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113 Cards in this Set
- Front
- Back
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FUNCTIONS OF REPRODUCTIVE SYSTEM
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Aside from producing offspring:
1. Initiate and maintain internal conditions needed for the production of gametes. 2. Promote secondary sexual characteristics 3. Facilitate joining of the gametes 4. Provide for early development and care of offsprings |
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Atresia
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* is the degeneration of primordial follicles
* ovaries have about 2 million primordial follicles at birth (each containing primary oocyte) * Histology of the follicle: simple squamous * By puberty, the number of follicles dropped to 400,000 |
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Oogenesis Process
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* Primary oocytes remain in suspended development until puberty
* At puberty: --rising FSH triggers start of ovarian cycle * Each month thereafter: --some primary oocytes are stimulated o develop further |
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Oogenesis---2 characteristics of Meiosis
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1. Cytoplasm of primary oocyte divides unevenly:
--producing 1 ovum (with original cytoplasm) --2 or 3 polar bodies (that disintegrate) 2. Ovary releases secondary oocyte (not the mature ovum): --suspended in metaphase of meiosis II --meiosis is completed upon fertilization |
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The Ovarian Cycle
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Starting from primordial follicles in egg nest
1. Formation of primary follicles 2. Formation of secondary follicle 3. Formation of tertiary follicle 4. Ovulation: part of ovary burst and release secondary oocyte with corona radiata 5. Formation of corpus luteum 6. Formation of corpus albicans |
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The Uterine Cycle
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* also called menstrual cycle
* is a repeating series of changes in endometrium * Last from 21 to 35 days (average cycle lasts 28 days) |
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Phases of Uterine Cycle
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1. Menses
2. Proliferative phase 3. Secretory phase |
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The Uterine Cycle
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* responds to hormones of ovarian cycle
* Menses and proliferative phase: --Occur during ovarian follicular phase * Secretory Phase: -- Occurs during ovarian luteal phase |
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Ovulation Steps
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1. High levels of estrogens from almost mature follicle stimulate release of more GnRH and LH
2. GnRH promotes release of FSH and more LH 3. LH Surge brings about ovulation |
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The Vagina
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* is an elastic, muscular tube
* extends between cervix and vestibule * between 7.5 to 9cm long * Highly distensable |
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Histology of vagina
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* Stratified squamous epithelium (non-keratinized)
* Smooth muscle * Blood vessels |
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Hormonal Control of Female Reproductive Cycle
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* involves secretions of pituitary gland and donads
* forms a complex pattern that coordinates ovarian and uterine cycles The Circulating Hormones: -- control female reproductive cycle -- coordinate ovulation and uterus preparation |
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GnRH
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* GnRH from hypothalamus:
--regulates reproductive function * GnRH pulse frequency and amplitude: -- change over course of ovarian cycle -- are controlled by estrogen (increase pulse frequency) and progestins (decrease pulse frequency) |
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The Endocrine Cells
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* of anterior pituitary gland
* each group of endocrine cells: -- responds to different GnRH pulse frequency -- is sensitive to some frequencies, insensitive to others |
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Follicular Development
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* Begins with FSH stimulation
* Monthly: --some primordial follicles develop into primary follicles * As follicles enlarge: --thecal cells produce androstenedione |
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Androstenedione
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* is a steroid hormone
* is an intermediate in synthesis of estrogens and androgens * is absorbed by granulosa cells: -- and converted to estrogens |
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Interstitial Cells
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* scattered throughout ovarian stroma
* also secrete small amounts of estrogens |
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Circulating Estrogens
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* are bound primarily to albumins:
-- lesser amounts carried by gonadal steroid binding globulin (GBG) |
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3 Circulating Estrogens
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1. Estradiol
2. Estrone 3. Estriol |
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Estradiol
