20251202223012_692f68740f839_biology_exam_revision.docx
Biology Exam revision:
Cell Division and Inheritance
Why cells divide?
Cells divide to
• Grow (baby to adult)
• Repair (replace damage cells)
• Reproduce (especially in single celled organisms)
There are two types of main types of cell division.
1. Mitosis (makes body Somatic cells.)
2. Meiosis has sex cells (gametes sperm and egg)
MITOSIS:
Mitosis is an organised division of the nucleus of the cell. There are four stages in mitosis.
(Prophase, metaphase, Anaphase and telophase) (PMAT).
• No genetic variation cells are clones.
• Think for it as ‘copy and paste’ for cells.
• Ech new cell have the same number of chromosomes as parent (so if human has 46
chromosomes as the parent daughter cells also have 46 chromosomes.
• Purpose to make new cells that are the same as the old once. This helps you grow
and heal.
• Process; one cell splits into two identical cells in four steps. (Prophase, metaphase,
Anaphase and telophase) (PMAT).
THE NUCLEAS IS STILL THERE AND ITS GOING TO GO AWAY
LATTER ON BUT THIS IS A STAGE.WHERE ITS ACTUALLY STILL
THEIR CHROMOSOMES ARE VISIBLE IN FACT WE CAN SAY
CONDESING.WHICH MEANS THEY ARE THICKNING AND
VISIBLE. (from video)
In prophase, chromatin continues to wind into a condensed
from of DNA called a bivalent chromosome. Each chromosome
has a distinctive ‘H’ shape in which two parallel ‘sister’
Chromatids are joined at the centromere.
20251202223012_692f68740f839_biology_exam_revision
, 20251202223012_692f68740f839_biology_exam_revision.docx
while the DNA molecule is condensing into a
chromosome the nuclear membrane breaks
down, and a number of protein threads spread
from one end of the cell to the other. These
protein threads link together at each cell pole to
form a spindle. (from book)
cell gets ready to split. DNA packs up nucleus goes
away and structure forms to pull apart DNA.
METAPHASE: M for middle
because in this stage the chromosomes line up in the middle of
the cell. The nucleus has been disassembled it’s no longer there,
so we have got the chromosomes in the middle waiting there.
From video
during metaphase the newly formed chromosome migrate to the canter (equator of the cell, the
spindle then attaches to the centromere of each chromosome. At this point checkpoint M checks that
the spindle fibre is correctly attached to each centromere before the cell progresses to the next stage.
(from book).
In metaphase chromosomes line up in the middle of the cell before being separated. (From Ai )
ANAPHASE: Away
The chromosomes move away they move to the
opposite sides of the cell, so they are moving towards to the poles of the cells
know one thing to point out this chromosome they are not moving by
themselves they have something called spindles are fibres that help move the
chromosomes to the end kind of helps them move along. (centriole also help)
(from video)
20251202223012_692f68740f839_biology_exam_revision
, 20251202223012_692f68740f839_biology_exam_revision.docx
During Anaphase the sister chromatids of each bivalent chromosomes separate
at the centromere. This breaks apart the distinctive ‘H’ shape into two
individuals (identical) DNA molecules, and each chromatid becomes a single
independent chromosome the spindle fibres pull each identical chromosomes to
opposite poles of the cell this occurs for each of the 46 chromosomes in a
human cell. The results is 46 individual chromosomes at each pole of the cell.
(from book)
Anaphase is when the chromosomes that were lined up in the middle get pulled
apart to opposite sides of the cell with help of spindles and centriole. (from Ai)
TELOPHASE: T FOR TWO
in telophase the chromosomes are actually at
complete opposite ends and new nuclei are forming
on each side to make two new cells the nuclei are
starting to surround the chromosomes to both sides I
like to think the T is for two you can really see this
steps that the end goal is going to be two cells and in
the human body they are each going to have 46
chromosomes and again remember they are
identical. (from book)
Telophase is a final stage of cell division where two new nuclei from around the
separated chromosomes its like creating two new rooms for one. (From Ai)
CYTOKINESIS:
20251202223012_692f68740f839_biology_exam_revision
Biology Exam revision:
Cell Division and Inheritance
Why cells divide?
