Cell ReproductionCell Reproduction

Reproduction of ProkaryotesReproduction of Prokaryotes

Prokaryotes reproduce through a process Prokaryotes reproduce through a process called binary fissioncalled binary fission

The single, circular chromosome (which is The single, circular chromosome (which is attached to the plasma membrane) replicatesattached to the plasma membrane) replicates

The cell grows & elongates, separating the The cell grows & elongates, separating the two chromosomestwo chromosomes

The plasma membrane and cell wall pinch The plasma membrane and cell wall pinch inward, eventually forming two daughter cellsinward, eventually forming two daughter cells

Eukaryotic Chromosomes and Eukaryotic Chromosomes and Cell DivisionCell Division

Almost all of a eukaryotic cell’s genes Almost all of a eukaryotic cell’s genes are found in the cell’s nucleus, and are are found in the cell’s nucleus, and are grouped into multiple chromosomesgrouped into multiple chromosomes

Chromosomes are only visible when a Chromosomes are only visible when a cell is in the process of dividingcell is in the process of dividing

The rest of the time, the DNA + protein The rest of the time, the DNA + protein threads exist as a diffuse mass called threads exist as a diffuse mass called chromatinchromatin

Before dividing, the eukaryotic cell Before dividing, the eukaryotic cell replicates its chromosomesreplicates its chromosomes

The two copies of the chromosome are The two copies of the chromosome are called chromatids, and they are called chromatids, and they are connected to each other at a region connected to each other at a region called the centromerecalled the centromere

The pair of chromatids is still only one The pair of chromatids is still only one chromosome, and the chromatids are chromosome, and the chromatids are not considered chromosomes until they not considered chromosomes until they separate from one anotherseparate from one another

The Eukaryotic Cell CycleThe Eukaryotic Cell Cycle

A eukaryotic cell spends most of its time in A eukaryotic cell spends most of its time in interphase, the period of time between cell interphase, the period of time between cell divisionsdivisionsDuring interphase, metabolic activity is During interphase, metabolic activity is high; the cell grows, produces cell parts, high; the cell grows, produces cell parts, and in the middle of interphase the cell’s and in the middle of interphase the cell’s chromosomes duplicatechromosomes duplicateInterphase accounts for 90% of the total Interphase accounts for 90% of the total time required for the cell cycletime required for the cell cycle

InterphaseInterphaseInterphase may be divided into three Interphase may be divided into three subphasessubphases

The first subphase is called GThe first subphase is called G11 (the G is (the G is

for gap); the cell is producing proteins and for gap); the cell is producing proteins and organellesorganelles

The second subphase is the S phase, The second subphase is the S phase, which is when DNA synthesis occurswhich is when DNA synthesis occurs

The third subphase is called GThe third subphase is called G22, which is a , which is a

time of metabolic activity; proteins needed time of metabolic activity; proteins needed for cell division are producedfor cell division are produced

Mitotic Phase (M Phase)Mitotic Phase (M Phase)Consists of two processes: mitosis and Consists of two processes: mitosis and cytokinesiscytokinesis

During mitosis, the chromosomes divide During mitosis, the chromosomes divide and are distributed into two daughter and are distributed into two daughter nucleinuclei

During cytokinesis, the cytoplasm is During cytokinesis, the cytoplasm is divided into twodivided into two

These two processes result in the These two processes result in the production of two genetically identical production of two genetically identical daughter cellsdaughter cells

Phases of Mitosis - ProphasePhases of Mitosis - Prophase

Chromatin fibers condenseChromatin fibers condense

Nucleoli disappearNucleoli disappear

Each chromosome has two chromatids Each chromosome has two chromatids joined at the centromerejoined at the centromere

The spindle begins to form; microtubules The spindle begins to form; microtubules grow out of the centrosomes, which grow out of the centrosomes, which contain centriolescontain centrioles

The nuclear envelope fragmentsThe nuclear envelope fragments

Microtubules grow until they can reach the Microtubules grow until they can reach the chromosomeschromosomes

Each chromatid has a special region at the Each chromatid has a special region at the centromere, called the kinetichore, where centromere, called the kinetichore, where the spindle will attachthe spindle will attach

Spindles that don’t attach to kinetichores Spindles that don’t attach to kinetichores extend toward the opposite side of the cellextend toward the opposite side of the cell

The chromosomes begin moving toward The chromosomes begin moving toward the center of the cellthe center of the cell

Phases of Mitosis - MetaphasePhases of Mitosis - Metaphase

The spindle is fully formedThe spindle is fully formed

All of the centromeres of the All of the centromeres of the chromosomes are lined up at the chromosomes are lined up at the metaphase plate (the middle of the metaphase plate (the middle of the cell)cell)

The kinetichores of the chromatids The kinetichores of the chromatids face opposite sides of the cellface opposite sides of the cell

Phases of Mitosis - AnaphasePhases of Mitosis - AnaphaseThe centromeres of the chromosome The centromeres of the chromosome come apart and the sister chromatids come apart and the sister chromatids separate (they are now considered separate (they are now considered daughter chromosomes)daughter chromosomes)

Motor proteins on the kinetichores walk Motor proteins on the kinetichores walk the chromosomes toward opposite sides the chromosomes toward opposite sides of the cellof the cell

Kinetichore microtubules shorten and non-Kinetichore microtubules shorten and non-kinetichore microtubules lengthen (the cell kinetichore microtubules lengthen (the cell elongates)elongates)

