Rod shaped structures inside the nucleus of Eukaryotic cells

Made of DNA and proteins Contain the genes that make you, you! Shape of the chromosome is

maintained by histones

3 forms of a chromosome› Chromatin – ball of

yarn› Chromatid – half of

an x, sometimes bent

› Chromosome – X Center of X is

called a centromere

Sex Chromosomes › Determine the sex of the organism› Males XY› Females XX› 2 out of 46 in the human cell

Autosomes› All the other chromosomes › 44 out of 46 in the human cell

Chapter 8

Click below to watch the Visual Concept.

Visual Concept

Sex Chromosomes and Autosomes

Section 1 Chromosomes

Also called homologues 2 copies of the

chromosome› One from Mom; One from

Dad Have the same size Have the same shape Have the same

information (genes)

Diploid › Cells that have

chromosomes in pairs

› Symbol 2n› Somatic cells or

body cells are like this

› Humans diploid number is 46.

Haploid› Cells that do not

have chromosomes in pairs

› Symbol 1n› Gametes are like

this Sex cells Sperm and egg cells

› Humans haploid number is 23.

Section 2 Cell DivisionChapter 8

Cell Division in Prokaryotes, continued

• Binary fission is the process of cell division in prokaryotes.

Asexual Reproduction› Production of

offspring from one parent

› Mitosis

Sexual Reproduction› Production of

offspring from 2 parents

› Meiosis

How do little elephants grow up to be BIG elephants?

The process of asexual reproduction begins

after a sperm fertilizes an egg.

Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.

Cell that reproduce by asexual reproduction reproduce constantly.

Animated Mitosis Cyclehttp://www.cellsalive.com/mitosis.htm

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase & Cytokinesis

• 3 phases• G1 – cell is growing• S – DNA is being copied• G2 – cell is preparing for mitosis

CELL MEMBRANENucleus

Cytoplasm

Nuclear MembraneAnd nucleolus are visible

CHROMATIN!

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

• Mitosis begins (cell begins to divide)• Chromosomes are visible• Centrioles (or poles) appear and begin to

move to opposite end of the cell. • Spindle fibers form between the poles.

CentriolesSister chromatids

Spindle fibers

Nuclear membrane & nucleolus disappear by end of prophase

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Spindle fibers

Centrioles

• Chromosomes attach to the spindle fibers at the centromere

Centrioles

Spindle fibers

CHROMOSOME

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

• Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.

Centrioles

Spindle fibers

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

• Two new nuclei form. • Chromosomes appear as chromatin

(threads rather than rods).• Mitosis ends.

NucleiNuclei

Chromatin

Nuclear membrane & nucleolus are visible by end of telophase

Overlaps with cytokinesis!

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

• Division of the cytoplasm• Cell membrane moves inward to create two daughter cells –

each with its own nucleus with identical chromosomes.• Animal cells – form a cleavage furrow• Plant cells – form a cell plate, which becomes the cell wall.

Animal Mitosis -- Review

Interphase

                                              

              

Prophase

                                             

               

Metaphase

                                              

              

Anaphase

                                             

               

Telophase

                                              

              

Interphase

                                             

               

Plant Mitosis -- ReviewInterphase

                                                        

    

Prophase

                                                       

     

Metaphase

                                                        

    

Anaphase

                                                       

     

Telophase

                                                        

    

Interphase

                                                       

     

IInterphasePProphaseMMetaphaseAAnaphaseTTelophaseCCytokinesis

IPMATIPMATCC

II PPrayray MMore ore AAtt TThe he CChurchhurch

32

http://www.cellsalive.com/mitosis.htm

Section 2 Cell DivisionChapter 8

Control of Cell Division

• Cell division in eukaryotes is controlled by many proteins.

• Control occurs at three main checkpoints.

1. G1 checkpoint – check to see whether the cell is healthy and is large enough to divide

2. G2 checkpoint – check to make sure DNA is copied correctly

3. Mitosis checkpoint – if cell divided correctly, then signals are made to exit mitosis

Chapter 8

Click below to watch the Visual Concept.

Visual Concept

Control of the Cell Cycle

Section 2 Cell Division

Section 2 Cell DivisionChapter 8

Control of Cell Division, continued

• When Control is Lost: Cancer– Cancer is uncontrolled growth of cells– Cancer may result if cells do not respond to

control mechanisms.– Can be caused by mutations in DNA

Section 3 MeiosisChapter 8

Formation of Haploid Cells

• Meiosis is a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. • Start with 46 and end with 23

• Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis.

• Done by germ cells• Meiosis produces haploid gametes.• Is considered sexual reproduction• Creates genetic diversity• Two divisions

Section 3 MeiosisChapter 8

Meiosis I

• Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I.

• Crossing-over, which is when portions of homologous chromosomes exchange genetics material, occurs during prophase I and results in genetic recombination.

Homologous chromosomes (paired chromosomes) become visible

Nuclear membrane and nucleolus disappear

Spindle fiber starts to appear

Crossing over occurs – portions of the chromatid break off and attach to other homologous chromosome

Chapter 8

Click below to watch the Visual Concept.

Visual Concept

Tetrads and Crossing-over of Genetic Material

Section 3 Meiosis

Homologous chromosomes (tetrads) line up at the equator and connect to spindle fibers at their centromeres

Homologous chromosomes split and individual chromosomes move to poles

They assort independently of one another- independent assortment

There are 2 new cells at this point

Each new cell has half the number of chromosomes as the parent germ cell

So they are now haploid

Has prophase II, metaphase II, anaphase II and telophase II

Exactly like mitosis Four new haploid cells result

› Four gametes› Depends on whether it is an animal or a

plant cell

Chapter 8Section 3 Meiosis

Spermatogenesis› Making of sperm

cells› Meiosis will result

in 4 mature sperm cells or spermatozoa

Oogenesis› Making of mature

egg cells, or ova› Meiosis will result

in 1 mature egg cell and 3 polar bodies that die