Exam 1 Review:  Chapter 3 - Meiosis and Cancer

meiosis  = reproductive cell division - The process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid, leading to the production of gametes.

diploid - Having a pair of each type of chromosome; having the same number of sets of chromosomes as a somatic cell or twice as many chromosomes as found in a germ cell; in humans, all cells except those produced by meiosis during gamete formation.

haploid - Having a single complete set of chromosomes; having the same number of sets of chromosomes as found in a germ cell or half as many chromosomes as in a somatic cell; in humans, only the cells produced by meiosis during gamete formation (eggs and sperms).

gametes - The reproductive cells produced by meiosis in the gonads, having the haploid number of chromosomes (mature sperm in males and mature eggs in females), and capable of fusing with a gamete of the opposite sex to produce the fertilized egg = zygote.

spermatogenesis - The production of sperms cells = spermatozoans involving both mitotic and meiotic divisions within the testes, regulated by pituitary and male reproductive hormones; the long (~70 days) and complex process within the seminiferous tubules of the testes, in which an elaborate succession of distinct cell types are generated by mitotic and meiotic divisions; in the initial stage, diploid spermatogonia repeatedly divide by mitosis, giving rise to diploid primary spermatocytes, which in turn undergo the first meiotic division I, leading to haploid secondary spermatocytes; secondary spermatocytes undergo the second meiotic division II, leading to round spermatids, which elongate during the spermiogenesis process to form elongated spermatids and finally differentiate into mature spermatozoa, by condensation of the chromatin, with the substitution of histones with protamines in DNA supercoiling, and the formation of the acrosome, flagellum, and the other sperm organelles; the progression moves from the periphery to the center of the seminiferous tubule and is regulated by androgens.

oogenesis - The formation by meisosis, and the development and maturation of an egg = ovum within the ovary, regulated by pituitary and female reproductive hormones; a long and complex process which (1) begins in the fetal period with the development of oogonial stem cells by mitosis, and (2) is followed by the initiation of meiosis division I which produces primary oocytes which are arrested in development in meiotic prophase I; (3) at puberty, in response to increasing blood levels of FSH and LH from the anterior pituitary, meiosis continues in certain follicles each month during the menstrual cycle, and (4) one egg = ovum and its surrounding follicle develop to the point of being mature follicle = vesicular follicle = Graafian follicle, (5) this egg = ovum. completes meiosis division I at the time of ovulation, and then meiosis is arrested until further external stimuli are provided; Note:  due to unequal cytoplasmic division, at the end of meiosis division I, one secondary oocyte and one polar body has been generated; (6) only if fertilization occurs will the secondary oocyte complete meiosis division II to form a mature egg = ovum (7) which will then immediately become a fertilized egg = zygote by the fusion of the haploid egg = ovum nucleus with the sperm nucleus.

autosomes - Those homologous chromosome pairs which is not sex chromosomes, i.e., not significantly involved in sex determination of the individual; in humans there are 22 pairs of autosomes and one pair of sex chromosomes, the X and Y.

sex chromosomes - The homologous chromosome pair which is not grouped with the autosomes; the homologous chromosome pair which is involved in sex determination of the individual; in humans there are 22 pairs of autosomes and one pair of sex chromosomes, the X and Y; the presence of a Y chromosome determines maleness.

homologous chromosomes - Each pair of similar DNA molecules, present in diploid cells, containing the same gene sequences (although the individual alleles may vary), each DNA molecule derived from one parent.  [Visit What Our Chromosomes Can Tell Us for more information.]

reduction division - The first of the two meiotic divisions in which the variety of genetic information in the daughter cells is decreased because paternal and maternal chromosomes are assorted in a random pattern between the two daughter nuclei.

synapsis - The close side-by-side association of homologous paternal and maternal chromosomes during the first prophase of meiosis which provides the physical arrangement of chromosomes so that the reduction division produces haploid daughter cells and which permits the rare exchange of hereditary material between different chromosomes, the process of "crossing over."

crossing over - The rare exchange of hereditary material between homologous chromosomes, due to the breakage and improper repair of DNA sugar-phospahte backbones, which may occur during the reduction division of meiosis and contributes to the genetic variability of gametes.

genetic recombination - The rare exchange of hereditary material between chromosomes, due to the breakage and improper repair of DNA sugar-phospahte backbones, which may occur during various nuclear processes and contributes to the genetic variability of cells; the most important example is "crossing over," which occurs uring the reduction division of meiosis.

apoptosis - A genetically determined process of cell self-destruction which is marked by the fragmentation of nuclear DNA; it is activated either by the presence of a stimulus or by the removal of a stimulus or suppressing agent; it is a normal physiological process eliminating DNA-damaged, superfluous, or unwanted cells (as immune cells targeted against the self in the development of self-tolerance or embryonic cells in the hands to permit the fingers to be separate structures), and when halted (as by genetic mutation) may result in uncontrolled cell growth and tumor formation; it is a form of programmed cell death which enables the organism control cell number and eliminate cells which threaten its survival.

fertilization - The specific part of the reproductive process in which male and female haploid gametes (sperm and egg) unite or fuse to form a diploid zygote, the fertilized egg.

zygote - The single diploid cell formed by the successful union of two gametes, sperm and egg, during reproduction before cleavage (cell divisions) begins; a fertilized ovum or egg.

cancer - Any of various neoplasms ("new growths"), whether benign or malignant, characterized by the uncontrolled proliferation of cells which tend to produce new and abnormal structures in various body sites; more than a hundred different types are recognized.  [See also the National Cancer Institute.]

oncology - The branch of medicine which deals with the physical, chemical, and biological properties of tumors and other cancers, including the study of their development, diagnosis, treatment, and prevention.

neoplasm - Any abnormal new growth of tissue which grows by cellular proliferation more rapidly than normal, continues to grow after the stimuli that initiated the new growth cease, shows partial or complete lack of structural organization and functional coordination with the normal tissue, and usually forms a distinct mass of tissue which may be either benign or malignant.

malignancy - A tumor or cancer which has the following properties:  the transformed cells are dedifferentiated to some degree, they lack contact inhibition and spread into surrounding tissues, as a result of this invasiveness, the body is unsuccessful in walling the growth off with a connective tissue capsule, and such cancers may have the property of metastasis, the ability to break off from the primary lesion and spread by means of the blood or lymphatics or through a body cavity to some other parts of the body; not all malignant tumors kill patients.
metastasis -

  1. The transmission of pathogenic microorganisms or cancerous cells from an original site to one or more sites elsewhere in the body, usually by way of the blood vessels or lymphatics or by spreadng through a body cavity; cancer cells capable of this type of spread are, by definition, a type of malignant cancer.
  2. A secondary cancerous growth formed by transmission of cancerous cells from a primary growth located elsewhere in the body; a secondary cancer is, by definition, a type of malignant cancer.

oncogenes - A diverse group of genes which may potentially induce neoplastic = cancerous transformation; they include genes for growth factors, growth factor receptors, protein kinases, signal transducers, nuclear phosphoproteins, and transcription factors; when these genes become unconditionally expressed, i.e., lose their normal regulation to become "turned on" at all times, after structural or regulatory changes, then uncontrolled cell proliferation may result; such genes have been recognized not only in tissue cells but in viruses.

 

Sketch and Label:

 9. meiosis.

 
Note:  In the figure below, a figure for Mitosis "A." is provided for contrast with Meiosis "B."
Note:  In the figure below, Prophase I has been subdivided into 5 subphases, leptotene, zygotene, pachytene, diplotene, and diakinesis.  You are not responsible for the subphases, but having the drawings accompanied by actual photographs is instructive.