Zusammenfassung der Ressource
Meiosis B5
- Meiosis
- Gametes are
produced by Meiosis
- Meiosis involves TWO
divisions. In humans it
only happens in the
ovaries and the testes.
- Produces cells which have half the
normal number of chromosomes
- <--- Before the cells starts to
divide, the DNA is duplicated- one
arm of each chromosome is the
exact copy of the other arm.
- First Division #1: The chromosome pairs
line up at the center of the cell
- First Division #2: The pairs are then pulled apart, so
each new cell has only one copy of each chromosome.
- Second Division #1: The chromosomes line up again at
the center of the cell. The arms of the chromosomes are
pulled apart. Like Meiosis, membranes form around each
sets of chromosomes.
- You get 4 gametes each with only a single set of
chromosomes in it. From each side of chromosomes, new
nuclei are formed. There is 4 in total
- After 2 gametes join at fertilisation, the
zygotes grows by repeatedly dividing by
MITOSIS.
- Basic Principles
- Gametes have half the usual
number of chromosomes
- During Sexual reproduction, the egg
and the sperm combine to form a new
cell called a zygote
- All human body cells have 2 copies of the 23
chromosomes (46 total). But gametes only have
one copy of each chromosome (23)
- So when the egg and sperm
combine, the zygote will
contain 46 chromosomes- one
set of 23 from each parent