Biology Lesson 8: Cellular Cycle Overview

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Questions and Answers

What is the primary role of cell division in single-celled organisms?

To increase the size of the organism

To generate new cells for reproduction (correct)

To replace old cells

To repair damaged tissues

What is stored in the genome of eukaryotic cells?

Pairs of chromosomes in the nucleus and additional circular chromosomes in organelles (correct)

A large chromosome and smaller plasmids

Only single linear chromosomes

Only circular chromosomes

What is the function of the centromere during cell division?

To divide the cytoplasm during cytokinesis

To attach sister chromatids and facilitate spindle fiber attachment (correct)

To unwind DNA for replication

To create new DNA strands

Which of the following statements about chromosomes in different species is true?

Different species may have different numbers of chromosomes in their cell nuclei Signup and view all the answers

What do ribosomes require from DNA to build proteins?

mRNA copies of DNA Signup and view all the answers

What is the primary role of checkpoints during the cell cycle?

To monitor and regulate the progression of the cell cycle Signup and view all the answers

Which type of cell would be classified as haploid?

Sperm cell Signup and view all the answers

What occurs during cytokinesis?

The division of the cytoplasm into two daughter cells Signup and view all the answers

What is the significance of homologous chromosomes?

They are chromosomes that have the same genes but may have different alleles. Signup and view all the answers

How does the growth of cancer cells differ from normal cells?

Cancer cells divide uncontrollably without regulation. Signup and view all the answers

What occurs to the nuclear envelope during prometaphase?

It is completely broken down. Signup and view all the answers

What role do cohesin proteins play during anaphase?

They hold sister chromatids together. Signup and view all the answers

During which mitosis phase do chromosomes align at the metaphase plate?

Metaphase Signup and view all the answers

What happens to the cell's organelles during prophase?

They migrate toward the edges of the cell. Signup and view all the answers

What is formed during telophase?

New nuclear envelopes around each set of chromosomes. Signup and view all the answers

What happens to sister chromatids during anaphase?

They are pulled apart to opposite edges of the cell. Signup and view all the answers

What is the final result of cytokinesis?

Two identical cells with separate cytoplasm. Signup and view all the answers

What happens to the proteins of the mitotic spindle during telophase?

They dissolve, and their components form the cytoskeleton. Signup and view all the answers

What is the primary activity of a cell during interphase?

Duplicating its organelles Signup and view all the answers

What does the S phase of interphase specifically involve?

DNA replication Signup and view all the answers

Which process occurs first during the mitotic phase?

Mitosis Signup and view all the answers

What proportion of a cell's lifecycle is typically spent in interphase?

90% Signup and view all the answers

Which statement is true regarding the phases of interphase?

Interphase consists of G1, S, and G2 phases. Signup and view all the answers

What are homologous chromosomes?

Matching pairs of chromosomes from each parent with the same genes at the same locus. Signup and view all the answers

Which of the following correctly defines alleles?

They are different versions of the same gene. Signup and view all the answers

What type of cells are gametes?

Haploid (n) cells that have one of each chromosome. Signup and view all the answers

Which statement about somatic cells is true?

Somatic cells are diploid and include all cells except gametes. Signup and view all the answers

How does a karyotype of a haploid cell differ from a diploid cell?

The haploid karyotype contains one of each chromosome. Signup and view all the answers

Which type of chromosome count characterizes human somatic cells?

46 chromosomes arranged in 23 pairs. Signup and view all the answers

Which of the following choices best describes how alleles can affect protein synthesis?

Different alleles can result in slightly different proteins due to variations in the gene. Signup and view all the answers

What is the significance of the TAS2R38 gene in relation to alleles?

It has different alleles that lead to varying sensitivities to bitter tastes. Signup and view all the answers

What is the final checkpoint in the cell cycle focused on?

Checking if sister chromatids are properly attached to the mitotic spindle Signup and view all the answers

What is a common consequence of nondisjunction during cell division?

Daughter cells have incorrect numbers of chromosomes Signup and view all the answers

What characterizes the behavior of cancer cells compared to normal cells?

They can divide with chromosomal issues Signup and view all the answers

What role does anchorage dependence play in normal mammalian cell division?

Cells must be attached to a surface to divide Signup and view all the answers

What initial change often leads to cancer development?

Mutations in genes regulating cell-cycle proteins Signup and view all the answers

In the context of Type 2 diabetes, what is a consequence of β cell overstimulation?

Decreased ability of β cells to divide Signup and view all the answers

How do density-dependent factors affect cell division?

They prevent division when cells are tightly packed Signup and view all the answers

What is a potential effect of mutations in cancer cells on normal cells?

Cancer cells can outnumber and displace normal cells Signup and view all the answers

Study Notes

Lesson 8: The (Cellular) Circle of Life

The life cycle of a cell contains interphase and the mitotic phase.
Cells spend about 90% of their life in interphase; it is when cell growth, protein building, and organelle duplication occur.
Interphase is made up of three phases: G1, S, and G2.
The mitotic phase is the short period when cell division occurs, first dividing genetic information with mitosis and then dividing its cytosol and organelles with cytokinesis.

Learning Objectives

Students will be able to list eukaryotic and prokaryotic genome structures
Students will explain homologous chromosomes and differentiate between genes and alleles.
Students will differentiate between chromosomes, sister chromatids, and chromatin
Students will describe the function of centromeres and list the parts of the cell cycle.
Students will describe what occurs during each stage of the cell cycle
Describe what occurs in each phase of mitosis
Identify each phase of mitosis in images, describe cytokinesis
Explain why regulating the cell cycle is important, describe checkpoints in mitosis, and explain how internal and external factors impact cell division.
Students will explain how cancer cell growth differs from normal cell growth.

