Biology Chapter on Cell Nucleus and Chromosomes
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Questions and Answers

What is the primary function of the nucleus in a cell?

  • It generates energy for cellular processes.
  • It ensures the structural integrity of the cell.
  • It stores nutrients for the cell.
  • It contains genetic information and controls cellular functions. (correct)

What happens when a nucleus from one species is grafted into a cell from a different species?

  • The recipient cell thrives and starts dividing normally.
  • The recipient cell can regenerate other organelles.
  • The recipient cell survives temporarily but does not divide. (correct)
  • The recipient cell becomes incapable of basic cellular functions.

In the observed algae, what was found to be necessary for the survival and reproduction?

  • The rhizoid containing the nucleus. (correct)
  • The cap and stalk of the algae.
  • Water and sunlight for photosynthesis.
  • The entire algae organism.

What conclusion can be drawn about the relationship between the nucleus and the characteristics of the cap in algae?

<p>The nucleus determines the characteristics of the cap, independent of the algae's origin. (C)</p> Signup and view all the answers

What happens to a cell that is enucleated?

<p>It survives for a few days but cannot regenerate or divide. (A)</p> Signup and view all the answers

What role does the nucleus play in the characteristics of a tadpole?

<p>It contains the genetic information that dictates the tadpole's traits. (A)</p> Signup and view all the answers

What technique is used to block cell division for establishing a karyotype?

<p>Colchicine application (D)</p> Signup and view all the answers

During which stage of cell division are chromosomes most effectively studied?

<p>Metaphase (C)</p> Signup and view all the answers

What is a key function of a karyotype?

<p>To establish the chromosomal structure of a species. (B)</p> Signup and view all the answers

What was the method used to demonstrate the differences in the caps of the two Acetabularia species?

<p>Cross-grafting of nuclei between the two species (C)</p> Signup and view all the answers

What is the primary component of a chromosome?

<p>Deoxyribonucleic acid and histones (B)</p> Signup and view all the answers

Which of the following statements about chromosomes is true?

<p>Chromosomes vary in thickness and can be studied when they are condensed. (D)</p> Signup and view all the answers

Which of the following statements about human chromosomes is incorrect?

<p>The sex chromosomes are always XX in males. (D)</p> Signup and view all the answers

What was the purpose of irradiating the unfertilized eggs in Gurdon's experiment?

<p>To destroy the nuclei and allow nuclear transplantation (D)</p> Signup and view all the answers

What distinguishes heterochromatin from euchromatin?

<p>Heterochromatin is darkly stained and euchromatin is lightly stained. (A)</p> Signup and view all the answers

Which experimental step was common to both Acetabularia and Gurdon's experiment?

<p>Transplanting nuclei into enucleated cells (C)</p> Signup and view all the answers

How many chromosomes are found in a human cell's nucleus?

<p>46 chromosomes (A)</p> Signup and view all the answers

What distinguishes Acetabularia mediterranea from Acetabularia crenulata based on the experimental setup?

<p>The morphology of their caps (B)</p> Signup and view all the answers

What type of organisms were primarily used for nuclear transplantation in Gurdon's experiment?

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

In which part of the cell are chromosomes primarily found?

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

What characteristic of Acetabularia contributes to its ability to grow up to 8cm in size?

<p>Its nucleus is located at the base of the stalk. (B)</p> Signup and view all the answers

In the merotomy experiment performed on amoeba, what is the main focus of the procedure?

<p>Removing a portion of the nucleus for further study. (D)</p> Signup and view all the answers

Which component of Acetabularia varies among different species and is crucial for identification?

<p>The shape of the cap. (A)</p> Signup and view all the answers

What aspect of the amoeba's nucleus regeneration is highlighted in the experiment?

<p>Regeneration can occur even with a portion of the nucleus removed. (B)</p> Signup and view all the answers

Which of the following structures is NOT part of the Acetabularia during its growth stages?

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

What is the purpose of grinding the onion or kiwi in the extraction process?

<p>To maximize the surface area for cellular contact with extraction products (C)</p> Signup and view all the answers

During the extraction of DNA, what is the role of salt in the procedure?

<p>To rupture cell membranes and release the nuclear contents (D)</p> Signup and view all the answers

Why is alcohol added slowly along the side of the test tube during the DNA extraction?

<p>To allow DNA to precipitate without agitation (A)</p> Signup and view all the answers

What results from the addition of methylene blue to the precipitated DNA?

<p>It specifically stains the DNA, confirming its presence (C)</p> Signup and view all the answers

In Avery's experiments, what role did the principle of transformation serve in bacterial cells?

