Switcharoo

How can recombination during meiosis be explained? Explain how the processes of meiosis increase genetic variation in a population.

Recombination occurs during meiosis in prophase I when chromosomes crossover and exchange DNA. The maternal and paternal chromosomes swap specific information concerning certain traits, and this exchange leads to genetic variation as there is a new chromosome as a result of this little switcharoo of genetic coding information.

Meiosis vs Mitosis

Compare the process of meiosis to the process of mitosis.

This image effectively and efficiently summarizes both processes, showing the similarities and differences.
[To better see the chart, right click and open in a new tab]

Mastering Biology | Pearson; Campbell Biology

Stages of Meiosis

Explain the events of all stages of meiosis

• Meiosis I
• Prophase I
• Centrosome movement, spindle formation, nuclear envelope breaks down, chromosomes condense
• Chromosomes align with their homolog pair, and crossing over occurs [this is the exchange of DNA between two non-sister chromatids]
• The chiasmata is visible in this stage, this is the location where crossing over occurs
• Microtubules from the centrosomes will begin to attach to the kinetochores of the homologous chromosome pairs
• Metaphase I
• Pairs of homologous chromosomes are arranged at the metaphase plate
• Both chromatids of one homolog pair are attached to a spindle fiber on either polar side of the cell
• Anaphase I
• Homologs separate as proteins responsible for sister chromatid cohesion along the chromatid arms break down
• Homologs move towards opposite poles of the cell
• Sister chromatid stay connected to each other as they separate and move
• Telophase I and Cytokinesis
• Each half of cell now has a complete haploid set of duplicated chromosomes
• Cytokinesis divides cytoplasm and splits cell in half
• Meiosis II - NO CHROMOSOME DUPLICATION
• Prophase I
• Spindle apparatus forms
• Chromosomes begin to line up along the metaphase plate
• Metaphase I
• Microtubules attach to kinetochores and pull apart sister chromatids
• Anaphase I
• Chromosomes move up the microtubules towards opposite ends of the cell
• Telophase I and Cytokinesis
• Nuclei form, chromosomes begin to condense
• Cell divides

NOW, at the end of meiosis in an animal cell, the end result is four daughter cells [when starting with one cell]

Diversity, Evolution, and All That Jazz

Justify the effects of a change in the cell cycle mitosis and/or meiosis will have on chromosome structure, gamete viability, genetic diversity, and evolution.

A change in the cell during mitosis or meiosis can cause cell division to go awry. Chromosomes may duplicate oddly, crossover in incorrect ways, etc. The end result may create two defective daughter cells. As a result, the gamete may not be as viable. For example, down syndrome occurs when there is an extra copy of chromosome 21 created during meiosis. But, such DNA mutations can drive evolution, and explain diversity.

Evolution, by definition, is genetic mutation. These mutations occur to help a species adapt to a specific environmental factor.

As for diversity, Meiosis I & Meiosis II [See Stages of Meiosis] have events such as crossing over, reduction to haploid cells, and random chromatid assignment that can lead to creating a unique set of DNA that eventually grows into a fully formed organism. This is why there is such diversity within species, there are plenty of different combinations of DNA, and typically no DNA is the exact same.

Animal Cell Dividing Or Something That Looks Like A Butt

Compare the process of mitosis in plant-like and animal-like cells.

The procedure of cell division is the same for plant and animal cells, until cytokinesis is reached.

In animal cells, a ring of microfilaments formed along the metaphase plate line will contract inwards and pinch off the parent cell membrane, creating two daughter cells. This process is known as creating a cleavage furrow.

Plant cells cannot divide like so because of the rigid cell wall. So instead, a cell plate forms along the metaphase plate line and joins with the pre-existing cell walls, closing off two sides of the parent cell and forming two daughter cells. This cell plate is created with vesicles that contain cellulose and other materials that form the cell wall of a plant.

Mastering Biology | Pearson; Campbell Biology

Cell Division Control: MPF

Explain how cell division is controlled in cells, using examples like MPF and PDGF.

Cells must pass through three checkpoints [in red below] in order to carry out cell division. If a cell does not meet the requirements to pass the checkpoint, it will be unable to continue on to the next phases of cell division.

Mastering Biology | Pearson; Campbell Biology

MPF for example, uses cyclins and cyclin-dependent kinases [Cdks] that come together to form a complex which triggers a cell’s passage past the checkpoints. Cyclin and Cdks concentration gradually increases, peaking at M-phase and fusing together here. After the cell divides, cyclin degrades and is recycled to be used again to create MPF.

Mastering Biology | Pearson; Campbell Biology

Stages of Mitosis

Explain the events of all stages of mitosis and track chromosome and chromatid number through all stages of mitosis.

[To better see the chart, right click and open in a new tab]

https://en.wikibooks.org/wiki/Cell_Biology/Cell_division/Mitosis

Mastering Biology | Pearson; Campbell Biology

4 Stages of the Cell Cycle

Explain the events of all stages of the cell cycle.

There are four parts of the cell cycle:

G₁- “first gap”: growth period, first part of interphase.

S - synthesis: DNA is copied, chromosomes duplicate

G₂ - “second gap”: growth period AFTER DNA has duplicated, second part of interphase

M - Mitosis and Cytokinesis: distribution of genetic material and cytoplasm to form two daughter cells. [See "Stages of Mitosis" under Ch 12 & 13 for more information on Mitosis]

A cell spends most of its life growing in interphase, and only a short amount of time in mitosis.

https://en.wikibooks.org/wiki/Cell_Biology/Cell_division/Mitosis

Chapter 11

Cellular Communication

Also, a little on Apoptosis and Cell Communication Regulation

Receptor Tyrosine Kinase