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Bio 150: Chapter 10
How Cells Divide
46
Biology
Undergraduate 1
03/29/2014

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Term
Are eukaryotic chromosomes linear or circular?
Definition
Linear
Term
How many chromosomes do humans have? What about dogs?
Definition
Human cells have 46 chromosomes consisting of 23 nearly identical pairs. Dogs have 78 chromosomes
Term
What is CHROMATIN? What is the difference between EUCHROMATIN and HETEROCHROMATIN?
Definition
CHROMATIN, a complex of DNA and Protein. Most chromosomes are about 40% DNA and 60% Protein. HETEROCHROMATIN and EUCHROMATIN are domains of chromatin. EUCHROMATIN: The portion of a eukaryotic chromosome that is transcribed into mRNA; contains active genes that are not tightly condensed during interphase. HETEROCHROMATIN: The portion of a eukaryotic chromosome that is NOT transcribed into RNA; remains condensed in interphase and stains intensely in histological preparations.
Term
What is the relationship between HISTONE PROTEINS, CHROMOSOMES, and NUCLEOSOMES?
Definition
Every 200 nucleotides, the DNA duplex is coiled around a core of eight HISTONE PROTEINS. HISTONES are positively charged because of an abundance of the basic amino acids arginine and lysine. Thus, the attracted to the negatively charged phosphate groups of the DNA, and the HISTONE cores act as "magnetic forms" that promote and guide the coiling of DNA. The complex of DNA and HISTONE proteins is termed a NUCLEOSOME.
Term
What does it means for and organism to be HAPLOID?
Definition
When defining the number of different chromosomes in a species, geneticists count the HAPLOID number or chromosomes. This refers to one complete set of chromosomes necessary to define and organism.
Term
What does it mean for an organism to be DIPLOID?
Definition
For humans and many other species, the total number of chromosomes in a cell is called the DIPLOID number, which is twice the haploid number.
Term
What does the term HOMOLOGOUS mean in biology?
Definition
Refers to similar structures that have the same evolutionary origin. Also refers to the same kind of chromosome in a diploid cell. Diploid chromosomes reflect the equal genetic contribution that each parents makes to offspring. We refer to the maternal and parental chromosomes as being homologous, and each one of the pair is termed homolouge.
Term
What is the difference between HOMOLOGOUS CHROMOSOME and sister CHROMATIDS?
Definition
HOMOLOGOUS CHROMOSOMES are the maternal and paternal copies of the same chromosome. SISTER CHROMATIDS are the two replicas of a single chromosome held together at their centromeres by cohesion proteins after DNA replication. Picture example Fig. 10.7 pg. 191
Term
What are COHESION molecules? On what type of moluecule Do they bond?
Definition
A protein complex that holds sister chromatids together during cell division.
Term

What are the events that happen during:

GPhase?

 

Definition

G(Gap Phase 1) is the primary growth phase of the cell. The term gap phase refers to its filling the gap between cytokinesis and DNA synthesis. For most cells, this is the longest phase.

[image]

Term

What are the events that happen during:

S Phase?


Definition

S (synthesis) is the phase in which the cell synthesizes a replica of the genome.

[image]

Term

What are the events that happen during:

GPhase?

Definition

G(gap phase 2) is the second growth phase and preparation for seperation of the newly replicatied genome. This phase fills the gap bewteen DNA synthesis and the beginning of Mitosis. During this phase, mitochondria and other organelles replicate, and microtubules begin to assemble at a spindle.

G1, S, and Gtogether institute interphase, the portion of the cell cycle bewteen cell divisions. 

[image]

Term

What are the events that happen during:

Mitosis?

Definition

Mitosis  is the phase of the cell cycle in which the spindle apparatus assembles, binds to the chromosomes, and moves the sister chromatides apart. Mistosis is the essential step in the seperation of the two daughter genomes. It is traditionally subdivided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.

[image]

 

Term

What are the events that happen during:

Cytokinesis Phase

Definition

Cytokinesis is the phase in the cell cycle when the cytoplasm divides, creating two daught cells. In animal cells the microtubule spindle helps position a contracting ring of actin the constricts like a drawstring to pinch the cell in two. In cells with a cell wall, such as plant cells, a plate forms bewteen the diving cells. 

