Lecture 24

Question 1

Define chromosomes

Answer 1

Threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Question 2

Define chromatin

Answer 2

Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures.

Question 3

Define Genome

Answer 3

Genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA

Question 4

When and how does chromosome duplication happen?

Answer 4

Chromosome duplication occurs during the S phase of the cell cycle through DNA replication, producing identical sister chromatids connected by a centromere. This process leads up to cell division.

Question 5

What are the cell cycle phases and what happens (including their relative timing)

Answer 5

G1 Phase:
Cell growth.
Variable duration.

S Phase:
DNA replication.
Follows G1.

G2 Phase:
Further growth and preparation.
Follows S phase.

M Phase (Mitosis):
Cell division.
Consists of prophase, metaphase, anaphase, and telophase.
Short duration.

Question 6

What are the mitosis phases and what happens?

Answer 6

Prophase:
Chromosomes condense.
Nuclear envelope breaks down.
Spindle fibers form.

Metaphase:
Chromosomes align at the cell’s equator.
Spindle fibers attach.

Anaphase:
Sister chromatids separate.
Cell elongates.

Telophase:
Chromatids decondense.
Nuclear envelopes reform.
Spindle fibers disassemble.
Cytokinesis occurs.

Question 7

What cytoskeleton components are involved in mitosis?

Answer 7

Microtubules:
Form the mitotic spindle, aiding in chromosome movement during mitosis.

Actin Filaments:
Participate in cytokinesis, facilitating the division of the cell into two daughter cells.

Question 8

Describe the process and structures involved in cytokinesis?

Answer 8

Animal Cells:
Cleavage furrow forms.
Contractile ring of actin and myosin pinches the cell.
Two daughter cells are created.

Plant Cells:
Cell plate forms from vesicles.
New cell wall develops.
Two daughter cells are formed.

Question 9

Where are the molecules controlling cell cycles located?

Answer 9

One near the end of G1, a second at the G2/M transition, and the third during metaphase.