Mitosis and Meiosis Flashcards
What is the role of the centromere ?
it is the most constricted part of the chromosome and can be identified on a single chromosome composed of two sisters chromatids
What is the role of the kinetochore ?
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.
What is the role of the centrosome?
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.
What is the mitotic spindle ?
is an apparatus of microtubules that controls chromosomes movement during mitosis.
The centrosome replicates in the S phase of the interphase.
What happens with kinetochores during prometaphase ?
some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes. and they are protein complexes
What is chromatin?
It is the DNA plus the associated proteins (histone and non- histone proteins)
What is the difference between euchromatin and Heterochromatin?
*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.
What is the difference between a chromatid and a chromosome ?
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.
Do cells replicate during interphase ?
No, the DNA replicates during interphase but not the whole cell.
G2 of interphase
the centrosomes are with centriole pairs and the chromatin is duplicated
Prophase
We have the early mitotic spindle and chromosomes consisting of two sister chromatids and a centromere.
Prometaphase
We have the fragments of the nuclear envelope and nonkinetochore microtubules and kinetochore in the chromosomes.
Metaphase
the metaphase plate centrosome at one spindle poles
Anaphase
Daughter chromosomes
Telophase and cytokinesis
The cleavage furrow is made and the nucleolus starts to form and also the nuclear envelope
What is the purpose of the cell cycle checkpoints controls ?
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.
Each copy of replicates chromosomes is called ….
Chromatid
What are sister chromatids ?
When the copy of the chromosomes is made and have as a result sister chromatids. And their genetic material is identical
How are sister chromatids held ?
They are held by proteins called cohesins in a constricted area ( centromere)
When do chromatids stop being chromatids and change to chromosomes ?
During cell division and the copy of chromosomes they are called chromatids once the sister chromatids are separated they are chromosomes again.
What are the centromeres ?
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.
What role does telomerase in cell division ?
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
What are the P and Q arms?
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.
Chromatin is made of ….
Complexes of DNA, Histones and non histone proteins present in the nucleus of eukaryotic cells
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
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.
What is the general overview of the mitotic phase?
It has 5 plus cytokinesis sub phases
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
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.
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.
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
What are the characteristics of prophase ?
Thick, visible chromosomes appear and the spindle apparatus begins to form.
Chromosomes condense
What are the characteristics for prometaphase?
More condensed chromosome, nuclear envelope breaks down, kinetochore microtubules attach to the chromosomes at kinetochore
What are the characteristic of metaphase ?
Chromosomes complete migration to the middle of the cell (metaphase plate)
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
What are the characteristics of TELOPHASE ?
The nuclear envelope re-forms, and the spindle apparatus disintegrates. chromosomes become less condensed