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Questions and Answers

What is the primary difference in chromosome pairing during mitosis compared to meiosis I?

  • Chromosome numbers double during mitosis.
  • Homologous chromosomes separate during mitosis.
  • Homologous chromosomes remain separate during mitosis. (correct)
  • Homologous chromosomes pair during mitosis.

At which stage does crossing over occur during meiosis?

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

What happens to the duplicated chromosome during the S phase of the cell cycle?

  • It is condensed for easier separation.
  • It is replicated to form two identical sister chromatids. (correct)
  • It is divided into two separate chromosomes.
  • It undergoes a second round of duplication.

How do chromosomes align during Metaphase I of meiosis compared to metaphase of mitosis?

<p>Pairs of homologous chromosomes line up during meiosis I. (C)</p> Signup and view all the answers

Which statement is true regarding the parent cell before the division process in mitosis and meiosis I?

<p>The chromosome number in the parent cell is the same in both processes. (D)</p> Signup and view all the answers

What are sister chromatids primarily composed of?

<p>Identical DNA sequences (B)</p> Signup and view all the answers

What characteristic defines a haploid cell?

<p>It contains only a single set of genes. (C)</p> Signup and view all the answers

During cell division, what is the role of the centromere?

<p>It connects sister chromatids together. (D)</p> Signup and view all the answers

What is the end result of the separation of sister chromatids during cell division?

<p>Formation of two identical daughter cells. (B)</p> Signup and view all the answers

What does a diploid cell contain?

<p>Two sets of homologous chromosomes. (D)</p> Signup and view all the answers

Which of these statements best describes the process of chromosome duplication?

<p>It happens before the cell division begins. (A)</p> Signup and view all the answers

What are chromatids related to during cell division?

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

Why do eukaryotic cells have more complex chromosome structures than prokaryotic cells?

<p>They have multiple chromosomes grouped in the nucleus. (D)</p> Signup and view all the answers

What is the result of crossing over during meiosis?

<p>Homologous chromosomes trade genetic material. (B)</p> Signup and view all the answers

In which phase does chromosome duplication occur in the cell cycle?

<p>S phase of interphase (B)</p> Signup and view all the answers

How many times do sister chromatids separate during meiosis?

<p>Twice, once in meiosis I and once in meiosis II. (B)</p> Signup and view all the answers

What is the end result of meiosis?

<p>Four genetically diverse haploid gametes. (A)</p> Signup and view all the answers

What distinguishes homologous chromosomes?

<p>They come from different parents and have similar but not identical genes. (C)</p> Signup and view all the answers

During which phase do homologous chromosomes line up at the metaphase plate in meiosis?

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

What is mitosis primarily used for?

<p>Development and growth of tissues. (D)</p> Signup and view all the answers

What occurs during anaphase I of meiosis?

<p>Homologous chromosomes separate to opposite poles. (D)</p> Signup and view all the answers

What best describes the role of gametes in reproduction?

<p>They combine to restore diploid chromosome number in offspring. (D)</p> Signup and view all the answers

What is the main outcome of meiosis II?

<p>Four haploid cells are formed (A)</p> Signup and view all the answers

During which phase of meiosis do sister chromatids separate?

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

What structural feature is involved in the separation of sister chromatids?

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

In what phase do homologous chromosomes remain attached?

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

Which of the following correctly describes the cells produced at the end of meiosis I?

<p>Two haploid cells (A)</p> Signup and view all the answers

What occurs during telophase II?

<p>Spindle fibers break down (C)</p> Signup and view all the answers

What essential event occurs in prophase I of meiosis?

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

How does meiosis II differ from meiosis I?

<p>Meiosis II involves sister chromatids separating (A)</p> Signup and view all the answers

What happens during meiosis I?

<p>Homologous chromosomes separate into two daughter cells. (C)</p> Signup and view all the answers

What is the primary outcome of meiosis?

<p>Reduction of chromosome number from diploid to haploid. (A)</p> Signup and view all the answers

During which phase do homologous chromosomes exchange segments?

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

What remains attached during anaphase I of meiosis?

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

How many times do cells divide during meiosis?

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

What is the result of crossing over?

<p>Increased genetic variation among offspring. (B)</p> Signup and view all the answers

What do the four haploid cells produced at the end of meiosis contain?

<p>One set of chromosomes. (A)</p> Signup and view all the answers

What is the primary role of the receptor protein in the signal transduction pathway?

<p>To receive growth factors and initiate a response (D)</p> Signup and view all the answers

What characteristic differentiates malignant tumors from benign tumors?

<p>Malignant tumors can invade other tissues. (A)</p> Signup and view all the answers

What is a potential outcome of excessive cell division in cancer cells?

<p>Formation of malignant tumors (C)</p> Signup and view all the answers

How many chromosomes are typically found in human somatic cells?

<p>46 chromosomes in 23 pairs (D)</p> Signup and view all the answers

What is a shared characteristic of homologous chromosomes?

