Lecture 19 - Meiosis

Question 1

What is asexual reproduction? What are some pros and cons?

Answer 1

Asexual reproduction is when organsims make individuals that are genetically identical. This is mostly used by prokaryotic cells through binary fission or mitosis.

Pros:
- all individuals give birth, thus population grows quickly
- no need for finding a mate

Cons:
- individuals are genetically identical

Question 2

What is sexual reproduction? What are some pros and cons?

Answer 2

Sexual reproduction is when organisms make individuals that are genetically different. This occurs through meiosis and allows for independent variation.

Pros:
- genetic mixing

Cons:
- population grows slower
- challenge finding a mate
- STD’s
- loss of advantageous alleles

Question 3

What occurs in Meiosis 1 Prophase 1?

Answer 3

Early Prophase 1
- chromatin condenses

Mid-Prophase 1
- centrosomes move to opposite poles

Pro-Metaphase 1
- Synapsis occurs (chromsomes lie on top of one another)
- tetrades form (necessary for crossing over)
- crossing over
- nuclear envelope disappears

Question 4

What occurs in Meiosis 1? (metaphase, anaphase, and telophase)

Answer 4

Metaphase 1
- homologous pairs line up in the middle of the cell

Anaphase 1
- Independent assortment
- the homologous chromosomes move to opposite poles of the cell (each with two chromatids)

Telophase 1
- the chromosomes gather into nuclei and the original cell divides

Question 5

What occurs in each phase of meiosis 2?

Answer 5

Prophase 2
- chromosomes condense again, following a bried interphase without DNA replication

Metaphase 2
- centromeres are lined up to the center of the cell

Anaphase 2
- chromatids finally seperate and move to the opposite poles of the cell

Telophase 2
- the chromosomes gather into nuclei, and the cells divide

Question 6

What is the input, action, and output of meiosis 2?

Answer 6

input: two haploid cells with replicated chromosomes

action: seperation of sister chromatids & independent assortment of chromatids

output: four haploid genetically different cells

Question 7

How is apoptosis regulated?

Answer 7

Signals to conduct apoptosis can be sent externally or internally. Externally it will bind to a receptor protein. Internally, it will bind to the mitochondria where it will release another signal. The signal then travels to an inactive caspase. Once the signal binds to the caspase, it changes its shape and activates. Once activated, it hydrolozyes nuclear proteins and nucleosomes which will result in apoptosis.