Phases of Mitosis - TelophasePhases of Mitosis - Telophase

Basically the reverse of prophaseBasically the reverse of prophase

Cell elongation that began in anaphase Cell elongation that began in anaphase continuescontinues

Daughter nuclei appear-nuclear envelope Daughter nuclei appear-nuclear envelope appearsappears

Chromatin fibers uncoilChromatin fibers uncoil

Nucleoli reappearNucleoli reappear

Spindle disappearsSpindle disappears

CytokinesisCytokinesis

Occurs along with telophaseOccurs along with telophase

In animal cells, cytokinesis involves a In animal cells, cytokinesis involves a cleavage furrow, which pinches the cleavage furrow, which pinches the cell in twocell in two

In plants, cytokinesis involves a cell In plants, cytokinesis involves a cell plate, which grows outward and plate, which grows outward and accumulates cell wall materialaccumulates cell wall material

The Cell Cycle & CancerThe Cell Cycle & Cancer

Cancer is a disease of the cell cycleCancer is a disease of the cell cycleSystems that control the cell cycle do Systems that control the cell cycle do not work in cancer cellsnot work in cancer cellsAs a result, cancer cells divide As a result, cancer cells divide excessively and can invade other excessively and can invade other body tissuesbody tissuesThe excessive growth can result in an The excessive growth can result in an abnormal mass called a tumorabnormal mass called a tumor

TumorsTumors

BenignBenign tumortumor-abnormal mass of normal -abnormal mass of normal cells; can cause problems if they grow in cells; can cause problems if they grow in an organ; remain in their original site; can an organ; remain in their original site; can usually be completely removed by surgeryusually be completely removed by surgeryMalignantMalignant tumortumor-cancerous; capable of -cancerous; capable of spreading to other body areas; displaces spreading to other body areas; displaces normal tissue; can form new tumors by normal tissue; can form new tumors by breaking apart and spreading through the breaking apart and spreading through the circulatory system (called metastasis)circulatory system (called metastasis)

Types of CancersTypes of Cancers

CarcinomasCarcinomas-originate in the external -originate in the external or internal coverings of the body or internal coverings of the body (skin)(skin)SarcomasSarcomas-originate in tissues that -originate in tissues that support the body (bone and muscle)support the body (bone and muscle)LeukemiasLeukemias and and LymphomasLymphomas-cancers -cancers of blood forming tissues (bone of blood forming tissues (bone marrow, spleen, and lymph nodes)marrow, spleen, and lymph nodes)

Treatments for CancerTreatments for Cancer

RadiationRadiation- parts of the body with - parts of the body with cancerous tumors are exposed to high cancerous tumors are exposed to high energy radiation, which disrupts cell energy radiation, which disrupts cell division (damage to ovaries or testes may division (damage to ovaries or testes may cause sterility)cause sterility)

ChemotherapyChemotherapy-administration of drugs that -administration of drugs that disrupt cell division; some interfere with disrupt cell division; some interfere with the formation or functioning of the spindlethe formation or functioning of the spindle

MeiosisMeiosis

Essential for the formation of gametes Essential for the formation of gametes (ova and sperm) that will be used for (ova and sperm) that will be used for sexual reproductionsexual reproductionOccurs in two consecutive cell Occurs in two consecutive cell divisionsdivisionsReduces the chromosome number by Reduces the chromosome number by ½ (for humans, this means creating ½ (for humans, this means creating gametes that have 23 chromosomes)gametes that have 23 chromosomes)

Human ChromosomesHuman Chromosomes

Occur in pairs (there are 23 pairs) in Occur in pairs (there are 23 pairs) in somatic cells (typical body cells); these are somatic cells (typical body cells); these are called diploid cells (di=2)called diploid cells (di=2)Occur unpaired (a single set of 23) in the Occur unpaired (a single set of 23) in the gametes; these are called haploid cellsgametes; these are called haploid cellsThe paired chromosomes in somatic cells The paired chromosomes in somatic cells are called homologous chromosomes, are called homologous chromosomes, because they have genes for the same because they have genes for the same traitstraits

Human ChromosomesHuman Chromosomes

22 of the chromosome pairs are called 22 of the chromosome pairs are called autosomesautosomes

The 23The 23rdrd pair consists of the sex pair consists of the sex chromosomeschromosomes

Human females have a pair of sex Human females have a pair of sex chromosomes called X chromosomes (XX)chromosomes called X chromosomes (XX)

Human males have one X chromosome Human males have one X chromosome and one Y chromosome (XY)and one Y chromosome (XY)

Inheritance of Human ChromosomesInheritance of Human Chromosomes

One chromosome from each pair is One chromosome from each pair is inherited from our mothers, and the other inherited from our mothers, and the other chromosome in the pair is inherited from chromosome in the pair is inherited from our fathersour fathersAt the time of fertilization, the two haploid At the time of fertilization, the two haploid gametes (sperm and ovum) unite to form a gametes (sperm and ovum) unite to form a diploid cell called the zygotediploid cell called the zygoteFertilization results in the formation of a Fertilization results in the formation of a diploid cell, thus restoring the normal diploid cell, thus restoring the normal diploid number of human chromosomesdiploid number of human chromosomes

Meiosis Produces GametesMeiosis Produces Gametes

Meiosis occurs in the reproductive organsMeiosis occurs in the reproductive organs