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Genes and disease > Mitosis and Meiosis > Flashcards

Mitosis and Meiosis Flashcards

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1
Q

What is the role of the centromere ?

A

it is the most constricted part of the chromosome and can be identified on a single chromosome composed of two sisters chromatids

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2
Q

What is the role of the kinetochore ?

A

is a group of proteins associates with specific sections of chromosomal DNA at the centromere. Each od the two sister chromatids of a duplicated chromosome has a kinetochore that face in opposite directions and during prometaphase, some of the spindle microtubules (kinetochore microtubules) attach to the kinetochores.

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3
Q

What is the role of the centrosome?

A

It is also called microtubule-organising center is a subcellular region in animal cells where the assambly of spindle microtubules begins and are organised throughout the cell cycle.

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4
Q

What is the mitotic spindle ?

A

is an apparatus of microtubules that controls chromosomes movement during mitosis.
The centrosome replicates in the S phase of the interphase.

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5
Q

What happens with kinetochores during prometaphase ?

A

some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes. and they are protein complexes

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6
Q

What is chromatin?

A

It is the DNA plus the associated proteins (histone and non- histone proteins)

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7
Q

What is the difference between euchromatin and Heterochromatin?

A

*Euchromatin is decondensed open chromatin. Allows the attachment to DNA of proteins required for DNA replication, transcription and DNA repair.
*Heterochromatin is condensed chromatin. Prevents the attachment of proteins required for transcription.

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8
Q

What is the difference between a chromatid and a chromosome ?

A

A chromosome is a single molecule of compacted DNA which consist of a double axis together with associated proteins. But when the DNA is replicated ready for cell division, the two resultant DNA molecules remain joined together and are called sister chromatids. Once they separate at anaphase there will be two separated chromosomes.

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9
Q

Do cells replicate during interphase ?

A

No, the DNA replicates during interphase but not the whole cell.

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10
Q

G2 of interphase

A

the centrosomes are with centriole pairs and the chromatin is duplicated

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11
Q

Prophase

A

We have the early mitotic spindle and chromosomes consisting of two sister chromatids and a centromere.

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12
Q

Prometaphase

A

We have the fragments of the nuclear envelope and nonkinetochore microtubules and kinetochore in the chromosomes.

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13
Q

Metaphase

A

the metaphase plate centrosome at one spindle poles

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14
Q

Anaphase

A

Daughter chromosomes

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15
Q

Telophase and cytokinesis

A

The cleavage furrow is made and the nucleolus starts to form and also the nuclear envelope

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16
Q

What is the purpose of the cell cycle checkpoints controls ?

A

A set of molecules triggers and coordinate key events in the cell cycle. The major check points are found in G1G2, and M phases. These signls are cricial cellular processes like DNA replication, DNA not damaged, adequate nutrients, presence of growth factors, chromosomes properly align.

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17
Q

Each copy of replicates chromosomes is called ….

A

Chromatid

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18
Q

What are sister chromatids ?

A

When the copy of the chromosomes is made and have as a result sister chromatids. And their genetic material is identical

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19
Q

How are sister chromatids held ?

A

They are held by proteins called cohesins in a constricted area ( centromere)

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20
Q

When do chromatids stop being chromatids and change to chromosomes ?

A

During cell division and the copy of chromosomes they are called chromatids once the sister chromatids are separated they are chromosomes again.

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21
Q

What are the centromeres ?

A

It is the constriction between sister chromatids it is required for cell division and the segregation occurring in the process. For example the Kinetchore is a specialized protein structure involved in cell division located at centromere.

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22
Q

What role does telomerase in cell division ?

A

In the telomere that are ending regions of the chromosome containing characteristic telómeros sequences that are replicated in some cells by a special process that is catalyzed by the telomerase. This process counteracts the end envy of the chromosome to be shortened during each round of replication

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23
Q

What are the P and Q arms?

A

Each chromosome has two arms on either side of the centromere. These are called the p and q arms. P is the short one PETIT and Q is the longer arm.

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24
Q

Chromatin is made of ….

