Meiosis and Mitosis Basics

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Questions and Answers

What would be the chromosome count in a zygote if meiosis did not occur?

  • 92 (correct)
  • 69
  • 23
  • 46

When does the first meiotic division complete in human females?

  • Before birth. (correct)
  • During the first menstrual cycle.
  • At the onset of puberty.
  • At fertilization with sperm.

When does meiosis begin in human males?

  • At fertilization
  • Immediately upon a sperm cell penetrating an ovum
  • Before birth
  • At puberty when testes produce sperm (correct)

What specific mechanism during meiosis contributes to genetic diversity?

<p>Crossing-over between homologous chromosomes (C)</p> Signup and view all the answers

Why does meiosis result in increased genetic variation in offspring?

<p>It produces haploid cells that have a random mix of parental genes. (D)</p> Signup and view all the answers

What is the primary outcome of mitosis?

<p>Two genetically identical diploid cells (C)</p> Signup and view all the answers

During which phase of mitosis do chromatids separate and move toward opposite ends of the cell?

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

What structure connects two chromatids together?

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

Which of these is NOT a characteristic of cells produced by mitosis?

<p>They are genetically diverse (A)</p> Signup and view all the answers

What happens to the nuclear membrane during the early stages of mitosis?

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

What is the role of spindle fibers during mitosis?

<p>To move chromosomes to opposite poles (D)</p> Signup and view all the answers

During which phase of the cell cycle do chromosomes make a copy of themselves?

<p>Before mitosis begins (D)</p> Signup and view all the answers

What is the term for a cell or organism containing a full set of paired chromosomes?

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

Where do the spindle fibers radiate from during mitosis?

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

Which of the following best describes a gene?

<p>A segment of DNA that controls a particular characteristic (C)</p> Signup and view all the answers

What is the function of the centromere during cell division?

<p>To attach to the spindle fibers and join chromatids together (C)</p> Signup and view all the answers

If a cell contains 23 chromosomes, what is this state called?

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

What is the relationship between allele and gene?

<p>Alleles are different forms of a gene (D)</p> Signup and view all the answers

Which structure is responsible for extending spindle fibres?

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

What is the definition of cytokinesis?

<p>The division of the cytoplasm (B)</p> Signup and view all the answers

What are homologous pairs?

<p>Identical pairs of chromosomes (C)</p> Signup and view all the answers

Which process ensures genetic continuity by passing the same genes from parent to offspring?

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

What is the main purpose of meiosis?

<p>Production of gametes (A)</p> Signup and view all the answers

How many daughter cells are produced from a single parent cell during meiosis?

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

Which of the following is a characteristic of the cells produced by meiosis?

<p>Genetically diverse due to mixed genes (A)</p> Signup and view all the answers

In which type of cells does mitosis typically occur?

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

What happens to chromosomes during the final stage of mitosis, before cytokinesis?

<p>They begin to get thinner and less visible. (A)</p> Signup and view all the answers

Which of the following best describes the primary function of mitosis?

<p>Producing cells for growth and repair with identical genetic information. (A)</p> Signup and view all the answers

Why is mitosis essential in the oesophagus?

<p>To replace cells scraped off during food passage. (A)</p> Signup and view all the answers

Which of the cell types listed below CANNOT undergo mitosis?

<p>Red blood cells. (D)</p> Signup and view all the answers

What is the primary function of meiosis?

<p>To produce gametes with half the number of chromosomes. (B)</p> Signup and view all the answers

Where does meiosis take place?

<p>In all sexually reproducing organisms. (C)</p> Signup and view all the answers

If a cell undergoes meiosis and produces a gamete with 23 chromosomes, what is the number of chromosomes in the zygote that results from fertilization?

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

What is the daily output of sperm cells by just one testis?

<p>Over 200 million. (D)</p> Signup and view all the answers

Flashcards

Diploid

A nucleus, cell, or organism containing the complete set of paired chromosomes (2n). In humans, this means 46 chromosomes (23 pairs).

Haploid

A nucleus, cell, or organism containing half the number of chromosomes (n). In humans, this means 23 chromosomes.

DNA

The double-stranded molecule found inside chromosomes that carries genetic information.

Chromosome

The genetic structure inside the nucleus of a cell that contains DNA. It can self-replicate, making copies of itself.

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Homologous Pairs

Identical pairs of chromosomes in a diploid organism. Humans have 23 homologous pairs.

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Gene

A segment of DNA on a chromosome that controls specific characteristics of an organism.

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Alleles

Alternative forms of a gene. For example, eye color genes have alleles for brown and black.

