Chapter 20 : Chapter 20 Reproduction
Lecture map : Lecture map Genetics
Development of sex organs
Endocrine regulation
Female reproductive structures
Male reproductive structures
Lecture map : Lecture map Lecture two:
Cycles
Sexual responses
Contraception
Fertilization
Pregnancy
Development
Parturition
Lactation
Slide4 :
Genetics
Genetics : Genetics Gregor Mendel
Worked with sweet pea
Figured all this out without knowing about cells, DNA, chromosomes, evolution!
Was unappreciated by peers: too much math!
Darwin ALMOST saw his paper…!
Genetics : Genetics Alleles—Different versions of a gene
“Flower color” is a gene;
“Purple” is one flower-color allele
“White” is another flower-color allele
A trait coded by one gene can have many alleles.
Genetics : Genetics Homozygous—both alleles same
Heterozygous— two different alleles
Genetics : Genetics Dominant— allele that is seen in phenotype of heterozygote.
Recessive—allele that is masked in heterozygote.
Incomplete dominance—heterozygote displays intermediate trait
Genetics : Genetics Often use initial letter of dominant allele
Capital letter represents dominant
Lower case of same letter represents recessive
If “purple” flower is dominant to “white”
“P” represents allele for purple
“p” represents allele for white
Genetics : Genetics Phenotype: what one can observe.
Purple flowers
White flowers
Genotype: what the genes are.
White flowers / White flowers
White flowers / Purple flowers
Purple flowers / Purple flowers
Genetics : Genetics Genotypes
PP = homozygous
Pp or pP = heterozygous
pp = homozygous
Phenotype which results from genotype:
PP = purple flower
Pp = purple flower
pP = purple flower
pp = white flower
Genetics : Genetics If you know the phenotype, do you know the genotype?
If you know the genotype, do you know the phenotype?
Genetics : Genetics Geneticist Reginald Punnett
Punnett squares
list only genes of interest
List sperm genotypes across top
List egg genotypes down side
Fill in boxes with zygote genotypes
Slide14 : P p Genetics Eggs of Heterozygous Plant Pollen of Heterozygous Plant P p p P P p P P p p
Slide15 : P p Genetics Eggs of Heterozygous Plant Pollen of Heterozygous Plant P p p P P p P P p p
Genetics : Genetics P p Eggs of Heterozygous Plant Pollen of Heterozygous Plant P p p P P p P P p p
Slide17 : Dihybrid Cross: SsYy X SsYy SY Sy sY sy SsYy Parent
Self-fertilizes 1 4 1 4 1 4 1 4 SY Sy sY sy 1 4 1 4 1 4 1 4 Eggs Sperm 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 1 16 SSYY SSYy SsYY SsYy SSyY SSyy SsyY Ssyy sSYY sSYy ssYY ssYy sSyY sSyy ssyY ssyy
Slide18 : AB Ab aB ab AB Ab aB ab Eye Color EGGS SPERM Mother AaBb Father AaBb AABB AABb AaBB AaBb black dark brown dark brown light brown
Slide19 : LINKAGE
If two genes are located close to each other on a chromosome, it is likely that they will sort together during meiosis and their traits will appear linked.
If the locus of two genes is far apart, they have a greater chance of sorting independantly during recombination in meiosis.
This is a powerful genetic tool. It helps “find” genes, such as one of the breast cancer genes.
Genetics
Slide20 : How to Read Pedigrees = male = female = parents or = individual who shows the trait or = heterozygous carrier of trait = offspring 1 2 3 I, II, III, IV, or V = generation
Slide21 : A Recessive (inbred!) Pedigree
Genetics : Genetics Hybrid vigor
Gender : Gender Each human:
22 autosomes
2 sex chromosomes
gender of zygote determined by fertilizing sperm.
Gender : Gender
Slide25 : Gender
Slide26 : Gender Sex-linked traits:
men have only one X
even a recessive trait on X will be expressed more often
shows up in men, transmitted through mother
e.g.: baldness, color-blindness
Slide27 : Imprinting- which parent donated the chromosome affects expression of a gene!
sheep with “golden rear end”
Epigenetics- chromosome shape
http://www.sciencemag.org/feature/plus/sfg/resources/res_epigenetics.shtml
Genetics
Slide28 :
Development
Development : Development Gonads
Testis-determining factor (TDF)
from SRY gene on Y chromosome
A) “default” -> ovaries
B) if TDF -> testes
Testes earlier in dev.; ovaries later
Note: estrogen filled environment!
Development : Development Accessory sex organs
A) mullerian ducts -> uterus, fallopian tubes
B) leydig cells of testis -> testosterone (first trimester) -> wolffian ducts -> accessory sex organs (epididymis, vas deferens, seminal vesicles, ejaculatory duct)
sertoli cells of testis -> MIF (müllerian inhibition factor) -> degenerate mullerian ducts
Development : Development
External genitalia
Various (urethral fold, labioscrotal swelling) ->
A) -> vagina, labia, clitoris
B) if testosterone -> penis, prostate, scrotum
Development : Development
Rare, unusual development : Rare, unusual development Hermaphroditism:
Both ovarian and testicular tissue is present in the body.
