MCAT Kaplan Chapter 2: Reproduction

G1/S checkpoint (restriction point)

Cell determines if condition of DNA is good enough for synthesis.

If there has been damage to DNA the cell cycle goes into arrest until DNA has been repaired.

Main protein in control is p53.

G2/M checkpoint

Cell concerned with achieving adequate size and having enough organelles replicated to support two daughter cells.

P53 also involved in this checkpoint.

Cyclins

proteins that regulate the timing of the cell cycle in eukaryotic cells

Concentrations increase and decrease during soecific stages.

Bind to CDKs.

cyclin-dependent kinases (Cdks)

A protein kinase that is active only when attached to a particular cyclin.

Cdk-cyclin complex

Phosphorylates transcription factors required to drive the cell cycle forward.

transcription factors

promote transcription of genes required for the next stage of the cell cycle

TP53 mutation

One of the most common mutations found in cancer.

When this gene is mutated the cell cycle does not stop to repair damaged DNA.

Chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones

microtubule organizing center (MTOC)

general term for any structure that organizes microtubules in cells

Include spindle fibers & basal body if flagellum or cilium.

Mitosis steps

prophase- chromosomes condense, spindle forms

metaphase- chromosomes align

anaphase- sister chromatids separate

telophase- new nuclear membrane forms

Meiosis 1

Results in homologous chromosomes being separated, generating haploid daughter cells

2 chromosomes —-> 1 chromosome

Reductional Division

Meiosis 2 is similar to mitosis- results in a separation of sister chromatids without a change in ploidy.

2 chromosomes —-> 4 chromosomes

Equational Division

hemizygous

The single set of genes that males acquire from their mother's X chromosome. A genetic occurrence when an organism has only 1 allele for a trait. In humans, males with only one X chromosome are _________.

Seniniferous tubules

Site of sperm cell production

Highly coiled

Sertoli cells

nourish sperm

Interstitial cells of Leydig

secrete testosterone and other male sex hormones (androgens)

Epididymis

Stores sperm cells

pathway of sperm during ejaculation

Seminiferous tubules, epididymis, vas deferens, ejaculatory ducts, urethra, penis

SEVEN UP

Soermatogenesis

The formation of haploid sperm through miosos

Occurs in seminiferous tubules

spermatogonia

The diploid cells in a testis that can give rise to primary spermatocytes.

primary spermatocyte

Diploid

Occurs after spermatogonia replicate their genetic material via the S phase.

secondary spermatocytes

Occurs after diploid primary spermatocytes undergo the first meiotic division resulting in haploid __________________.

spermatids

Occurs after secondary spermatocytes undergo meiosis 2

Spermatazoa (sperm)

Mature sperm cell

Oogenesis

the production, growth, and maturation of an female egg, or ovum

Primary oocytes

Diploid cells resulting from the activation of anoogoium; primary oocytes are ready to enter meiosis I. remember: cyte means ready to undergo meiosi

secondary oocyte

An oocyte in which the first meiotic division is completed. The second meiotic division usually stops short of completion unless fertilization occurs.

Remains arrested in metaphase 2 unless fertilization occurs.

zona pellucida

A thick, transpartent coating rich in glycoproteins that surrounds an oocyte.

Contain compounds necessary for sperm cell binding.

corona radiata

Outer layer of cells surrounding the oocyte. These cells are secreted by follicle cells.

corpus luteum

Endocrine tissue which produces hormones, estrogen, and progesterone which prepares the uterine lining for receiving an embryo

follicular phase of ovarian cycle

period of follicle growth (days 1-14)

GnRH concentration increases

Increased secretion of FSH and LH

Follicle development

Decreased concentration of estrogen and progesterone

Ovulation occurs

The release of the ovum from the ovary into the andominal cavity

Follicles secrete higher and higher concetrations of estrogen

Positive feedback causing GnRH, LH, and FSH levels to spike

Spike in LH induces ovulation

luteal phase of ovarian cycle

LH causes ruptured follicle to form corpus luteum

Secretion of progesterone: maintains uterine lining for zygote implantation

Progesterone levels rise

Estrogen remains high

High progesterone causes negative feedback to GnRH, LH, and FSH

Menstruation

The shedding of the uterine lining

Occurs if implantaimtion does not occur

Progesterone levels decline

Estrogen levels low