Cell Division and Chromosome Theory Quiz
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Questions and Answers

Which stage of meiosis involves the maximum condensation of chromosomes?

  • Metaphase I (correct)
  • Prophase I
  • Telophase I
  • Anaphase II

Chiasmata are the points where homologous chromosomes are drawn apart during diplotene.

False (B)

How many products are formed from one parent cell after meiosis?

Four

The process of pairing homologous chromosomes begins in __________.

<p>Zygotene</p> Signup and view all the answers

Match the following stages of meiosis with their characteristics:

<p>Leptotene = Thin thread-like chromosomes Pachytene = Bivalents are formed and pairing is stabilized Diakinesis = Short thick cross-shaped configurations Metaphase I = Alignment of bivalents in the equatorial plane</p> Signup and view all the answers

What is the main outcome of meiosis?

<p>Four haploid cells (D)</p> Signup and view all the answers

Metaphase I is referred to as the reductional division.

<p>True (A)</p> Signup and view all the answers

During __________, the nuclear membrane and nucleolus disappear.

<p>Prophase I</p> Signup and view all the answers

What happens to the nuclear envelope during prophase?

<p>It breaks up into small vesicles (C)</p> Signup and view all the answers

Maximum condensation of chromatin occurs during metaphase.

<p>True (A)</p> Signup and view all the answers

What enzyme is thought to play a role in chromosome condensation during metaphase?

<p>topoisomerase II</p> Signup and view all the answers

Each chromosome consists of two _______ during metaphase.

<p>chromatids</p> Signup and view all the answers

What is the function of the kinetochore?

<p>To attach microtubules for movement (B)</p> Signup and view all the answers

The centromere divides longitudinally during telophase.

<p>False (B)</p> Signup and view all the answers

Match the following components with their respective functions:

<p>Centromere = Region of central constriction on each chromosome Chromatids = Identical halves of a chromosome Kinetochore = Site of microtubule attachment Microtubules = Fibers that pull chromatids apart</p> Signup and view all the answers

Misalignment of chromosomes in the equatorial region may _______ cells at metaphase.

<p>arrest</p> Signup and view all the answers

What type of gene is responsible for the segregation distorter (SD) mutation in Drosophila males?

<p>Dominant gene on chromosome II (A)</p> Signup and view all the answers

Drosophila males experience crossing over in meiosis.

<p>False (B)</p> Signup and view all the answers

What effect does the recovery disrupter (RD) mutation have on male Drosophila?

<p>It causes fragmentation of Y-bearing sperm, resulting in an excess of female flies in the progeny.</p> Signup and view all the answers

The microtubules in the spindle apparatus are assembled from __________ proteins.

<p>α and β tubulin</p> Signup and view all the answers

Match the following mutations with their effects:

<p>Segregation Distorter (SD) = Transmits mutant gene to 50% of progeny Recovery Disrupter (RD) = Causes fragmentation of Y-bearing sperm mei-S8 = Causes nondisjunction in females mei-218 = Reduces recombination or interferes with chromosome segregation</p> Signup and view all the answers

Which stage of meiosis is primarily affected by most meiotic mutants in Drosophila?

<p>Meiosis I (D)</p> Signup and view all the answers

Spindle fibers are composed of microtubules that have a diameter of 20 nm.

<p>False (B)</p> Signup and view all the answers

What are the smaller circles observed in the cross section of a microtubule called?

<p>Protofilaments</p> Signup and view all the answers

Which protein kinase is responsible for phosphorylating tyrosine-15 on Cdc2?

<p>Wee1 (A)</p> Signup and view all the answers

Cdc2 kinase activity is activated through the phosphorylation of tyrosine-15.

<p>False (B)</p> Signup and view all the answers

What process degrades cyclin B and inactivates Cdc2?

<p>Ubiquitin-mediated proteolysis</p> Signup and view all the answers

The transition from G1 to S phase is regulated by Cdk2 and Cdk4 in association with cyclins _____ and _____.

