CHAPTER 8 – CELLULAR REPRODUCTION: CELLS … Notes... · Slide 34 Copyright © 2003 Pearson...

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

CHAPTER 8 – CELLULAR REPRODUCTION: CELLS

FROM CELLS

Slide 2


State StandardsStandard 2:

Standard 5a:

Standard 5b:

Slide 3


State StandardsStandard 2a:

Standard 2b:


• The life cycle of a multicellular organism includes

• This sea star embryo (morula) shows one stage in the development of a fertilized egg

– The cluster of cells will continue to divide as development proceeds

Slide 5


Introduction to Cell Division

Life cycle – the sequence of life stages leading from the adults of one generation to the adults of the next

• Development phase –

• Reproduction phase – formation of new individuals from preexisting ones

Slide 6


• Cell division is at the heart of the reproduction of cells and organisms

• Organisms can reproduce sexually or asexually

CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION


In asexual reproduction, single-celled organisms reproduce by simple cell division.

Slide 8


• Some multicellular organisms can divide into pieces that then grow into new individuals.

– This sea star is regenerating a lost arm

– Regeneration

Slide 9


• Some organisms make exact copies of themselves, asexual reproduction

Like begets like, more or less

Figure 8.1A


• Other organisms make similar copies of themselves in a more complex process, sexual reproduction

Figure 8.1B

Slide 11


Introduction of Cell Division

• Sexual reproduction –

• Asexual reproduction – production of offspring by a single parent

Slide 12


Comparing Asexual and Sexual Reproduciton

• See What Cell Reproduction Accomplishes reading notes


• All cells come from cells

• Cell division –

• Main roles:

– The development of a fertilized egg to an adult, how organisms grow to adult size

– Asexual reproduction or the formation of eggs and sperm

Cells arise only from preexisting cells

Slide 14


• Prokaryotic cells divide asexually

– These cells possess a single chromosome, containing genes

– The chromosome is replicated

– The cell then divides into two cells, a process called

Prokaryotes reproduce by binary fission

Figure 8.3B

Prokaryotic chromosomes

Slide 15


Figure 8.3A

• Binary fission of a prokaryotic cell

Prokaryoticchromosome

Plasmamembrane

Cell wallDuplication of chromosomeand separation of copies

Continued growth of the cell and movement of copies

Division intotwo cells


– Almost all of the genes of a eukaryotic cell are located on chromosomes in the cell nucleus.

• Chromosome – DNA containing structure found in the nucleus of an eukaryotic cell. It carries the organism’s genetic information

• Gene – a unit of hereditary information consisting of a specific nucleotide sequence of DNA

Chromosomes

Slide 17


Eukaryotic Chromosomes

– Each eukaryotic chromosome contains

• Proteins – help organize the DNA and control the activity of the genes

– The number of chromosomes in a eukaryotic cell depends on the species.

Slide 18

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.3


Chromosomes

• Chromosomes can exist as

– Chromatin –

– Compact, distinct structures that are visible under the light microscope. Occur when the cell is dividing.

Slide 20


Slide 21


• Before a cell starts dividing, the chromosomes are duplicated– This process

produces sister chromatids –

– Centromere –

Centromere

Sister chromatids

Figure 8.4B


• When the cell divides, the sister chromatids separate

– Two daughter cells are produced

– Each has a complete and identical set of chromosomes

Centromere Sister chromatids

Figure 8.4C

Chromosomeduplication

Chromosomedistribution

todaughter

cells

Slide 23


The Cell Cycle

Cell cycle – orderly sequence of events that occur from the formation of a new cell by division to that cell dividing.

Slide 24


• The cell cycle consists of two major phases:

– Interphase, where chromosomes duplicate and cell parts are made

– The mitotic phase, when cell division occurs

The cell cycle multiplies cells

Figure 8.5


The Cell CycleThe cell cycle can be divided into:

1. Interphase

a. G1 phase – the cell increases in size,

the number of organelles and proteins

increase

b. S phase –

c. G2 phase – period of rapid growth, cell

prepares to divide by producing the

proteins needed for cell division.

Slide 26


Slide 27



DNA ReplicationDNA Replication

Origins of replication – the specific sites on the DNA where DNA replication begins.