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Chromatid

One copy of a duplicated chromosome that can divide by mitosis or meiosis.

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Mitosis

A type of cell division where a parent cell divides into two identical daughter cells.

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Clones

The cells produced by mitosis, genetically identical to the parent cell.

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Prophase

The phase of mitosis where the duplicated chromosomes become shorter and thicker, visible under a microscope.

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Centromere

The point where the two chromatids are attached.

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Spindle fibers

Structures that radiate from the centrioles and help separate the chromatids to opposite poles of the cell.

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Anaphase

The phase of mitosis where the replicated chromosomes are pulled apart by the spindle fibers towards opposite poles of the cell.

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Telophase

The phase of mitosis where the chromosomes reach the poles of the cell, the nuclear membrane reforms, and the cytoplasm divides to form two new cells.

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Chromosome Duplication

The process that occurs before mitosis where the chromosomes make a copy of themselves.

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Karyokinesis

The process by which a cell's nucleus divides.

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Haploid cells

Cells with half the number of chromosomes as the parent cell.

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Crossing-over

The process where chromosomes from the mother and father exchange genetic material, resulting in unique combinations.

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Cytokinesis

The division of the cytoplasm, resulting in two separate daughter cells.

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DNA replication

The genetic material of a cell is duplicated.

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Genetic variation

The process of mixing parental chromosomes during meiosis, leading to increased genetic variation in offspring.

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Fertilization

The fusion of a sperm and egg cell, resulting in a zygote with a full set of chromosomes.

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Haploid cells

Cells that have half the number of chromosomes of a normal cell.

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Diploid cells

Cells that have the full number of chromosomes of a normal cell.

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Fertilization

The fusion of a sperm cell and an egg cell to form a zygote.

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Study Notes

Cell Division

  • Diploid (2n): A cell, nucleus, or organism containing a complete set of paired chromosomes. Humans have 46 chromosomes (23 pairs).
  • Haploid (n): A cell, nucleus, or organism containing half the number of chromosomes. Humans would have 23 chromosomes in this case.
  • DNA (Deoxyribonucleic Acid): A double-stranded molecule inside chromosomes that contains genetic information.
  • Chromosome: The genetic structure within a cell's nucleus, containing DNA. Chromosomes self-replicate.
  • Homologous Pairs: Identical chromosome pairs. Humans have 23 homologous pairs comprising 46 chromosomes. One set from each parent.
  • Gene: A segment of DNA on a chromosome that controls organism traits.
  • Alleles: Alternative forms of a gene. Eye color, for example, has brown and blue alleles.
  • Chromatid: One copy of a duplicated chromosome. Chromatids are attached at the centromere.
  • Centromere: The point where chromatids attach.
  • Centriole: A structure from which spindle fibers radiate during cell division.
  • Spindle Fibers: Thread-like structures connecting to the centromere, essential during cell division.

Cell Division Types

  • Mitosis: A type of cell division producing two identical diploid daughter cells, crucial for growth and repair.
  • Meiosis: Cell division creating four haploid daughter cells. Used for sexual reproduction in organisms that reproduce sexually. Meiosis reduces the chromosome number allowing for the restoration of the correct diploid number in the zygote after fertilization. This is important to prevent doubling of chromosomes across generations.

Mitosis Stages

  • Prophase: Duplicated chromosomes become visible, the nuclear membrane disappears, centrioles separate.
  • Metaphase: Chromosomes align at the cell's center.
  • Anaphase: Sister chromatids separate and move to opposite ends of the cell.
  • Telophase: New nuclear membranes form around each set of chromatids (now chromosomes). Chromosomes become less visible. Cytokinesis follows.

Meiosis Stages

  • Meiosis I: Homologous chromosomes pair and separate.
  • Meiosis II: Sister chromatids separate, resulting in four genetically unique haploid cells.

Importance of Mitosis

  • Growth and development.
  • Cell repair.
  • Tissue renewal.
  • Asexual reproduction.

Importance of Meiosis

  • Genetic variation in offspring.
  • Production of gametes (sex cells—sperm and egg).

Differences between Mitosis and Meiosis

  • Mitosis makes two identical daughter cells. Meiosis makes four unique daughter cells.
  • Mitosis results in diploid cells. Meiosis results in haploid cells.
  • Mitosis occurs in somatic cells (body cells). Meiosis occurs in germ cells (sex cells).
  • Mitosis is for growth, repair, and asexual reproduction. Meiosis is for sexual reproduction.

Importance of Meiosis (cont.)

  • Meiosis mixes the parental chromosomes, increasing genetic variation in offspring. Offspring are different from each other, as well as their parents.

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