Biology pg. 153 #1-22

List three characteristics of all stem cells.

All stem cells- regardless of their source- have three general properties: They are capable of dividing and renewing themselves for long periods, they are specialized, and they can give rise to specialized cell types. Stem cells are capable o dividing and renewing themselves for long periods.

Briefly describe how cell differentiation occurs in the developing animal embryo.

Animals are made up of many different cell types, each with specific functions in the body. However, during the embryonic development, the embryo possesses these varied cells, this is where embryonic differentiation comes into play.

What is the relationship between a cell's surface area and its volume?

As cells increase in size, the surface area and volume does not usually increase in proportionally to length. The greater the diameter of a single-celled organism, the lower the surface area to volume ratio. It is this relationship that restricts the size of the particular cell.

You pull a leaf from a plant and put it in water. After a week, roots start to grow from the leaf. What type of reproduction has occurred, and what role does mitosis play in it?

Asexual reproduction has occurred and mitosis has happened in the new root cells to make them grow.

How does the process of cytokinesis differ from the process of mitosis?

Basically, mitosis is a process by which is duplicated genome in a cell is separated into two halves that are identical in nature. Cytokinesis is the process where the cytoplasm of the cell divides to form two 'daughter' cells. There are subtle differences between the two.

List one similarity and one difference between binary fission and mitosis.

Binary fission happens to bacteria in prokaryotes, it occurs in non-membrane bound organelles. Mitosis occurs in eukaryotes and it is the process of multiplying (splitting into) membrane bound organelle cells. They both divide and replicate in two halves.

Telophase

Last phase of mitosis when a complete set of identical chromosomes is a positioned at each pole of the cell, the nuclear membranes start to form, the chromosomes begin to uncoil, and the spindle fibers disassemble.

The term mitosis comes from the Greek roots mitos, which means "thread". How does this meaning relate to the process of mitosis.

Mitosis has little threads that go to the nucleus and attach themselves to the nucleus.

Compare the rates of cell division occurring in your neurons and your hair follicles.

Neurons appear to stay permanently in the GO phase because they don't really wear out hair follicles divide more frequently, otherwise one would become bald.

Cytokinesis

Process by which the cell cytoplasm divides.

The prefix pro- means "earlier than" or "prior to". Explain how this meaning relates to the word prophase.

Prophase is the 1st phase and means before nucleus.

Describe what happens in each main phase of mitosis- Prophase, Metaphase, Anaphase, and Telophase.

Prophase- The nuclear membrane starts to get broken down and the chromosomes start attaching spindle fibers. Metaphase- All of the chromosomes line up in the middle. Anaphase- The chromosomes are getting split up (sister chromatids separate). Telophase- New nucleus starts to form. Cytokinesis- Cytoplasm and organelles separate.

You know that a chromosome is a very long, continuous strand of DNA. How do proteins help condense chromosomes?

Proteins (Histones) wrap around DNA around to make sure they don't get tangled which allows them to be shrunken down into a chromosome.

Centromere

Region of condensed chromosome that looks pinched, where spindle fibers attach during meiosis and mitosis.

Telomere

Repeating nucleotide at the ends of DNA molecules that do not form genes and help prevent the loss of genes.

Metaphase

Second phase of mitosis when spindle fibers align the chromosomes along the cell equator.

The prefix telo- means "distant, far, or end". How does this meaning relate to the words telophase and telomere.

Telophase is the last phase of mitosis and means end.

Prophase

The first stage of mitosis when chromatin condenses, the nuclear envelope breaks down, the nucleus disappears, and the centrosomes and centrioles migrate to opposite sides of the cell.

The cell cycle has four main stages--- G1, S, G2, and M. What occurs in the cell during each stage?

The length of the cell cycle can vary, resulting in different rates of cell division. This variability is based on the body's need for different cell types. Cells also divide because they need a sufficient surface area-to-volume ratio to move materials into and out of the cell.

Increased levels of cyclin help trigger to divide. Do you think a growth factor would increase or decrease cyclin levels? Explain.

The presence of a growth factor is going to increase cyclin levels because growth factor is a hormone that makes the cell want to divide.

Describe how uncontrolled cell division is dangerous in organisms.

They divide more often then healthy cells. (cancer cells) uncontrolled cell division can be dangerous. They can divide rapidly without communication from other cells.

Anaphase

Third phase of mitosis during which chromatids separate and are pulled to opposite sides of the cell.