A

Complexes of DNA, Histones and non histone proteins present in the nucleus of eukaryotic cells

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25
What is the difference between heterochromatin and euchromatin
Herpterodhromatin is condensed chromatin and when highly condensed little gene expression happens, on the other hand euchromatin is less condensed chromatin and includes most of the regions where genes are expressed are active
26
What are the 3 sub phases of interphase ?
-G1 S= chromosomes are copied (Synthesis ) G2 In interphase the the DNA is uncoiled and and the cell is considered active in terms of gene expression and replication.
27
What is the general overview of the mitotic phase?
It has 5 plus cytokinesis sub phases Prophase Prometaphase Metaphase Anaphase Telophase
28
Why is the mitotic spindle indispensable for mitosis
It consist of microtubules and associated proteins . It assembles in the cytoplasm during prophase. There are centrioles located at the center of the centrosome. And during interphase it duplicates. Each moves apart during prophase and prometaphase as spindle microtubules grow out of them. By the end of prometaphase the two centrosomes are at the opposite end of the cell. An aster, radial array of short microtubules, extend from each centrosome.
29
Where do centromeres attach when separating the two sister chromatids?
At the kinetochore, the two kinetochore face in opposite directions. During prometaphase, a certain spindle microtubules attach to each kinetchore, with the help of an enzyme called separase each sister chromatids separates and goes to the other side.
30
What is the function of the non kinetochore microtubules.?
The non kinetochore microtubules are responsible for elongating the whole cell. Non kinetochore microtubules from opposite poles overlap each other extensively during metaphase. During Anaphase, the microtubules lengthen and walk them away from another , using energy from ATP . As they push apart from each other , the cell elongates
31
What are the characteristics of prophase ?
Thick, visible chromosomes appear and the spindle apparatus begins to form. Chromosomes condense
32
What are the characteristics for prometaphase?
More condensed chromosome, nuclear envelope breaks down, kinetochore microtubules attach to the chromosomes at kinetochore
33
What are the characteristic of metaphase ?
Chromosomes complete migration to the middle of the cell (metaphase plate)
34
What are the characteristics of Anaphase ?
Sister chromatids separate the sister chromatids now becoming chromosomes pulling the sister chromatids to the Opposite poles of the cell
35
What are the characteristics of TELOPHASE ?
The nuclear envelope re-forms, and the spindle apparatus disintegrates. chromosomes become less condensed
36
What happens at cytokinesis ?
Actin-myosin ring causes the plasma membrane to begin pinching in, the cytoplasm is divided and the DNA decondenses
37
How do prokaryotic cells divide ?
They divide by binary fission. It is a simplified cell cycle where DNA is replicated and the cell division happens right away. No special structures are needed and there is no DNA condensation. The single circular DNA molecular attached to the membrane gets replicated and the cell wall is divided.
38
What is said to be the evolution of mitosis?
Mitosis probably evolved from binary fission. Some protists show a intermediate between mitosis and binary fission.
39
What is the cell cycle ?
The cells cycle is the timing and rates of cell division in different parts of an animal or plants. It is crucial for normal growth, development and maintenance.
40
What are the cell cycle check points ?
They regulate the cell cycle progression, the cell has several check points stationed at intervals. This determines the fate of the cell and whether to proceed with the cycle and divides or goes into a non-dividing state called G0 phase
41
What are the three major checkpoints?
There are found in G1, G2 and M phases. The G1 checkpoint is the important " restriction point". The cell is checked for size, nutrients, social signals and DNA damage.
42
Why is the G1 is the most important checkpoint ?
Because when the cell receives a go ahead signal at the G1 checkpoint, it will usually complete the cell cycle and divide. With out a go signal at this point it will abandon the cycle and go into a G0 phase. Most of the cell of the body are at G0, however they can be called out of this phase by certain signals.
43
How do signals in the cell cycle work ?
The cell cycle appears to be driven by a specific chemical signal present in the cytoplasm called a mitosis promoting factor (MPF). The MPF contains a protein kinase and a cyclin . Other internal and external chemical or physical signals are also involved.
