Biology Unit Three C - Mitosis Mrs. Pearson’s First Semester Biology *For those watching by recording, watch for questions on the slides throughout the presentation. Email me the answers to the questions within two days of the lesson being presented in order to receive credit for watching the recording.

Lesson Objectives Describe the stages of the cell cycle. Identify internal and external factors that regulate cell division.

The cell cycle has four main stages. The cell cycle is a regular pattern of growth, DNA replication, and cell division. What is the longest lasting phase in the cycle? What is taking place in that phase?

Gap 1 (G1): cell growth and normal functions The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis. Gap 1 (G1): cell growth and normal functions DNA synthesis (S): copies DNA Gap 2 (G2): additional growth Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis) Mitosis occurs only if the cell is large enough and the DNA undamaged. **Those watching by recording, include in your email the main stages of the cell cycle

Cells divide at different rates. Why? The rate of cell division varies with the need for those types of cells. Some cells are unlikely to divide (G0).

Cell size is limited. Volume increases faster than surface area. Why would this limit how big a cell can get?

Surface area must allow for adequate exchange of materials. Cell growth is coordinated with division. Cells that must be large have unique shapes.

Chromosomes condense at the start of mitosis. DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA **Those watching by recording, include in your email the name of the proteins that condense DNA

DNA plus proteins is called chromatin. chromatid telomere centromere One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomeres protect DNA and do not include genes. How do you think they protect the DNA? Why is this important? Condensed, duplicated chromosome

Interphase prepares the cell to divide. Mitosis and cytokinesis produce two genetically identical daughter cells. Why is this important? Parent cell centrioles spindle fibers centrosome nucleus with DNA Interphase prepares the cell to divide. During interphase, the DNA is duplicated.

Mitosis divides the cell’s nucleus in four phases. During prophase, chromosomes condense and spindle fibers form.

Mitosis divides the cell’s nucleus in four phases. During metaphase, chromosomes line up in the middle of the cell.

Mitosis divides the cell’s nucleus in four phases. During anaphase, sister chromatids separate to opposite sides of the cell.

Mitosis divides the cell’s nucleus in four phases. During telophase, the new nuclei form and chromosomes begin to uncoil. **Those watching by recording, include in your email what forms in the telophase stage.

Cytokinesis differs in animal and plant cells. In animal cells, the membrane pinches closed. In plant cells, a cell plate forms. Why do you think plant cells need the cell wall?

Internal and external factors regulate cell division. External factors include physical and chemical signals. Growth factors are proteins that stimulate cell division. Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells. Why would that be a good thing?

Apoptosis is programmed cell death. a normal feature of healthy organisms caused by a cell’s production of self-destructive enzymes occurs in development of infants webbed fingers

Cell division is uncontrolled in cancer. How could this harm the body? Cancer cells form disorganized clumps called tumors. Benign tumors remain clustered and can be removed. Malignant tumors metastasize, or break away, and can form more tumors. **Those watching by recording – include in your email the difference between benign and malignant tumors. cancer cell bloodstream normal cell

Cancer cells do not carry out necessary functions. Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation.

Carcinogens are substances known to promote cancer. Standard cancer treatments typically kill both cancerous and healthy cells. **Those watching by recording, include in your email what type of cells the standard cancer treatments typically kill.

Binary fission is similar in function to mitosis. Asexual reproduction is the creation of offspring from a single parent. Why would this be beneficial? Why would it be detrimental? Binary fission produces two daughter cells genetically identical to the parent cell. Binary fission occurs in prokaryotes. parent cell DNA duplicates cell begins to divide daughter cells

Environment determines what form of reproduction is most advantageous. Asexual reproduction is an advantage in consistently favorable conditions. Why? Sexual reproduction is an advantage in changing conditions. Why? **Those watching by recording, include in your email what determines the form of reproduction that is most advantageous

Some eukaryotes reproduce through mitosis. Budding forms a new organism from a small projection growing on the surface of the parent. bud Hydra Yeast

Fragmentation is the splitting of the parent into pieces that each grow into a new organism. Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant. **Those watching by recording, include in your email why tearing up the starfish did not help clam and oyster fishers.

Review The cell cycle has four main stages – Gap 1, DNA synthesis, Gap 2, and Mitosis Cells divide at different rates Cell size is limited Mitosis results in identical daughter cells Mitosis divides the cell’s nucleus in four stages – prophases, metaphase, anaphase, and telophase Internal and external factors regulate cell division Cell division is uncontrolled in cancer

Questions?