– Enzymes (DNA helicase) attach to the origins of replication and break the hydrogen bonds between the bases

– Causes the 2 DNA strands to separate

– Creates a replication bubble

Slide 29


DNA Replication

• The separated strands act as a template to create the new complementary strands

– New nucleotides are added to the bases of each parent strand

– DNA polymerase adds the new DNA nucleotides

• Only adds nucleotides to the 3’ end of the growing strand

• The new strand only grows from

Slide 30


DNA Replication

• One strand is synthesized in one continuous piece – leading strand

• Other strand is synthesized in pieces (Okazaki fragments) – lagging strand

• DNA ligase joins the pieces in the lagging strand


DNA Replication

• Once daughter strands are completed DNA polymerase checks for any errors and corrects them (proofreads)

Slide 32


DNA Replication

Result of DNA Replication

• 2 DNA molecules are formed that are exactly alike

• Each DNA molecule contains

– 1 nucleotide chain from the original DNA

– 1 new nucleotide chain formed during replication

– This makes DNA replication

Slide 33


Quickwrite

• Describe the process of DNA replication. Include the following terms in your description.

DNA polymerase Okazaki fragments

Origin of replication ligase

helicase

Leading strand semiconservative replication

Lagging strand


• Cells continue dividing until they touch one another

– This is called

Cells anchor to dish surface and divide.

Figure 8.8A

When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).

If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).

Slide 35


• Most animal cells divide only when stimulated, and others not at all

• In laboratory cultures, most normal cells divide only when attached to a surface

– They are

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

Slide 36


• Growth factors are

• Density dependent inhibition may be due to an inadequate supply of growth factor

After forming a single layer, cells have stopped dividing.

Figure 8.8B

Providing an additional supply of growth factors stimulates further cell division.


• Growth factors within the cell control the cell cycle

– Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide

Growth factors signal the cell cycle control system

G1 checkpoint

M checkpoint G2 checkpoint

Controlsystem

Figure 8.9A

Slide 38


Growth factors control the cell cycle at 3 key checkpoints

1. In the G1 phase – for many cells this is the most important

2. In the G2 phase

3. In the M (metaphase) phase

Slide 39


• Cancer cells have abnormal cell cycles

– They divide excessively and can form abnormal masses called tumors

– Are unrestrained by the systems that normally control cell division

• Don’t need growth factors to move past checkpoints

• Synthesize own growth factors

Growing out of control, cancer


Slide 41


Slide 42

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.20b


CancerTumor – an abnormal mass of cells due to

excessive growth

- benign

stay at original site

don’t usually impair normal function

can be completely removed by surgery

Slide 44


Cancer

malignant

– mass of cancer cells

- can impair normal function of tissue,

organ

Slide 45

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.20a


• Malignant tumors can invade other tissues and may kill the organism

Tumor

Figure 8.10

Glandulartissue

1 2 3A tumor grows from a single cancer cell.

Cancer cells invade neighboring tissue.

Lymphvessels

Cancer cells spread through lymph and blood vessels to other parts of the body.

Metastasis

Slide 47

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 11.1

Slide 48


Cancer

Cancer Treatment

Radiation – expose cancerous tumors to high energy radiation which disrupts cell division

Chemotherapy – drugs are administered that disrupt cell division


Cancer Prevention

• Self Examination

– Breast

– Testicular

– Skin

• Healthy Lifestyle

– Sunblock

– Avoid tobacco, drugs

– Balanced diet

– Exercise

• Medical Tests

– Pap smear

– Colonoscopy

Slide 50


The Cell Cycle2. Mitotic Phase – two daughter cells are produced that

are identical to one another.

