The Mitotic Cell Cycle

Question 1

Chromatid

Answer 1

One of two identical parts of a chromosome, held together by a centromere, formed during interphase by the replication of the DNA strand

Question 2

Telomeres

Answer 2

Repetitive short base sequences of DNA regions at ends of chromatids.
(just extra DNA needed for a correct base if a mistake is made)
Act as caps that protect chromatids and wear down every time they go through DNA replication until cell death.
Enzyme : telomerase builds them back up

Question 3

Chromatin

Answer 3

Mixture of DNA and proteins
chromosomes are made of chromatin

Question 4

Chromosomes overview

Answer 4

• made up of 2 identical chromatids
  -each chromatid contains a DNA molecule (copy)
• 2 chromatids are held together by a centromere
  -end regions called telomeres
  chromatin = DNA+ proteins
  -chromosomes are made of chromatin

Question 5

Importance of mitosis

Answer 5

1. growth of multicellular organisms from unicellular zygotes due to genetically identical daughter cells (can be entire body or just regions eg. meristems in plants)
   2.replacement of dead or damaged cells and repair of tissues by cell replacement
2. asexual reproduction, production of offspring from a singular parent, genetically identical offspring
   4.immune response, cloning of B and T lymphocyte cells

Question 6

The cell cycle

Answer 6

in order of picture : Mitosis, Cytokinesis, G1, Synthesis, G2 (G1&2&S all interphase)
during interphase cell grows to normal size and carries out normal functions.
In G1 cells make; RNA, protein needed for growth eg. enzymes.
Synthesis is the replication of DNA.
G2 DNA (eg. tubulin made for spindles) made in S is checked for any errors and repaired and prepared for mitotic division.
Mitosis is nuclear division.
Cytokinesis only takes place in animal cells, its the formation of a new cell wall between the nucleus.

Question 7

Mitosis

Answer 7

PMAT acronym
- Early prophase : chromosomes start to appear centrosomes begin replication
-Late prophase: Nuclear envelope disappears, nucleolus disappears, chromosomes consisting of 2 chromatids are visible, centrosomes start moving to opposite poles
-Metaphase: each centrosome reaches pole and produces spindle fibers, chromosomes line up in the middle and attach to spindle by centromere
- Anaphase: chromatids are pulled apart at their centromeres by spindle fibers and move towards opposite poles
- Telophase: Nuclear envelope reappears, spindle fibers break down, chromatids uncoil, cytokinesis, kinetochores split

Question 8

kinetochore

Answer 8

a protein structure found at the centromere of a chromatid to which microtubules attach during nuclear division

Question 9

STEM cells

Answer 9

An unspecialized cell which can divide an unlimited number of times and can either remain a stem cell or differentiate to a specialized cell.
ability to produce different cells is called POTENCY.
totipotent - can produce any cell
pluripotent - embryonic stem cells
multipotent- adult cells which lost potency only produce few types

Question 10

Cancers

Answer 10

group of diseases that result from a mutation in genes that regulate cell division, mutated genes are called oncogenes, some cell divide uncontrollably forming tumors from which cells may break away and form secondary tumors in other areas of the body(metastasis).
Carcinogen - substance or environmental factor causing cancer.
Not all tumors cause cancer some are benign which don’t spread while others are malignant which leads to metastasis.