Chapter 7 – Meiosis and Sexual Reproduction
Section 1 - Meiosis
I. Formation of Haploid Cells
a. some organisms reproduce by ______
to form the first cell of a new individual.
b. Gametes are haploid - ______
______
What would happen if chromosome reduction did not occur? ______
______
c. Meiosis – is a form of ______
______
when forming specialize reproductive cells, such as ______
d. Meiosis – involves ______divisions of the nucleus, ______
______
e. DNA in the original cell is ______. Thus meiosis starts
______chromosomes.
Meiosis I
Step I – Prophase I
a. chromosomes ______, and the nuclear envelope
______.
b. Homologous chromosomes pair, ______may occur.
c. Crossing-over – when portions of a ______on one homologous chromosome are broken and ______
With the corresponding chromatid portions of the other homologous chromosome.
Step 2 – Metaphase I
a. Homologous chromosomes are moved by the ______
to the equator of the cell.
Step 3 – Anaphase I
a. homologous chromosomes ______.
b. Chromosomes of each pair are ______of the cell by the spindle fibers.
c. The chromatids DO NOT ______. Each chromosome is still composed of two ______.
Step 4 – Telophase
a. Nucleus ______
b. ______cells produced – each containing one chromosome from each pair of homologous chromosomes.
c. ______begins
d. Cells are now ______!!
e. Chromosomes do not replicate between meiosis I and meiosis II.
Meiosis II
Step 5 - Prophase II
a. a new ______forms around the chromosomes
Step 6 – Metaphase II
a. The chromosomes ______
______
Step 7 - Anaphase II
a. ______divide, and the ______
move to opposite poles of the cell.
Step 8 – Telophase II
a. ______forms around each set of chromosomes.
b. the ______breaks down and the cell undergoes
______.
***The result of meiosis is ______haploid cells!!!
II. Meiosis and Genetic Variation
1. Meiosis is an important process that allows for the ______
______.
2. There are 3 mechanisms involved - ______
______.
A. Independent Assortment
1. Independent assortment - ______
______
ex. Humans have ______pairs of chromosomes. Gametes receive
______of each pair but which one they receive is pure ______.
2. Each of the 23 pairs of chromosomes ______(separates) ______.
3. Thus about ______with different gene combinations can be produced from ______original cell.
Draw figure 2 (in color)
B. Importance of Genetic Variation
1. What is evolution? (you must look this up!) ______
______
a. Why is evolution important and how is it sped up? ______
______
______
B. Crossing-over and Random Fertilization
1. Cross-over - ______
______
***This increase genetic variation!
2. ______- the zygote that forms a new individual is created by the random joining of two gametes.
______possible outcomes.
III. Meiosis and Gamete Formation
***** Meiosis occurs in all sexually reproducing organisms
A. Meiosis in Males
1. ______- process by which sperm are produced in male animals.
2. Occurs in the ______- male reproductive organs.
3. A diploid cell increases in size. The large cell undergoes meiosis I. ______
cells are produced. Each of the 2 cells produced undergo Meiosis II and in turn produce a total ______haploid cells.
4. The four cells change in form and develop a ______to become male gametes called ______.
Draw figure 3 pg 148 – Spermatogenesis only!!!!
B. Meiosis in Females
1. ______- process by which gametes are produced in female animals.
2. Occurs in ______- female reproductive organs
3. During ______in meiosis I the cytoplasm divides ______, one of the resulting cells gets all of the ______. It is this cell that will eventually give rise to an ______cell.
4. The other cell is small and called a ______
5. The larger cell undergoes meiosis II, and the division of the egg cell during cytokinesis is again ______. The larger cell develops into a gamete called an ______of ______.
6. Because of the larger share of cytoplasm, the mature ovum has a ______
______to nourish the developing organism.
Draw figure 3, pg. 148 Oogenesis
7.2 Sexual Reproduction
I. Sexual and Asexual Reproduction
a. Reproduction -______, can be asexual or sexual.
b. ______- a single paren passes copies of all of its genes to each of its offspring. There is no ______of haploid cells, such as gametes.
c. ______- an organism that is genetically identical to its parent.
* Recall – Prokaryotes reproduce by ______, a type of asexual reproduction.
d. Sexual Reproduction - ______parents each form reproductive cells that have ______the number of chromosomes.
Diploid mother and father produce à______which join to formà______offspring
Why don’t you look exactly like your parents?______
______
**** sexual reproduction occurs in ______.
EXAMPLES: Animals, Plants, Fungi, Protists!!!! – NOT just humans!!!
A. Types of Asexual Reproduction
Examples of asexual reproduction include: Fission, fragmentation, budding
a. ______- the separation of a parent into two or more individuals of about equal size. ex. ______
Draw picture
b. Fragmentation - ______
______
c. ______- new individuals split off from
existing ones. ex. Budding of hydra:
Genetic Diversity
Asexual Reproduction / Sexual ReproductionAdvantages and Disadvantages / Advantages and Disadvantages
B. Sexual Life Cycle
1. Life Cycle- ______
______
2. Diploid Life Cycle
3. Use the picture above to explain the diploid life cycle!
______
4. Cloning by Pathogenesis
a. Parthenogenesis-______
______
b. Since there is no male that contributes ______
______, the offspring is a ______(genetically identical) of the mother.
c. Clones are usually produced in nature by ______reproduction.
d. Parthenogenesis in snakes has usually occurred in ______females that have lived many years without male companionship, such as those in a zoo.
How does Parthenogenesis Occur?
e. It is ______that in the mother snake, her own chromosomes are ______in place of the missing father’s ______, thereby self-fertilizing her egg.
f. Other scientists think that after a long absence of males, some unknown signal (such as a hormone) ______the egg to start ______.
Organisms that Undergo Parthenogenesis
a. List 3 organisms that can reproduce using parthenogenesis
1)______
2)______
3)______
b. Parthenogenesis is not thought to be possible in ______.
c. Embryos of mammabls that ______have genes from both a ______and a ______parent do not develop normally.
d. The only natural mammalian clones known are ______, which develop when a fertilized egg ______and two individuals develop.