Cell Division and Reproduction

Cell Division and Reproduction
Cell Division and Reproduction
Cell Division and Reproduction
Cell Division and Reproduction
Cell Division and Reproduction
Cell Division and Reproduction
Cell Division and Reproduction
Cell Division and Reproduction
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Presentation (Powerpoint) File

(11 MB|80 pages)
Product Description

This PowerPoint presentation contains all of the following terms and definitions:

•Cell Reproduction


Cancer cells start out as normal body cells.

Cancer cells undergo genetic mutations.

Cancer cells lose the ability to control the tempo of their own division.

Cancer cells run amok, causing disease.

•Normal Cell Division

•In a healthy body, cell division allows for:


–The replacement of damaged cells

–Development from an embryo into an adult

•Normal Cell Division

•In sexually reproducing organisms, eggs and sperm result from mitosis and meiosis.

•Cell Division and Reproduction

•Cell division plays many important roles in the lives of organisms.

–One of the characteristics of being considered living is the ability to reproduce.

•Cell Division

•Reproduction at the cellular level

•Cell division requires the duplication of chromosomes and sorts new sets of chromosomes into the resulting pair of daughter cells.

•Cell Division is used…

•For reproduction of single-celled organisms,

•Growth of multicellular organisms from a fertilized egg into an adult,

•Repair and replacement of cells, and

•Sperm and egg production.

•2 Methods in which living organisms Reproduce

•Asexual reproduction

–Produces offspring that are identical to the original cell or organism and

–Involves inheritance of all genes from one parent.

•Sexual reproduction

–Produces offspring that are similar to the parents, but show variations in traits, and

–Involves inheritance of unique sets of genes from two parents.

•2 Types of Cells


•Unicellular organism with NO nucleus or organelles.


•Uni- or multi-cellular organism with organelles and a nucleus.


•Prokaryotes reproduce by binary fission.

–“Dividing in half”

•Bacteria and archaea


•The chromosome of a prokaryote is:

–A singular circular DNA molecule associated with proteins and

–Much smaller than those of eukaryotes.

•Binary fission of a prokaryote occurs in 3 stages:

•Duplication of the chromosome and separation of the copies

•Continued elongation of the cell and movement of the copies, and

•Division into two daughter cells

•The Eukaryotic Cell Cycle and Mitosis

•Eukaryotic cells

•Are more complex and larger than prokaryotic cells,

•Have more genes, and

•Store most of their genes on multiple chromosomes within the nucleus

•Eukaryotic chromosomes are composed of chromatin consisting of:

•One long DNA molecule and

•Proteins that help maintain the chromosome structure and control the activity of its genes.

•To prepare for division, the chromatin becomes:

•Highly compact and

•Visible with a microscope.

•Before a eukaryotic cell begins to divide, it duplicates all of its chromosomes resulting in:

•Two copies called sister chromatids

•Joined together by a central “waist” called the centromere.

•When a cell divides, the sister chromatids:

•Separate from each other, now called chromosomes, and sort into separate daughter cells.

•The Cell Cycle

•The cell cycle multiplies cells.

•The Cell Cycle

•The cell cycle is an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division.

•The Cell Cycle consists of two stages, characterized as follows:

•Interphase: Duplication of cell contents

–G-growth, increase in cytoplasm

–S- duplication of chromosomes

–G- growth, preparation for division

•Mitotic phase: Division

–Mitosis- division of the nucleus

–Cytokinesis- division of cytoplasm


•Mitosis progresses through a series of stages.






•(Cytokinesis often overlaps telophase.)

•A mitotic spindle is:

•Required to divide the chromosomes, composed of microtubules, and

•Produced by centrosomes,

•Structures in the cytoplasm that:

–Organize microtubule arrangement and

–Contain a pair of centrioles in animal cells.


•The cytoplasmic contents double,

•Two centromeres form,

•Chromosomes duplicate in the nucleus during the S phase, and

•Nucleoli, sites of ribosome assembly, are visible.


•In the cytoplasm

–Microtubules begin to emerge from centrosomes, forming the spindle.

•In the nucleus

–Chromosomes coil and becomes compact

–Nucleoli disappear


•Spindle microtubules reach chromosomes, where they

–Attach at kinetochores on the centromeres of sister chromatids and

–Move chromosomes to the center of the cell through associated protein “motors”

–Other microtubules meet those from the opposite poles

–The nuclear envelope disappears


•The mitotic spindle is fully formed

•Chromosomes align at the cell equator

•Kinetochores of sister chromatids are facing the opposite poles of the spindle


•Sister chromatids separate at the centromeres

•Daughter chromosomes are moved to opposite poles of the cell as

–Motor proteins move the chromosomes along the spindle microtubules, and

–Kinetochore microtubules shorten.