<p>They have genes for the same characteristics at the same locus. (B)</p> Signup and view all the answers

Flashcards

Sister chromatids

Two identical copies of a chromosome after duplication

Diploid (2n)

A cell containing two sets of homologous chromosomes

Haploid (n)

A cell containing only one set of genes

Chromosome duplication

Creating an identical copy of a chromosome

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Homologous chromosomes

Chromosome pairs with similar genes

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Centromere

The region where sister chromatids are joined

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Cell division

The process of a cell dividing into two daughter cells

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Daughter cells

The two new cells produced from a single parent cell

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Gamete

A sex cell (sperm in males, eggs in females)

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Meiosis

Cell division for making sex cells

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Crossing Over

Homologous chromosomes swap parts

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Interphase

Cell growth and DNA copy phase

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Mitosis

Cell division for creating identical copies

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Prophase I

Homologous chromosomes pair up

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Metaphase I

Homologous chromosome pairs line up

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Anaphase I

Homologous chromosomes separate

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Cell Cycle Checkpoints

Points in the cell cycle where internal and external conditions are checked before the cell proceeds to the next stage.

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G1 Checkpoint

The first checkpoint in the cell cycle, where the cell checks for adequate cell size, nutrients, and growth factors before committing to replication.

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Growth Factor

A signaling molecule that promotes cell growth and division.

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Signal Transduction Pathway

A series of molecular events that relay a signal from the cell's exterior to its interior.

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Relay Proteins

Proteins within the signal transduction pathway that transmit the signal from one molecule to the next.

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Tumor

An abnormal mass of cells resulting from uncontrolled cell division.

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Malignant Tumor

A tumor that can invade surrounding tissues and spread to other parts of the body (metastasis).

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Metastasis

The spread of cancer cells from a primary tumor to other parts of the body.

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What happens in Meiosis I?

The first division in meiosis, where homologous chromosome pairs separate, reducing the chromosome number from diploid (2n) to haploid (n).

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What is the result of Meiosis I?

Two haploid daughter cells, each containing one chromosome from each original homologous pair.

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What happens in Meiosis II?

The second division in meiosis, where sister chromatids separate, producing four haploid daughter cells.

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What is the result of Meiosis II?

Four haploid cells, each with one complete set of chromosomes.

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What is the role of Meiosis?

To produce gametes (sex cells) with half the number of chromosomes as the parent cell, ensuring genetic diversity in offspring.

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How does Meiosis create genetic diversity?

Through crossing over, where homologous chromosomes exchange segments during Prophase I, swapping genetic information and creating unique combinations.

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What happens during Prophase I?

Homologous chromosomes pair up and exchange genetic material through crossing over.

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What happens during Metaphase I?

Homologous chromosome pairs line up at the metaphase plate, ready to be pulled apart.

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What is the difference between Mitosis and Meiosis?

Mitosis produces two identical daughter cells with the same number of chromosomes as the parent cell, while Meiosis produces four genetically diverse daughter cells with half the number of chromosomes.

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Why is Meiosis important?

It ensures genetic diversity in offspring through the production of gametes with unique combinations of genes, leading to evolution and adaptation.

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Mitosis vs. Meiosis

Mitosis produces two identical daughter cells with the same number of chromosomes as the parent cell. Meiosis produces four genetically diverse daughter cells with half the number of chromosomes.

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What happens during Meiosis I?

Homologous chromosomes pair up and exchange genetic material through crossing over. These pairs then line up at the metaphase plate and separate, reducing the chromosome number from diploid to haploid.

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Meiosis I vs. Mitosis

Meiosis I involves the separation of homologous chromosomes, while mitosis involves the separation of sister chromatids. Meiosis I results in two haploid cells, while mitosis results in two diploid cells.

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Prophase I: Synapsis and Crossing Over

During prophase I, homologous chromosomes pair up (synapsis) and exchange genetic material (crossing over). This exchange contributes to genetic diversity.

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Metaphase I: Homologous Pairs Line Up

In metaphase I, homologous chromosome pairs line up at the metaphase plate, preparing to split apart during anaphase I.

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Anaphase I: Homologous Chromosomes Separate

During anaphase I, homologous chromosomes separate, moving towards opposite poles of the cell. Sister chromatids remain attached.

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Telophase I and Cytokinesis

Telophase I marks the end of meiosis I. The nuclear envelope reforms around each set of chromosomes. Cytokinesis divides the cytoplasm, forming two haploid daughter cells.

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Meiosis II: Sister Chromatids Separate

Meiosis II is similar to mitosis, where sister chromatids separate, resulting in four haploid daughter cells with a single set of chromosomes.

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Haploid Daughter Cells

The final result of meiosis is four haploid daughter cells. These cells have only one set of chromosomes, which is half the number of chromosomes in the original parent cell.

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Genetic Diversity

Meiosis contributes to genetic diversity by shuffling the chromosomes and creating new combinations of genes in the gametes through processes like crossing over.

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Study Notes

Cellular Basis of Reproduction and Inheritance

  • Cell replication is a normal process for maintaining a healthy body.
  • Mitosis allows for asexual reproduction, while meiosis permits sexual reproduction.
  • Asexual reproduction involves a single parent, producing identical offspring.
  • Sexual reproduction requires gametes from two parents, creating genetically diverse offspring.
  • Errors in cell division can cause cancer, infertility, or genetic disorders in offspring.

