BIOL10003 Chapter Notes - Chapter ILT 3 : Cell Nucleus, Microtubule, Cell Plate

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lilaccaribou574

9 May 2018

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University of Melbourne

Department

Biology

Course

BIOL10003

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All

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Tuesday, 14 March 2017

ILT 3 : Mitosis and lecture 5

Process by which new cells are made from pre-existing ones:

-Cells divide in two.This cycle ensures that a pair of genetically identical daughter cells

are produced. Involves the reproduction of the cell organelles as well as exact

replication of the DNA and protein in the chromosomes.

PHASES OF THE MITOTIC CELL CYCLE !

interphase

-G1-when arrived it’s just divided First gap phase. The cell grows during G1 and

monitors its own size so that it will not proceed to the S stage until it is large enough. A

cell may remain in G1 for weeks or even years and may die without leaving G1 ( cells

in our brain stay in this phase.T he cell nucleus maintains a granular appearance, due

to the loosely coiled DNA. Can't go back after this phase.

-S- synthesis of a cell’s DNA. Each molecule of DNA is copied exactly so that two new

molecules identical to the parent molecule are produced.The DNA and protein at the

beginning of the S stage are loosely coiled. about 6 hours !

———————- DNA replication ——————!

1.Each chromosome is a single stranded structure, the DNA and protein are very

tightly coiled.Each chromosome is one molecule of DNA. DNA is a double helix in

which two polynucleotide chains are linked by hydrogen bonds.Adenine is linked with

thymine OR cytosine is linked with guanine. These pairs of bases are called

complementary bases.!

2. Enzymes disrupt the hydrogen bonds between the bases and the two strands open

out exposing unpaired bases.!

3. Enzymes bring new bases into position using the “old” DNA molecule as a

template.Complementary base pairing occurs ie. A=T and C=G.Replication on one

strand is continuous and on the other strand is discontinuous.!

4.The two new DNA molecules formed after replication are identical to each other.The

two molecules of DNA are joined in the region of the centromere.!

5. The chromosomes at the end of the S stage (although not visible) are composed of

two identical strands.

-G2 (growth phase)- At this stage you have two identical sister chromatid held together

at the centromere, nucleus double in size. the second gap phase between S and M,

allows the cell time for additional growth and time to check DNA replication is

complete before moving into mitosis.the centrosomes outside the nucleus divide. In

animals the centrosomes are associated with centrioles. The centrosomes serve as a

mitotic centre, which organises microtubules, some of which become the polar

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Tuesday, 14 March 2017

microtubules of the spindle.Throughout interphase, the cell nucleus maintains a

granular appearance, due to the loosely coiled DNA. Check at the end, killed off if

chromosomes and DNA aren’t good, cancer is a result of this getting through.!

———————————————————-

-M- !

Mitosis is the process of chromosome condensation, nuclear envelope breakdown,

sister chromatids separation and formation of two daughter nuclei in eukaryotes!

Mitosis is a continuous process which is arbitrarily divided into four major phases:!

1. prophase: The nuclear envelope breaks up.The chromatin, visible in the nucleus

during interphase, slowly condenses into chromosomes.The spindle microtubules

assemble. Centromere have duplicated and are moving away !

2. Prometaphase: Each chromosome has duplicated during the S phase of interphase

and consists of two sister chromatids.A pair of specialised protein complexes called

kinetochores develop at the centromere of each duplicated chromosome.The

chromosomes line up across the metaphase plate, halfway between the

poles.Microtubules attached to the kinetochores assist in this alignment. Kinetochore

microtubules grow and retreat (dynamic instability) they keep doing this till they hit the

kinetirchore region of the chromosomes and they stabilise once they do it !

3. early metaphase:The chromosomes line up across the metaphase plate, halfway

between the poles.Microtubules attached to the kinetochores assist in this alignment.!

4.late metaphase: Each chromosome is held in tension by the kinetochores and their

associated microtubules, which attach to opposite poles of the spindle.!