<p>D, E</p> Signup and view all the answers

Match the following Cdk proteins with their associated phases:

<p>Cdk1 = G2 to M phase Cdk2 = G1 to S phase Cdk4 = G1 restriction point Cdk6 = G1 progression</p> Signup and view all the answers

Which of the following describes the role of Cdc25 in the cell cycle?

<p>It dephosphorylates threonine-14 and tyrosine-15 of Cdc2. (C)</p> Signup and view all the answers

Cdks are only controlled by cyclin associations and have no other regulatory mechanisms.

<p>False (B)</p> Signup and view all the answers

What is the original member of the Cdk family known as?

<p>Cdk1</p> Signup and view all the answers

What is the role of D-type cyclins in cell cycle progression?

<p>They regulate progression through the restriction point in late G1. (C)</p> Signup and view all the answers

Growth factors must be present throughout G1 for cells to progress through the restriction point.

<p>True (A)</p> Signup and view all the answers

What happens to cells when growth factors are removed prior to G1?

<p>Cells become quiescent or enter G0.</p> Signup and view all the answers

Defects in cyclin D regulation contribute to the loss of growth regulation characteristic of _____.

<p>cancer cells</p> Signup and view all the answers

Match the following cyclin-related components with their functions:

<p>Cdk/cyclin complex = Regulates cell cycle progression Cdk inhibitors (CkIs) = Inhibits Cdk activity Rb protein = Regulates progression through G1 D-type Cyclins = Induced in response to growth factors</p> Signup and view all the answers

Which of the following is a key substrate protein of Cdk4, 6/cyclin D complexes?

<p>Rb protein (A)</p> Signup and view all the answers

Mutations leading to continuous expression of cyclin D1 are unrelated to human cancers.

<p>False (B)</p> Signup and view all the answers

What are the consequences of phosphorylating the Cdc threonine residue at position 160?

<p>Activation of Cdk/cyclin complex.</p> Signup and view all the answers

What percentage of cells showed the unpaired chromosome passing to one pole with the larger homologue in grasshoppers?

<p>50% (D)</p> Signup and view all the answers

Boveri's work on sea urchins contradicted Blakeslee's findings with Datura.

<p>False (B)</p> Signup and view all the answers

What is the normal diploid chromosome number in Datura?

<p>24</p> Signup and view all the answers

T.H. Morgan demonstrated that the gene for white eye color in Drosophila was linked to the ______.

<p>sex chromosome</p> Signup and view all the answers

Match the scientists with their contributions:

<p>Carothers = Studied grasshopper chromosomes Boveri = Explored chromosomes in sea urchins Blakeslee = Worked with Datura Sutton = Contributed to the Sutton-Boveri theory</p> Signup and view all the answers

Which of the following is NOT one of the characteristic features of chromosomes as discovered by Boveri and Sutton?

<p>Chromosome replication occurs at the same rate (A)</p> Signup and view all the answers

Each of the 12 plant types in Datura had morphologically identical fruit capsules.

<p>False (B)</p> Signup and view all the answers

What phenomenon describes the inability of Mendel's law of independent assortment to apply to some genes?

<p>linkage</p> Signup and view all the answers

Flashcards

What is metaphase?

The stage of mitosis where chromosomes are maximally condensed and aligned at the center of the cell.

What is a centromere?

A region on a chromosome where sister chromatids are held together. It's the site where microtubules attach during cell division.

What is a kinetochore?

A protein structure on the outer surface of the centromere that serves as the attachment point for microtubules during mitosis.

What are spindle fibers?

A bundle of microtubules that connect to the kinetochores of chromosomes and move them during cell division.

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What are chromosomal microtubules?

Microtubules that attach to the kinetochore of chromosomes and pull them towards the poles of the cell.

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What is chromosome condensation?

The process of tightly packing and winding chromosomes into a compact form.

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What is topoisomerase II?

The enzyme responsible for untangling DNA during chromosome condensation. It's crucial for proper chromosome separation.

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What is a mitotic spindle apparatus?

Structures that form during prophase and attach to the chromosomes, facilitating their movement during cell division.

