Mitosis

Question 1

Intro to chromosomes

Answer 1

• All of the genetic material contained within a cell is
called its genome
• This genome needs to be replicated before each cell
cycle
• The large amounts of DNA that is needed to be
copied is made possible by the packaging of DNA
into chromosomes
• Chromosomes:
o Long thread-like structures forming
chromatin network
o Made of strand of DNA wrapped around
protein core – histone
o Carry up to thousands of genes

Question 2

In somatic cells of diploid organisms:

Answer 2

• Chromosome number is same in each cell
• Chromosomes are made up of two sets
• One chromosome of each pair comes from the
mother – Maternal
• And one comes from the father – Paternal
• Therefore, called diploid cells – 2n (abbr.)
• For each paternal chromosome there is a matching
maternal chromosome – homologous pair
• Chromosomes forming each pair are the same size
shape and have the same genes in the same place
• But alleles for each trait my not be the same
• The DNA of each chromosome replicates to form
two identical threads or sister chromatids joined by a
centromere
• This takes place in interphase of the cell cycle
• Threads only become visible when they shorten and
thicken as cell divides DNA replication is very
important to ensure that each daughter cell receives
a full complement of all genetic material
• Each species has a specific number of
chromosomes in somatic cells
• During gamete formation 2n diploid number of
chromosomes reduces to haploid n number

Question 3

The cell cycle

Answer 3

• Mitosis is just one part of the cell cycle
• The mitotic phase (M), which includes mitosis and
cytokinesis is the shortest part of cycle
• It alternates with the longer (90%) stage called
interphase
• Interphase can be divided into sub phases:
o G1 phase
o S phase
o G2 phase
• Intense metabolic activity and growth occurs during
interphase à produces proteins and cytoplasmic
organelles such as mitochondria and ER
• Duplication of chromosomes occurs in S phase
• Grows in both G phases and divides in M phase
• The purpose of the cell cycle and mitosis in particular
is for organismal growth and repair

Question 4

Stages of Mitosis

Answer 4

Is Peter Meeting Anne Today

1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase

Question 5

Interphase

Answer 5

• DNA is period between two consecutive cells
divisions
• Chromatin network is visible
• Cell growth and DNA replication takes place

Question 6

Prophase

Answer 6

• Threads of the chromatin network shorten and
thicken to become visible as chromosomes
• Chromosome consists of two identical chromatids
joined by centromere
• Nuclear membrane and nucleolus disappears
• The centrosome duplicates and the centrioles move
to opposite poles of the cell
• Spindle fibers develop between the centrioles

Question 7

Metaphase

Answer 7

• Chromosomes move to the Equator and position
themselves in a single row
• Some spindle fibres attached to the centrosomes

Question 8

Anaphase

Answer 8

• The centromere of each chromosome divides into
two
• Chromatids separate move to the opposite poles
• The chromatids are known as daughter
chromosomes
• Cytokinesis (division of cytoplasm) begins

Question 9

Telophase

Answer 9

• Daughter chromosomes position themselves at
the poles
• Spindle fibres disappear
• Nuclear membrane and nucleolus form
• Invagination occurs to separate each cell