Cell Cycle, Cancer, Stem Cells, and DNA Science

What are the 4 stages of the cell cycle?

G1 phase (gap 1), S phase (synthesis), G2 phase (gap 2), and M phase (mitotic)

What is happening during G1 and G2?

During G1, the cell grows and makes proteins needed for DNA replication.
During G2, the cell continues to grow and prepares for mitosis by producing necessary proteins and organelles.

What is happening during S phase?

The cell’s DNA is replicated

What is happening during M phase?

The cell undergoes division where the replicated DNA is separated into two separate daughter cells

How many checkpoints are there and in what phases do they occur?

There are three major checkpoints: one at the end of G1, one at the transition of G2 and M, and one during the metaphase in mitosis

What does it mean when a cell stays in G₀?

The cell is not actively dividing or preparing to divide

What does it mean when the cell cycle keeps going uncontrollably?

The cell is continuously dividing without the normal regulatory mechanisms in place

How many cell cycle turns (doubling of cells) does it take to make a 36 trillion cell human?

Approximately 46

What do mutations in checkpoints tend to lead to?

Uncontrolled cell division, genetic instability, and cancer

What is an example of liquid cancer?

An example of liquid cancer, which is a cancer of the blood, bone marrow, or lymphatic system is leukemia

  What do we call a solid clump of cancer cells?

A tumor

What stage of the cell cycle does Mitosis take place in?

The M phase

Distinguish Mitosis from cytokinesis.

Mitosis is the division of the nucleus while cytokinesis is the division of the cytoplasm.

By initials, what are the 4 stages of Mitosis?

PMAT

What happens during prophase to the DNA, nuclear membrane, and the centrosome spindle fibers?

DNA condenses into visible chromosomes, the nuclear membrane breaks down, the centrosomes move to opposite poles of the cell, initiating the formation of spindle fibers

What grows out of the centrosomes?

Microtubules

What protein does DNA super coil on to?

Histone

How many times does DNA coil upon the histone to form a chromosome?

Approximately 1.65 times

If we say a chromosome looks like the letter “H,” what are the two long  vertical segments? What is the horizontal bridge between the two long segments?

The two long vertical segments are the chromosome arms. The horizontal bridge is called the centromere

How many chromosomes do chimpanzees have?

48

How many chromosomes do Fruit Flies have?

8

How many chromosomes do Walking Catfish have?

Between 48 and 100

How do you know if a cell is in metaphase?

When its chromosomes are lined up in the middle of the cell

How do you know if a cell is in anaphase?

When the sister chromatids of each chromosome are visibly separating at the centromere and moving towards opposite poles of the cell.

What happens during telophase to the chromosomes, nuclear membrane, centrosome spindle fibers, and the cell in general?

Chromosomes reach the poles of the cell and begin to uncoil, the nuclear membrane reforms around each set of chromosomes, the centrosomes spindle fibers disassemble, and the cell prepares for cytokinesis

What is the protein on the centromere that the microtubules attach to?

Kinetochore

In animals, what is in the middle of a centrosome? 

A pair of centrioles which are organelles made of microtubules

Plants don’t have centrioles. What is responsible for microtubule growth in a centrosome?

Microtubule organizing center

What is the official name of a fertilized egg?

A zygote

What is the name of the 16 cell stage of embryogenesis after the fertilization of the egg cell?

A morula.

What type of stem cells are those 16 cells in the morula?

Totipotent stem cells

What can totipotent stem cells make that the other stem cells cannot make

They can develop into a complete organism including the embryo and extra embryonic tissues

What do we call the “hollow ball’ of cells stage?

A blastula

What type of stem cells are in a blastula?

Pluripotent stem cells

What do we call the stage where all the cell tissues are present? 

The gastrula

What do we call the stem cells in the gastrula?

Multipotent stem cells

What are the three tissue layers?

Ectoderm, mesoderm, and endoderm

What body parts are made of the endoderm?

Liver, lungs, pancreas, stomach, and intestines

What body parts are made of the mesoderm?

Muscles, bones, heart, and kidneys

What body parts are made of the ectoderm?

Skin, brain, spinal cord, hair, nails, and sweat glands

How many changes do you have to make to a skin cell to reprogram it into a pluripotent stem cell?

You need to add 4 genes

Planaria have lots of stem cells.  What type of stem cells are they?  What do we call them?

They have a lot of pluripotent stem cells called neoblasts

How would you describe the regenerative abilities of a Planaria?

Planaria have remarkable regenerative abilities, being able to regenerate a whole body from a small piece of tissue.

What is the shape of DNA?

A double helix

What does DNA stand for?

Deoxyribonucleic acid

What are the 4 nucleotides that make up DNA?

Adenine, thymine, guanine, and cytosine

What are the three parts of nucleotide?

The nitrogenous base, a pentose sugar, and a phosphate group

What part of a nucleotide represents the 5’ end?

The phosphate group attached to the 5’ carbon of the sugar

What is Chargaff’s rule?

The amount of adenine is always equal to the amount of thymine, and the amount of guanine is always equal to the amount of cytosine. 

What was the name of Franklin’s famous x-ray crystallography picture of DNA (B-form). From her photo she deduced the structure was a double helix. 

photo 51

What was Crick’s contribution to the structure? What does “antiparallel” mean?

Discovering that the two strands are anti parallel meaning that they run alongside each other but in opposite directions.

What was Watson’s contribution? How did chance (serendipity) play a role in his contribution?

Creating a model of DNA’s structure with Crick. Chance played a role in his contribution because he saw Franklin’s x-ray crystallography images

How many H-bonds are between A and T? G and C?

There are 2 hydrogen bonds between A and T. There are 3 hydrogen bonds between G and C.

What phase of the cell cycle does DNA replication take place?

The S phase

DNA is the only molecule that can replicate itself (a requirement for life).  But it doesn’t actually replicate itself. Explain.

DNA doesn’t actually replicate itself because it requires a complex system of proteins and enzymes to replicate.

What enzyme opens up the strand? What bonds does it break?

The enzyme helicase opens up the DNA strand. It breaks the hydrogen bonds between the nitrogenous bases.

What do we call the opening of the strands (hint: think eating utensil)?

The opening of the DNA strands is called a replication fork

What enzyme adds nucleotides?

DNA polymerase

What is the one limitation to the enzyme that adds nucleotides?

it can only add nucleotides to the 3’ end of a DNA strand, working in a 5’ to 3’ direction.

What does it mean to copy along the leading strand (in terms of the replication fork)?

It means to synthesize a new DNA strand continuously in the same direction that the replication fork is moving.

What does it mean to copy along the lagging strand (in terms of the replication fork)?

It means to synthesize a new DNA strand in a discontinuous manner, moving away from the replication fork, creating short fragments of DNA called Okazaki fragments.

How many base pairs are there in the human genome? A typical bacteria’s genome? An amoeba’s genome?

There are approximately 3 billion base pairs in the human genome. A typical bacteria’s genome has a few million base pairs. An amoeba’s genome has about 670 billion base pairs.

How many rings are in A, G, C, T

A and G: 2

P and C: 1

How many rings are in a purine? How many rings are in a pyrimidine?

2. 1.