44
What are the chemical signals at the cell cycle ?
They include growth factors , hormones and other chemical messengers. For example, injured cells at the site of a wound send signals to other surrounding cells, which respond by growing and dividing and eventually sealing the wound.
45
What is an example of a growth factor?
The platet-derived growth factor PDGF released by platelets when an injury occurs. PDGF binds to fibroblasts a type of connective tissue) initiating cell division and wound healing.
46
When can a cell fire stop signals ?
When the cell finds itself in a nutrient-poor environment.
47
How can physical signals influence the cell cycle ?
Density-dependent inhibition is a phenomenon in which crowded cells stop dividing. furthermore, for animal cells to divide, they most be attched to a sub-stratum, such as the inside of a culture jar or the extracellular matrix of a tissue.
48
How the phenomena of cell density and anchorage appear to involve signaling to the cell (animal cells )?
Via pathways involving plasma membrane proteins and elements of cytoskeleton.
49
What does density-dpendency means ?
occurs when cells grow to a limited density then growth becomes inhibited, possibly by cell-cell contacts. Tumor cells have often lost density-dependent inhibition.
50
How does cancer relates to the cell cycle ?
When the cell cycle go signals are produced when they shouldnt be, or stop signals arent sent or heeded. Both scenarios can result in uncontrolled cell division and cancer.
51
What are the characteristics of cancer cells ?
cancer cells divide excessively and invade other tissues because they are free of the bodies mechanisms. They divide 20-50 times under culture conditions before they stop , age and die.
52
Can cancer cells be immortal ?
HeLa cells from a tumor removed from a woman in 1951 are still reproducing in culture.
53
When does the abnormal behavior of cells begins ?
when a single cell of the body undergoes transformation that converts it from a normal cell to an abnormal cell. Normally the immune recognizes it and destroys the cells.
54
How do cancer cells that evade the destruction of the immune system proceed?
They start to proliferate an form a tumur or mass of abnormal cells
55
What is the difference between a benign and malignant tumor?
The benign tumors remain in the originating site and the lump is called benign tumor. When the cells start to become invasive enough to impair the functions of one or more organs. an individual with malignant tumor is said to have cancer.
56
What it i the term used to describe when cancer cells spread to distant locations ?
Metastasis
57
What are the abnormalities of cancer cells ?
they may have -Abnormal number of chromosomes -their metabolism may be disabled and cease to function in a constructive way -No growth factors to grow and divide - exhibit neither density dependent nor anchorage dependence. -Poorly defined boundaries - Poorly defined boundaries
58
What are the two factors that influence the "transformation" in cells to happen ?
Alteration of the genes and in the cell cycle control system.
59
What are the cancer treatments ?
Chemotherapy these treatment interferes with specific steps of the cell cycle. Taxol freezes the mitotic spindle which stops actively dividing cells from proceeding past metaphase.
60
What is meiosis?
Sexually reproducing organisms use meiosis, a special kind of cell division that occurs only in cells of the reproductive organs to produce gametes.
61
how many chromosomes do somatic humans cells have?
46 chromosomes; 22 pairs of autosomes and two sex cells chromosomes (XX in females or XY in males)
62
What happens to chromosomes condense and they can be seen under the light microscope ?
Thy can be distinguished from each other by their size, centromere position and banding patterns when satined .( the DNA gets condensed)
63
What is karytotype?
The displayed of chromosomes condensed and with all of they characteristics
64
What are homologous chromosomes ?
chromosomes that are similar size, shape and gene content are called homologous. Human have 22 pairs of homologous autosomes.
65
What are the characteristics of somatic cells ?
the humans have 46 chromosomes in our somatic cells are actually two sets of 23 chromosomes, a maternal set and a parental set. Humans inherit a set of 22 autosomes and an X from their mother or either an X or Y from their father.
66
What is cytogenetics ?
It is the study of chromosomes.They use microscopically using fluorescent or giemsa dyes. Selective staining results in characteristics bands for specific chromosomes. At metaphase when more consensed.
67
What are R,Q and G banding ?
Q- quinacrine fluorescence R- stains complementary regions to those stained with G- banding G- Giemsa
