Imagine a healthy cell in your body and explain in a few wor

Imagine a healthy cell in your body and explain in a few words how the process of mitosis will help make exact copies of the heritable information that you possess, making genetically identical cells? Refer to Chapter 12 in the text. What are some uses of ATP in mitotic/meiotic cells?

Solution

before mitosis, interphase is present where the cell makes an identical copy of its genetic information. therefore, chromosomes in the nucleus possess 2 connected copies which are the sister chromatids which are connected by centromeres.

mitosis is a multi step process where chromosomes are duplicated, aligned and seperated to form identical cells.mitosis has two phases: karyokinesis, the nuclear division and cytokinesis, the cytoplasm division.

karyokinesis has 5 different phases-prophase, prometaphase, metaphase, anaphase and telophase.

initially in the prophase, chromosomes consisting of 2 sister chromatids start condensation into X shape structures by condensin proteins and become visible. the nuclear envelope dissociates into vesicles and nucleolus disappears. centrosomes start moving to the opposite poles giving rise to spindle fibres, made of microtubules.

in prometaphase (late prophase), nuclear envelope completely dissociates to release chromosomes. chromosomes complete the condensation process and become discrete. kinetochores appear at the centromeres. they are microtubules attached to the centromeres of a chromosome. the kinetochore attracts spindle fibres and binds to it. mitotic spindle fibres from opposite poles attach to sister chromatids at the kinetochore region.

in metaphase, centrosomes start pulling the chromosomes towards opposite poles. due to the tension, all chromosomes are aligned in an imaginary equatorial plane known as metaphase plate. the two sister chromatids are firmly attached by the cohesin proteins. after the chromosomes are properly aligned, a check point is present to ensure identical distribution of information, kinetochores are checked for their proper attachment to the microtubules, so that sister chromatids are split evenly.

during anaphase, the cohesin proteins degrade and sister chromatids pull part making them two separate chromosomes. the non-kinetochore spindle fibres, which are not attached to the chromosomes, lengthen making the cell elongated.

in the telophase, the chromosomes start decondensation, mitotic spindle fibres depolymerise and help in the cytoskeletal development of the daughter cells. nuclear envelopes and nucleolus reappear.

later cytokinesis occurs, where cell division takes place by separation of cell components into two daughter cells. In a healthy human cell, a contractile ring is formed which is composed of actin filaments where a metaphase plate was formed earlier. these filaments pull the cell forming a fission which is called cleavage furrow which deepens giving rise to two cells.

to ensure exact copies are carried in each cell, there are two check points. one before mitosis and another during the mitosis.

Before mitosis, during interphase, if cells fail to replicate the chromosomes, then cells don\'t undergo mitosis. this is performed by recognition of the unreplicated DNA thereby inhibiting the activity of mitosis-promoting factor.

The mitotic spindle check point or metaphase check point occurs when chromosomes are aligned on a metaphase plate. this is very important for equal distribution of chromosomes. the bipolar attachment creates a tension which initiates the cells to enter anaphase. if the alignment is not proper, anaphase promoting complexX(APC) is inhibited. In general, APC degrades cyclin B which breaks down securin protein. The securin protein inhibits separase whose function is to break the cohesins which are responsible for binding of sister chromatids. so APC inhibition blocks all this process halting mitosis till the repair is done or the cell division stops.

uses of ATP in mitosis/meiosis

in anaphase, the contractile fibres and pull the chromatids apart which requires energy in the form of ATP which is stored in the G2 phase. the kinetochores have the microtubules and the motor proteins which utillize ATP and help in pulling chromatids towards the spindle.

other processes such as chromosome condensation, separation, mitotic signalling and protein synthesis also require ATP but at low levels.

for activation of specific proteins such as cyclins and microtubules, GTP is used.