Download GN #2 Meiosis - Liberty Union High School District

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)
.
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
Cell 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 
Meiosis
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 I
b). anaphase I
c). prophase II
d). 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/four
b). diploid/two
c). diploid/four
d). 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.