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* is most abundant
* has most pronounced effects on target tissues * is dominant hormone prior to ovulation |
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Estrogen Synthesis
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* Androstenedione is converted to testosterone
* Enzyme aromatase converts testosterone to estradiol * Estrone and estriol are synthesized from androstenedione |
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5 Functions of Estrogen
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1. Stimulates bone and muscle growth
2. Maintains female secondary sex characteristics: --body hair distribution --adipose tissue deposits 3. Affects CNS activity (especially in hypothalamus, where estrogens increase sexual drive) 4. Maintains functional accessory reproductive glands and organs 5. Initiates repairs and growths of endometrium |
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Gamete Production
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* the primary function of the gonads is to produce ''gametes''
* in species with sexual reproduction gametes are special cells that carry half of genetic material (chromosomes) of their parents * this occurs through the 2 steps process of meiosis, a special type of cell division |
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Spermiogenesis
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* is the last step of spermatogonosis
* each spermatid matures into 1 spermatozoon (sperm) --attached to cytoplasm of sustentacular cells |
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Spermiation
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* at spermiation, a spermatozoon:
-- losses attachment to sustentacular cell -- enters the lumen of seminiferous tubule * spermatogonial division to spermiation: --takes about 9 weeks |
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Sustentacular Cells
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* Aka: Sertolli cells
* Affect: --mitosis --meiosis --spermiogenesis in seminiferous tubules |
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6 Major Functions of Sustentacular cells:
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1. Maintain blood-testis barrier
2. Support meiosis and mitosis 3. Support spermiogenesis 4. Secrete inhibin 5. Secrete androgen-binding protein 6. Secrete Mullerian-inhibiting factor |
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Maintenance of Blood-Testis Barrier
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* Blood-testes barrier:
--isolates seminiferous tubules * Sustentacular cells: --joined by tight juction --divide seminiferous tubule into compartments |
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Seminal Fluid
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* is a mixture of secretions from many glands:
--each with distinctive biochemical characteristics * important glands include: --seminal vesicles --prostate gland --bulbourethral glands (does not contribute to semen) |
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Composition of Vesicular Fluid
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1. High concentrations of fructose
--easily metabolized by spermatozoa 2. Prostaglandins: --stimulate smooth muscle contractions (male and female) 3. Fibrinogen: --forms temporary clot in vagina |
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Prostatic Fluid
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* is slightly acidic
* forms 20-30% of semen volume * contains antibiotic sminalplasmin * is ejected into prostatic urethra: --by peristalsis of prostate wall |
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Emission (passage of sperm):
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1. occurs under sympathetic ctimulation
2. Peristaltic contractions of ampulla: -- push fluid and spermatozoa into prostatic urethra 3. Seminal vesicles contract: -- increasing in force and duration 4. Peristaltic contractions in prostate gland: --moves seminal mixture into urethra 5. Sympathetic contraction of urinary bladder and internal urethral sphincter |
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Ejaculation
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* occurs as powerful rythmic contractions:
--in ischioavernosus and bulbospongiosus muscles --that stiffens penis --push semen out toward external urethral opening * caused by pleasurable sensations * followed by subsidence of erectile tissue (detumescence) |
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Impotence
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also called male sexual dysfunction:
-- is an inability to achieve or maintain an erection -- caused by physical or psychological factors (prostate/ testicular cancer or cardio vascular issues) |
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Female Sexual Arousal:
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1. Parasympathetic activation leads to engorgement of erectile tissues
--increased secretion of cervical mucous and greater vestubular glands * Blood vessels in vaginal walls fill with blood (become more sensitive) * Fluid moves from underlying connective tissues to vaginal surfaces |
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Female orgasm
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* Is accompanied by:
-- peristaltic contractions of uterine and vaginal walls -- rhythmic contractions of bulbospongiosus and ischiocavernosus muscles (sympathetic) |
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Clinical Male:
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1. Testicular Cancer:
*most frequent in 20-35 y.o. males * about 1 to 20,000 - can metastasize systemically, spreading to lungs and brain * 95% arise from seminiferous tubules (not the leydig cells) |
