Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

1

Topic 3D- Life Structure, Function and Control (Cell Cycle)

H. Cell Cycle

This handout is for lecture use only and not for commercial reproduction and

distribution.

The Cell Cycle:

what are the

implications to you

The Cell Cycle

consists of

Interphase (cell growth and copying of chromosomes in preparation for cell division)

Mitotic (M) phase (mitosis and cytokinesis)

Interphase (about 90% of the cell cycle) can be divided into subphases:

G1 phase (first gap)

S phase (synthesis)

G2 phase (second gap)

the cell grows during all three phases, but chromosomes are duplicated only during the S phase

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cell Cycle

A cell grows (G1), continues to grow as it copies/duplicates its

chromosomes (S), grows more as it completes preparations for cell division

(G2), and divides (M).

Mitosis is conventionally divided into five phases:

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cell Cycle

Cell division- reproduction of cells

Mitosis- the division of the nucleus

Cytokinesis- division of the

cytoplasm

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

2

The mitotic (M) phase of the cell cycle alternates with the much longer interphase.

The M phase includes mitosis and cytokinesis.

Interphase accounts for 90% of the cell cycle.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

G2 of Interphase

-Chromosomes, duplicated during S phase,

cannot be seen individually because they

have not yet condensed.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Prophase

Each duplicated chromosome appears as two identical sister

chromatids joined together at their

centromeres

The mitotic spindle begins to form

The centrosomes move away from each other.

Prometaphase

The nuclear envelope fragments.

The chromosomes have become even more condensed.

Each of the two chromatids of each chromosome now has a

kinetochore, a specialized protein

structure located at the

centromere.

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

3

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Metaphase

Metaphase is the longest stage of mitosis, often lasting

about 20 minutes.

The centrosomes are now at opposite poles of the cell.

The chromosomes and chromosomes' centromeres

convene on the metaphase

plate.

Anaphase

Anaphase is the shortest stage of mitosis, often lasting only a few minutes,

Two sister chromatids of each pair to part suddenly. Each chromatid thus

becomes a full-fledged chromosome.

The two liberated daughter chromosomes begin moving toward

opposite ends.

By the end of anaphase, the two ends of the cell have equivalent-and complete-

collections of chromosomes.

Telophase

Two daughter nuclei form in the cell.

Nuclear envelopes arise

Nucleoli reappear.

The chromosomes become less condensed.

Mitosis, the division of one nucleus into two genetically identical nuclei, is now complete,

Cytokinesis

The division of the cytoplasm is usually well under way by late telophase.

In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches

the cell in two.

A eukaryotic cell has

multiple chromosomes.

Before duplication, each

chromosome has a single

DNA molecule

Once replicated, a

chromosome consists of

two sister chromatids

connected along their

entire lengths by sister

chromatid cohesion. Each

chromatid contains a copy

of the DNA molecule

Mechanical processes

separate the sister

chromatids into two

chromosomes and

distribute them to two

daughter cells.

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

4

Cytokinesis, division of the cytoplasm, typically follows mitosis.

In animals, the first sign of cytokinesis (cleavage) is the appearance of a cleavage furrow in the cell surface near the old metaphase plate.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

During telophase in plants, vesicles from the Golgi coalesceat the metaphase plate, forming a cell plate.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The frequency of cell division varies with cell type.

Investigation of the molecular mechanisms regulating these differences provide important insights into how normal cells operate, but also how cancer cells escape controls.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Regulation of the Cell Cycle

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Meiosis

preceded by the replication of chromosomes

reduces the number of chromosome sets

takes place in two sets of cell divisions, called meiosis I and meiosis II

Copyright 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Genetics - the scientific study of heredity and hereditary variation

Offsprings acquire genes from parents by inheriting chromosomes

Homologous chromosomes, or homologs two chromosomes composing a pair have the same length, centromere, position, and

staining pattern

.

