Bio 140 Ch 11

What are three examples of checkpoints that the cell monitors before proceeding through the cell cycle?

1) checkpoint for spindle attachment, which is active before anaphase and ensures that all chromosomes are attached to the spindles 2) DNA damage checkpoint, which is active in the G1 phase and checks for DNA damage 3) DNA replication checkpoint, which is active in G2 and makes sure all the DNA is replicated

What two processes during meiosis results in genetically unique daughter cells?

1) crossing over, which occurs at essentially random positions along the chromosomes and creates unique combinations of genetic differences that may be present in the maternal and paternal chromosomes 2) random alignment of the homologous chromosomes on the spindle in metaphase I, so each nucleus receives a random combination of maternal and paternal homologs

What are three situations in which mitotic division occurs?

1) development of multicellular organisms 2) maintenance and repair of organs and tissues 3) asexual reproduction of unicellular eukaryotes

In a human cell at the end of prophase I, how many chromatids, centromeres, and bivalents are present?

92 chromatids, 46 centromeres, 23 bivalents

What would be the consequence if a cell underwent mitosis but not cytokinesis?

A cell that undergoes mitosis but not cytokinesis will become a single cell with two nuclei (and therefore with twice the normal amount of DNA); this type of cell is called a multinucleate cell.

How do oncogenes, proto-oncogenes, and tumor suppressor genes differ from one another?

An oncogene is a gene that causes cancer. A proto-oncogene is a gene that has the potential to cause cancer when mutated. A tumor suppressor gene blocks specific steps in the development of cancer.

How does cytokinesis differ between animals and plant cells?

In animal cells, cytokinesis involves a contractile ring, which forms against the inner phase of the cell membrane at the equator of the cell. When the rain contracts, the cytoplasm is pinched in half, forming two new daughter cells. In plant cells, cytokinesis involves the growth of a new cell wall called a cell plate in the middle of the dividing cell that fuses with the original cell wall at the perimeter of the cell and two new daughter cells are formed

What are three ways in which meiosis I differs from mitosis?

In meiosis I, homologous chromosomes pair, undergo crossing over, and segregate from each other. These events do not occur in mitosis. In mitosis, centromeres divide and sister chromatids separate, events that do not take place in meiosis I.

What are the roles of cyclins and cyclin-dependent kinases in the cell cycle?

In the cell cycle, cyclins bind to and activate cyclin-dependent kinases (CDKs). Once activated, the CDKs phosphorylate target proteins involved in promoting cell division.

How is cell division similar and different in prokaryotic cells and eukaryotic cells?

Prokaryotic cells reproduce by a process called binary fission. During this process, the cell replicates its DNA, increases in size, and divides into two daughter cells, each having one copy of the parental DNA. Eukaryotic cells divide by mitotic cell division. In this process, cells first replicate their chromosomes in the nucleus. The nuclear envelope then dissolves and each pair of chromosomes is separated. Once the two full sets of chromosomes are separated, a nuclear envelope forms around each one. The cell then goes through a process called cytokinesis, where it is split into two new daughter cells. Binary fission is similar to mitotic cell division in that one parent cell gives rise to two daughter cells, and the two daughter cells are genetically identical to each other and the parent cell, except for rare mutations. The two processes differ in a few key aspects: (1) The size and shape of the genetic material; bacteria have a single circular chromosome, whereas eukaryotic cells have one or more linear chromosomes. (2) The DNA of prokaryotes is attached to the plasma membrane, allowing separation of DNA into the daughter cells by cell growth. In eukaryotic cells, the chromosomes are not attached to the cell or nuclear membrane.

What are two ways in which the function of p53 can be disrupted?

The function of the p53 protein can be disrupted by a mutation in the p53 gene or by an inhibitor. For example, certain viral proteins, such as the E6 protein of HPV discussed in Case 2: Cancer, can inhibit the function of the p53 protein