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Document Summary

Process by which new cells are made from pre-existing ones: Cells divide in two. this cycle ensures that a pair of genetically identical daughter cells are produced. Involves the reproduction of the cell organelles as well as exact replication of the dna and protein in the chromosomes. G1-when arrived it"s just divided first gap phase. The cell grows during g1 and monitors its own size so that it will not proceed to the s stage until it is large enough. A cell may remain in g1 for weeks or even years and may die without leaving g1 ( cells in our brain stay in this phase. t he cell nucleus maintains a granular appearance, due to the loosely coiled dna. Each molecule of dna is copied exactly so that two new molecules identical to the parent molecule are produced. the dna and protein at the beginning of the s stage are loosely coiled. about 6 hours.

Related Questions

Part A:

In prokaryotes and eukaryotes cell reproduction is similar in that it requires some kind of signal to proceed, DNA replication, careful separation of the DNA into two equal portions, and division of the cytoplasm. How is cell reproduction different in prokaryotes and eukaryotes?

Select one:

a. In a eukaryotic organism, the signals for cell division are usually not related to the environment but to the function of the entire organism.

b. Eukaryotic cells constantly divide whenever environmental conditions are adequate and the cells are large enough.

c. The linear chromosomes in prokaryotes are constantly being updated.

d. Prokaryotic cell division requires cytokinesis before mitosis because of their small size.

e. The sexual phase of most prokaryotes (bacteria) is essential to the rapid cell division required for infection.

Part B:

What does the name Cyclin Dependent Kinase stand for?

Select one:

a. A protein important to the cell cycle that is dependent on DNA synthesis.

b. An enzyme that cuts DNA so that chromosomes can segregate.

c. An enzyme that phosphorylates other proteins using ATP only when the protein Cyclin is bound to the enzyme.

d. An enzyme that rolls along microtubules dragging a vesicle.

e. An enzyme that connects chromosomes to the spindle fiber.

Part C:

The Cell Cycle is divided into Mitosis, Cytokinesis, and Interphase. Mitosis can be ordered into the following phases:

Select one:

a. Prophase/Prometaphase/Metaphase/Anaphase/Telophase

b. Anaphase/Prometaphase/Metaphase/Prophase/Telophase

c. Metaphase/Anaphase/Telophase/Prophase/Prometaphase

d. Telophase/Prophase/Prometaphase/Metaphase/Anaphase

e. Anaphase/Telophase/Prophase/Prometaphase/Metaphase

Part D:

The Cell Cycle is divided into Mitosis, Cytokinesis, and Interphase. Interphase can be ordered into the following phases:

Select one:

a. S/G1/G2

b. G2/G1/S

c. G1/S/G2

d. G2/S/G1

e. G1/G2/S

amethystyak657

Match the term with its correct definition or explanation.

Chromatin

Homologous Chromosomes

Sister chromatids

Diploid

Interphase

S Phase

Synapsis

Crossing Over

Cell Plate

Cleavage Furrow

A. The exchange of genetic material between homologous chromosomes during meiosis I.

B. The pairing or tight association of homologous chromosomes in meiosis I. Results in the formation of a tetrad.

C. Non-identical copies of the same chromosome. Present in all diploid cells, even before replication. These chromosomes are the same length and contain genes for the same characteristics, but may have different alleles for each gene. D.

The period of the cell cycle that includes G1, S phase, and G2. E. A structure that develops during cytokinesis in plants.

F. Condensed chromosomes.

G. An invagination that develops during cytokinesis in animal cells.

H. When an organism has two copies of every chromosome (2n).

I. Two identical copies of a chromosome. These are only present after DNA replication.

J. The phase of the cell cycle when DNA is replicated.

1) A tissue in a mouse contains two types of cells: one that divides rapidly and one that divides more slowly. The most likely difference between these two cell types is that the slow-dividing cell type spends more time in phase

G1, G2, G3, M, or S

2) In meiosis II

a- four genetically identical cells are generated

b- sister chromatids are separated

c- DNA replication occurs