEMJ- w6H_9ZVR1afcwiGeaCSDXB40XTGPpoBUMpxhPzTUwMg_Iip_Nadi- o060OX4RCC0hA4hp6RZHgPlfEgb4APobURwDBjFx-J6l-3gB4%3D&attredirects=0

DNA fingerprinting It is based on analyzing an individual ’ s DNA, deoxyribonucleic acid, a molecule that is found in almost every cell of one ’ s body. DNA of all humans is similar, but it varies enough from one person to the next to give each person a unique DNA signature. Summation: DNA is unique DNA is found in every cell except RBCs. ü Each person has his or her own unique DNA fingerprint. ü Restriction enzymes are molecular scissors used to cut DNA. DNA is technique that can be used for medicinal as well as criminal investigations.

What stages of the cell cycle does cell division include?

What happens in DNA replication?

–During DNA replication, an exact copy of DNA is made.

What are the two ladders of the DNA made up of?

–The two ladders of the DNA made up of chemical (sugar molecules).

Questions?????