Diploid cell - any cell with two chromosome sets with a diploid

number of chromosomes, abbreviated 2n

Haploid cell- contain a single chromosome set, abbreviated n

Meiosis- type of cell division that reduces the number of sets of

chromosomes from two to one in the gametes

- reduces the number of chromosome sets from diploid to

haploid

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

5

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

6

Fertilization restores the diploid condition

Methods in the Study of Biology

Scientific inquiry is used to ask and answer questions about nature

The word science is derived from a Latin verb meaning to know. Science is a way of knowing.

Scientists

use inductive reasoning to draw general conclusions from many observations and

deductive reasoning to come up with ways to test a hypothesis, a proposed explanation for a set of observations.The logic flows from general premises to the specific results we should expect if the premises are true.

2012 Pearson Education, Inc.

The Scientific Method

Inductive Reasoning

Discovering general principles through examination of specific cases.

The Nature of Science

The Scientific Method

The Nature of Science

Deductive Reasoning

Examining individual cases by applying accepted general principles.

Mathematics

Philosophy

Politics

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

7

1.8 Scientific inquiry is used to ask and answer questions about nature

How is a theory different from a hypothesis? A scientific theory is

much broader in scope than a hypothesis,

usually general enough to generate many new, specific hypotheses, which can then be tested, and

supported by a large and usually growing body of evidence.

2012 Pearson Education, Inc.

1.9 Scientists form and test hypotheses and share their results

We solve everyday problems by using hypotheses.

A common example would be the reasoning we use to answer the question, Why doesnt a flashlight work?

Using deductive reasoning we realize that the problem is either (1) the bulb or (2) the batteries.

Further, a hypothesis must be

testable and

falsifiable.

In this example, two hypotheses are tested. 2012 Pearson Education, Inc.

Figure 1.9A_s1

Observation

Question

Hypothesis 1:

Dead batteries

Hypothesis 2:Burned-out bulb

Figure 1.9A_s2

Observation

Question

Hypothesis 1:

Dead batteries

Hypothesis 2:Burned-out bulb

Prediction: Prediction:

Replacing batteries

will fix problem.

Replacing bulb

will fix problem.

Experiment: Experiment:

Test prediction by

replacing batteries.

Test prediction by

replacing bulb.

Figure 1.9A_s3

Test falsifies

hypothesis. Revise

hypothesis or

pose new one.

Observation

Question

Hypothesis 1:

Dead batteries

Hypothesis 2:Burned-out bulb

Prediction: Prediction:

Replacing batteries

will fix problem.

Replacing bulb

will fix problem.

Experiment: Experiment:

Test prediction by

replacing batteries.

Test prediction by

replacing bulb.

Test does not

falsify hypothesis.

Make additional

predictions and

test them.

The Scientific Method

Scientific Process

Observation - Careful observation of a process or phenomenon

Hypothesis - Guess concerning the observation

May generate multiple hypotheses.

Prediction - Expected consequences of a correct hypothesis

Experiment - Test of a hypothesis

Biology 1 Topic 3D- Life Structure,

Function and Control (Cell Cycle)

8

The Scientific Method

Scientific Process

Experiment - Test of a hypothesis

Controlled Experiment - All factors influencing the experiment (controls) must be kept constant.

Conclusion - Draw a conclusion from the results

Reject or fail to reject hypothesis

Theory and Certainty

Theory - set of hypotheses that have been thoroughly tested over time, and generally accepted by the scientific community

acceptance is always provisional

to the general public a theory is synonymous with a guess due to lack of knowledge

The Scientific Method The Scientific Method

Limitations of Science

Scientific study is limited to area that can be observed and measured.

Cannot be used to address all questions.

Bound by practical limits

Temporal and spatial considerations

1.9 Scientists form and test hypotheses and share their results

Science is a social activity with most scientists working in teams.

Scientists share information in many ways.

Science seeks natural causes for natural phenomena.

2012 Pearson Education, Inc.

1.10 CONNECTION: Biology, technology, and society are connected in important ways

Many issues facing society are related to biology. Most involve our expanding technology.

The basic goals of science and technology differ.

The goal of science is to understand natural phenomena.

The goal of technology is to apply scientific knowledge for some specific purpose.

2012 Pearson Education, Inc.