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Prostate Disorders
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1. Prostate Cancer
* slow developing, not metastastic * leading cause of cancer death in US males * PSA (Prostate Specific Antigen) test is used to screen 2. Prostatitis * inflammation of prostate * Acute: prostate becomes swollen and tender * Chronic: enlarged prostate * Cause urination problems and sexual dysfuntion * lead to erectile dysfunction |
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Clinical Female: cancers
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1. Breast Cancer
* genetic links * early detection is essential * increases with hormone replacement therapy, radiation exposure, excessive alcohol consumption, having no children /giving birth after 35 y.o, smoking and age * preferred treatment is surgery often followed by chemo or radiation |
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Ovarian Cancer
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* 6th most common form of cancer in women
* difficult to detect, mestastasize * many of the same risk factors as breast cancer in addition to dietary fibers (high fat, low fiber and vit.A) |
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Cervical Cancer
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* Often associated with Human Papilloma Virus (HPV), which also causes genital warts
* usually does not metastasize as rapidly as other cancers |
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Sexually Transmitted Diseases (STDs)
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* Pelvic Inflammatory Disease (PID)
* Chlamydia * Gonorrhea * Syphilis * Herpes * Genital Warts * Chancroid * AIDS ** Are transferred by sexual intercourse (oral/vaginal) ** Include bacterial, viral and fungal infection |
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Chlamydia
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-- most common STD in US
-- caused by bacteria -- leads to painful urination/ intercourse and is the leading cause for PID in women -- increases risk of ectopic pregnancy and may lead to infertility (in men and women) -- easily treated with tetracycline -- incubation period is 1 week |
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Gonorrhea
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-- caused by bacteria (Neisseria gonorrhea
-- mucus discharge from urethra (in male) or vagina (female) -- painful urination in males, uterine bleeding and possible PID in females -- treatment with antibiotics -- fairly common, especially in young adults (teens) |
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Syphilis
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-- caused by Treponema pallidum (a spirochete bacterium)
--Progresses in 3 stages: 1. Primary stage: chancre in penis/vulva/cevix. Symptoms disappear in few weeks 2. Secondary: rash, fever, joint, aches, occurs as it spreads systemically. Symptoms show 6-24 wks later. 3. Tertiary: after a latency period of highly viable length (months to years). Symptoms: organ damage accumulates, cardiac/skin/bone and neurological lesions. Can lead to blindness, insanity, and death. |
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Other STDs:
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1. Genital Herpes
-- caused by herpes simplex virus -- no cure yet, only treatments -- it is a retrovirus (studying it led to early breakthroughs in understanding HIV) 2. Genital Warts: -- external form of HPV (Human Papilloma Virus) -- painful and disfiguring 3. Vaginitis: -- can be bacterial, fungal, or protozoan |
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TESTES
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1. Tunica albuginea: dense layer CT
2. Tunica Vaginalis 3. Seminiferous Tubules 4. Rete Testes 5. Lobule 6. Interstitial cells (Leydig cells) 7. Spermatogonic cells 8. Sustentacular cells (Sertoli cells) 9. Gubernaculum testis: --- connective tissue fibers that give rise (direct) to the testes development in male fetus |
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SCROTUM
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1. Raphe: raised thickening scrotal surface
2. Scrotal Cavity: --- separate chambers where testes lay 3. Tunica Vaginalis: -- serous membrane lines scrotal cavity to reduce friction between scrotal and testicular surfaces 4. Cremaster muscle: -- skeletal muscle, causing scrotum to move testes closer to body 5. Dartos muscle: -- smooth muscles, more superficial than cremaster muscle -- elevates testes, causing characteristic wrinkling of scrotal surface |
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SPERMATIC CORD
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* Ductus Deferens and :
1. Blood vessels of the spermatic cords: -- deferential artery -- testicular artery -- pampiniform plexus of testicular vein --genitofemoral nerve from lumbar plexus provide innervation |
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EPIDIDYMIS
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* the beginning of the male reproductive tract
* almost solid lumen, almost like cells in the seminiferous tubule without the Sertolli cells * pseudostratified columnar epithelial lining of the epididymis has stereocillia, increasing the surface area for absorption * FUNCTIONS of epididymis: 1. monitors and adjusts the composition of fluid produced by seminiferous tubule 2. recycle old damaged spermatozoa to be released to interstitial cells 3. Stores and protects spermatozoa and facilitates their maturation * spermatozoa leaving epididymis are mature but immobile until they undergo CAPACITATION process (mixed with seminal fluids) |
