Exam 3

Question 1

What are the two main requirements for cell division to happen?

Answer 1

The cell has to be large enough and be able to provide full genetic material to the daughter cells.

Question 2

What is the method of cellular division used by prokaryotic cells?

Answer 2

Binary fission

Question 3

What is the method of cellular division used by eukaryotic cells?

Answer 3

Meiosis and Mitosis and cytokinesis

Question 4

What are the three main steps of binary fission and how do they happen?

Answer 4

Binary fission is divided in replication, growth, and division. The prokaryotic DNA is attached to the membrane by proteins; the DNA replication starts bi-directionally and the second DNA remains attached at the same place. The cell then elongates symmetrically around the midpoint, separating the DNA sites. Cell division begins with the synthesis of new cell membrane and cell wall material at the midpoint. Continued synthesis completes the constriction and separates daughter cells.

Question 5

What are the main differences between meiosis and mitosis?

Answer 5

Mitosis happens in somatic cells, during the Eukaryotic Somatic Cell Cycle. The main goal of mitosis is to produce somatic cells so tissues can grow and repair; mitosis is also responsible for asexual reproduction in some species. Meiosis focus on the production of haploid gametes (sperm and eggs) through specialized cells located in the gonads. It is responsible for the sexual reproduction.

Question 6

What is the interphase?

Answer 6

It is the time between cell divisions, where the cell with be preparing for mitosis. It is divided into G1 (where there is a presynthesis growth; lasts for 10h), S phase (only phase where there is DNA replication, lasts for 9h), and G2 (preparation for division; lasts for 4 h).

Question 7

How many chromosomes do humans have?

Answer 7

46 chromosomes divided in 23 pairs

Question 8

How many autosomes do humans have?

Answer 8

44 autosomes divided into 22 pairs

Question 9

How many sex chromosome pairs do humans have?

Answer 9

1

Question 10

What are homologous chromosomes?

Answer 10

They are chromosomes carrying the same type of information in different versions.

Question 11

What are the phases of mitosis?

Answer 11

Prophase, prometaphase, metaphase, anaphase, and telophase

Question 12

What happens during mitosis’ prophase?

Answer 12

The chromosomes condensate, proteins will assemble the mitotic spindles, centrosomes will migrate to opposite poles of the cell.

Question 13

What happens during mitosis’ prometaphase?

Answer 13

Breakdown of nuclear envelope, mitotic spindles fibers attach to centromeres through the kinetochores

Question 14

What happens during mitosis’ metaphase?

Answer 14

Chromosomes will be aligned in the middle of the cell

Question 15

What happens during mitosis’ Anaphase?

Answer 15

Sister chromatids are separated and pulled to opposite poles; the centromeres divide.

Question 16

What happens during mitosis’ telophase?

Answer 16

Breakdown of mitotic spindle fibers, reform of nuclear envelope, decondensation of chromosomes; this phase represents the end of mitosis.

Question 17

There is a reduction in the ploidy during mitosis.

Answer 17

False, there is no reduction in ploidy during mitosis.

Question 18

What happens during cytokinesis?

Answer 18

There is the formation of a contractile ring formed by actin filaments that will pinch the cell in the middle and finalize the creation of the daughter cells.

Question 19

What is the difference between cytokinesis in animal cells and plant cells?

Answer 19

In plant cells, a phragmoplast is formed in the middle of the cells, attracting vesicles that are filled with cell wall components. They will form a cell plate which will connect to the original cell wall, forming the new cells.

Question 20

What is the order of DNA coiling?

Answer 20

Double-helix DNA -> histone (formed by lysine and arginine) -> nucleosomes -> chromatins -> chromosome