Cell Cycle Chapter 5.1

Table of Contents  What is the cell cycle and what are the stages and phases of it?  Describe and detail the process of mitosis (asexual reproduction)  Describe and detail the process of meiosis (sexual reproduction)  Explain how cells regulate themselves and how mutations in this process can cause cancer  How are mitosis and meiosis similar and different from each other?  What are the chromosome numbers at the end of these processes?

Cell Cycle  Regular pattern of growth, replication, and division.  Has four main stages:  Gap 1  Synthesis  Gap 2  Mitosis  First 3 stages is called Interphase.

Start Gap 2 Gap 1 Synthesis Interphase Mitosis Cytokinesis

Interphase  Gap 1 (G1)  Cell carries out it’s normal functions  Usually the cell grows in size and makes more organelles.  Spends most of it’s time in this phase.

Synthesis  Synthesis  This is where DNA is replicated.  By the end of this stage there are two complete sets of DNA for the cell.  This usually appears grainy in photos.

Gap 2  Gap 2  Much like Gap 1.  Cell carries out normal functions and some growth may occur.  This is where the cell checks to make sure it’s not damaged for division.

Mitosis  Has two stages:  Mitosis- The division of the nucleus and its contents (DNA)  Cytokinesis – When the cell’s cytoplasm divides. (Organelles are moved at this time)  After this phase two genetically identical daughter cells are created.

Mitosis

Cell Division  Prokaryotic cells divide much faster than eukaryotic cells.  Your cells probably take 12 hours from S phase to M stage.  What kind of people/animals would you expect to have fast cell growth?

Gap 0  Gap 0 stage is when you have a cell that doesn’t divide for a long time (years.)  Many scientists think this happens until they need to be used in some way or they may stay here permanently.

Cell Size  If cells are too small, they can’t contain everything they need to survive.  If too big, they won’t be able to get enough nutrients to keep them at that size.

Chapter 5.2 Mitosis and Cytokinesis

Chromosomes  A chromosome is a long continuous thread of DNA.  You have 46 chromosomes in each cell.  These long threads wrap around proteins called histones.  This helps pack DNA in a small area.  A long line of your DNA with histones intertwined is called chromatin.

Chromosome  After S phase you create a completely new and identical set of DNA.  Forms an X shape.  ½ of this is called a chromatid.  Center is called centromere.  Long arm is referred to as the Q arm  Short arm is referred to as the P arm Short Arm (P arm) Chromatid Centromere Long Arm (Q arm)

The human genome contains 46 chromosomes, or 23 pairs of chromosomes. These are called homologous chromosomes Always keep in mind the perspective here. Think how complex each chromosome is and how tightly woven it is

Stages of Mitosis  Remember: Mitosis is the division of DNA and the nucleus. Nothing else.  Mitosis is made up of 4 stages.  Prophase  Metaphase  Anaphase  Telophase  Cytokinesis occurs AFTER mitosis.

Prophase  Chromatin condenses  Nuclear envelope breaks down  Nucleolus disappears.  Spindle fibers grow  Centriole holds the spindle fibers.  Asters are short fibers attached to centriole.

Metaphase  Spindle fibers attach to centromere.  Chromosomes align in center of cell

Anaphase  Chromatids separate.  Spindle fibers shorten.  Move parts on both sides of cell.

Telophase  Two sets of nuclear material is divided.  Nuclear membranes form again.

Prophase Metaphase Telophase Anaphase

Meiosis and Sexual Reproduction Chapter 6.1

Sexual Reproduction  This only takes place with cells designed for the purpose of overall reproduction of a genetically different organism.  This involves sex cells (also called gametes)  Eggs and Sperm only  Makes haploid cells  Most of your body reproduces (repairs/grows) with mitosis  This involves body cells (also known as somatic cells)  All body cells (EX: leg muscle, heart tissue, stomach lining, bone marrow…)  Makes diploid cells

Diploid vs. Haploid  The reason for haploid is because this means another haploid cell must mix in order to make another diploid cell for normal cell functions.  This means one haploid cell from your mother is mixed with another haploid from your father.  This new mix makes a genetically different diploid cell

Two phases of Meiosis Meiosis I Chromosomes don’t split, they rearrange in 1 st division Independent assortment & crossing over Meiosis II Chromosomes split and we have 2 nd division Result is 4 different haploid cells

Crossing over  Happens only in Meiosis I  This is when the chromosomes exchange some genetic info with each other  This increases genetic variation so no offspring are exactly alike so traits can carry on into future populations

Name the stages!