a. Mitosis

-

- the duplicated chromosomes are

separated and evenly distrubuted to form

2 daughter nuclei

Slide 51


The Cell Cycle

Interphase

• Chromosomes not visible – in the form of chromatin

• Nucleus visible

• Nucleus contains 1 or more nucleoli

• Centrosomes have duplicated


Stages of Mitosis

Prophase

• Nuclear envelope breaks into fragments

• Nucleoli disappear

• Mitotic spindle begins to form

• Chromosomes coil and are visible

Slide 53


Stages of Mitosis

Metaphase

• Mitotic spindle is fully formed

• Chromosomes are lined up along the metaphase plate

Slide 54


Stages of Mitosis

Anaphase

• Sister chromatids separate

• Kinetochore fibers move the separated chromatids to opposite sides of the cell

• Non-kinetochore fibers elongate the cell


Stages of Mitosis

Telophase

• Daughter nuclei appear as nuclear envelope forms around separated chromosomes

• Nucleoli form in each nucleus

• Mitotic spindle breaks down

• Chromosomes uncoil to form chromatin

Slide 56


Write the name of the stage of cell cycle being described

1. The chromosomes are lined up in the middle of the cell

2. The 2 groups of chromosomes have reached the cell poles

3. Period of cell growth

4. Mitotic spindle is fully formed

5. Sister chromatids of each chromosome separate

6. The nuclear envelope breaks up

7. The chromosomes are duplicated

8. Daughter chromosomes are “walked” by motor proteins toward opposite poles

9. Chromosomes uncoil

10. Each chromosome appears

Slide 57


The Cell Cycle

b. Cytokinesis – the division of the cytoplasm


• In animals, cytokinesis occurs by cleavage

– This process pinches the cell apart

Cytokinesis differs for plant and animal cells

Figure 8.7A

Cleavagefurrow

Cleavagefurrow

Contracting ring ofmicrofilaments

Daughter cells

Slide 59


• In plants, a membranous cell plate splits the cell in two

Vesicles containingcell wall material

Cell plateforing

Figure 8.7BCell plate Daughter

cells

Wall ofparent cell

Daughternucleus

New cell wall

Slide 60


• Somatic cells of each species contain a specific number of chromosomes

– Human cells have 46, making up 23 pairs of homologous chromosomes

MEIOSIS AND CROSSING OVER

Chromosomes are matched in homologous pairs

Chromosomes

Centromere

Sister chromatids Figure 8.12


Homologous Chromosomes

• Humans have 23 pairs of homologous chromosomes

– 22 pairs – autosomes –

– 1 pair – sex chromosomes,

XX = female,

XY= male

Slide 62


Homologous Chromosomes• Matched pairs of chromosomes

• Similar in

• Both carry genes controlling the same inherited characteristics (the version of the gene may be different)

• The genes are located

• One chromosome of each pair is inherited from the mother, the other from the father

Slide 63


• The human life cycle

Figure 8.13

MEIOSIS FERTILIZATION

Haploid gametes (n = 23)

Egg cell

Sperm cell

Diploidzygote

(2n = 46)Multicellular

diploid adults(2n = 46)

Mitosis anddevelopment


Human Life Cycle

Diploid cells (2n) – cells that contain both homologous chromosomes. In humans

Haploid cells (n) – cells with one copy of each homologous chromosome. The gametes (egg and sperm) are haploid. In humans

Slide 65


Meiosis

Meiosis

• In animals, meiosis results in the formation of haploid egg and sperm cells.

Slide 66


Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.16.2

Slide 68


MeiosisTwo nuclear divisions occur:

1. Meiosis I

a. During prophase I homologous chromosomes pair –

b. During prophase I the paired chromosomes exchange chromosome parts –

c. Homologous chromosomes are separated

d. 2 cells produced each containing one copy of each homologous chromosome

Slide 69


Model of Meiosis Conclusion

Meiosis I – Explain what happens during each of the stages of meiosis one and what is produced at the end of meiosis I. In your explanation include the following:

DNA Replication Interphase

Homologous chromosomes Prophase I

Synapsis Metaphase I

Crossing over Anaphase I

Telophase I

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.16.3

Slide 71


Meiosis

2. Meiosis II

a. Not preceded by the replication of DNA

b. Sister chromatids of each chromosome are separated

c. Produces

Slide 72


Model of meiosis conclusion

• Describe what occurs during each phase of meiosis II and what is formed at the end of this phase.


Meiosis

Meiosis produces 4 cells that

• Are haploid

• Chromosome makeup of each is

Slide 74


Slide 75


Comparing Mitosis and MeiosisMitosis

1.

2.

3. Involves one cell division

4.

5. Individual chromosomes line up at the metaphase plate

Meiosis

1. Produces haploid cells

2. Cells produced are unlike the parent

3.

4. Homologous chromosomes pair and then separate

5.


Comparing Mitosis and Meiosis

Mitosis

6. No crossing over occurs

7.

Meiosis

6.

7. Needed for sexual reproduction

Slide 77


Slide 78


Meiosis

Spermatogenesis

• Formation of sperm by meiosis

• Occurs in special cells (spermatogonia) in the testes


Slide 80


Meiosis

Oogenesis

• Formation of an egg by meiosis

• Occurs in special cells (oogonia) in the ovaries

• Unequal divisions of the cytoplasm during meiosis I and meiosis II result in the formation of 1 haploid egg and 3 haploid polar bodies

Slide 81



Identify if statement is describing oogenesis, spermatogenesis or both.