Type 2 Diabetes and Cell Division

Type 2 diabetes results from insufficient division of beta cells in the pancreas which leads to decreased insulin secretion.
Beta cells becoming tired due to high fat and sugar diets affects the production of insulin.
Reduced beta cell number due to defective proliferation and/or death results in insufficient insulin.

Why Do Cells Divide?

Cell division creates new cells identical to the original parent cell.
Single-celled organisms use cell division for reproduction
In multicellular organisms, cell division is crucial for growth, repair, and replacing worn-out cells.
This includes the process of zygotes growing into adults.

Cells & Their DNA

Cells are the smallest living units.
Genetic information is stored in DNA.
Ribosomes use mRNA to create proteins, critical for life.
The genome is a cell’s complete set of genetic information,
Prokaryotic cells include a large chromosome and smaller plasmids.
Eukaryotic cells contain chromosome pairs in the nucleus and circular chromosomes in mitochondria and chloroplasts.

Background on Chromosomes

Centromeres are constricted regions of a chromosome and help divide up genetic information during mitosis and meiosis.
Centromeres are the site for spindle fiber attachments.
Sister chromatids are attached and duplicated.

Eukaryotic Genomes

Different species have different numbers of chromosomes in their cells. This can be seen, for example, in humans (46 chromosomes) and chimpanzees (48 chromosomes).
Members of the same species maintain the same number of chromosomes.
These matching pairs of chromosomes are called homologous chromosomes.
Each homologous chromosome pair contains one copy that comes from each parent.
Homologous chromosomes contain the same genes in the same position (locus).

Alleles

Alleles are different versions of the same gene.
Different alleles create slight variations in protein synthesis.
An example of this variance is the TAS2R38 gene on chromosome 7, which develops receptors for bitter compounds such as PTC.
Some alleles enhance bitter taste perception, while others inhibit it

Chromosome Number and Cells

Diploid cells have two copies of each chromosome, one copy from each parent cell.
Somatic cells are diploid, except for gametes.
Haploid cells have one copy of each chromosome, used in sexual reproduction (eggs and sperm).

Visualizing the Genome

A karyotype is a picture of a cell's genome.
A karyotype of a haploid cell contains one of each chromosome.
A karyotype of a diploid cell shows homologous chromosomes in pairs..

Stop & Think It Through

Determine if statements describe somatic or gamete cells (A cell with 23 chromosomes or a cell with 23 pairs of chromosomes is a gamete. A cell that is diploid or haploid describes the cell’s chromosome makeup).

The (Cellular) Circle of Life (part 2)

Interphase is when cell growth, protein building, and organelle duplication occur.
Interphase is made up of the G1,S, and G2 phases.

Organelles and the Cell Cycle

Organelles are duplicated during interphase.
ATP is produced during interphase, in preparation for mitosis and cytokinesis.
DNA is duplicated during interphase to produce identical sister chromatids, which are X-shaped.

Mitosis Phases

Prophase: Chromatin condenses to form compact chromosomes, the nuclear envelope starts to break down, nucleolus disappears. Centrosomes migrate to cell edges. Centrosomes build microtubule proteins, the mitotic spindle.
Prometaphase: Nuclear envelope is completely broken down; two identical sister chromatids (X shape) are easily visible. Cohesions attach sister chromatids at the centromere. Kinetochore proteins attach the mitotic spindle to chromosomes.
Metaphase: Chromosomes line up along the metaphase plate (the center of the cell).
Anaphase: Enzyme processes and spindle force break down cohesion proteins; sister chromatids separate. Pulled to opposite cell edges, causing cell to elongate.
Telophase: Chromosomes arrive at opposite poles and begin to decondense to become chromatin again. New nuclear envelopes form around each set of chromosomes. Mitotic spindle dissolves.
Cytokinesis: Cytoplasm divides to form two identical cells. This process follows mitosis in animal cells resulting in the plasma membrane making a cleavage furrow and separating the two cells. In plant cells, a cell plate separates the two new cells.

Regulating the Cell Cycle

Cells monitor internal conditions to determine if they should divide (e.g., DNA mutations, chromosome number).
(Growth factors or other external signals)Cells also monitor external conditions to determine if they should divide.
External monitoring influences how crowded the environment is and the presence or absence of growth factors..
There are checkpoints throughout the cycle to control processes.

Checkpoints

Three checkpoints ensure the cell cycle operates correctly.
The final cell cycle checkpoint is in mitosis.
Checks to ensure sister chromatids properly attach to mitotic spindles to check for nondisjunction.
Nondisjunction leads to daughter cells with incorrect chromosome numbers.
Example of chromosomal issues arising from nondisjunction is Down Syndrome.

External Conditions Influencing Cell Division

Anchorage dependence: prevents mitosis if cells are not attached to a surface or another cell.
Density-dependent inhibition: prevents mitosis if cells are too crowded.

Cancer

Cancer refers to cells that exhibit uncontrolled growth
They divide without external growth signals, and may have mutations or issues with chromosome duplication or spindle attachment.
Cancer typically begins with a mutation in a cell cycle regulatory protein.
Mutated cells reproduce constantly, ultimately outnumbering normal cells. This forms a tumor.

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Description

This quiz covers the essential aspects of the cellular circle of life, focusing on the cell cycle's interphase and mitotic phase. Students will explore the life stages of eukaryotic and prokaryotic cells, highlighting crucial concepts like chromosome structure, mitosis, and cytokinesis. Prepare to dive into the fascinating processes that sustain cellular growth and division!