Biology Chapter 12 HW Flashcards

Questions and Answers

Nucleoli are present during _____

interphase

Cytokinesis often, but not always, accompanies _____

telophase

Chromosomes become visible during _____

prophase

Centromeres divide and sister chromatids become full-fledged chromosomes during _____

anaphase Signup and view all the answers

Spindle fibers attach to kinetochores during _____

prometaphase Signup and view all the answers

DNA replication produces two identical DNA molecules, called _____________

sister chromatid(s) Signup and view all the answers

The __________ is the region where the identical DNA molecules are most tightly attached to each other.

centromere(s) Signup and view all the answers

During mitosis, microtubules attach to chromosomes at the _____

kinetochore(s) Signup and view all the answers

In most eukaryotes, division of the nucleus is followed by ____________

cytokinesis Signup and view all the answers

The ______________ are the organizing centers for microtubules involved in separating chromosomes during mitosis.

centrosome(s) Signup and view all the answers

Which of these is NOT a carcinogen?

All of the above are carcinogens Signup and view all the answers

_____ is a carcinogen that promotes colon cancer.

Fat Signup and view all the answers

Study Notes

Cell Cycle and Mitosis Overview

Nucleoli are present during interphase, facilitating ribosome production.
Cytokinesis, the division of the cytoplasm, often follows telophase but is not always simultaneous.
Chromosomes, composed of chromatin fibers, become visible during prophase as they condense.

Key Phases of Mitosis

In anaphase, centromeres divide, resulting in sister chromatids becoming individual chromosomes as they move to opposite cell poles.
Spindle fibers connect to kinetochores during prometaphase, enabling chromosome alignment and movement.
The mitotic spindle, formed from microtubules, plays a crucial role in separating chromosomes.

Cell Cycle Phases

The cell cycle consists of interphase (G1, S, G2 phases) and M phase (mitosis and cytokinesis).
DNA replicates during the S phase, producing sister chromatids, which are tightly connected at the centromere until anaphase.
Interphase represents a significant portion of the cell cycle, wherein the cell grows and prepares for division.

Chromosome Behavior During Division

The sister chromatids form through DNA replication during the S phase. Once separated in anaphase, they become individual chromosomes.
The cell’s DNA content doubles during the S phase, returning to a normal state only after cytokinesis completes.

Stages of Mitosis

Prophase: Microtubules assemble, while chromatids condense and are held together by cohesin proteins.
Prometaphase: Nuclear envelope fragments; spindle fibers attach to chromosomes via kinetochores.
Metaphase: Chromosomes align at the metaphase plate, held in place by motor proteins on kinetochores.
Anaphase: Cohesin cleavage allows sister chromatids to separate and move toward cell poles.
Telophase: Nuclear envelopes reform as chromosomes reach the poles and begin to de-condense.

Motor Proteins in Mitosis

Motor proteins in kinetochores are responsible for pulling chromosomes along microtubules during anaphase.
If motor protein function is inhibited during metaphase, chromosomes will not move to the poles but can still separate due to cell elongation.

Bacterial vs. Eukaryotic Chromosome Separation

Bacterial cells, lacking a mitotic spindle, separate a single, shorter chromosome without full condensation.
The bacterial chromosome separates via attachment to the plasma membrane at the origins of replication.

Cytokinesis Mechanisms

Animal cells undergo cytokinesis via cleavage furrow formation, constricting the cell membrane to divide it.
Plant cells utilize a different mechanism due to their cell walls, forming a cell plate that eventually develops into a new cell wall.

Carcinogens and Health Risks

Various substances, including cigarette smoke, UV light, and high-fat diets, are classified as carcinogens due to their cancer-promoting properties.
A high-fat diet is specifically linked to increased risks for colon and breast cancer.

Description

Test your knowledge on key concepts from Biology Chapter 12 with these flashcards. Covering essential terms like nucleoli, cytokinesis, and chromosomes, this quiz will reinforce your understanding of cellular processes during different phases. Perfect for students preparing for exams.