[ Gen Bio ] Lesson 8: Cell Cycle and Cell Divisions

deoxyribonucleic acid (DNA)

Almost every cell in our bodies has genetic material in the form of _______.

deoxyribonucleic acid (DNA)

Most biological traits such as eye color, hair color, and height are coded for by the _____

deoxyribonucleic acid (DNA)

the primary genetic material of living organisms, stores genetic information in the sequences of its nucleotides.

Histone

Positively charged ______ proteins aid in DNA packaging.

Chromatin

Interphase DNA is found in the form of _____, a complex of DNA and proteins.

Chromosome

Chromatin will sometimes need to further condense into a highly coiled and compact structure.

46 Individual

23 pairs of chromoses

Humans have __ individual chromosomes (or __ pairs of) chromosomes.

Cell Cycle

The life cycle of a cell is known as the _____, and this describes how cells grow, develop, and reproduce.

Cell Cycle

involves different phases that constitute a series of preparations for a cell to divide to produce new cells.

• Interphase

• M phase

• Cytokinesis

Three Stages of the Cell Cycle

Events during the G1 phase

• Growth of cytoplasm and doubling of organelles

• Highest rate of protein synthesis

• Movement of centrioles of the centrosomes away to await and assist the events of mitosis

• Produce proteins, enzymes, nutrients, and energy

Events during the S phase

This stage is named so because it is when the cell synthesizes a copy of its DNA in a very notable process called DNA replication.

DNA replication

This refers to the event when an existing DNA produces another copy of itself.

Events during the Gap 2 phase

• Continued growth and the production of materials that are necessary for cell division to occur

• Protein synthesis but not at the rate similar to that of the G1 phase

M phase

This phase, in eukaryotic organisms involves either one of two processes, namely, mitosis and meiosis.

Sex cells or gametes

undergo meiosis

somatic cells or non-sex cells

undergo mitosis.

Cytokenesis

is marked by the formation of a cleavagefurrow in animal cells.

Cytokenesis

is marked by the formation of a cell plate in plant cells.

• G1-to-S checkpoint

• G2-to-M checkpoint

• Metaphase checkpoint

Cell Cycle Checkpoints (3)

Interphase

is the stage when the cell prepares itself for eventual cell division, which can either be mitosis or meiosis.

Cytokinesis

refers to the division of the cell’s cytoplasm and other components.

G1-to-S Checkpoint

• Is there any damage in the cell’s DNA?

• Is the cell large enough with all the necessary energy reserves and doubled organelles?

G2-to-M Checkpoint

• Are the environmental conditions favorable for cell division to take place?

• Is the DNA properly replicated?

• Is there a presence of DNA damage?

M Checkpoint

Are the spindles properly attached?

Interphase

It is also the stage when the cell is metabolically active and performs its specialized function.

• G1

• S Phase

• G2

• M Phase

4 Phases of Cell Cycle