Chapter 2- Achieve Hw

A section of Elodea leaf is stained and examined under a microscope. The total number of cells in each stage of the cell cycle is recorded and presented in the table. If the complete cell cycle in an Elodea leaf requires 24 hours, what is the average duration of metaphase in the cycle? Assume no cells are in Go. nterphase 150 Prophase 20 Prometaphase 11 Metaphase 6 Anaphase 5 Telophase 1 Total 193.000

0.75 6/193 is 0.031 multiply by 24hrs to get the hrs 0.75

Place the steps of the prokaryotic cell cycle in order.

1.) Prokaryotic chromosomes attach to the plasma membrane 2.) Prokaryotic chromosomes replicate 3.) cell elongates, pulling each chromosome to an opposite end of the cell 4.) PLasma membrane and cell wall grow inward and divide the cell 5.) two genetically identical daughter cells are produced

phases of interphase

G1G1 phase occurs after the formation of a new cell and is the first phase of interphase. During G1G1 , the cell grows in size and synthesizes mRNA and protein. During G1G1 , the cell must pass a checkpoint called the restriction point (R), after which the cell becomes committed to DNA replication and cell division. If the cell passes R, it eventually enters S phase, during which it replicates its DNA. After S phase, the cell enters G2G2 phase, during which the cell grows further, synthesizes more mRNA and protein, and prepares for mitosis. G2G2 is the last phase of interphase. After passing another checkpoint, the cell enters M phase, the cell division phase comprising both mitosis and cytokinesis. If a cell does not pass R, it instead enters G0G0 phase, also known as a resting or quiescent phase. Cells in G0G0 do not divide, prepare to divide, or replicate their DNA, although they are still alive and functional. Some cells in G0G0 can reenter the cell cycle at G1G1 when stimulated by injury, starvation, or signals from other cells.

Meiosis and mitosis are both forms of cell division. However, the outcomes of these processes differ. Consider a diploid organism with two sexes. Select the reasons why meiosis typically produces genetic variation, whereas mitosis does not.

Gametic chromosomes have a different combination of alleles than parental chromosomes as a result of independent assortment. Genetic material is exchanged between homologous chromosomes in meiosis during crossing over. Meiosis produces four genetically different haploid cells.

What happens during metaphase I of meiosis?

Homologous chromosomes are randomly arranged in the middle of the cell.

Process of mitosis

In prophase, the chromosomes condense from relatively diffuse chromatin into highly compacted structures composed of identical sister chromatids joined by a centromere. The nuclear membrane remains intact until it breaks down at the end of prophase. In metaphase, the chromosomes align at the equator of the cell. There, the centromeres of each chromosome attach to spindle fibers. In anaphase, the centromeres divide, and the sister chromatids of each chromosome are pulled apart to opposite poles of the cell by the spindle fibers. Finally, in telophase, the chromosomes are completely separated to the opposite poles of the dividing cell. Nuclear membranes reform around the chromosomes, and the chromosomes revert to their diffuse, loosely packed form.

Consider two cells, where one cell is haploid and the other is diploid.

In the haploid cell, only one pair of DNA molecules are present, whereas in the diploid cell, two pairs of DNA molecules are present.

Cells are categorized as either prokaryotic or eukaryotic. Classify the characteristics as being unique to prokaryotic cells, common to both cell types, or unique to eukaryotic cells. Move each description into the correct category.

Prokaryotes- small 10um in size, lack true cytoskeleton Both-contain DNA, use ribosomes to synthesize proteins Eukaryotes-nuclear membrane surrounds DNA

What happens during anaphase II of meiosis?

Sister chromatids separate from each other and migrate to opposite ends of the cell.

A cell has a circular chromosome and histone proteins associated with its DNA, but lacks a nuclear membrane.

The cell belongs to Archaea because it has histone proteins, which are present in Archaea and Eukaryota but absent in Eubacteria.

What are the functions of mitotic cell division?

cell regeneration asexual reproduction organism growth

G2/M checkpoint

detection of DNA damage after replication

Spindle‑assembly checkpoint

ensures that each chromosome is attached to the spindle fibers from opposite poles

46 Chromatids

g1 prior to mitosis

G1/S checkpoint

maintains until cell necessary enzymes for replication are needed

92 Chromatids

primary oocyte arrested prior to ovulation

23 Chromatids

spermatazoa secondary polar body

What are checkpoints?

transition points during the cell cycle that ensure all cellular components are functioning properly

Cell division by mitosis is a mechanism of asexual cell replication. Some single‑celled organisms reproduce by cell division, and cell division enables multicellular organisms to grow and to repair damaged cells.

two daughter cells with identical chromosomes