Regulation of Cell Cycle Chapter 5.3

Factors  Cell division is controlled by external and internal factors.  If cells weren’t controlled in some way, they would likely grow out of control.

External Factors  This can consist of chemical and physical factors.  An example of a physical external factor is cell-cell contact.  This means when one cell touches another it will stop growing.

External Factors  Chemical factors that are external are usually in the form of chemical signals.  These travel from one cell to another.  These are called growth factors.  Different factors have different effects

Internal Factors  These can happen after external factors attach themselves to other cells.  Common ones are kinases and cyclins.

Apoptosis  This is programmed cell death.  Internal or external factors can activate self-destructive enzymes.  This can be part of normal cell function, or if a mistake is noticed in the cell cycle

Cancer  Uncontrolled cell growth is what cancer is.  This means there is no regulation for the cell cycle, so it continues to grow.  Cancers can be benign or malignant.  Benign – cells stay together and are pretty harmless  Malignant – cells break away and can metasize (spread through body)

Cancer  Cancer cells won’t carry out normal cell functions  This is why cancers are dangerous if they spread. They can cause entire tissues to shut down.  Cancer is usually caused by damage or mutation that occur in the cell.  Carcinogens are cells that can promote cancer.

These are leukemia cells that can be found in the blood of somebody with this form of blood cancer. These cells are clearly larger and misshapen, showing that the cells can no longer function in their normal manner. This is the danger of mutations in cells that are so important. This is also the danger of metasizing (or spreading) in the body

Asexual Reproduction Chapter 5.4

Reproduction  Reproduction is when organisms come from one or more other organisms.  Can come in two forms  Sexual  Asexual  Sexual – Joining of gametes from each parent  Asexual – No gametes, offspring from one parent

Binary Fission  This is how most prokaryotes reproduce.  This is a form of asexual reproduction.  Similar results as mitosis, but differs in a few ways.  The cell just pulls itself apart and brings half of the DNA

Comparing asexual and sexual reproduction Notice how simple the DNA separation in binary fission is. Asexual Reproduction Sexual Reproduction

Differences  Binary Fission  Does not have nucleus division (no nucleus)  No spindle fibers  Much less DNA  Mitosis  Division of nucleus  Uses spindle fibers  Many different chromosomes.

Advantages in Binary Fission  In environments that don’t change, having a copy of a survivor is good.  If it ain’t broke, don’t fix it  All asexual reproducers don’t need a partner, so they call all potentially reproduce.

Disadvantages in Binary Fission  If conditions change then similar organisms may die easily.  Low genetic diversity lower chances of finding a “better version”

Eukaryotes  Some eukaryotes use asexual reproduction  Budding – small organism grows off of parent organism and can drop off or stay attached.  Fragmentation – Parent splits into pieces. Each piece becomes a new organism.  Some can reproduce both sexually and asexually.

Chapter 5.5 Multicellular Life

Interactions  All multicellular organisms are made of different kinds of cells.  All types of cells need to fit and work together.  Tissue – group of cells that work together to perform a specific function.

Groupings  Organs – groups of tissues that work together to perform a specific function.  When organs work together they form organ systems.  All of these parts work to maintain homeostasis.

Differentiation  Early cells must specialize in order to form different kinds of cells.  This is called cell differentiation.  A cell can change it’s whole function based on where it is.  That means cells can change how they function.

Stem Cells  Stem cells can do one of three things:  Divide and renew themselves for a long time.  Remain undifferentiated (unspecialized)  Develop into a wide range of specialized cells.  Two kinds of stem cells:  Adult Stem Cells  Embryonic Stem Cells

Stem cells  Adult stem cells can be found all over the body. This is good for a specific purpose.  Depending of what kinds of cells they are, they can only become that kind of cell again.  Embryonic stem cells that are formed during an embryo’s first 3-5 days.  These can develop into any kind of cell in the body.