Cell Cycle & Cell Division – Comprehensive Study Notes

Cell cycle

The series of phases that a cell goes through from its formation to its division. It includes interphase and the mitotic phase, allowing for growth, DNA replication, and preparation for cell division.

Phases of Cell cycle

The distinct stages of the cell cycle, including G1, S, G2, and M phases, that regulate cell growth, DNA synthesis, and division.

Describe M phase

The M phase, or mitotic phase, is the stage of the cell cycle where cell division occurs, resulting in two daughter cells. It includes processes like mitosis and cytokinesis, where the chromosomes are separated and the cell's cytoplasm divides.

Describe Interphase

Interphase is the longest phase of the cell cycle, where the cell prepares for division through growth and DNA replication. It consists of G1, S, and G2 phases, ensuring the cell is ready for mitosis.

Sub phases of interphase

The sub phases of interphase include G1, S, and G2 phases, where the cell grows, replicates its DNA, and prepares for mitosis.

Describe G1 phase

G1 phase is the first sub phase of interphase, where the cell grows, synthesizes proteins, and produces organelles in preparation for DNA replication.

S phase

S phase is the second sub phase of interphase, during which DNA replication occurs, ensuring that each daughter cell will receive an identical set of chromosomes.

G2 phase

phase is the final sub phase of interphase, where the cell continues to grow and prepares for mitosis by producing proteins and organelles necessary for cell division.

where do centrioles duplicate

Centrioles duplicate in cytoplasm during G2 phase

karyokinesis

is the process of nuclear division in eukaryotic cells, resulting in the separation of duplicated chromosomes into two daughter nuclei.

somatic cells

are any cells of the body that are not reproductive cells. They undergo mitosis for growth and repair.

quiscent stage

is a phase in the cell cycle where cells are in a non-dividing state but are metabolically active, typically also known as G₀ phase.

how do haploid cells divide in honey bees

they divide through mitosis

sub phases of m phase

include prophase, metaphase, anaphase, and telophase.

prophase

the first stage of mitosis where chromatin condenses into visible chromosomes, the nuclear envelope begins to break down, and the spindle apparatus forms.

how many chromatids are present in chromosome

es after DNA replication, there are two sister chromatids in each chromosome.

asters

star shaped microtubules forming spindle apparatus

mitotic apparatus

the structure that organizes and separates chromosomes during mitosis, consisting of spindle fibers, centrioles, and asters.

metaphase

the stage of mitosis where chromosomes align at the cell's equatorial plane, maximizing their interactions with the mitotic spindle.

kinetochores

protein structures on chromosomes that attach to spindle fibers during cell division, facilitating chromosome movement.

what do kinetochores do

Kinetochores are protein structures on chromosomes that bind to spindle fibers, enabling the proper alignment and separation of chromosomes during cell division.

metaphase plate

the imaginary plane during metaphase where chromosomes are aligned prior to separation in mitosis.

features of metaphase plate

The metaphase plate is characterized by the alignment of chromosomes at the cell's equatorial plane, facilitating equal division during mitosis.

anaphase

The stage of mitosis where sister chromatids are separated and pulled towards opposite poles of the cell, ensuring equal genetic distribution.

key events of anaphase

During anaphase, sister chromatids are pulled apart by the spindle fibers and move toward opposite poles of the cell. This ensures that each daughter cell receives an identical set of chromosomes.

telophase

The final stage of mitosis, telophase involves the reformation of the nuclear envelope around each set of separated chromosomes, leading to the decondensation of chromosomes and the formation of two distinct nuclei in the daughter cells.

how is cytokinesis achieved in animal cells

In animal cells, cytokinesis is achieved through the formation of a cleavage furrow, where the cell membrane pinches inward, ultimately dividing the cell into two daughter cells.

cell plate

A structure that forms during cytokinesis in plant cells, leading to the separation of the daughter cells as the cell wall material is deposited in the middle of the dividing cell.

syncytium

A multinucleated cell formed by the fusion of several smaller cells, typically found in certain tissues, such as skeletal muscle and placental tissue.

meiosis

A type of cell division that reduces the chromosome number by half, resulting in four genetically unique gametes, essential for sexual reproduction.

homologous chromosomes

Chromosome pairs, one from each parent, that are similar in shape, size, and genetic content.

stages of prophase 1

The first stage of meiosis, where homologous chromosomes undergo pairing and crossing over, leading to genetic recombination. This stage includes several sub-stages: leptotene, zygotene, pachytene, diplotene, and diakinesis.

leptotene

The first sub-stage of prophase 1 in meiosis, where chromosomes condense and become visible, initiating homologous chromosome pairing.

zygotene

The second sub-stage of prophase 1 in meiosis, where homologous chromosomes continue to pair and form synaptonemal complexes, facilitating genetic recombination.

synaptonemal complex

A protein structure that forms between homologous chromosomes during zygotene, facilitating their pairing and the exchange of genetic information.

tetrad or bivalent

A structure formed during prophase 1 of meiosis, consisting of a pair of homologous chromosomes, each made up of two sister chromatids, resulting in a total of four chromatids.

pachytene

The third sub-stage of prophase 1 in meiosis, characterized by the further condensation of chromosomes and the completion of genetic recombination through crossing over.

crossing over leads to

genetic diversity in offspring

diplotene

the fourth sub-stage of prophase 1 in meiosis, where homologous chromosomes begin to separate, and chiasmata become visible.

chiasmata

points of contact between homologous chromosomes during recombination.

diakinesis

the final sub-stage of prophase 1 in meiosis, characterized by the complete separation of homologous chromosomes and the condensation of chromatin.

metaphase 1

the stage in meiosis where homologous chromosomes align at the cell's equator, preparing for separation during anaphase.

anaphase 1

The homologous chromosomes separate, while sister

chromatids remain associated at their centromere

telophase 1

The nuclear membrane and nucleolus reappear,

cytokinesis follows and this is called as dyad of cells

interkinesis

The stage between the two meiotic divisions is called interkinesis and is generally short lived. There is no replication of DNA during interkinesis. Interkinesis is followed by prophase II, a much simpler prophase than prophase I

prophase II

The nuclear membrane disappears by the end of prophase II. The chromosomes again become compact.

metaphase II

At this stage, the chromosomes align at the equator and the microtubules from opposite poles of the spindle get attached to the kinetochores of sister chromatids.

anaphase II

It begins with the simultaneous splitting of the centromere of each chromosome (which was holding the sister chromatids together), allowing them to move toward opposite poles of the cell

telophase II

Meiosis ends with telophase II, in which the two groups of chromosomes once again get enclosed by a nuclear envelope; cytokinesis follows resulting in the formation of tetrad of cells i.e., four haploid daughter cells

what is the enzyme involved in crossing over

recombinase