•The cell elongates due to lengthening of non-kinetochore microtubules.


•The cell continues to elongate.

•The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei.

•Chromatin uncoils and nucleoli reappear.

•The spindle reappears.

•During cytokinesis, the cytoplasm is divided into separate cells.

•The process of cytokinesis differs for plants and animals.

•In plant cells, cytokinesis occurs as:

–A cell plate forms in the middle, form in the middle, from vesicles containing cell wall material.

–The cell plate grows outward to reach the edges, dividing the contents into two cells.

–Each cell now possesses a plasma membrane and cell wall.

•In animal cells, cytokinesis occurs as:

–A cleavage furrow from a contracting ring of microfilaments, interacting with myosin, and

–The cleavage furrow deepens to separate the contents into two cells.

•Anchorage, cell density, and chemical growth factors affect cell division

•The cells within an organism’s body divide and develop at different rates.

•Cell division is controlled by

–The presence of essential nutrients,

–Growth factors, proteins that stimulate division,

–Density-dependent inhibition, in which crowd cells stop dividing, and

–Anchorage dependence, the need for cells to be in contact with a solid surface to divide.

•Growth factors signal the cell cycle control system

•The cell cycle control system is a cycling set of molecules in the cell that

–Triggers and

–Coordinates key events in the cell cycle.

•Checkpoints in the cell cycle can

–Stop an event or

–Signal an event to proceed.

•Growth factors signal the cell cycle control system

•There are three major checkpoints in the cell cycle.

–G1 checkpoint

•Allows entry into the S phase or

•Causes the cell to leave the cycle, entering a non-dividing G0 phase.

–G2 checkpoint, and

–M checkpoint

•Research on the control of the cell cycle is one of the hottest areas in biology today.

•Connection: Cell Reproduction and Cancer

•Growing out of control, cancer cells produce malignant tumors.

–Cancer currently claims the lives of 20% of the people in the United States and other industrialized nations.

–Cancer cells escape controls on the cell cycle.

•Connection: Cancer cells…

•Divide rapidly, often in the absence of growth factors,

•Spread to other tissues through the circulatory system , and

•Grow without being inhibited by other cells.

•Connection: Tumor

•A tumor is an abnormally growing mass of body cells.

–Benign tumors remain at the original site.

–Malignant tumors spread to other locations, call metastasis.

•Connection: Cancers are named according to the organ or tissue in which they originate.

•Carcinomas arise in external or internal body coverings.

•Sarcomas arise in supportive and connective tissue.

•Leukemias and lymphomas arise from blood-forming tissues.



•Connection: Cancer treatments

•Localized tumors can be…

–Removed surgically and/or

–Treated with concentrated beams of high-energy radiation.

•Chemotherapy is used for metastatic tumors.

•Meiosis and Crossing Over

•Chromosomes are matched in homologous pairs

•In humans, somatic cells have

–23 pairs of homologous chromosomes and

–One member of each pair from each parent.

•The human sex chromosomes X and Y differ in size and genetic composition.

•The other 22 pairs of chromosomes are autosomes with the same size and genetic composition.

•Homologous chromosomes are matched in…


•Centromere position, and

•Gene locations.

•A locus (plural, loci) is the position of a gene.

•Different versions of a gene may be found at the same locus on maternal and paternal chromosomes.

•Gametes have a single set of chromosomes.

•An organism’s life cycle is the sequence of stages leading…

•From the adults of one generation

•To the adults of the next.

•Humans and many animals and plants are diploid, with body cells that have

•Two sets of chromosomes,

•one from each parent.

•Meiosis is a process that converts diploid nuclei to haploid nuclei.

•Diploid cells have two homologous sets of chromosomes.

•Haploid cells have one set of chromosomes.

•Meiosis occurs in the sex organs, producing gametes-



•Fertilization is the union of sperm and egg.

•The zygote has a diploid chromosome number, one set from each parent.

•All sexual life cycles include an alternation between

•A diploid stage and

•A haploid stage.

•Producing haploid gametes prevents the chromosome number from doubling in every generation.

•Meiosis reduces the chromosome number form diploid to haploid.

•Meiosis is a type of cell division that produces haploid gametes in diploid organisms.

•Two haploid gametes combine in fertilization to restore the diploid state in the zygote.

•Meiosis and mitosis are preceded by the duplication of chromosomes. However,

–Meiosis is followed by two consecutive cell division and

–Mitosis is followed by only one cell division.