Pseudohermaphrodite:
Individual with either testes or ovaries and mixed sex characteristics
(from a little later in development)
Continued development : Continued development Puberty:
more GnRH from hypothalamus
less sensitivity to negative feedback of testosterone and estradiol
-> more FSH and LH during sleep
-> more testosterone or estradiol
-> secondary sex characteristics (menarche, growth then sealing of bones, etc.)
Continued development : Continued development Onset of puberty:
exercise, body fat
Leptin from adipocytes?
(also a satiety factor!)
females: generally earlier
melatonin from pineal gland?
Further development : Further development Menopause:
cessation of menses
Only estrogen is estrone from adipose tissue
(from DHEA, etc. from adrenal cortex)
osteoporosis, cardiovascular, hot flashes, vaginal lubrication
HRT (hormone replacement therapy)?!
Further development : Further development Andropause?
Gradual decrease of testosterone, but not GnRH.
Note: males have ~ constant levels of LH and FSH as adults.
Slide38 :
Endocrine regulation
Endocrine Regulation : Endocrine Regulation GnRH (gonadotropin releasing hormone)
from hypothalamus
Gonadotropins:
LH (luteinizing hormone).
FSH (follicle-stimulating hormone).
from anterior pituitary
Secreted in pulsatile fashion to prevent desensitization and down regulation of receptors.
Endocrine Regulation : Endocrine Regulation In womyn:
Menstrual cycle!
In men:
FSH -> Sertoli cells -> spermatogenesis
LH -> Leydig cells -> testosterone
Maintenance of gonadal structure.
Endocrine Regulation : Endocrine Regulation Negative feedback:
-l secretion of GnRH.
-l secretion of FSH, LH.
Female: Estrogen and progesterone.
Male: Testosterone.
Also: inhibin from both genders -l FSH
Slide42 :
Female Reproductive Structures
Female Reproductive Structures : Female Reproductive Structures
VULVA!!!
Labia majora
Labia minora
Clitoris
Female Reproductive Structures : Female Reproductive Structures Vagina:
Cervix
Uterus:
Perimetrium:
Outer layer of connective tissue.
Myometrium:
Smooth muscle layer.
Endometrium:
Inner layer of (stratified, squamous, nonkeratinized) epithelium.
Shed during menstruation.
Female Reproductive Structures : Female Reproductive Structures
Fallopian (uterine) tubes:
Ova drawn into the tubes by cilia and possible movement of fallopian tubes.
Ovaries:
large number of follicles which enclose ova.
Female Reproductive Structures : Female Reproductive Structures
Female Reproductive Structures : Female Reproductive Structures
Womyn’s health : Womyn’s health Pap smears (cervical cancer)
Endometriosis
Cysts
Menopause, HRT
Slide49 :
Male Reproductive System
Testosterone : Testosterone Testosterone: 5a reductase -> DHT (dihydrotestosterone)
DHT is active form in most cells
Testosterone may directly affect wolffian duct derivatives (epididymis, vas deferense, ejactulatory duct, seminal vesicles)
DHT -> 3a diol, 3b diol
Slide51 : Testosterone Insert fig. 20.14
Testosterone : Testosterone DHT: aromatase in brain-> estradiol 17b -l LH
Sertoli and Leydig cells also secrete estradiol.
Possible roles:
negative feedback in brain.
sealing of bones.
spermatogenesis.
Note: no aromatase -> infertility
Testes : Testes Leydig cells also secrete b-endorphin, ACTH, MSH…?!
Also paracrine growth factors.
Testes : Testes Testes:
Seminiferous tubules:
Sertoli cells.
spermatogenesis
Leydig cells:
testosterone.
Insert fig. 20.12
Testes : Testes
Seminiferous tubules of testes:
Spermatogenesis
in concentric circles!
Testes : Testes Insert 20.16
Testes : Testes Spermatogenesis:
Spermatogonia (mitosis) ->
primary spermatocytes ->
meiosis -> secondary spermatocytes ->
spermatids (n, arrested)
Note: arrested at primary spermatocyte stage until puberty.
Testes : Testes Spermiogenesis:
Sertoli cells phagocytose the cytoplasm of spermatids -> spermatozoa (n, still arrested)
Testes : Testes Sertoli cells:
- Form blood-testes barrier:
Prevents autoimmune destruction of sperm which may have new MHC, due to recombination during meiosis!
Produce FAS ligand -> binds to the FAS receptor on T cells -> apoptosis
- Surround, nourish spermatogonia, etc.
- FSH -> Sertoli -> spermatogenesis
- spermiogenesis
Men’s health : Men’s health Prostate cancer:
PSA test
Circumcision
Fertility
lower sperm counts
(environmental causes? Frogs in florida?)
Sperm motility