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Middle lamella

The first layer formed between two newly formed cells during cell division; acts as the initial glue holding them together.

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Primary wall

Additional layer of cell wall material deposited inside the middle lamella, strengthening and defining the cell.

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Meiosis

A special type of cell division that occurs in germ cells (sperm and egg cells), resulting in four daughter cells with half the original number of chromosomes.

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Prophase I

The first stage of meiosis, where homologous chromosomes pair up and exchange genetic material.

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Zygotene

A substage of Prophase I where homologous chromosomes pair up, aligning perfectly.

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Pachytene

A substage of Prophase I where the paired chromosomes condense and become visible as thick ribbon-like structures.

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Diplotene

A substage of Prophase I where the paired chromosomes begin to separate, but remain connected at points called chiasmata, where genetic crossing over occurs.

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Diakinesis

The final substage of Prophase I, where the chromosomes are fully condensed and ready for the first meiotic division.

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Nondisjunction in Drosophila Males

During meiosis in Drosophila males, chromosomes fail to separate properly and move to opposite poles, leading to an uneven distribution of chromosomes in daughter cells.

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Segregation Distorter (SD) Mutant

A dominant gene on chromosome II in Drosophila males that disrupts chromosome segregation during meiosis, leading to a skewed inheritance pattern.

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Recovery Disrupter (RD) Mutant

An X-linked gene in Drosophila males that affects sperm development, causing fragmentation of Y-bearing sperm and resulting in an excess of female offspring.

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Spindle Apparatus

The structure that forms during cell division, composed of microtubules and responsible for separating chromosomes.

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Microtubules

Protein filaments that are the building blocks of the spindle apparatus, composed of α and β tubulin.

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α and β Tubulin

Globular proteins that assemble to form microtubules, playing a crucial role in chromosome segregation.

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Protofilaments

Long strands of α and β tubulin dimers that form the core structure of microtubules.

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Tubulin Dimer

A pair of α and β tubulin molecules joined together, forming the basic building block of protofilaments and ultimately microtubules.

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What is a kinase?

An enzyme that adds a phosphate group to a molecule.

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What is a phosphatase?

A protein that removes a phosphate group from a molecule.

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What is Cdc2?

A protein that controls cell cycle progression by activating or inhibiting specific enzymes.

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What is cyclin B?

A protein that binds to Cdc2 and helps regulate its activity.

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What is the S phase?

The phase in the cell cycle where the cell replicates its DNA.

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What is the G2 phase?

The phase in the cell cycle where the cell prepares for division.

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What is the M phase?

The phase in the cell cycle where the cell divides.

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What are Cyclin-dependent kinases (Cdks)?

A family of enzymes that regulate the cell cycle by phosphorylating target proteins.

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Restriction Point

The point in late G1 where cells commit to completing the cell cycle. Without growth factors, cells stop at this point and enter G0 (resting phase).

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Cdk Inhibitors (CKIs)

Proteins that bind to and inhibit the activity of cyclin-dependent kinases (CDKs).

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D-type Cyclins

A family of cyclins expressed in response to growth factors, promoting cell cycle progression through G1.

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Rb Protein

A key substrate of Cdk4, 6/cyclin D complexes, often mutated in cancer. Originally identified as the gene responsible for a childhood eye tumor.

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Cyclin-Dependent Kinases (CDKs)

A group of enzymes vital for cell cycle regulation. They activate specific proteins by adding phosphate groups.

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Cyclins

Proteins that help regulate the activity of CDKs, forming complexes that control cell cycle progression.

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Phosphorylation

The process of adding a phosphate group to a molecule, often altering its activity. A key mechanism in cell signaling.

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Loss of Growth Regulation

The loss of normal growth control, often seen in cancer cells. It can result from mutations in cell cycle regulation or growth factor signaling pathways.

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Sutton-Boveri Theory

The principle that explains the relationship between Mendelian inheritance and chromosomes. It was proposed by Walter Sutton and Theodor Boveri, based on their independent observations.

