Cell CycleAP Biology Chapters 12-13

Remember the Cell Theory!

• All Living things are made of cells.

• All cells reproduce to create new cells

• Cells are the basic unit of structure and function in all living things.

CHAPTER 12 HIGHLIGHTS

• The Cell Cycle• Somatic cells vs. gametes

Cell Cycle

Interphase (3 stages)….mitosis…..cytokinesis

Terms for DNA in different stages

Chromosome Duplication

Remember- each shape of DNA acquires a new name.

Cell Cycle

NOTE ON THE NEW EXAM

• Paperwork from the college board states that students do not have to know the names and what happens in each step of mitosis…

• HOWEVER

• I have seen their questions. If you don’t know PMAT, you will STRUGGLE to answer their questions! It’s quick and easy- just learn it!

Onion mitosis

Whitefish mitosis

Stages of Mitosis in Detail

Spindles and Kinetochores

• Centrosome- organelle that organizes microtubules for the cell

• Spindle- microtubules in the cell that form during prophase

• Kinetochore- structure of proteins and specific sections of chromosomal DNA at the centromere

Kinetochores

Cytokinesis in animals- cleavage

Cytokinesis with cell walls- cell plates

Binary fission

• Prokaryotic cell division

• DNA loop duplicates

• Origin of replication zones move to opposite ends of cell

• Plasma membrane grows in and new cell wall forms

• Next pictures

Binary fission in pictures

Evolution of mitosis

Regulation of Cell Cycle

Molecular control of cell cycle

Explanation of molecular control

• Protein kinases- enzymes that give “go-ahead” signals at checkpoints

• Protein kinase + cyclin = activation and “go-ahead” begins

• Cdk- cyclin dependent kinases• MPF (maturation promotion

factor)- complex of cyclin + kinase• Cyclin increases in G1, S, G2• Cyclin decreases sharply in M

Messages from kinetochores

• Anaphase can’t happen until all kinetochores are attached to spindle microtubles in metaphase

• APC- anaphase promoting complex becomes active then, triggers breakdown of cyclin and inactivation of proteins holding sister chromatids together

• NOTE it is unlikely that the exam will specifically ask you what APC, MDF, and Cdk do. You should know cyclin’s job and the generic job of protein kinases.

Growth factors

• Protein released by body cells telling other cells to divide

• PDGF- platelet derived growth factors made by platelets

• Yet another example to help you understand the role of proteins in the cell cycle and the their bigger application in the human body.

• Needed for fibroblasts to divide (connective tissue cells with PDGF receptors)

• Leads to tyrosine kinase receptor pattern….go back and review!!!

Practical application

• PDGF receptors are responsible for telling fibroblasts to divide and heal a cut

• Density dependent inhibition- when a single layer of cells forms and fills all space available, division stops

• Anchorage dependence- cells must be attached to a surface to divide

Cancer Cells Break Every Rule

• Lack density dependent inhibition

• Lack anchorage dependence

Cancer terminology

• Transformation- normal cell cancer cell

• Tumor- mass of transformed cells that are not destroyed

• Benign tumor- stay at original site• Malignant tumor- invasive tumor,

impairs more than one organ• Metastasis- spread of cancer cells• Cancer patients have malignant

tumors

How might cancer cells work???

• 1. do not need growth factors?• 2. make their own growth factors?• 3. abnormality in cell cycle control

system?

• We do know that they• don’t follow normal checkpoints in

cell cycle• Are immortal if given constant

nutrients (HeLa since 1951)

What makes a cell transform?

• Alteration of genes that control cell cycle

• How this happens, still a mystery!

CHAPTER 13 HIGHLIGHTS

• Meiosis and Sexual Life Cycles

• Basic terms: • Heredity• Variation• Genetics• Genes• Asexual vs sexual reproduction

Visible forms of Human DNA

• Somatic cells 46 chromosomes

• Karyotypes

Key words for karyotypes

• Autosomes v sex chromosomes

• Haploid cells v diploid cells

• Fertilization zygote

Human life cycle

Comparison of Sexual life cycles

We will learn the generic form of alternation of generations NOW in order to make the plant unit shorter later this year.

Alternation of generations

• Both diploid and haploid multicellular stages

• Many variations– Plants, fungi, some protists

• Sporophyte- diploid • Produces haploid spores• Divides with mitosis to create a

multicellular gametophyte• Produces haploid gametes with

mitosis• Syngamy forms diploid organism

Example Alternation of generations

Summary of meiosis

As in general biology, you only need to learn the timing and important of crossing over, and the differences/similarities b/n mitosis and meiosis.

Steps of Meiosis in Pictures

Comparing Mitosis and Meiosis

Independent assortment

Independent assortment of chromosomes

• All chromosomes are randomly arranged during metaphase I

• Calculate out….about 8 million possible combinations of chromosomes for each individual human conceived

• Ensures variety in the human species

Crossing over

Crossing Over

• Prophase I meiosis

• Chromosomes get mixed up- recombinant chromosomes form

• Causes variety in the human species

Random Fertilization

• One egg + one sperm = zygote

• Each egg has 1 of 8 million combinations of chromosomes,

• Each sperm has one of 8 million combinations of chromosomes

• + crossing over (impossible to quantify)• There are trillions of possible

combinations for that child

Human Variation

Evolutionary Dead EndThere are 9000-12000 cheetahs left in the world, and they live in a relatively small portion of the world (Namibia mainly). Therefore, all cheetahs are essentially inbred. DNA tests have shown that every cheetah tested has nearly identical DNA. Demonstrates the importance of needing a large pop for genetic diversity.

Link to Evolution

• Variation is what causes natural selection to happen

• Sexual reproduction creates this variation

• No matter how the earth changes…some organisms will be able to survive and deal with the changes