[image]

Term
What phases of the cell cycle are part of interphase?
Definition
The events that occur during interphase-- the G1, S, and G2 phases, are very important for the sucessful completion of Mitosis
Term
What key events happen during the phases that take part during interphase?
Definition
During the G1 phase, cells undergo the major portion of their growth. During the S phase, each chromosome replicates to produce two sister chromatides, which remain attached to each other at the centromere. In the Gphase, the chromosomes coil even more tightly.
Term
What is a centromere? What is kinetochore? How are these two things related?
Definition
The centromere is the point of construction on the chromosome containing certain repeated DNA sequences that bind specific proteins. These proteins make up a dislike structure called the kinotochore. This disk functions as an attachment site for microtubules necessary to seperate the chromosomes during cell division. Figure 10.9 pg 193 in book.
Term
Illustrate the connection of sister chromatides after s phase:
Definition
After the s phase, the sister chromatids appear to share a common centromere, but at the molecular level the DNA of the centomere has actually already replicated, so there are two complete DNA molecules. figure 10.10 pg 193
Term
What are the names on the phases of Mitosis in the order they occur?
Definition

1.) Prophase

        2.) Prometaphase

  3.) Metaphase

4.) Anaphase

 5.) Telophase

Term
What key events happens during Prophase (the first phase of mitosis)?
Definition
During Prophase, the mitotic apparatus forms (pg.195)
  • Chromosomes condense and become visible
  • Chromosomes appear as two sister chromatides held together at the centomere.
  • Cytoskeleton is disassembled; spindle begins to form
  • Golgi and ER are dispersed 
  • Nuclear envelope breaks down
Term
What key events happen during Prometaphase (the second phase of mitosis)?
Definition

During prometaphase, chromosomes attach to the spindle (pg. 196)

  • Chromosomes attach to microtubules at the kinetochores
  • Each chromosome is oriented such that the kinetochore of sister chromatids are attached to microtublues from opposite poles.
  • Chromosomes move to equator of the cell
Term
What key events happen during Metaphase (the third stage of mitosis)?
Definition

In metaphase, chromosomes align at the equator 

(pg. 196)

  • All chromosomes are aligned at equator of the cell, called the metaphase plate. 
  • Chromosomes are attached to opposite poles and are under tension.
Term
What key events happen during Anaphase (the fourth phase of mitosis)?
Definition

At anaphase, the chromatids seperate (pg.196)

  • Proteins holding centromeres of sister chromatids are degraded, freeing individual chromosomes.
  • Chromosomes are pulled to opposite poles. (anaphase a)
  • Spindle poles move apart (anaphase b)
Term
What key events happen during Telophase (the fifth and final stage of mitosis)
Definition

During telophase, the nucleus re-forms (pg. 197)

  • Chromosomes are clustered at opposite poles and decondense 
  • Nuclear envelopes re-form around chromosomes
  • Golgi complex and ER re-form
Term
What happens during cytokinesis? How is the process different in animal and plant cells?
Definition

The phase of the cell when the cell actually divides is called Cytokinesis. It gennerally involves the cleavage of the cell into roughly equal halves.

In animal cells and the cells of other eukaryotic cells without cell walls, cytokinesis is achieved by the means of a constricting belt of actin filaments.

Plant cell walls are far too rigid to be squeezed in two actin filaments. Instead, these cells assemble membrane components in their interior, at right angles to the spindal apparatus. This expanding membrane partion, called a cell plate,  continues to grow until it reaches the interior plasma membrane, fuses with it, and splits it into two.

Term
What is a check point?
Definition
The cell can be put on hold at specific points called Checkpoints. at any of these points, the process can be checked for accuracy and halted if there are any errors.
Term
What are the three main checkpoints in cells? What does each "check" for? Where does each occur in the cell cycle?
Definition

1.) G1/S Checkpoint: is the primary point at which the    cell "decides" whether or not to divide. 

