chapter 9 Q/A

Seite 1

9.1 Q/A

1) Define and Explain Diploid, Haploid, Homologous chromosomes, paternal and maternal homologs.

Diploid: 2 "copies" of each chromosome (2n)

Haploid: 1 "copy" of each chromosome (1n)

Homologous Chromosomes: The 2 things that make up those chromosomes are similar, but not the same. (Everybody has hair chromosomes, but not everybody has the same alleles in those chromosomes.)

Paternal homologs: Part of a chromosome you get from your father.

Maternal homologs: Part of a chromosome you get from your mother.

2) Explain the structure of DNA (make sure to talk about Deoxyribose, purines and pyrimidines, phosphate groups, and phosphodiester bonds). What is the difference between the backbone and the base pairs?

DNA is a double helix, like a twisted ladder. The outside of the ladder/backbone is made up of deoxyribose, a sugar, bonded to phosphate groups. The steps/rungs of the ladder are made up of nitrogenous bases. They are A, T, C, and G. They stick out from the sugar they are bonded to and then make a weak bond with their partner base.

3) Explain how DNA is organized in a cell (or in a nucleus for eukaryotic cells). Why does it make sense to organize DNA in this way? Why would DNA need to be organized more when it will be moved?

DNA is organized by either a circular structure in prokaryotes or a linear piece called a chromosome in the nucleus of a Eukaryote. These structures keep the large amounts of DNA in an easier to find, alter, move, and keep track of. Organized DNA would be easier to move than a jumbled mess of DNA because organized things are easier to move than brute-forcing a mess of chaos.

4) What is Karyotyping? How many chromosomes do the majority of humans on this planet have?

Karyotyping is the counting of chromosomes that is usually done during metaphase because that's when they are easiest to discern. A human diploid number of chromosomes is 46.

Other:

Telomere- ends of a chromosome.

Centromere-connecting(?) gene of 2 chromosomes. Not always in the center of the chromosome

Seite 2

9.2 Q/A

1) List the phases of the cell cycle from cell birth to cell division.

G1

G0

S

G2

2) What are the major events of G1, G0, S, and G2 phases?

G1-growth then returns to "normal" metabolism.

G0-Growth and then no split. No more division.

S-DNA replication happens during this phase. By the end of this Humans should have 46 duplicate chromosomes-each having 2 sister chromatids

G2-synthesis of all the proteins and membranes needed for cell division

3) What controls the cell cycle?

The thing that controls the cell cycle is regulators like proteins inside the cell. (cyclin)

4) List and explain the events for each of the phases of mitosis: prophase, prometaphase, metaphase, anaphase, and telophase.

Prophase- Chromosomes compact to form an X-like shape. Where the center of the x is called a centromere, which is where the sister chromatids are connected.

Prometaphase- Nuclear envelope breaks down into membranous vesicles. The mitotic spindle sends out microtubules. Kinetochore microtubules connect the chromosomes to the Mitotic spindle. Non-Kinetochore microtubules allow for the stretching of the cell. Astral microtubules anchor the mitotic spindle into the rest of the cytoskeleton.

Metaphase- The duplicated sister chromatids still attached at the centromere line up at the midplane/metaphasic plate. Basically the middle of the cell.

Anaphase- Chromatids separate at the centromeres and are now referred to as chromosomes. They are pulled by the kinetochore microtubules to the poles and form a v shape.

Telophase- Nuclear envelope reforms, condensed chromosomes de-condense and expand once more, and the nucleoli reappear. Returns to conditions similar to interphase as it moves back into the G1 phase.

5) What happens if a cell undergoes mitosis without cytokinesis?

It cannot split.

6) Compare and Contrast cytokinesis of animal cells to cytokinesis in plant cells.

Cytokinesis in animal cells- 2 proteins cause a cleavage furrow that encircles the equatorial region. Actin and myosin tighten like a belt until the two cells pop apart.

Cytokinesis in plant cells- Vesicles form a new cell wall in the middle of the cell and then splits it once it has joined both sides of the cell wall together.

Seite 3

9.3 Q/A

1) What controls the cell cycle (hint: autocrine signaling)? What are the roles of cyclins and CDKs?

What controls the cell cycle are cyclin and cyclin-depended kinases (CDKs), which act as regulatory signals.

2) What is the role of genetic mutations in cell cycle control errors?

They cause either the cell to be destroyed in order to prevent harmful mutations from spreading or become cancer.

3) Define cancer. Explain why there will never be just one cure for cancer.

Cancer is a malfunction in cell cycle control that allows a cell to rapidly go through the cell cycle over and over even if the cell's DNA has been damaged.