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DUCTUS DEFERENS
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* begins at the tail of the epididymis
* Pseudostratified columnar epithelium with thick layer of smooth muscles * star-shaped lumen |
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SEMINIFEROUS TUBULE
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* tubules inside the testis
* cells have roundish-shaped lumen (like a cross section of kiwi fruit) * look for interstitial cell (Sertolli) and spermatogenesis stages |
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ACCESSORY GLANDS OF MALE REPRODUCTIVE SYSTEM
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Includes:
* seminal glands * prostate gland * bulbo-urethral glands Functions of these glands: -- activating spermatozoa -- providing the nutrients spermatozoa needed for motility -- propelling spermatozoa and fluids along the reproductive tract (by peristaltic contraction) -- producing buffers that counteract acidity of the urethral and vaginal environments |
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SEMINAL GLANDS (SEMINAL VESICLES)
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* sandwiched between posterior wall of urinary bladder and the rectum
* histology: secretory pockets lined with smooth muscles * Secretions of the seminal glands contain: -- higher concentration of fructose -- Prostaglandins (can stimulate smooth muscle contractions along male and female reproductive tracts) -- Fibrinogen (which after ejaculation, forms temporary clot with the vagina). Secretios of the seminal glands are slightly alkaline (neutralize acids within the vagina) and will assist the capacitation of the spermatozoa. |
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PROSTATE GLAND
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* histology: glandular tissues, with smooth muscles (look similar to bulbourethral gland)
* prostate gland produces prostatic fluid, containing seminalplasmin (antibiotic that help prevent UTI in males), ejected into prostatic urethra via peristaltic contractions of muscular prostate wall. |
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What happens during fertilization
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* Oocyte is only viable for ~24hr.
* Sperm is only viable for 12- 24hr (some super sperm may be viable for up to 72hr) * Therefore, coitus must occur within 24 hour window on either side of ovulation |
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Barriers of Fertilization
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* Low vagina ph
* Sperm getting lost * Numerous defective sperm * Uterine contractions * Phagocytes in the vaginal canal * By the time sperm reaches oocyte, there are only a few dozen to a couple hundreds left. |
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Capacitation
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* Must occur before spermatozoa can fertilize secondary oocyte
-- contact with secretions of seminal vesicles -- exposure to conditions in female reproductive tract |
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What is this thing called?
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* Zygote = the single cell after fusion of the pronuclei of the oocyte and the sperm
* Cenceptus = covers the period of the development following first cleavage and differentiation of cells into embryo * Morula = the conceptus as a solid ball of 16 cells (pre- embryonic ball of cells) * Blastomeres: identical cells produced by cleavage divisions * Blastocyst = a hollow ball of cells formed of blastomeres (from day 4) Hatching occurs at this stage, when the blastocyst emerges from the zona pellucida * Blastocoele = a hollow ball with inner cavity * Trophoblast = outer layer of cells that separates the outside layer from blastocoele (provide nutrients to developing embryo) * Inner cell Mass = second group of cells clustered on one end of blastocyst. * Embryo = lasts about 8 weeks * Fetus = from embryo stage until it is born |
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Development from Zygote to Implantation
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1. Fertilization
(within 12-24hr after ovulation) 2. Cleavage First cleavage completed about 30 hrs after fertilization 3. Morula (~4days after fertilization) 4. Blastocyst (4-5 days after fertilization) 5. Implantation process (about 6 days after fertilization) Implantation - occurs on about day 6 or so, as the blastocyst burrows into the endometrium |
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Fertilization Process
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* Ovulation releases a secondary oocyte and first polar body (both surrounded by corona radiata). Oocyte is suspended in metaphase of meiosis II.
1. Fertilization and oocyte activation 2. Pronucleus formation begins 3. Spindle formation and cleavage preparation 4. Amphimixis occurs and cleavage begins (metaphase on first cleavage division) 5. Cytokineses begins |
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What happens after Implantation?
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After implantation, the BLASTOCYST differentiates into:
* TROPHOBLAST = the outer layer ball of cells that eventually beccomes the PLACENTA and ''extra-embrionic'' membranes * INNER CELL MASS (ICM), which will become the EMBRYO Following events above happens over the course of the second week following the conception |
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Hatching
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= a shedding process of zona pellucida via enzyme released by the trophoblast during blastocyst formation.
