Unit 6 Flashcards
What are the 4 stages of the cell cycle?
G1, S, G2, M
What is happening during G1 and G2?
G1: Cell growth and preparation for DNA replication. G2: Preparation for mitosis and error checking.
What is happening during S?
DNA replication occurs.
What is happening during M?
Mitosis and cytokinesis occur, leading to cell division.
How many checkpoints are there and in what phases do they occur?
Three checkpoints: G1, G2, and M phase.
What does it mean when a cell stays in G0?
It exits the cycle and does not divide, often becoming a specialized cell.
What does it mean when the cell cycle keeps going uncontrollably?
It can lead to cancer due to unchecked cell division.
How many cell cycle turns (doubling of cells) does it take to make a 36 trillion cell human?
About 46 divisions.
What do mutations in checkpoints tend to lead to?
Cancer and other cell cycle-related diseases.
What is an example of liquid cancer? What do we call a solid clump of cancer cells?
Leukemia (liquid cancer), Tumor (solid cancer).
What stage of the cell cycle does Mitosis take place in?
M phase.
Distinguish Mitosis from cytokinesis.
Mitosis: Nuclear division. Cytokinesis: Cytoplasmic division.
By initials, what are the 4 stages of Mitosis?
P, M, A, T (Prophase, Metaphase, Anaphase, Telophase).
What happens during prophase to the DNA, nuclear membrane, and the centrosome spindle fibers?
DNA condenses, nuclear membrane breaks down, spindle fibers form.
What grows out of the centrosomes?
Microtubules.
What protein does DNA supercoil on to? How many times does it coil upon itself to form a chromosome?
Histones; Coils 5 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?
Chromatids; Centromere.
How many chromosomes do chimpanzees have? Fruit Flies? Walking Catfish?
48, 8, 54.
How do you know if a cell is in metaphase?
Chromosomes are aligned in the middle.
How do you know if a cell is in anaphase?
Sister chromatids are pulled apart.
What happens during telophase to the chromosomes, nuclear membrane, centrosome spindle fibers, and the cell in general?
Chromosomes decondense, nuclear membrane reforms, spindle fibers break down, 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? Plants don’t have them. What is responsible for microtubule growth in a centrosome?
Centrioles; Microtubule Organizing Centers (MTOCs).
What is the official name of a fertilized egg?
Zygote.
What is the name of the 16-cell stage of embryogenesis after the fertilization of the egg cell? What type of stem cells are those 16 cells? What can they make that other stem cells cannot make?
Morula; Totipotent; Placenta.
What do we call the “hollow ball” of cells stage? What type of stem cells are they?
Blastocyst; Pluripotent.
What do we call the stage where all the cell tissues are present? What do we call those stem cells?
Gastrula;
Pluripotent.
What are the three tissue layers?
Ectoderm, Mesoderm, Endoderm.
Distinguish what body parts are made of the outer, middle, and inner tissues.
Outer: Skin, Nervous System; Middle: Muscle, Bones, Blood; Inner: Digestive and Respiratory Systems.
How many changes do you have to make to a skin cell to reprogram it into a pluripotent stem cell?
Four genetic changes.
Planaria have lots of stem cells. What type of stem cells are they? What do we call them?
Pluripotent; Neoblasts.
How would you describe the regenerative abilities of a Planaria?
They can regenerate entire bodies from small fragments.
What can you use to reprogram a Planaria to grow 2 heads instead of a tail (note: you do not change the genes)?
Disrupting the Wnt signaling pathway.
What is the shape of DNA?
Double helix.
What does DNA stand for?
Deoxyribonucleic Acid.
What are the 4 nucleotides that make up DNA? (Full names)
Adenine, Thymine, Cytosine, Guanine.
What are the three parts of a nucleotide? What part represents the 5’ end?
Sugar, Phosphate, Nitrogenous Base; Phosphate.
What is Chargaff’s rule?
A=T, G=C.
What was the name of Franklin’s famous x-ray crystallography picture of DNA (B-form)?
Photo 51.
What was Crick’s contribution to the structure? What does “antiparallel” mean?
DNA helix model; Strands run in opposite directions.
What was Watson’s contribution? How did chance (serendipity) play a role in his contribution?
DNA base-pairing model; He saw Franklin’s data by chance.
How many H-bonds are between A and T? G and C?
A-T: 2, G-C: 3.
How many base pairs are there in the human genome? A typical bacteria’s genome? An amoeba’s genome?
~3 billion, ~5 million, >100 billion.
What phase of the cell cycle does DNA replication take place?
S phase.
DNA is the only molecule that can replicate itself (a requirement for life). But it doesn’t actually replicate itself. Explain.
Enzymes like DNA polymerase facilitate replication.
What enzyme opens up the strand? What bonds does it break?
Helicase; Hydrogen bonds.
What do we call the opening of the strands (hint: think eating utensil)?
Replication fork.
What enzyme adds nucleotides?
DNA polymerase.
What is the one limitation to the enzyme that adds nucleotides?
It can only add to the 3’ end.
What does it mean to copy along the leading strand (in terms of the replication fork)?
Continuous replication.
What does it mean to copy along the lagging strand (in terms of the replication fork)?
Discontinuous replication in Okazaki fragments.
