38 Questions
What is the primary function of mitosis?
To produce somatic cells
What is the term for the union of a male and a female gamete?
Fertilization
What is the product of fertilization?
Zygote
What is the role of meiosis in sexual reproduction?
To produce gametes
What is a karyotype?
A visual representation of chromosomes
What are the three stages of sexual reproduction?
Gamete production, syngamy, and zygote production
What is the primary purpose of mitosis?
To construct an exact copy of each chromosome
What happens to the chromosomes during interphase?
They duplicate and exist as a pair of chromatids joined together by a centromere
What is the term for the process by which one cell results in two daughter cells, each with a set of chromosomes identical to that of the parental cell?
Mitosis
What is the duration of interphase dependent on?
The function of the cell
What occurs during the G2 phase of the cell cycle?
Cells synthesize organelles and increase in size
What is the term for the nuclear material that will stain during interphase?
Chromatin
How many daughter cells are produced as a result of mitosis?
Two
What is the stage of the cell cycle that occurs before mitosis?
Interphase
What is the site of exchange between chromatids?
Chiasmata
During Meiosis I, what happens to the centromeres in anaphase?
They continue to hold sister chromatids together
What is the result of genetic crossing over in meiosis?
Genes from one chromosome become attached to genes of another chromosome
What is the significance of meiosis in terms of chromosome conservation?
It maintains the same number of chromosomes in offspring
What is the period between Meiosis I and Meiosis II called?
Interkinesis
What happens to the chromosomes during Metaphase II?
They align on the equatorial plane
What is the result of nondisjunction during meiosis?
Gametes with two copies of each chromosome
What is the significance of meiosis in terms of hereditary traits?
It increases the variation of hereditary traits
What is the outcome of Meiosis II?
Four haploid cells
What happens during Telophase II?
Nuclear membrane reappears
Which phase of the cell cycle comes before mitosis?
G2
What happens to the nuclear envelope during prophase?
It disintegrates into small vesicles
What is the function of the centrioles during prophase?
They move to the opposite poles of the cell
What happens to the chromatids during prophase?
They shorten and thicken through spiralisation and condensation of the DNA
What is the significance of the metaphase plate?
It is the stage where the centromeres line up
What is the function of the spindle fibres during metaphase?
They attach the centromeres to the spindle fibres
What happens to the centromeres during metaphase?
They line up across the equator of the spindle
What is the characteristic of the metaphase stage of the cell cycle?
The chromosomes are aligned in a ring along the inner circumference of the cell
What is the primary function of histones in chromosome morphology?
To help organize the long strands of DNA into structures
What is the term used to describe the complex of nucleic acid and proteins?
Chromatin
How many pairs of chromosomes do autosomes (somatic) consist of?
22 pairs
What is the term used to describe the position or location of the centromere?
Position
What is the function of the centromere in a chromosome?
To separate the chromosome into two arms of varying length
What is the term used to describe the structure composed of chromatin?
Nucleosomes
Study Notes
The Cell Cycle
- The cell cycle involves the production of gametes, the union of a male and a female gamete (syngamy or fertilization), and the production of a zygote.
- The cell cycle consists of interphase, mitosis, and cytokinesis.
Chromosomes
- Chromosomes are composed of nucleic acid associated with a variety of proteins.
- Chromatin is a complex of nucleic acid and proteins.
- Histones help organize the long strands of DNA into structures called nucleosomes.
- Chromosomes can be distinguished by their length, position of the centromere, and arm length.
Mitosis
- Mitosis is the process by which a cell nucleus divides to produce two daughter nuclei containing identical sets of chromosomes to the parent cell.
- It is a non-reductional nuclear division by which one cell results in two daughter cells, each with a set of chromosomes identical to that of the parental cell.
- The end result of mitosis is to construct an exact copy of each chromosome and distribute, through division of the original (mother) cell, an identical set of chromosomes to each of the two progeny or daughter cells.
- Mitosis occurs in four phases: prophase, metaphase, anaphase, and telophase.
Interphase
- Interphase is the portion of the cell cycle in which the condensed chromosomes are not visible under the light microscope.
- It includes the G1, S, and G2 phases.
- The duration of the interphase depends on the function of the cell.
- During interphase, cells synthesize organelles and increase in size.
- Chromosomes and centrioles duplicate during interphase.
Prophase
- Prophase is the longest phase of mitosis.
- Chromatids shorten and thicken through spiralization and condensation of the DNA protein coat.
- Centrioles move to the opposite poles of the cell.
- Short microtubules (asters) may be seen radiating from the centrioles.
- Nucleoli decrease in size.
- By the end of prophase, the nuclear envelope disintegrates into small vesicles which disperse, and a spindle is formed.
Metaphase
- In metaphase, the pairs of chromatids attach their centromeres to the spindle fibers.
- The chromatids move by the microtubules (spindle fibers) to align them into what is called the metaphase plate.
- Their centromeres line up across the equator of the spindle and at right-angles to the spindle axis.
Meiosis I
- Prophase I involves genetic crossing over, where genes from one chromosome become attached to genes of the other chromosome, leading to new gene combinations in the resulting chromatids.
- Metaphase I involves the orientation of the bivalents at random on the equatorial plane.
- Anaphase I involves the movement of the paired homologous chromosomes to opposite poles.
- Telophase I involves the reforming of the nuclear membrane and the separation of the chromosomes.
Meiosis II
- Interkinesis is the period between the first and second meiotic divisions.
- Prophase II involves the recondensation of the chromosomes and the reformation of the spindle fibers.
- Metaphase II involves the alignment of the chromosomes on the metaphase plate.
- Anaphase II involves the separation of the sister chromatids.
- Telophase II involves the reappearance of the nuclear membrane and the division of the cell into four haploid cells.
Significance of Meiosis
- Meiosis makes possible the conservation of the number of chromosomes from generation to generation.
- Crossing over between non-sister chromatids contributes to the recombination of hereditary traits in gametes.
Learn about the cell cycle, including interphase, mitosis, and cytokinesis, and the structure of chromosomes, including chromatin and nucleosomes.
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