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4 General process of the first trimester
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1. CLEAVAGE
= a sequence of cell divisions that begins immediately after fertilization. Zygote becomes pre-embryo, then develops into multicellular complex (blastocyst). Cleavage ends when blastocyst touches the uterine wall 2. IMPLANTATION begins with the attachment of blastocyst to endometrium of uterus. Blastocyst invades maternal tssues. 3. PLACENTATION occurs as b.vessels form around blastocyst until placenta develops Placenta = complex organ that permits exchange between maternal and embryonic circulatory system 4. EMBRYOGENESIS = the formation of viable embryo (establish foundations for all major organ system) |
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Formation of Amniotic Cavity
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* ICM separated from trophoblast, creating a fluid-filled chamber called Amniotic Cavity (day 10-12)
*Trophoblast will separate from amniotic cavity by layers of cells originated in ICM and line the amniotic cavity (this layers form AMNION) * When amniotic cavity appears, 2 layers forms from ICM: the superficial layer faces amniotic cavity (becomes ectoderm during gastrulation), and the deep layer facing the fluid contents of blastocoele (will be endoderm) |
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GASTRULATION
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= creation of 3 distinct germination layers
* cells in specific areas of the surface move toward the central line forming the ''primitive streak'', which will create 3 embryonic layers: 1. Ectoderm: superficial cells that did not migrate towards interior of ICM 2. Mesoderm: sandwiched between ectoderm and endoderm 3. Endoderm: cells that face the blastocoele Gastrulation also produces an oval, 3-layered sheet (embryonic disc) that will form the body of embryo, the rest of the blastocyst will form the extraembrionic membranes |
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Extra Embryonic Membranes
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1. Yolk Sac (endoderm and mesoderm) - site of blood cell formation
2. Amnion (ectoderm and mesoderm) - including amniotic cavity 3. Allantois (endoderm and mesoderm), later gives rise to urinary bladder 4. Chorion (mesoderm and trophoblast) * somites: cells that give rise to muscular and skeletal systems |
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Ectopic Pregnancy
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* Implantation occurs other than in the uterus (ie: in the fallopian tube)
* does not produce viable pregnancy * can be life threatening |
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All the Deciduas Layers
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1. Decidua Basalis
-- disc shaped area in the deepest portion of endometrium -- where placental functions concentrated 2. Decidua Capsularis -- thin portion of endometrium -- no longer participates in nutrient exchange and chorionic villi in the region dissapear 3. Decidua Parietalis -- the rest of the uterine endometrium -- has no contact with the chorion |
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Hormones in the Placenta
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* Synthesized by syncyntial trophoblast, released into the maternal bloodstream
-- human chorionic gonadotropin -- human placental lactogen -- placental prolactin -- relaxin -- pregesterone -- estrogens |
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Human Placental Lactogen (HPL)
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* helps prepare mammary glands for milk production
* stimulatory effect on other tissues comparable to growth hormone (GH) |
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Placental Prolactin
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* Helps covert mammary glands to active status
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Relaxin
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* is a peptide hormone
* is secreted by placenta and corpus luteum during pregnancy * increases flexibility of pubic symphysis, permitting pelvis to expand during delivery causes dilation of cervix * suppresses release of oxytocin by hypothalamus and delays labor contractions |
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Embryogenesis and Organogenesis
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Embryogenesis:
* body of embryo begins to separate from embryonic disc * body of embryo and internal organs start to form * folding, differential growth of embryonic disc produce bulge that projects into amniotic cavity (projections are head fold and tail fold) Organogenesis: * process of organ formation |
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Second Trimester
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* Fetus grow faster than surrounding placenta
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Third Trimester
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* most of organ systems become ready
* growth rate starts to slow * largest weight gain * fetus and enlarged uterus displace mother's many abdominal organs |
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PROGESTERONE
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* Released by the placenta
* Has inhibitory effect on uterine smooth muscle * prevents extensive, powerful contractions |
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Opposition to Progesterone
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3 Major Factors:
- rising estrogen levels - rising oxytocin levels - prostaglandin production |
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False Labor vs True Labor
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false Labor:
-- occasional spasms in uterine musculature -- contractions not regular/ persistent True Labor: --Results from biochemical and mechanical factors --Continues due to positive feedback loop |
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Hormone Levels Throughout Pregnancy
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-- Fertilization spiked up the human Chorionic Gonadotropin hormon (hGC)
