Cell Processes: Cell Division. Studying a Cell’s Size: Finding surface area to volume ratio 2.3 cm...

Cell Processes:

Cell Division

Studying a Cell’s Size:Finding surface area to volume ratio

2.3 cm 2.3

4.5 cm

Cell Size

Surface Area (length x width x 6)

Volume (length x width x height)

Ratio of Surface Area to Volume

Ratio of Surface Area to Volume in CellsSection 10-1

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Cell’s Are Limited in Size!

• DNA Overload- not enough information to support large cells

• Exchanging Materials across the cell’s membrane is affected

Oxygen GlucoseWaste

Structure of a Chromosome

Chromosome

Supercoils

Nucleosome

Histones

double

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Chromosome Structure in Eukaryotes

Organism Number (2n) of Chromosomes

Yeast 16

Mosquito 6

Housefly 12

Garden Pea 14

Corn 20

Fern 480-1,020

Frog 26

Human 46

Orangutan 48

Dog 78

Chromosome Numbers for Various Organisms

M phase

G2 phase

S phase

G1 phase

The Cell CycleSection 10-2

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Gap 1 Cells grow,

photosynthesize/respire, make proteins and

organelles~12 hours

M phase

G2 phase

S phase

G1 phase

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S phaseChromosomes are

replicated Each chromatid gets a

“sister”~ 6 hours

M phase

G2 phase

S phase

G1 phase

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Gap 2 Any organelles or

molecules needed for cell division are produced-

“getting prepared”~ 6 hours

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

Figure 10–5 Mitosis and Cytokinesis

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Telophase

Anaphase

Metaphase

Centriole

Spindle

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Telophase

Anaphase

Metaphase

Centriole

Spindle

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Telophase

Anaphase

Metaphase

Centriole

Spindle

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Telophase

Anaphase

Metaphase

Centriole

Spindle

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

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Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Telophase

Anaphase

Metaphase

Centriole

Spindle

(paired chromatids)

Prophase

Centromere

Spindle forming

Section 10-2

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Drawing Mitosis

Pneumonic devices!• Cell Cycle: G1, S, G2, Mitosis, Cytokinesis

Go Sally Go! Make Children!

• Mitosis: (Prophase, Metaphase, Anaphase and Telophase)

• People Meet And Talk!

Cell Division TimesCell Type Process Time

fly embryo mitosis 8 minutes

bacteria mitosis 20 minutes

yeast mitosis 2 hours

human skin mitosis 20 - 24 hours

human sperm meiosis about 64 days

human liver mitosis 1 year or more

human egg meiosis up to 40 years or more

human nerve mitosis never, once mature

Triffle?

What is a homologous pair of chromosomes?

Chromosomes that “match” because

they carry information for the

same traits. Organism created

by sexual reproduction

receive one from their mother and one from their

father.

Diploid

• Definition: A diploid cell is a cell that contains two sets of chromosomes. One set of chromosomes is donated from each parent.

• Cells made through Mitosis are “Diploid”

#6 uses the word Allele

• Alelle- fancy word for “different forms of a gene”

• Example- Gene for ear lobe placement: ear lobes attached or ear lobes free

Diploid Number

• The diploid number of a cell is the number of chromosomes in the cell. This number is commonly abbreviated as 2n, where ‘n’ stands for the number of chromosomes.

• Humans Diploid Number: 2N= 46• Fruit Fly Diploid Number: 2N=8

includes

is divided into is divided into

Concept MapSection 10-2

Cell Cycle

M phase (Mitosis)

Interphase

G1 phase S phase ProphaseG2 phase Metaphase TelophaseAnaphase

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How many chromosomes would a human sperm or an egg

contain if either one resulted from the process of mitosis?

Section 11-4

Interest Grabber continued

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• If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?

• In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?

Instead of “Diploid” Sex Cells, we need “Haploid” Sex cells

What’s the difference?

Diploid Cells• “two sets” of chromosomes• Cells made in Mitosis

• Humans 2N= 46• Fruit Fly 2N=8

Haploid Cells• “one set” of chromosomes• Cells made in Meiosis

• Humans N= 23• Fruit Fly N=4

Meiosis I

Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a round of DNA replication, forming duplicate Chromosomes.

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

Spindle fibers attach to the chromosomes.

The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Section 11-4

Figure 11-15 Meiosis

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Meiosis I

Section 11-4

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Meiosis I

Section 11-4

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Meiosis I

Section 11-4

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Section 11-4

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Meiosis II

Section 11-4

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Meiosis II

Section 11-4

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Meiosis II

Section 11-4

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Special Events Of Meiosis:

• Crossing Over during Prophase I• Interaction between non-sister chromatids of a

homologous pair of chromosomes• Chromatids break at same places along the length

and exchange corresponding segments

Section 11-4

Crossing-Over

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Section 11-4

Crossing-Over

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Section 11-4

Crossing-Over

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Another Special Event of Meiosis

• Alignment of Homologous Pairs in Metaphase I• The alignment of homologous chromosomes is a

random event which places maternal and paternal chromosomes in a random location

• Possible combinations:

• Crossing over + Random alignment = ?

Another Special Event of Meiosis

• Alignment of Homologous Pairs in Metaphase I• The alignment of homologous chromosomes is a

random event which places maternal and paternal chromosomes in a random location

• Possible combinations:

2n = 223

• Crossing over + Random alignment = ?

Results of Meiosis In Males

• 4 genetically different, but equal in size sperm result each time Meiosis occurs

• This happens at sexual maturity and as needed in the testes

In Females• One viable egg is produced

the other three cells are called polar bodies

• This process occurs in the ovaries of the female in utero. The eggs will become ready at sexual maturity.

Country

People

Chromosome

Chromosome fragment

Nucleotide base pairs

Section 11-5

Comparative Scale of a Gene Map

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Mapping of Earth’s Features

Mapping of Cells, Chromosomes, and Genes

Cell Processes: Cell Division. Studying a Cell’s Size: Finding surface area to volume ratio 2.3 cm...

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