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Flashcards in Mitosis Deck (9)
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Intro to chromosomes

• All of the genetic material contained within a cell is
called its genome
• This genome needs to be replicated before each cell
• 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


In somatic cells of diploid organisms:

• 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
• 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


The cell cycle

• 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 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


Stages of Mitosis

Is Peter Meeting Anne Today
1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase



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



• 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



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



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



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