-- hGC level peaks at 12 weeks, then decline until 32 wks. -- Progesterone and estrogen hormones levels go up all the way till birth (at the same levels at wk24-25) |
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Contractions
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* begins near the top of the uterus, sweep in wave towards cervix
* strong, occurs at regular intervals, increase in force and frequency * fetus change position, move toward cervical canal |
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Stage of Labor
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1. Dilation stage (of cervix)
2. Expulsion Stage (pushing/ hard labor) 3. Placental Stage (delivery of placenta) |
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Dilation stage
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-- begins with onset of true labor
-- cervix dilates -- fetus begins to shift towards cervical canal -- highly variable in duration (typically over 8hrs) -- frequency of contractions steadily increasing -- amnio-chorionic membrane ruptures (water breaks) |
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Expulsion Stage
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-- begins as cervix completes dilation
-- contractions reach maximum intensity -- continues until fetus has emerged from vagina (typically in less than 2 hours after dilation-- longer than 2 hours might increase risk of complication) |
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Delivery
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-- arrival of the newborn infant into outside world
EPISIOTOMY = --incision through perineal musculature --needed if vaginal canal is too small for fetus to pass --repaired with sutures after delivery |
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Cesarean Section
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-- removal of infant by incision made through the abdominal wall
-- opens uterus enough to pass infant's head -- needed if complications arise during dilation/expulsion stages |
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Placental Stage
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-- muscle tension builds in walls of partially empty uterus
-- tears connections between endometrium and placenta -- ends within hour of delivery with the ejection of placenta after birth -- accompanied by loss of blood |
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Premature Labor
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-- when true labor begins before fetus has completed normal development
-- newborn's chances of survival directly related to body weight at delivery |
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Immature Delivery
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-- refers to fetuses born at 25-27 wks of gestation
-- most die despite of intensive neonatal care -- survivors have high risk of developmental abnormalities |
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Premature Delivery
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-- refers to birth at 28-36 weeks
-- newborns have good chance of surviving and developing normally |
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Forceps Delivery
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-- needed when fetus faces mother's pubis instead of sacrum
-- risk of infant and mother are reduced using forceps (resembles large, curved salad tongs and are used to grasp fetus' head) |
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Breech Birth
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-- legs/ buttocks of fetus enter vaginal canal first instead of head
-- umbilical cord can become constricted, cutting off placental blood flow -- cervix may not dilate enough to pass head -- prolongs delivery -- subjects fetus to severe distress and potential injury |
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5 Life Stages
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1. Neonatal (from birth - 1 month)
2. Infancy (1 month-2 years of age) 3. Childhood (2 years to adolescence) 4. Adolescence (period of sexual and physical maturation) 5. Maturity |
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Colostrum
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-- secretion of mammary glands
-- ingested by infants during frst 2-3 days -- contains more proteins and less fat than breast milk (many proteins are antibodies that help ward off infections until immune system is functional -- mucins present inhibit replication of rotaviruses -- as production drops, mammary glands convert to milk production |
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Milk Let Down reflex
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-- mammary gland secretion triggered when infant sucks on nipple
-- continues to function until weaning (1-2 years) |
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Benefits of Breast Feeding
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1. Acquired immune defenses:
-- neutrophils, macrophages, Tcells and Bcells -- Immunoglobulin A (IgA) 2. Reduced incidence of later disease in child -- lymphoma, heart disease, GI disorders, diabetes mellitus and meningitis 3. For mother: -- reduced incidence of osteoporosis and breast cancer -- stronger bonding, less post-partum depression -- more rapid weight loss, uterine recovery |
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Genetic Vocabularies
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* Genetics = study of inheritance
* Autosome = the 22 pairs of chromosomes in the body, that do not determine genetic sex * Sex chromosome = the 23rd pair (X and Y) * Karyotype = the diploid chromosomes displayed in their condensed form and paired as homologs * Allleles = a matched pair of 2 genes, coding for the same trait or alternate form of a particular trait (found at the same location/locus on homologous chromosomes) * Homozygous = having the same alleles for a trait * Heterozygous = having different alleles for the same trait * Allele pairs are expressed as a pair of letters representing the trait Heterozygote for height would be Tt (t=recessive) Homozygot tall would be TT (dominant * Dominant = an allele that expresses itself and masks its partner * Recessive = reverse of the dominant * Genotype = the actual alleles an organism has (ie: for the heterozygote plant, would be Tt) * Phenotype: the alleles expressed * Penetrance: % of individuals with particular genotype that shows the ''expected phenotype'' * expressivity: exten to which particular allele is expressed * teratogens: factors that result in abnormal development (environment factor that damage the genes, like radiation/poison) * suppression: when 1 gene suppresses the other and the second gene has no effect on phenotype |