68
what makes the stains dark ?
When heterochromatin is condensed so it gets dark when stained, euchromatin is not condense so it is light.
69
What does the term Ploidy means ?
It is the number of chromosomes sets (n). Human somatic cells are diploid. (2^n= 2 sets of chromosomes )
70
What is the ploidy of human gametes?
They are haploid (n) as they only contain one copy of each chromosome. During fertilisation, gmamates fuse and a new diploid cell is formed .
71
what is the human life cycle ?
The number of chromosomes sets doubles at fertilization, but is halved during mitosis. For humans, the number of chromosomes in a haploid cell is 23 consisting of one set , the number of chromosomes in the diploid zygote and all somatic cells arising from it is 46, consisting of two sets. 2(23)= 46
72
How many somatic cells does a human has ?
100 trillion somatic cells each containing 46 chromosomes
73
Mitosis vs Meiosis
-there is a duplication of chromosomes on interphase phase(s) -After that two consecutive cell divisions, called meiosis I and meiosis II Meiosis I= the first division separates the homologous chromosomes. i Meiosis II= in the second division , the sister chromatids separate resulting in four daughter cells (RATHER THEN TWO DAUGHTER CELLS IN MITOSIS), each with only half as many chromosomes as parent cell .
74
what is allele?
Homologous may have different versions of genes, each called an allele, at corresponding loci (position on a chromosomes)
75
Prophase in meiosis I
-chromosomes begin to condense -in synapsis , homologous chromosomes loosely pair up. -In crossing over , non sister chromatides exchange DNA segments. Each pair of chromosomes forms a tetrad, a group of four chromatids. Each tetrad usually has a chiasmata, X shaped regions where crossing over occurred.
76
Metaphase meiosis I
Tetrads line up at the metaphase plate, with one chromosome facing each pole. Microtubules attach to Kinetochores .
77
anaphase meiosis I
Pairs of homologous chromosome separate.
78
Telophase and cytokinesis and Telophase I
The cell divides into two haploid daughter cells with sister chromatids still attached . Because of crossing over in meiosis I, the two sister chromatids of each chromosomes are no longer genetically identical.
79
What are some differences between mitosis and meiosis
- Meiosis there is cross over exchanging genetic material between alleles. -In meiosis the number of chromosomes are haploid (one) and in mitosis they are diploid (Two different shaped sets of chromosomes. - Mitosis creates the same replication of parent cells and ends with two daughter cells while in meiosis there are 4 daughter cells and the genetic material changes.
80
What are some consequences of sexual reproduction (meiosis)?
Mutations (changes in the genome ) that happen because of genetic diversity creating versions called alleles. A) independently assorts chromosomes B )Crossing over creates recombinant chromosomes.
81
What is independent assortment?
Each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the pair. The resulting possible number of different gamates calculates by using the formula 2^n in which the n represents the the homologous pairs
82
What are the variety of cells due to the independent assortment?
alone would be 2*23 or 8.5 billion possibilities.
83
Why does crossing ver creates recombinant chromosomes ?
ly at It is the combination of the DNA inherited from both parents. Crossing over begins very early prophase I . In crossing over , homologous portions of two non-sister chromatids trade places. Crossing over contributes to genetic diversity
84
W-hat is the evolutionary significance of genetic variation
Sexual reproduction contributes to the genetic variation in the population due to mixing of different allels during meiosis. Mutations are the origin source of the new alleles. Individuals with the most favolable alleles in a particular selection results in accumulation of genetic variation facorated by the environment.
85
What is a locus ?
"The chromosomal or genomic location of a gene or any other genetic element is called a locus and alternative DNA sequences at a locus are called alleles
86
what is the difference in ending result between meiosis II and mitosis?
mitosis ends with two diploid daughter cells and Meiosis II ends with four haploid daughter cells.
87
What does meiosis II is similar to mitosis in that ...
sister chromatids separate during anaphase.
88
If the DNA content of a diploid cell in the G1 phase of the cell cycle is represented by x, then the DNA content of the same cell at metaphase of meiosis I would be 2x. If we continued to follow the cell lineage, the DNA content of a cell at metaphase of meiosis II would be
x

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