Mcat Biology (Chapter 2)

diploid (2n), which means they contain two copies of each chromosome; for humans, diploid cells have 46 chromosomes

haploid (n), which means they contain only one copy of each chromosome; for humans, haploid cells have 23 chromosomes

G1

S

G2

M

first three stage of the cell cycle (G1, S and G2); longest part of cell cycle (90%);

cell is simply living and serving its function without any preparation for division; offshoot of G1 phase

less condensed form of chromosomes during interphase; available for RNA polymerase to transcribe genes

presynthetic gap; cell creates organelles for energy and protein production while also increasing in size; must pass a restriction point before it goes onto S stage

synthesis of DNA; cell replicates its genetic material so two identical chromatids which are bound together at the centromere are formed;

*although there are 92 chromatids now, still only 46 chromosomes

postsynthetic gap; includes another quality control checkpoint before going onto M stage

consists of mitosis and cytokinesis;

prophase

metaphase

anaphase

telophase

splitting of cytoplasm and organelles into two daughter cells

main protein involved in checkpoint between G1 and S stages (restriction point); if there is any damage to DNA, cell does not go onto S stage until it is fixed; also plays role in G2/M checkpoint

during cell cycle, cyclins bind to CDKs, creating an activated CDK-cyclin complex which phosphorylates transcription factors which promote transcription of genes required for next stage of cell cycle

gene that produces p53; mutation of this gene leads to cancer because cell cycle is not stopped when DNA is damaged

distant spread of cancerous cells through the bloodstream or lymphatic systems

chromosomes condense, nuclear membrane dissolves, nucleoli disappear, centrioles migrate to opposite sides of the cell, and the spindle apparatus begins to form; kinetochore of each chromosome is contacted by a spindle fiber

microtubules also coming out of centrioles that anchor them to cell membrane

chromosomes are aligned at the metaphase or equatorial plate

centromeres split so each chromatid has its own distinct centromere; sister chromatids are split and pulled to opposite poles of cell

reverse of prophase; spindle apparatus disappears; nuclear membrane reforms around each set of chromosomes and nucleoli reappear; chromosomes uncoil

takes place during meiosis I; homologous chromosomes are separated, generating haploid daughter cells

takes place during meiosis II; similar to mitosis because sister chromatids are separated

the same events occur as in prophase of mitosis, except that homologues come together and intertwine in a process called synapsis; the four chromatids are referred to as a tetrad, and crossing over exchanged genetic material from a chromatid in the homologous chromosome

point of synapsis where chromatid of homologous chromosome in tetrad may break

the inheritance of one allele has no effect on the likelihood of inhering certain alleles of other genes; crossing over explains this

during anaphase I, homologous pairs separate and are pulled to opposite poles of the cell; accounts for Mendel's first law of segregation;

separating of the two homologous chromosomes in meiosis

can only carry the X chromosome (female equivalent of sperm)

this is the term for males with respect to many of the genes on the X chromosome because they only have one copy

no-table gene on the Y chromosome which codes for a transcription factor that initiates testis differentiation and, thus, the formation of male gonads

seminiferous tubules and interstitial cells (of Leydig)

produce sperm through spermatogenesis

nourish sperm

secrete testosterone and other male sex hormones (androgens)

where sperm is stored until ejaculation once they are formed and gain motility

sperm travel through the vas deferens (or ductus deferens) to the ejaculatory duct to the urethra and out through the penis

contribute fructose to nourish sperm and produce alkaline fluid (seminal fluid)

also produces alkaline fluid (seminal fluid)

produce a clear viscous fluid (seminal fluid) that cleans out any remnants of urine and lubricates the urethra during sexual arousal

in males, the diploid stem cells

in males, germ cells after S stage

in males, germ cells after meiosis I

in males, germ cells after meiosis II

in males, germ cells after maturation

contains the genetic material of sperm

generates ATP from fructose for sperm; filled with mitochondria

for motility of sperm

cap which covers sperm head; derived from the Golgi apparatus and is necessary to penetrate the ovum

make up ovaries; multilayered sacs that contain, nourish and protect immature ova (eggs)

lines the abdominal cavity; once a month an egg is ovulated through there

egg is drawn into there after peritoneal sac; lined with cilia to propel the egg forward

lower end of the uterus; connects to the vaginal canal

production of female gametes; one haploid ovum and a variable number of polar bodies are formed from an oogonium

all oogonia which have already undergone replication before birth; arrested in prophase I; 2n

ovulated egg each month which is arrested in metaphase II; does not complete remainder of meiosis II unless fertilization occurs

oocyte which has been fertilized and undergone meiosis II

formed because cytokinesis is uneven in oogenesis; cell which receives very little cytoplasm and organelles

surrounds oocyte itself; acellular mixture of glycoproteins that protect the oocyte and contain the compounds necessary for sperm binding

lies outside zona pellucida; layer of cells that adhered to the oocyte during ovulation

first menstrual cycle

haploid; nucleus of either the sperm or the egg right before they merge

created when the pronuclei of the sperm and ovum join; diploid

produced at the start of puberty when hypothalamus lifts restriction of its production; triggers anterior pituitary gland to synthesize and release follicle stimulating hormone (FSH) and luteinizing hormone (LH) the functions of which depend on the sex of the individual

in males: stimulates the Sertoli cells and triggers sperm maturation

in females: leads to estrogen secretion

in males: causes the interstitial cells to produce testosterone

in females: tells the corpus luteum to secrete progesterone

lining of the uterus

lead to thickening of the lining of the uterus (endometrium)

involved in the development and maintenance of the lining of uterus (endometrium)

follicular phase

ovulation

luteal phase

menstruation

begins when the menstrual flow begins; GnRH secretion stimulates FSH and LH secretion, which promotes follicle development; estrogen is released, stimulating vascularization and glandularization of the decidua

stimulated by a sudden surge in luteinizing hormone (LH); surge occurs because estrogen stops having negative feedback effects at a certain threshold and begins to have positive feedback effects

luteinizing hormone (LH) promotes the ruptured follicle to become the corpus luteum, which secretes progesterone that maintains the uterine lining; high estrogen and progesterone levels cause negative feedback to GnRH, LH and FSH

as estrogen and progesterone levels drop, the endometrial lining is sloughed off and the block on GnRH production is removed

produced by the blastula if fertilization occurs; luteinizing hormone (LH) analogue; can maintain corpus luteum; near the end of the first trimester, hCG levels drop as the placenta takes over progesterone production

occurs when ovaries stop producing estrogen and progesterone; FSH and LH levels rise