Mitosis

Question 1

Chromosomes

Answer 1

A Chromosome is a long single stranded DNA molecule that is organized in a more packaged format.
→ Humans have 46 diploid chromosomes
↑→ Humans have 22 pairs of numbered chromosomes (called autosomes) and one pair of sex chromosomes for a total of 46
↑→ Each pair of chromosomes has a paternal and maternal chromosome
→ Vary in size and number
→ Ends of the chromosomes are called Telomeres

Question 2

Chromatids

Answer 2

A chromatid is one of the two identical halves that make up a full chromosome.

The two “sister” chromatids are joined at the center by a protein called the centromere.

Question 3

Chromatin

Answer 3

The unpacked version of the proteins (like histones) and DNA that make up Chromosomes.

→ Chromatin makes DNA replication, transcription, DNA repair, genetic recombination and cell division possible.

Question 4

Centromere

Answer 4

A tight protein ball at the center of the cell that holds the two chromatids together.
Additionally, a place for the spindle fibers to attach via a macromolecular structure called the kinetochore which gets assembled at the centromere of each chromosome during mitosis.

Question 5

Why do cells divide?

Answer 5

1) Growth
2) Replace
2) Reproduction

Question 6

Interphase G1 (GAP 1) Phase {Mitosis}

Answer 6

→ Make more organelles
→ Synthesize protein and enzymes
→ Repair Thymine Dimers (UV light can cause two thymine next to each other to covalently bond causing a disruption in interaction)
→ DNA is in chromatin form

Question 7

Interphase S (Synthesis) Phase {Mitosis}

Answer 7

→ DNA Replication (Usually after mitosis there is only one chromatid per chromosome so it just replicates the chromatin to make enough genetic material for two chromatid chromosomes)

Question 8

Interphase G2 (GAP 2) Phase {Mitosis}

Answer 8

→ The cell grows in size by increasing cytoplasm and organelles

Question 9

Early Prophase {Mitosis}

Answer 9

→ Start of Mitosis
→ Chromatin starts to condense into chromatids
→ Nuclear membrane starts to dissolve/disappear by phosphorylation (Adding a phosphate group to the phospholipid which activates enzymes to break it down)

Question 10

Late Prophase (aka Prometaphase) {Mitosis}

Answer 10

→ Sister chromatids formed in the early prophase are joined together by centromeres to create chromosomes with two chromatids.
→ Centrosomes (2 Centrioles) start to go to the poles and create spindle fibers that start to attach to the centromeres of the chromosomes.
↑→ The spindle fibers attach to the centromeres and start to guide the chromosomes to the equator of the cell (Actual movement is helped by motor proteins)

Question 11

Centrosomes (and Centrioles)

Answer 11

A cell structure that, along with protein microtubules called spindle fibers, helps separate the replicated chromosomes into the daughter cells. A centrosome has two centrioles (barrel-shaped proteins) [Centrioles are made of 9 sets of 3 microtubules in a star like formation].

→ Facilitates the organization of the spindle fibers during mitosis

Question 12

Metaphase {Mitosis}

Answer 12

→ Once the chromosomes are aligned at the equator plate(imaginary equator line of the cell) via the spindle fibers we enter the metaphase

Question 13

Anaphase {Mitosis}

Answer 13

→ Sister chromatids separate (centromere divides) with help of the spindle fibers which are shortening (This is aided by motor proteins Dynein and Kinesin)
→ Once detached, they are pulled to either end of the cell as the spindle fibers shorten.
→ Cleavage starts to occur in this phase

Question 14

Telophase {Mitosis}

Answer 14

→ Begins once the separated sister chromatids reach the opposite ends of the cell.
→ Different actin(contracting proteins) and myosin(contracting proteins) start to squeeze the middle of the cell producing a constriction ring (Called a cleavage furrow).
→ Nuclear membrane forms
→ Nucleolus starts to form
→ Chromosomes go to a more relaxed state, chromatin
→ Both sides have an equal amount of ribosomes, mitochondria and cytoplasm
→ Most cells go through cytokinesis at this phase

Question 15

Cytokinesis {Not Mitosis}

Answer 15

→ The constriction ring pinches, eventually splitting the one cell into two new cells.
→ Cytokinesis is just the process of breaking off and usually happen around the same time has telophase

Important to note: In a plant cell, instead of pinching off, a new cell wall is created that divides the cell into two new cells.

Question 16

Product of Mitosis

Answer 16

2 new daughter cells that can either go back to Interphase, or a rest phase called G0 (Quiescent) phase
→ The somatic cell has the same function as the parent cell
→ As people get older, telomeres get short to a point where they cannot enter the cell cycle again

Question 17

Somatic Cells

Answer 17

Any cell that has a full set of chromosomes (so not sperm or egg cells)