Cell Division Flashcards
What best distinguishes living things from non-living things?
The ability to reproduce.
To reproduce, cells must divide, and will continue to do so until a unicellular organism becomes a multicellular organism.
Why do cells divide?
- Reproduction (creation if offspring)
- Growth and development (maturing of offspring)
- Replace old or damaged tissues (healing and regeneration)
What does most cell division result in?
Daughter cells! Which have identical genetic information (DNA) as the parent and as each other.
What is the genome?
All the DNA in a cell - either a single DNA molecule (prokaryotic cells) or several DNA molecules (eukaryotic cells)
Where and how is DNA packaged?
DNA is packaged into chromosomes inside the nucleus of cells
Chromosomes are made from chromatin, a complex of DNA and protein that condenses during cell division.
Describe the difference in chromosomes of reproductive and non-reproductive cells
Somatic cells (non-reproductive) have two sets of chromosomes (2x23 =46)
Gametes (reproductive cells, ex: eggs and sperm) have half as many chromosomes (1x23) as somatic cells
How long is the human genome and how is it stored in small nuclei?
The human genome contained in each cell is about 2m long. The double strands are wound around
histone proteins, creating nucleosomes. Nucleosomes include 8 histones which allow the DNA to wrap around 1.65 times. In conjunction with an H1 histone, this structure is now called a chromatosome. These chromatosomes then coil up in tight loops about 300 nanometers long. These fibres are compressed and folded further, resulting in the chromatids of a chromosome.
How long is the human genome and how is it stored in small nuclei?
The human genome contained in each cell is about 2m long. The double strands are wound around
histone proteins, creating nucleosomes. Nucleosomes include 8 histones which allow the DNA to wrap around 1.65 times. In conjunction with an H1 histone, this structure is now called a chromatosome. These chromatosomes then coil up in tight loops about 300 nanometers long. These fibres are compressed and folded further, resulting in the chromatids of a chromosome.
What changes do chromosomes undergo in preparation of cell division?
DNA is replicated and chromosomes are condensed.
The replicated chromosome copy is joined to the original by cohesion proteins at the centromere, and is now called sister chromatids.
What happens to sister chromatids during cell division?
They separate at the centromere, move into separate nuclei, and are renamed chromosomes.
What is the cell cycle?
The life of a cell from formation to its own division
Involves sequence of events from one cell division to the next
Every cell is derived from a cell
What are the two types of cell division in eukaryotes?
- Mitosis - the division of the genetic material in the nucleus. Involves cytokinesis (the division of the cytoplasm). Produces somatic cells
- Meiosis - yields non-identical daughter cells that have half as many chromosomes as the parent cell. Produces gametes
What are the two phases of cell division?
Interphase and Mitotic Phase
Describe and name the stages of Interphase
The cell begins interphase by exiting the G0 phase (cell cycle arrest) and entering
G1 Phase - growth of organelles and proteins. Ensures conditions are appropriate for DNA replication
S Phase - DNA is synthesized in the nucleus
G2 Phase - is characterized by presence of nuclear envelope, nucleoli, and 2 centrosomes. Chromosomes are duplicated (from S phase) but are not condensed
Name the stages in the mitotic phase (where the nucleus divides)
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
P.P MAT where a dog pees
What is Cytokinesis?
The phase of cell division when the cytoplasm splits. It overlaps the end portion of mitosis.
Describe prophase stage of mitosis (5 steps).
-first stage and longest stage of mitosis.
-Nuclear envelope is still visible
-Nucleoli disappear
-To Centrosomes present and begin to form
-chromosomes duplicated and condensed; visible as 2 sister chromatids
Describe prometaphase in mitosis (3)
-Nuclear envelope dissolves
-Spindle canal attach to chromosomes at the Kinetochore
-Chromosomes further condense
Describe metaphase stage in mitosis (2)
-chromosomes are now on the metaphase plate
-The spindle is complete 
Describe anaphase stage in mitosis (4)
-Shortest phase of mitosis
-Cohesin proteins are inactivated; Sister chromatids fall apart.
-Daughter chromosomes are pulled to opposite poles from the shortening of the kinetochore motor proteins
-The cell elongates
Describe the telophase stage in mitosis (3)
-Nuclear envelopes form around daughter chromosomes
-Chromosomes become less condensed
-Marks the end of mitosis
Describe the cytokinesis stage of cell division (3)
-Begins during telophase
-Pinches the cell into two at field metaphase plate using contractile proteins myosin and actin
-Also known as cleavage
Describe the mitotic spindle
-Made of microtubules that control chromosome movement during mitosis
-Assembly begins at the centosome in the microtubule organizing centre (MOT)
-Form the Aster that extends from each centrosome
What are kinetochores?
-Protein complexes that form in association with the centromeres of chromosomes
-Microtubules attach to the kinetochore during prometaphase stage
What four things is the spindle made up of?
Centrosome, Aster, attached microtubules, and associated proteins
What is meant by cleavage furrow in relation to mitosis?
During cytokinesis, the cleavage furrow is the contracted area of the cell as it undergoes the split necessary for cell division
What difference marks cytokinesis in animal cells from plant cells
A cell plate forms to create a new cell wall during cell division
How do prokaryotic cells replicate?
They replicate through binary fission
Describe the Process of binary fission in prokaryotic cells
The chromosome replicates at the origin of replication and to daughter chromosomes move apart. The plasma membrane pinches in word dividing cell in two.
The chromosomes in bacteria are circular.