1. Occurs in the testes.

2. Produces 4 haploid cells.

3. Only one cell can take part in fertilization.

4. A continuous process.

5. Begins before birth.

Slide 83


Genetic Recombination

• Genetic Recombination –

• There are 4 processes that contribute to genetic recombination.

Slide 84



Independent Assortment of Chromosomes

• The large number of possible arrangements of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametes

– This results in 2n possible combinations of gametes

– For humans 2n = 223 = 8 million possible combinations

Slide 86


Figure 8.17A, B

Coat-color genes Eye-color genes

Brown Black

C E

c e

White Pink

C E

c e

C E

c e

Tetrad in parent cell(homologous pair of

duplicated chromosomes)

Chromosomes ofthe four gametes

Slide 87


• The differences between homologous chromosomes are based on the fact that they can carry different versions of a gene at corresponding loci

Homologous chromosomes carry different versions of genes


Figure 8.18A

TetradChaisma

Centromere

Slide 89


Slide 90


Genetic Recombination

Crossing over

• The exchange of genetic information between 2 homologous chromosomes.

Random fertilization

• Depends on which sperm cell and its chromosome combinations fertilizes which egg


Identify the process that contributes to genetic recombination

1. Occurs during prophase I

2. Occurs during metaphase I

3. The reason homologous chromosomes can be different from one another.

4. The possible arrangements of the homologous chromosomes when lining up along the equator.

5. Depends on which sperm cell fertilizes which egg.

6. The exchange of info between homologous chromosomes

7. Results in 2n possible combinations of gametes

Slide 92


• Preparation of a karyotype

Figure 8.19

Blood culture

1

Centrifuge

Packed redAnd white blood cells

Fluid

2

Hypotonic solution

3

Fixative

WhiteBloodcells

Stain

4 5

Centromere

Sisterchromatids

Pair of homologouschromosomes

Slide 93


• To study human chromosomes microscopically, researchers stain and display them as a karyotype

– A karyotype usually shows

ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE

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


• Abnormal chromosome count is a result of nondisjunction

– Either homologous pairs fail to separate during meiosis I

8.21 Accidents during meiosis can alter chromosome number

Figure 8.21A

Nondisjunctionin meiosis I

Normalmeiosis II

Gametes

n + 1 n + 1 n – 1 n – 1Number of chromosomes

Slide 95


– Or sister chromatids fail to separate during meiosis II

Figure 8.21B

Normalmeiosis I

Nondisjunctionin meiosis II

Gametes

n + 1 n – 1 n nNumber of chromosomes

Slide 96


• Fertilization after nondisjunction in the mother results in a zygote with an extra chromosome

Figure 8.21C

Eggcell

Spermcell

n + 1

n (normal)

Zygote2n + 1


• This karyotype shows three number 21 chromosomes

• An extra copy of chromosome 21 causes Down syndrome

Connection: An extra copy of chromosome 21 causes Down syndrome

Figure 8.20A, B

Slide 98


The chance of having a Down syndrome child goes up with maternal age

Slide 99


Alterations of Chromosomes

• In most cases abnormal chromosome number results in spontaneous abortion long before birth.

• Nondisjunction in the sex chromosomes has less of an affect on survival


• Nondisjunction can also produce

• Unusual numbers of sex chromosomes upset the genetic balance less than an unusual number of autosomes

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

Slide 101

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 8.1

Slide 102



• Chromosome breakage can lead to rearrangements that can produce genetic disorders or cancer

– Four types of rearrangement are deletion, duplication, inversion, and translocation

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

Slide 104


Figure 8.23A, B

Deletion

Duplication

Inversion

Homologouschromosomes

Reciprocaltranslocation

Nonhomologouschromosomes

Slide 105



Abnormalities in the structure of the chromosome may cause disorders (Figure 8.23A)

1. Deletion – a chromosome breaks and a fragment is lost.

2. Duplication – the fragment joins to a homologous chromosome.



3. Inversion – the fragment reattaches to the original chromosome but in reverse orientation.

4. Translocation (Figure 8.23B) – attachment of a chromosome fragment to a nonhomologous chromosome. May/may not be harmful.

Slide 107


• Chromosomal changes in a somatic cell can cause cancer

Figure 8.23C

Chromosome 9

– A chromosomal translocation in the bone marrow is associated with chronic myelogenous leukemia

Chromosome 22Reciprocaltranslocation

“Philadelphia chromosome”

Activated cancer-causing gene

CHAPTER 8 – CELLULAR REPRODUCTION: CELLS … Notes... · Slide 34 Copyright © 2003 Pearson...

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