Cell Cycle

reproduction, growth and development, tissue renewal

What are the main functions of cell division

Signal

• Interphase

• The cell receives a signal for cell division related to the needs of the entire organism

Replication

The genetic material that makes up an organism is called the genome. All of this DNA must be copied so that each daughter cell has a complete genome.

Segregation

The newly replicated chromosomes come in pairs that are called sister chromatids. A mechanism, mitosis, will segregate the sister chromatids into two new nuclei.

Cytokinesis

• The division of cytoplasm after mitosis into two cells

Binary Fission

What is cell division called in prokaryotes?

True

True or False

Mitosis in Eukaryotes accurately copy the chromosome, and segregate the copies into two genetically identical daughter cells

Somatic Body cells

Where does mitosis in eukaryotes occur?

G1 —> S —> G2

What are the processes during Interphase?

Prophase —> Metaphase —> Anaphase —> Telophase

What are the processes during Mitosis?

G1 phase

In this phase of interphase, cells recover from previous cell division as cell prepares for cell growth and DNA synthesis

S phase

DNA synthesizes and replicates, creating two identical copies of the chromosome

G2 phase

In this phase of interphase, the cell ensures DNA is replicated well as the cell grows more. Chromosomes condenses to become tightly coiled

Phragmoplast

• Plant cell-specific structure that forms during late cytokinesis.

• Serves as a scaffold for cell plate assembly and subsequent formation of a new cell wall separating the two daughter cells.

Mitotic Index

The ______ is a measure of the rate at which cells divide within a population.

False

True or False

A low mitotic index indicates a greater rate of cell division, often suggesting increased cell growth or potentially abnormal cell growth, like in tumors.

Interphase

large spherical nucleus, with the nuclear membrane intact, grainlike chromosomes and one to two nucleoli

Early Prophase

• large, spherical nucleus with a nucleolus and nuclear membrane intact and with thickened, more distinctly ribbonlike chromosomes.

• chromosomes may look like a dish of spaghetti

Late Prophase

• cell in which the chromosomes appear as a loose knot in the center of the cell.

• nuclear membrane, if still present, is indistinct. The nucleolus may start to fade.

Metaphase

• cell in which the chromosomes are aligned in the equatorial plane of the cell.

• Chromosomes attach to spindle fibers that are clearly visible

Anaphase

• cell in which the chromatids are moving to opposite poles of the cell

• centromere breaks up separating sister chromatids

• spindle fibers begine to break down

Telophase

• cell in which the chromatids, though fairly distinct are close to the opposite poles of the cell.

• cell plate may be forming at the middle of the cell

• A nuclear envelope forms around both sets of chromosomes

• DNA begins to uncoil again

• Spindle and astral fibers completely disappear

Cell Plate

• a structure that forms in dividing plant cells, eventually becoming the new cell wall between the two daughter cells

• end product of cytokinesis in plants

Interphase because cells spend most of their time focusing on cell growth and segregation

What stage of the cell cycle has the longest duration? Why?

Meristems

Where does cell division occur in?

Mitosis (nuclear division) and interphase

What are the two phases of cell division?

Mitosis

• growth, development, repair, and asexual reproduction

• executed by somatic or nonreproductive cells

• one series of cell division per cycle

• results in 2 diploid (2n) cells or cells with 2 sets of chromosomes

• daughter cells identical to parent

(number of cells in mitosis/total number of cells) x 100

How to compute for mitotic index

(no of cells at stage/total no of cells) x (16h/1c) x (60m/1h)

How to compute for duration of mitotic stage

7.1 minutes

What is the published value duration of the mitotic stage for prophase?

6.5 minutes

What is the published value duration of the mitotic stage for metaphase?

2.4 minutes

What is the published value duration of the mitotic stage for anaphase?

3.8 minutes

What is the published value duration of the mitotic stage for telophase?

prophase because important addjustments and preparations take place before dividing the cell into two daughter cells

What stage of mitosis has the longest duration and why?

No because cells are in various phases of the cell cycle during this time

Are the stages of mitosis occurring simultaneously on a meristem?

the daughter cells formed during mitosis have the same number of chromosomes as the mother

What should be the chromosome number in daughter nuclei formed by mitotic division of cells?

Cell cycle

Repeated series of processes that a cell undergoes in order to grow and divide

method of direct reproduction

For unicellular organisms (bacteria and binary fission), the cell cycle is used as a…

develops fertilized cells, promotes growth, and repairs damage to an organism

For multicellular organisms, the cell cycle…

DNA

Made up of long chains of nucleotides located in the nucleus

Genome

Consists of 1 or more DNA molecules

Chromatin

Spread-out version of DNA where the cell is not actively dividing or undergoing specific processes

Chromosomes

Packaged form of DNA that holds several hundred to a few thousand genomes that is a condensed form of chromatin

Histones

Proteins that organize DNA and chromosomes are wrapped with these

Nucleosome

A unit of DNA wrapped around histones is called…

Sister chromatids

Replicated chromosomes that stay together and are attached at the center called centromeres by a protein called cohesins

Kinetochore

Connect chromosomes to microtubules of spindles

Meiosis

• sexual reproduction

• gameters or reproductive cells

• two series of cell division per cycle

• results in 4 haploid (n) cells or cells with 1 set of chromosomes

• daughter cells not identical to parents due to “crossing over”

Interphase

What phase of the cell cycle is this?

Prophase

What phase is this?

metaphase plate

Chromosomes line up along the center of the cell in a place called the __________ in metaphase

Metaphase

What phase is this?

Prophase

• Chromatin condenses and becomes visible

• Nuclear envelope disappears

• Spindle apparatus begins to form

Anaphase

What phase is this?

Cytokinesis

What phase is this?

Telophase

What phase is this?

specific chemical signals present in the cytoplasm (cyclin proteins and cyclin-dependent kinase enzymes)

What drives/controls the cell cycle

cyclin proteins

regulate passage of cell through checkpoints

cyclin-dependent kinase enzymes

activated only when bound by a cyclin; drives cell cycle

True

True or False

The duration of the cell cycle in a typical onion root tip is about 16 hours