•Because in meiosis, one duplication of chromosomes is followed by two divisions, each of the four daughter cells produced has a haploid set of chromosomes.

•Mitosis and meiosis have important similarities and differences

•Mitosis and meiosis both…

–Begin with diploid parent cells that

–Have chromosomes duplicated during the previous interphase.

–However, the end products differ.

•Mitosis produces two genetically identical diploid somatic daughter cells.

•Meiosis produces four genetically unique haploid gametes.

•Independent assortment of chromosomes in meiosis and random fertilization lead to varied offspring.

•Genetic variation in gametes results from

•Independent orientation at metaphase I and

•Random fertilization

–The combination of each unique sperm with each unique egg increases genetic variability.

•Independent orientation at metaphase I

•Each pair of chromosomes independently aligns at the cell equator.

•There is an equal probability of the maternal or paternal chromosome facing a given pole.

•The number of combinations for chromosomes packaged into gametes is 2n where n= haploid number of chromosomes.

•Random fertilization

–The combination of each unique sperm with each unique egg increases genetic variability.

•Homologous chromosomes may carry different versions of genes

•Separation of homologous chromosomes during meiosis can lead to genetic difference between gametes

–Homologous chromosomes may have different versions of a gene at the same locus.

–One version was inherited from the maternal parent and the other came from the paternal parent.

–Since homologues move to opposite poles during anaphase I, gametes will receive either the maternal or paternal version of the gene.

•Crossing over further increases genetic variability

•Genetic recombination is the production of new combination of genes due to crossing over.

•Crossing Over

•Crossing over is an exchange of corresponding segments between separate (Non-sister) chromatids on homologous chromosomes.

–Nonsister chromatids join at a chiasma (plural, chiasmata) the site of attachment and crossing over.

–Corresponding amounts of genetic material are exchanged between maternal and paternal (nonsister) chromatids.

•Alterations of Chromosome Number and Structure

•A karyotype is a photographic inventory of an individual’s chromosomes.

•A karyotype is an ordered display of magnified images of an individual's chromosomes arranged in pairs.


–Are often produced from dividing cells arrested at metaphase of mitosis and

–Allow for the observation of

–Homologous chromosome pairs,

–Chromosome number, and

–Chromosome structure.

•Connection: An extra copy of chromosome 21 causes Down syndrome

•Trisomy 21

–Involves the inheritance of three copies of chromosome 21 and

–Is the most common human chromosome abnormality.

•Connection: Down Syndrome

•Trisomy 21, called Down Syndrome, produces a characteristic set of symptoms, which include:

–Mental retardation,

–Characteristic facial features

–Short stature

–Heart defects

–Susceptibility to respiratory infections, leukemia, and Alzheimer’s disease, and

–Shortened lifespan

•The incidence increases with the age of the mother.

•Accidents during meiosis can alter chromosome number

•Nondisjunction is the failure of chromosomes or chromatids to separate normally during meiosis. This can happen during:

–Meiosis I, if both members of a homologous pair go to one pole or

–Meiosis II if both sister chromatids go to one pole.

•Fertilization after nondisjunction yields zygotes with altered numbers of chromosomes.

•Connection: Abnormal numbers of sex chromosomes do not usually affect survival.

•Sex chromosomes abnormalities tend to be less severe, perhaps because of:

–The small size of the Y chromosomes or

–X-chromosomes inactivation.

•In general, a single Y chromosome is enough to produce “maleness,” even in combination with several X chromosome, and

•The absence of a Y chromosome yields “ femaleness”

•Evolution Connection: New species can arise from errors in cell division

•Errors in mitosis or meiosis may produce polyploid species, with more than two chromosome sets.

•The formation of polyploid species is:

–Widely observed in many plant species but

–Less frequently found in animals

•Connection: Alterations of chromosome structure can cause birth defects and cancer

•Chromosome breakage can lead to rearrangements that can produce

–Genetic disorders, or

–If changes occur in somatic cells, cancer.

•Connection: Alterations of chromosome structure can cause birth defects and cancer

•These arrangements may include

–A deletion, the loss of a chromosome segment,

–A duplication, the repeat of a chromosome segment, an diversion, the reversal or a chrome segment, or a translocation, the attachment of a segment to a non-homologous chromosome that can be reciprocal.

•Connection: Alterations of chromosome structure can cause birth defects and cancer

•Chronic myelogeous leukemia (CML)

–Is one of the most common leukemias,

–Affects cells that give rise to white blood cells (leukocytes), and

–Results from part of chromosome 22 switching places with a small fragment from a tip of chromosome 9.

Total Pages
80 pages
Answer Key
Teaching Duration
1 Week
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