Sex Determination & Gametogenesis Flashcards
initial event that determines whether the gonads will develop as testes or ovaries.
Sex determination
subsequent events that ultimately produce either the male or female phenotype.
Sex differentiation
Responsible for making the gametes
gonads
the formation of gametes
gametogenesis
Sex determination in mammals
Sex Determination: The Jost Paradigm
Chromosomal sex -> Gonadal sex -> Phenotypic sex
*Expanded model
Chromosomal sex -> Gonadal sex -> Hormonal sex -> Phenotypic sex -> Brain/Behavioral sex
Sex-specific reproductive tract system
Primitive female tract = ________
Primitive male tract = ________
Mullerian duct; Wolffian duct
BRAIN SEX DETERMINATION
Chromosomal (Genetics)
Hormonal (Endocrine)
Environmental (Epigenetics)
is the study of heritable phenotype changes that do not involve alterations in the DNA sequence
Epigenetics
Anteroventral periventricular nucleus (AVPV) in mouse brain is longer in (males, females)
Principal nucleus of the bed nucleus of the stria terminals (pBNST) is larger in (males, females)
Sexually dimorphic nucleus (SDN) is larger in (males, females)
females; males; males
Which part of the mouse brain controls sexual behavior
Preoptic area (POA)
Epigenetic mechanisms by which sex differences in the brain are established
Testosterone - Estradiol - Inhibit Dnmt - methyl groups are removed from DNA = Expression of genes necessary for masculinization of the POA and behavior
minus testosterone
Acetylation of histones results in the increased expression of genes necessary for programmed cell death in the female BNST - Constitutive Dnmt activity - Methylation of DNA in the POA = Repression of genes necessary for masculinization of the POA and behavior
means “marriage partners”
gametes
is the process by which sperm and eggs are produced from the germ cells in the gonads (testes and ovaries)
Gametogenesis
Disorders of Sexual Development (DSD)
Turner syndrome
Klinefelter syndrome
GMD
Ovotesticular DSD
different gene expression in males and females
dimorphism
Endocrine Disrupting Effects on Sex of Bisphenol A (BPA)
Feminization of male fetuses
Infertility
Prostate cancer
Menstrual irregularities
Endometriosis
Breast cancer
Sexual differentiation of the human brain is most likely a multifactorial process including both sex chromosome and sex hormone effects, acting in parallel or in combination
gametogenesis in males
Spermatogenesis
Gametogenesis in females
oogenesis
in indifferent gonads, where do testes and ovaries originate?
intermediate mesoderm
In the absence of SRY, _______ form
ovaries
Sex Determination in Placental Mammals
Genital ridge - Bipotential gonad -
Ovary = Follicles - Estrogen = Female genitalia
Testis = Sertoli cells (AMH) & (Leydig cells) Testosterone - DHT = male genitalia
a group of genetic disorders that affect the adrenal glands
Congenital Adrenal Hyperplasia (CAH)
Site of Spermatogenesis
Testis
Functional Organization of Testis
- Seminiferous tubules (spermatogenesis)
- Interstitial compartment (steroidogenesis)
Parts of testis
Ductus deferens
Epididymis
Rete testis
Tunica albuginea
Seminiferous tubules
Septae
Testicular lobes
Site of Oogenesis
Ovary
Parts of female reproductive system
Vagina
Cervix
Uterus
Fallopian tube
Ovary
Endocrine organ in ovary
Corpus luteum
Origin of Primordial Follicles
Germ cell cyst formation in fetal ovary
Mechanisms of germline specification
Preformation (Localized germ plasm)
Induction (No maternal germ plasm)
Life Cycle in Most Animals
(Diplontic) = Main form is diploid
Phases of Gametogenesis
- Migration of germ cells (into the gonads)
- Increase in the number of germ cells
- Reduction in chromosomal material of germ cells (meiosis)
- Differentiation of the sperm and egg
is the chromosomal foundation of reproduction, errors in this important process may lead to aneuploidy and/or infertility.
Meiosis
Meiotic prophase I
- Leptotene = Recondensing
- Zygotene = Synaptonemal complex
- Pachytene = Crossing over/Recombination
- Diplotene = Chiasmata in bivalent; separation of homologues; 1st meiotic arrest (Dictyate arrest)
- Diakinesis = Chromosomes are fully condensed
Type A vs. Type B spermatogonia
Type A undergoes mitosis to produce type B spermatogonia
Type B undergoes meiosis to produce primary spermatocytes
Development of the mammalian ovarian follicle. Follicles, consisting of somatic cells (blue) surrounding an oocyte (yellow), grow within the ovary. Oocytes within the smallest (primary and preantral) follicles are meiotically incompetent and will not mature spontaneously
Early antral with FSH -> Preovulatory = meiotically competent
sequence of post-meiotic changes by which spermatids are transformed into spermatozoa
Spermiogenesis
Phases of spermiogenesis
Spermatid
Golgi phase
Acrosomal phase
Early maturation phase
Mid-maturation phase
Parts of spermatozoa
Head
Neck
Middle piece
Principal piece
End piece
Formation of acrosome in developing spermatids as seen under EM.
- Appearance of a proacrosomal granule in an acrosomal vesicle
- Enlargement of the acrosomal vesicle and its adherence to the pole of the nucleus.
- Spreading of the acrosomal vesicle over the anterior hemisphere of the nucleus to form an acrosomal cap
is a technology that creates gametes outside the body (in vitro) from somatic (non‐reproductive) cells, stem cells or progenitor cells
In Vitro Gametogenesis (IVG)
Haplodiplontic life cycle in plants.
Sex Determining Pathways in Land Plants:
- Environmental determination of sex in the homosporous fern
Exogenous cue: + Antheridiogen = male
- Chromosomal determination of sex in persimmons
- Sex determination in monoecious melons
Endogenous cue: Ethylene Off = male
GAMETOGENESISa : PLANTS
Lack of pre-determined germ line, instead, possess reproductive meristem
Gametes are formed by meiosis followed by mitosis and differentiation
Function of synergids
Will become the endosperm
Gamete Formation in Arabidopsis
Meiosis first before mitosis