<p>It highlighted the hereditary information transferred through DNA (D)</p> Signup and view all the answers

How did the extraction of liquid from bacteria contribute to understanding the DNA's role in transformation?

<p>It allowed for the identification of genetic material responsible for traits (A)</p> Signup and view all the answers

What was the main finding of the 1944 experiments conducted by Avery and his colleagues?

<p>DNA can transform non-virulent bacteria into virulent forms (C)</p> Signup and view all the answers

Which statement accurately represents the bacterial transformation process?

<p>It is facilitated by extracting liquids from one bacterial strain and introducing them to another (C)</p> Signup and view all the answers

Flashcards

Significance of the Nucleus

The nucleus is essential for cell synthesis, regeneration, and division.

Enucleated Cell Survival

Cells without a nucleus survive briefly and cannot regenerate or divide.

Grafting and Species Compatibility

Transferring a nucleus only works among the same species for cell survival.

Rhizoid Function in Algae

The rhizoid with a nucleus is vital for the survival and reproduction of algae.

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Nucleus and Genetic Information

The nucleus holds genetic information dictating characteristics of cellular structures.

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Acetabularia Species

Two species of green algae with different cap shapes: smooth (A.m) and crenulated (A.c).

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Cross-grafting Experiment

Transplanting nuclei between two Acetabularia species to observe effects on cap formation.

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Gurdon's Experiment

A 1960 study on frog nuclei showing nuclear transfer effects using albino tadpole cells.

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Nucleus Transplantation

Technique where nuclei from one cell are moved to another cell, often yielding unexpected traits.

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Xenopus

A genus of African frogs used in biological research, notably for nuclear transfer studies.

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DNA Extraction

Process of isolating DNA from cells through chemical treatments.

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Cell Lysis

Breaking down cell membranes to release contents, typically using salt.

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Alcohol Precipitation

Adding alcohol to separate DNA from other cellular components.

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Methlyene Blue Staining

Using methylene blue to visualize DNA in a sample by color change.

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Avery's Transformation Experiment

Research showing DNA as the transforming principle in bacteria.

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Transformed Bacteria

Bacteria that have taken up new genetic information from DNA.

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Bacterial Transformation

Process where bacteria take up foreign DNA from their environment.

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Role of DNA

DNA contains genetic instructions essential for life and function of cells.

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Karyotype

A representation of all chromosomes in a species.

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Diploid Cell

A cell containing two sets of chromosomes (2n), like humans with 46 chromosomes.

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Homologous Chromosomes

Chromosome pairs inherited from each parent, similar in size and shape.

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Sex Chromosomes

The 23rd pair of chromosomes that determine biological sex (XX or XY).

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Chromatin

Complex of DNA and proteins in chromosomes; exists as euchromatin and heterochromatin.

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Merotomy

A surgical procedure on amoeba to study cell regeneration.

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Acetabularia

A species of green algae that grows up to 8cm and has a distinct stalk and cap.

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Nucleus in Acetabularia

Located at the base of the stalk, crucial for its growth and function.

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Stages of Merotomy

Different phases during the merotomy process in amoeba, including nucleus removal and regeneration.

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Growth Direction of Acetabularia

Growth proceeds from the nucleus up the stalk to the cap.

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Tadpole Development

Tadpoles inherit characteristics from the donor's nucleus, not the egg.

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Genetic Information Location

Genetic information determining heredity is found in the nucleus of all organisms.

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Chromosomes During Division

Chromosomes appear as filaments during cell division.

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Role of Colchicine

Colchicine blocks cell division to analyze chromosomes at metaphase.

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Establishing a Karyotype

Karyotype is established by analyzing chromosome structure and number.

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Study Notes

Analysis of Experiences

  • A cell with part of its volume removed (amputated) can still maintain its functions, synthesise, and divide, implying that all its functions are typical.
  • A cell without its nucleus (enucleated) will not survive, regenerate, or divide because the nucleus is vital for cellular syntheses.
  • Transplanting a nucleus from one cell to another enables the recipient cell to thrive and sustain functionality, as indicated by the instance with the algae.
  • The nucleus holds the genes that give rise to an organism's traits.
  • The form of a head (of an algae) is determined by the type of nucleus in the rhizoid.
  • When a head's rhizoid contains the nucleus, it will display the characteristics of the corresponding species.

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Description

This quiz explores the essential functions of the nucleus within various types of cells. It includes questions about cell division, karyotyping, and the relationship between nuclear characteristics and organism traits. Test your understanding of cell biology concepts!

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