Two Types of Cell Division

  • Life begins as a single cell (zygote), formed by the union of an egg and sperm.
  • Meiosis creates gametes (sperm and eggs) with half the number of chromosomes as the parent cell.
  • Mitosis produces identical body cells for growth and repair.

Form of Chromosomes

  • Chromosomes are located in the cell nucleus.
  • Chromosomes are a tightly coiled combination of DNA and proteins (histones).
  • DNA carries genetic information, directing development and maintenance.
  • Histones support and control gene activity.
  • Specific segments of DNA (genes) direct protein synthesis, impacting structure or function.
  • Somatic cells (all cells except gametes in humans have 46 chromosomes, two sets of 23 chromosomes from the parents).
  • Homologous chromosomes are chromosome pairs with genes for the same traits, one from each parent.
  • A diploid cell has two sets of chromosomes.
  • A haploid cell has one set of chromosomes (e.g., gametes).
  • Sex chromosomes (X and Y) determine gender (XX = female, XY = male)
  • Autosomes are the remaining 22 chromosome pairs involved in determining characteristics.

Principles of Inheritance

  • Genetic information is carried in equal numbers in egg and sperm chromosomes.
  • Homologous pairs of chromosomes pair up with the corresponding chromosomes from each parent.
  • Each member of a homologous pair carries genes for the same traits.
  • A trait is a characteristic produced by one or more gene-directed proteins.
  • Alleles are different forms of the same gene, producing different versions of traits.
  • Example trait: freckles are caused by one allele, while another allele doesn't cause them.

Mitosis and Meiosis

  • Mitosis produces two identical diploid daughter cells from one parent cell.
  • Meiosis produces four unique haploid daughter cells (gametes) from one parent cell, via two successive cell divisions.
  • Meiosis involves pairing of homologous chromosomes and crossing over (exchange of genetic material), resulting in genetically unique daughter cells

Cytokinesis

  • Cytokinesis is the cell division process that overlaps the end of mitosis. This phase differs for animal and plant cells.
  • Animal cells divide via a cleavage furrow that pinches inward to separate parent cells.
  • Plant cells form a membranous cell wall to divide parent cells.

Cell Cycle

  • The cell cycle consists of interphase (G1, S, and G2 phases) and the mitotic phase.
  • During G1 (first gap phase), the cell grows and carries out metabolic activities.
  • During S (synthesis phase), the cell duplicates its DNA.
  • During G2 (second gap phase), the cell continues growth and generates proteins necessary for mitosis.
  • The M (mitosis) phase involves the segregation of sister chromatids, creating two identical daughter cells.

Environmental Factors Affecting Cell Division

  • Most normal cells in lab cultures divide only when attached to a surface.
  • Cell division stops when cells touch one another.
  • Most animal cells divide when stimulated by growth factors, and some do not divide at all.

Growth Factors and Cell Cycle Control

  • A set of inter-related proteins controls the cell cycle, influencing critical checkpoints.
  • The binding of growth factors to specific receptors and their signal transduction pathways affect cell division.

Cancer

  • Cancer cells divide excessively and form a mass (tumor).
  • Malignant tumors can invade other tissues.
  • Radiation and chemotherapy are effective cancer treatments as they interfere with cell division.
  • Benign tumors are non-cancerous and are contained within the tissue.
  • Malignant tumors are cancerous and can spread throughout the body.

Meiosis and Crossing Over

  • In meiosis, chromosome duplication occurs prior to two successive cell divisions.
  • In crossing over, homologous chromosomes exchange corresponding segments during prophase I.
  • Sexual reproduction results in genetically unique offspring due to independent orientation of chromosomes and random fertilization.

Accidents during Meiosis

  • Nondisjunction during meiosis results in abnormal chromosome numbers, either missing or extra chromosomes.
  • Nondisjunction can affect both autosomes and sex chromosomes.
  • Nondisjunction in sex chromosomes is less harmful than nondisjunction in other chromosomes.

Karyotype Preparation

  • A karyotype is a photographic inventory of an individual's chromosomes.
  • Karyotypes are prepared by isolating and culturing white blood cells, arresting them in metaphase for observation under a microscope, and photographing chromosomes showing their ordered pairs.

Trisomy 21 and Down Syndrome

  • Trisomy 21, an extra copy of chromosome 21, can result in the development of Down syndrome.
  • Down Syndrome: the most common chromosome abnormality, causing developmental and health effects that vary among individuals.
  • Maternal age plays a role in the risk of trisomy 21.

Polyploidy

  • Polyploidy involves organisms with extra sets of chromosomes, arising from nondisjunction which may lead to the evolution of new species.

Chromosome Structure Alterations

  • Chromosomal rearrangements (deletions, duplications, inversions, and translocations) can cause genetic disorders or, if present in somatic cells, cancer.
  • Several conditions result for errors regarding chromosome structure during cell divisions, including deletions, duplications, inversions and reciprocal translocations.

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