Cells divide to
• Grow (baby to adult)
• Repair (replace damage cells)
• Reproduce (especially in single celled organisms)
There are two types of main types of cell division.
1. Mitosis (makes body Somatic cells.)
2. Meiosis has sex cells (gametes sperm and egg)
MITOSIS:
Mitosis is an organised division of the nucleus of the cell. There are four stages in mitosis.
(Prophase, metaphase, Anaphase and telophase) (PMAT).
• No genetic variation cells are clones.
• Think for it as ‘copy and paste’ for cells.
• Ech new cell have the same number of chromosomes as parent (so if human has 46
chromosomes as the parent daughter cells also have 46 chromosomes.
• Purpose to make new cells that are the same as the old once. This helps you grow
and heal.
• Process; one cell splits into two identical cells in four steps. (Prophase, metaphase,
Anaphase and telophase) (PMAT).
THE NUCLEAS IS STILL THERE AND ITS GOING TO GO AWAY
LATTER ON BUT THIS IS A STAGE.WHERE ITS ACTUALLY STILL
THEIR CHROMOSOMES ARE VISIBLE IN FACT WE CAN SAY
CONDESING.WHICH MEANS THEY ARE THICKNING AND
VISIBLE. (from video)
In prophase, chromatin continues to wind into a condensed
from of DNA called a bivalent chromosome. Each chromosome
has a distinctive ‘H’ shape in which two parallel ‘sister’
Chromatids are joined at the centromere.
20251202223012_692f68740f839_biology_exam_revision
, 20251202223012_692f68740f839_biology_exam_revision.docx
while the DNA molecule is condensing into a
chromosome the nuclear membrane breaks
down, and a number of protein threads spread
from one end of the cell to the other. These
protein threads link together at each cell pole to
form a spindle. (from book)
cell gets ready to split. DNA packs up nucleus goes
away and structure forms to pull apart DNA.
METAPHASE: M for middle
because in this stage the chromosomes line up in the middle of
the cell. The nucleus has been disassembled it’s no longer there,
so we have got the chromosomes in the middle waiting there.
From video
during metaphase the newly formed chromosome migrate to the canter (equator of the cell, the
spindle then attaches to the centromere of each chromosome. At this point checkpoint M checks that
the spindle fibre is correctly attached to each centromere before the cell progresses to the next stage.
(from book).
In metaphase chromosomes line up in the middle of the cell before being separated. (From Ai )
ANAPHASE: Away
The chromosomes move away they move to the
opposite sides of the cell, so they are moving towards to the poles of the cells
know one thing to point out this chromosome they are not moving by
themselves they have something called spindles are fibres that help move the
chromosomes to the end kind of helps them move along. (centriole also help)
(from video)
20251202223012_692f68740f839_biology_exam_revision
, 20251202223012_692f68740f839_biology_exam_revision.docx
During Anaphase the sister chromatids of each bivalent chromosomes separate
at the centromere. This breaks apart the distinctive ‘H’ shape into two
individuals (identical) DNA molecules, and each chromatid becomes a single
independent chromosome the spindle fibres pull each identical chromosomes to
opposite poles of the cell this occurs for each of the 46 chromosomes in a
human cell. The results is 46 individual chromosomes at each pole of the cell.
(from book)
Anaphase is when the chromosomes that were lined up in the middle get pulled
apart to opposite sides of the cell with help of spindles and centriole. (from Ai)
TELOPHASE: T FOR TWO
in telophase the chromosomes are actually at
complete opposite ends and new nuclei are forming
on each side to make two new cells the nuclei are
starting to surround the chromosomes to both sides I
like to think the T is for two you can really see this
steps that the end goal is going to be two cells and in
the human body they are each going to have 46
chromosomes and again remember they are
identical. (from book)
Telophase is a final stage of cell division where two new nuclei from around the
separated chromosomes its like creating two new rooms for one. (From Ai)
CYTOKINESIS:
20251202223012_692f68740f839_biology_exam_revision
