THE PROCESS OF MEIOSIS
OBJECTIVES
1. What is the product of meiosis? (MCA-II standard)
2. What happens during each step of meiosis?
INTRODUCTION
1. Meiosis is a process that reduces the number of chromosomes in new cells to ________ the number.
2. The halving of the chromosome number counteracts the _________________ of cells in reproduction.
3. Meiosis produces _________________, which are haploid reproductive cells.
√ A haploid (1N) cell has only one set of chromosomes.
4. Human gametes are _________________ cells and _________________ cells.
5. Human sperm and egg cells each have _____ chromosomes.
6. The fusion of a human sperm cell and an egg cell results in a zygote that has _____ chromosomes.
7. The resultant zygote is said to be a _________________ cell.
√ A diploid (2N) cell has two sets of chromosomes.
8. Cells preparing for meiosis first enter _________________, the phase meaning “between cell divisions.”
9. Interphase is subdivided into 3 phases: ________, ________, and ________.
10. Replication of DNA occurs during which of the interphase subdivisions? ________
MEIOSIS
chromosome
chromosome
chromosome
chromosome
cell membrane
nuclear envelope
centriole
centromere
aster
spindle
1.
The __________________ envelope
PROPHASE I
is starting to disappear .
1.
How many chromosomes do you see?
_______
2.
Each chromosome has 1 or 2 chromatids? _____
3.
Each chromosome lines up with its matching
chromosome, called a __________________.
4.
Because there are two sets of chromosomes
present, the cell is said to be ______________ (2N).
5.
Sometimes chromatids can break off and attach
to adjacent chromosomes – a process called
__________________ __________________.
METAPHASE I
1.
How many chromosomes do you see?
_______
2.
Each chromosome has 1 or 2 chromatids? _____
3.
The chromosomes line up very similar to
of mitosis but with one key difference:
________________________________________
4.
_______________________ have formed in
between the centrioles and the chromosomes.
5.
The newly formed spindle fibers latch onto
ANAPHASE I
the __________________ of the chromosomes.
1.
How many chromosomes do you see?
2.
Each chromosome has 1 or 2 chromatids? _____
3.
The chromosomes move very similar to
mitosis but with one key difference:
________________________________________
1.
TELOPHASE I
_______
What structure is re-forming around the
chromosomes?
2.
_________________________
How many chromosomes do you see in each
re-forming nucleus? _______
3.
Each chromosome has 1 or 2 chromatids? ______
4.
Because there is now only one set of chromosomes
in each nearly-formed cell, the cells are said to
PROPHASE II
be ______________________ (1N).
1.
At this point meiosis has created _____ cells.
2.
Each cell has _____ chromosomes.
3.
Each chromosome has 1 or 2 chromatids? _____
3.
Each chromosome has 2 chromatids because
________ was copied in the S phase of interphase.
4.
Note the re-appearance of ___________________
between the centrioles.
METAPHASE II
1.
Each cell has _____ chromosomes.
2.
Each chromosome has _____ chromatids.
3.
Note that the spindle fibers have reached
and attached to the ___________________.
4.
Note that metaphase II is very similar to
metaphase I of meiosis with one difference:
ANAPHASE II
___________________________________
1.
What is pulling the chromosomes apart?
__________________________________
2.
Each cell now has _____ chromosomes.
3.
Each chromosome has _____ chromatids.
4.
Note that anaphase II is very similar to
anaphase I of meiosis with one difference:
__________________________________
1.
What structure is re-forming around the
chromosomes?
TELOPHASE II
2.
_________________________
How many chromosomes do you see in each
reforming nucleus?
_____
3.
Each chromosome has _____ chromatids.
4.
List one similarity to telophase I of meiosis.
_______________________________________
5.
State how telophase II differs from telophase I
in two different ways:
a.
___________________________________
b.
___________________________________
KEY CONCEPTS
1. Meiosis produces reproductive cells called ____________________________.
2. Gametes are specialized cells that have _______ the number of chromosomes of the parent cell.
3. Gametes have only one set of chromosomes or are said to be __________________________ (1N) cells.
4. Gametes are genetically unique because of the prophase I process called ____________________________.