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Violation of Mendel's Law
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Mendel law is valid if:
-- there is random fertilization -- alleles are located on separate chromosomes -- alleles have simple dominant/recessive relationship -- there are only alleles for that trait -- the alleles are not lethal to the zygote |
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Complementary Gene Action
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-- dominant alleles on 2 genes interact to produce a phenotype different from when 1 gene contains recessive alleles
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Sources of individual Variation
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* during meiosis, maternal and paternal chromosomes are randomly distributed
* each gamete has unique combination of maternal and paternal chromosomes |
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Genetic Recombination
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* During meiosis, various changes can occur in chromosome structure, producing gametes with chromosomes that differ from those of each parent
* Greatly increases range of possible variation among gametes * Can complicate tracing of inheritance of genetic disorders |
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Crossing Over
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-- when parts of chromosomes become rearranged during synapsis
-- when tetrads form, adjacent chromatids may overlap |
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Translocation
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-- reshuffling process
-- chromatids may break, overlapping segments trade places |
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Genome Imprinting
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-- during recombination, portions of chromosomes may break away and be deleted
-- effects depend on whether abnormal gamete is produced through oogenesis or spermatogenesis |
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Chromosomal Abnormalities
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-- damaged, broken, missing, or extra copies of chromosomes
-- few survive to full term -- produce variety of serious clinical conditions |
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Mutation
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= changes in nucleotide sequence of allele.
Spontaneous Mutations = -- results in random errors in DNA replication -- errors relatively common, but in most cases error is detected and repaired by enzymes in nucleus -- errors that go undetected and unrepaired have potential to change phenotype -- can produce gametes that contain abnormal alleles (then become inherited) |
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Human Genome Project and Karyotyping
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Human Genome Project =
* goal is to transcrobed entire human genome * has mapped more than 38,000 genes Karyotyping = determination of individual's complete chromosomal complement |
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Types of Inheritance
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* Incomplete Dominance = a dominant allele does not completely mask the recessive
(red + white flowers = pink flowers) * Codominance = when both traits are expressed together (red+white flowers = stripes) * Multiple alleles = when more than one allele for a trait (ie: ABO blood group) * Polygene = several alleles interact to produce a trait. Results are continuous/ quantitative phenotype (ie: skin color) * Carriers = individuals who are heterozygous for an abnormal allele but do not show effects of mutation (ie: color-blindness or hemophilia genes) |
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Codominance of Multiple alleles
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* Parents are A+A =kids are A,O, Parents B+B = kids are B,O
* Parents are A+B = kids are A,B, AB or O * Parents are A+AB = kids are A, B, AB * Parents are A+O= kids are A, O * Parents are B+AB= kids are A,B, AB * Parents are B+O= kids are B,O * Parents are AB+AB= kids are A,B,AB * Parents are AB+O = kids are A, B * Parents are O+O= kids are O |
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Sex-Linked Inheretance
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* males only have 1 X chromosome. Therefore, if a trait is found only on the X it will be expressed in a male regardless its dominance/ recessive.
* X inactivation occurs in females. Every normal female has 2Xs but only they only need 1X, the other X is turned off (forming a Barr body) * Because X-inactivation is random in most cases, it leads to a fine mosaic in females |
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Environmental influences
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Phenocopy - developmental influences impact genetic expression in ways that appear to be genetic but are not inheritable
temperature, nutrition, non-genetic pathologies can have impacts that are expressed in ways that appear genetic |
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Genetic Defects
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* Aneuploidy = a defective set of genes
* Triploidy = an extra set of chromosomes * Trisomy = an extra single chromosome * Monosomy = a missing homolog * Trisomy of the 23rd chromosome = -- XXX = Super Female -- XXY = Kleinfelter's syndrome * Trisomy of the 21st chromosome = Down's Syndrome * Turner's syndrome = monosomy of the 23rd chromosome |
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Screening for genetic disorder
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* Amniocentesis
* Chorionic villi sampling |