2.) G2/M checkpoint: This checkpoint asses the success of DNA replication and can stall the cycle if DNA has not been acurately replicated.

3.) Spindle checkpoint ensure that all of the chromosomes are attached to the spindle in preparation for anaphase. 

Term
The book indicates that "cancer is a failure of cell control" -- why is this?
Definition
Cancer is essentially a disease of cell division -- a failure of cell division control.
Term
What is a tumor-suppressor gene? A proto-oncpgene?What is p53? What is Rb? How do these proteins function?
Definition
p53 has been identified as one of the culprits of cancer. This gene plays a key role in the G1 checkpoint. The gene's product, the p53 protein, monitors the integrity of DNA, checking that is is undamaged. If damage is detected the p53 halts cell divion and either repairs of sends the cell off to kill itself. By halting divison in damaged cells, the p53 gene prevents the developement of many mutated cells and is therefore considered a tumor-suppressor gene. Scientist have found that the p53 gene is completely absent or damaged in cancer patients. oncogenes are genes that can, when introduced to a cell, cause it to become a cancer cell. pro-oncogenes are normal cellular genes that become oncogenes when mutated. The first tumor-supressor identified was teh retino-blastoma susceptibility gene (rb) which predisposes people from a rare cancer of the retina in the eye.
Term
How are bacterial chromosomes different from eukaryotic chromosomes? Provide at least three comparisons!
Definition
  1. Bacterial chromosomes are circular and eukaryotic is linear
  2. Bacterial usually has a single chromosome and eukaryotic have multiple chromosomes.
  3. Bacterial cell seperate by binary fission and eukaryotic seperate through mitosis. 
Term
Describe how sister chromatids and homologous chromosomes are different:
Definition

Homologous chromosomes are the maternal and paternal copies of some chromosomes

Sister chromatids are the two replicas of a single chromosome held together at their centromere by cohesion proteins of the DNA replication

Term
What type of cell divison occurs in bacteria?
Definition
Binary Fisson
Term
What is the purpose of mitosis?
Definition
Mitosis is divided into five stages which act together to seperate duplicated chromosomes
Term
If a cell contained a mutation in the gene that encodes FtsZ, what process would be affected?
Definition
Septation
Term
A somatic cell from a corn plant normally contains 20 chromosomes. How many sister chromatids would that cell contain during G2 of the cell cycle?
Definition
40!!
Term
A duplicate copy of all the hereditary information contained in the nucleus of eukaryotic cells is made during what stage of the cell cycle?
Definition
S phase
Term
What type of proteins bind at the centromere and serve as an attachment site for microtubules?
Definition
Kinetochore
Term
At what stages of the cell cycle are sister chromatids bound together by cohesion?
Definition
S, G2, prophase, and metaphase.
Term
Through a microscope you can see a cell plate beginning to develope across the middle of a cell and nuclei re-forming on either side of the cell place. This cell is most likely ____________.
Definition
A plant cell in the process of cytokinesis
Term
Explain why cell cycle check points are important:
Definition
It uses the points G1/S, G2/M. and spindle check point to both access its internal state and intergrade external signals. It also checks whether proper condition have been acheived before passing the check points.
Term
This check point verifies that all of the DNA has been repicated prior to mitosis:
Definition
G2/M
Term
What does the p53 protein normally do in a cell?
Definition
p53 plays a key role in the G1 Checkpoint of cell division. It destroys cells that have inreparable damage to their DNA
Term
What are the consequences for the cell if the p53 gene is mutated and produces a nonfunctioning p53 protein?
Definition
abnormal p53 protein fails to stop cell division or repair DNA, and as damaged cells replicate, cancer developes.
Term
whats the difference between and oncogene and a proto-oncogene?
Definition
Oncogenes, when introduced to a cell cause it to become a cancer cell. Proto-oncogene are normal cellular genes that become oncogenes when mutated.
Term
Growth factors are proteins released by cells that trigger other cells to grow and divide. If a gene coding for growth factor expiriencesd a mutation causing the cell to grow and replicate out of control, this gene would most likely be labled an_______.
Definition
Oncogene
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