Ch. 28 - Female Reproductive System Flashcards
Gametogenesis
process of forming human sex cells. Begins with cell division, meiosis. Is a similar process in both females and males.
sex cells
gametes
female gametes
oocytes
male gametes
sperm
Overview of Meiosis
sex cell division that has 4 haploid daughter cells genetically different from parent cell. start with diploid parent cell (46) and produces haploid daughter cells (23) called gametes. Includes crossing over where genetic material is exchanged between homologous chromosomes to get genes from both parents in one chromosome.
Mitosis
somatic cell division, produces 2 genetically identical diploid daughter cells and does not cross over.
Interphase
cell phase prior to meiosis where dna on each cell is replicated. The replicated chromosomes are now composed of 2 sister chromatids (structures with identical copies of dna)
centromere
place where sister chromatids are attached.
meiosis 1 - reduction division
begins after interphase, 4 phases plus cytokinesis. Homologous pairs of chromosomes separate when cell divides Results in 2 cells, each with 23 chromosomes of replicated sister chromatids held together at centromere
Prophase 1
first phase of meiosis I. Pairing up homologous replicated chromosomes that bind to form a tetrad (2 sets of 2 sister chromatids) through process of synapsis. Crossing over then occurs with maternal chromosome and paternal chromosomes to ensure diversity. Ends with breakdown of nuclear envelope.
Metaphase I
second phase, lining up of homologous pairs of tetrad on cell midline. It has random alignment. Spindle fibers form by microtubules and extend from centrioles to centromeres of each homologous replicated chromosomes.
Anaphase I
third phase, homologous pairs of chromosomes separate and are pulled apart to opposite ends of cell. Each daughter cell receives half number of chromosomes called reduction division. Each chromosome still with 2 sister chromatids.
Telophase 1 and cytokinesis
reformation of nuclear envelope, cleavage furrow forms, cell cytoplasm divides in cytokinesis to produce 2 new cells. The daughter cells have 23 replicated chromosomes each with 2 sister chromatids bound together.
independent assortment
refers to the random alignment and whether maternal or paternal ends up on one side or the other in metaphase I.
Meiosis II
functions to separate sister chromatids to become single chromosomes in haploid cell instead of replicated ones.
Prophase II
resembles prophase I, breaks nuclear envelope, chromosomes collect together, and no crossing over. No homologous chromosome pairs are present; they were already separated.
Metaphase II
Spindle fibers extend from centrioles to centromeres and sister chromatids align along cell midline
Anaphase II
sister chromatids are pulled apart and single stranded chromosomes separate to opposite poles
Telophase II and cytokinesis
reformation of nuclear membrane, cleavage furrow forms to produce 4 haploid cells; 22 autosomes and 1 sex chromosome. Mature into oocytes and sperm.
Failure to separate homologous chromosomes or sister chromatids
results in gamete with 22 or 24 chromosomes most commonly which causes the individual to have 45 or 47 chromosomes instead of 46.
monosomy
individual with 1 copy of a chromosome (45 chromosomes)
Trisomy
individual with 3 copies of one chromosome. (47 chromosomes)
down syndrome
intellectual disability, slanting eye creases, heart defects, poor muscle tone, short stature. Due to nondisjunction of oocyte (more common) or sperm. Incidence increases with mother’s age.
primordial follicles
most primitive type of ovarian follicle. Has primary oocyte and single flattened layer of follicle cells. primary oocyte arrested in first meiotic prophase. 1.5 million present at birth.