Unit 5 Cellular Replication GN #2 Meiosis Name: ______
Slides # 36-70
Only two types of cells in sexually reproducing eukaryotes undergo MEIOSIS and these are the cells that generate
SEX CELLS (Gametes) EGG CELLS and SPERM CELLS.
Facts about Egg Cells in females:
A human female is born with ______
Egg cells are generated through a process called______
Each egg cell has only ______and is called ______. Human
egg cells have ______.
This reproductive cell is called a ______.
Facts about Sperm Cells in males:
Sperm cells are made in the ______through a process called______
Sperm cells are derived from ______
Sperm cells have only ______(23) and is called ______.
This reproductive cell is called a ______.
How can cells duplicate and yet wind up with only ½ the number of chromosomes??? MEIOSIS!!!
Meiosis is very similar to ______WITHOUT ______
In Meiosis, 1 cell ______called ______.
When the two gametes come together (fertilization) the new cell is called a ______
Gamete + Gamete=______
It is important to start with HAPLOID CELLS (gametes) (1n)
Fertilization is the union of a ______and ______creating a ______.
The chromosome number is reduced in sperm and egg cells so at ______
______.
The process of meiosis:______, ______
______, ______
Each organism must inherit a ______
______.
In Meiosis, the two sets of chromosomes are separated and each gamete winds up with one set!
Slide#47
The two sets of chromosomes are said to be ______.
Human cells have 23 chromosomes from the egg (maternal) and 23 chromosomes from the sperm (paternal) =46
Chromosomes #s 1-23 + Chromosomes #s 1-23 = 46 (diploid)
Humans have 23 PAIRS or a total of
______
2n=46
A homologous pair means the same
Chromosome from each parent carrying
the same genes
The above is a duplicated chromosome, ready to go through the first meiotic division, the left from maternal and the right from paternal. =4n
The first meiotic division will half the chromosome number to 2n=diploid
The second meiotic division will then half the chromosome number again to 1n=haploid sperm and egg cell
Phases of Meiosis: Meiosis I is a process of reduction division where the number of chromosomes per cell is ______
______
Meiosis II the diploid cell has now divided again to produce 4 haploid cells
Lets see how this happens:
Meiosis I Interphase I: Cells undergo a round of ______
Cells are now 4n 92 chromosomes (human)
Prophase I: Chromosomes pair with its homologous chromosome to form a
______
There are 4 ______
Duplicated chromosome 1 pairs up with duplicated chromosome 1 etc…..
Chromatids exchange portions of their chromatids in a process called:
______
Crossing over produces ______!!!!
This is how genes (traits) get exchanged!!
VARIATION is created!!!!
Metaphase I : Chromosomes line up opposite of their homologous pairs!!!! (THIS IS
DIFFERENT THAN MITOSIS WHERE THEY LINE UP SINGLE FILE!!!
Spindle fibers ______
Anaphase I: The fibers separate ______
DUPLICATED CHROMOSOMES SEPERATED (not CHROMATIDS LIKE MITOSIS)
Telophase 1 and Cytokinesis: Nuclear membranes form. The cell______
______.
The two cells ______
______
The two new cells are now 2n………..split of the 4n into 2 cells = 2n. both new cells have 46 chromosomes (human) with blended genes.!
MEIOSIS II : The two cells produced in Meiosis 1 now enter another ______
These 2 new cells DO NOT GO THROUGH ______!!
Each of the ______.
Meiosis II is JUST LIKE MITOSIS!!!!
Prophase II: Centrioloes ______
No duplication of chromosomes!!!
Metaphase II: Chromosomes line up ______, single file!
Anaphase II: ______(chromosomes pulled apart at middle)
Telophase II and Cytokinesis: Meiosis results in ______
Gamete formation is different for males and females.
In male animals, meiosis results in ______In Female animals, only ______
______The other 3 cells, ______
______
Meiosis reduces ______
______
______
The first division, ______
______
The second division, ______
______
Please fill in the chart:
Differences between Mitosis and Meiosis
Mitosis / MeiosisCell Type of Parent
(2n or n)
Number of DNA replications
Number of times cell divides
Involves pairing of homologous chromosomes
Crossing over and sharing of genes
Involves only splitting of sister chromatids
Involves separating homologous chromosomes and then splitting of sister chromatids
Cell type of daughter cells
(2n or n)
Number of daughter cells produced
Genetic relationship of daughter cells
To parent and to each other
(Identical or Unique)
Number of cell divisions
STOP PPT AT SLIDE #70….will do the rest in semester 2 J
Questions to answer after writing your notes:1). Fertilization results in
a). a zygote.b). a diploid cell.c). a cell with a new genetic combination.d). All of these are correct.
2). The diploid number of chromosomes in humans is 46. The haploid number is
a). 138.b). 92.c). 46.d). 23.
3). After chromosome replication and during synapsis,
a). homologous chromosomes pair along their lengths.b). sister chromatids pair at the centromeres.
c). homologous chromosomes pair at their ends.d). sister chromatids pair along their lengths.
4). During which stage of meiosis does crossing over occur?
a). prophase Ib). anaphase Ic). prophase IId). telophase II
5). Synapsis is the process whereby
a). homologous pairs of chromosomes separate and migrate toward a pole.
b). homologous chromosomes exchange chromosomal material.
c). homologous chromosomes become closely associated.
d). the daughter cells contain half of the genetic material of the parent cell.
6). Which of the following occurs during anaphase I?
a). Chromosomes cluster at the two poles of the cell.b). Crossing over occurs.
c). Chromosomes align down the center of the cell.d). One version of each chromosome moves toward a pole.
8). Mitosis results in two ______cells, while meiosis results in ______haploid cells.
a). haploid/fourb). diploid/twoc). diploid/fourd). haploid/two
9). Genetic diversity is greatest in
b). sexual reproduction.c). asexual reproduction.d). binary fission.
10). An organism has 56 chromosomes in its diploid stage. Indicate how many chromosomes are present in the following, and explain your reasoning:
a). somatic cells
b). metaphase (mitosis)
c). metaphase I (meiosis)
d). metaphase II (meiosis)
e). gametes
11. What is the difference between metaphase I and Metaphase II?______
______
______
12. What is the difference between Anaphase I and Anaphase II?______
______
______
13. Which stage of Meiosis (I or II) is most like Mitosis? EXPLAIN:______
______
______
14. What is a tetrad?______
______
15. What are homologous chromosomes?______
______
______
16. Do homologous chromosomes have the same number of genes?______
Do they carry identical genes? EXPLAIN______
______
______
17. Explain why crossing over (synapsis) leads to exchange of genetic information.
______
______
______
18. A muscle cell of a mouse contains 22 chromosomes. Based on this info, how many chromosomes are there in the following types of mouse cells?
a. daughter muscle cell formed from mitosis______
b. Mouse egg cell______
c. fertalized egg cell of mouse______
19. When meiosis occurs in females, the cytoplasm is not divided equally among the resulting four cells. Explain why?
______
______
20. During which phase of the meiotic cell cycle does DNA replication occur?______
21. A human cell containing 44 autosomes and one X and one Y chromosomes is:
a. a somatic cell of a male b. a sperm cell c. an egg cell d. a somatic cell of a female
22. What is the name for a complete set of chromosomes of an organism arranged and displayed in pairs and ordered by size?______23. Which 2 cells would be more genetically similar to each other?
a. 2 gametes produced by the same person b. 2 somatic cells produced by the same person
c. 2 eggs produced by the same woman d. 2 sperm produced by the same man.