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Independent Assortment of Chromosomes

The idea that chromosomes, specifically their pairs, separate independently from one another during meiosis, leading to a random assortment of parental chromosomes in offspring.

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Qualitative Differences in Chromosomes

The observation that different chromosomes have distinct characteristics, like shape and size, and contribute to unique traits. This was demonstrated in the work of Blakeslee with the Jimson weed.

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Pairing of Maternal and Paternal Chromosomes

This concept describes how maternal and paternal chromosomes pair up during meiosis, ensuring that each offspring receives one chromosome from each parent.

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Trisomic

When a cell has more than the normal number of chromosomes, specifically one extra chromosome, it is known as a trisomic. This was observed by Blakeslee in Jimson weed.

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Linkage

The phenomenon where genes reside on the same chromosome and therefore are inherited together, not independently. This is an exception to Mendel's law of independent assortment.

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Nondisjunction

The process where a chromosome doesn't separate properly during cell division, resulting in an abnormal number of chromosomes in the daughter cells.

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Carothers Experiment

The experiment conducted by Carothers, a student of McClung, demonstrated the independent assortment of chromosomes by observing the behavior of one pair of unequal chromosomes and a single unpaired chromosome in grasshopper cells during meiosis.

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Study Notes

Cell Division and Chromosome Theory of Inheritance

  • The cell cycle is the period from a cell's formation by division to its next division. It has four phases: G1, S, G2, and M (mitosis or meiosis).
  • Interphase comprises G1, S, and G2 phases.
  • DNA synthesis occurs during the S phase. Protein synthesis occurs throughout interphase.
  • Mitosis is the division of somatic (body) cells in diploid organisms.

Mitosis Stages

  • Prophase: Chromatin condenses into chromosomes. The nucleolus and nuclear membrane disappear.
  • Metaphase: Chromosomes align along the metaphase plate (equatorial plate).
  • Anaphase: Sister chromatids separate and move to opposite poles.
  • Telophase: Chromosomes decondense. Nuclear membrane and nucleolus reform.

Meiosis

  • Meiosis is cell division in germ cells (sex cells) resulting in four haploid cells.
  • Meiosis requires two divisions, meiosis I and II.

Meiosis I Stages

  • Leptotene: Chromosomes become visible as long, thin threads.
  • Zygotene: Homologous chromosomes begin to pair. Synapsis occurs (pairing).
  • Pachytene: Chromosomes condense further, and crossing over occurs.
  • Diplotene: Homologous chromosomes begin to separate, held together at chiasmata (sites of crossing over).
  • Diakinesis: Chromosomes condense further. Nuclear membrane and nucleolus break down.
  • Metaphase I: Homologous chromosome pairs align along the metaphase plate.
  • Anaphase I: Homologous chromosomes separate and move to opposite poles.
  • Telophase I: Chromosomes reach the poles. Nuclear envelope may reform. Cytokinesis occurs.

Meiosis II Stages

  • This division is similar to mitosis. Meiosis II separates sister chromatids.

Cytokinesis

  • In animal cells, a cleavage furrow forms.
  • In plant cells, a cell plate forms.

Regulation of the Cell Cycle

  • Cell cycle progression is regulated by checkpoints.
  • Checkpoints ensure completion of each phase before the next.
  • Checkpoints detect and repair DNA damage.
  • Growth factors regulate progression through the cell cycle.
  • Cyclins are proteins that activate cyclin-dependent kinases (Cdks).
  • Cdk activity regulates cell cycle progression through phosphorylation.

Chromosome Theory of Inheritance

  • Chromosomes carry hereditary information (genes).
  • Homologous chromosomes have similar genetic information but may have different alleles.
  • Chromosomes segregate during meiosis, maintaining genetic diversity.

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Cell Division and Chromosome Theory of Inheritance PDF

Description

Test your knowledge on the cell cycle, mitosis, and meiosis. This quiz covers the phases of mitosis and the stages of meiosis, including key processes involved in cell division. Perfect for biology students looking to enhance their understanding of genetic inheritance.

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