HG 5 Development and Sex Determination Flashcards

Vocabulary flashcards based on lecture notes about development and sex determination.

Gamete

Unfertilized sex cell

Gonads

Organs which produce gametes (testes and ovaries)

Oocyte

Immature egg cell

Spermatocyte

Immature sperm cell

Zygote

Fertilized egg

Testes

Organ producing sperm

Scrotum

External pouch containing the testes

Spermatogenesis

Begins in the testes in the seminiferous tubules; spermatocytes divide to form sperm

Spermiogenesis

Process of maturation changing spermatid to spermatozoa

Epididymis

Sperm move via peristalsis

Seminal vesicles

Adds fructose and prostaglandins

Prostate gland

Adds neutralizers and aids motility

Bulbourethral gland

Makes pre-ejaculate for lubrication and to neutralize any urine

Ovaries

Organs producing eggs (oocytes)

Fallopian tube

Connects ovary to uterus

Uterus

Nourishes fertilized embryo

Cervix

Lower neck of uterus

Vagina

External opening and birth canal

Oogenesis

Primary oocytes undergo meiosis to form one egg and 2-3 polar bodies. Cell division is uneven

Fertilization

Fusion of oocyte and sperm

Zona pellucida

Assists in oocyte development and fertilization, allowing only one sperm in. Also assists in preventing premature implantation in the fallopian tube – ectopic pregnancy

Mitosis

Mitosis begins before the zygote reaches the uterus

Blastocyst

At about day 5 the zygote becomes a blastocyst

Trophoblast

Outer cells that assist in implantation and develop membranes to protect the embryo.

Chorion

Releases enzymes to assist in implantation; Chorion partly forms from the trophoblast and releases hCG (Human Chorionic Gonadotropin) to maintain the corpus luteum

Chorionic villi

Finger-like projections which extend into the uterine wall

Ectoderm

Skin and nervous system

Mesoderm

Connective tissues and muscles

Endoderm

Internal linings

Teratogens

Environmental agent that can produce foetal abnormalities

Foetal Alcohol Spectrum Disorders (FASD)

Leading preventable cause of birth defects; Miscarriage, growth and mental retardation, facial abnormalities, learning disabilities

Foetal Alcohol Syndrome (FAS)

Chronic constipation, irritable cry, weak sucking reflex, susceptible to illness

Sexual Development

Male and females identical until about week 9 of gestation

SRY gene

The SRY gene expressed (sex-determining region of the Y chromosome)

Testosterone

Turns on a cascade of other genes; Gonads develop into testes and secrete 2 hormones; Testosterone stimulates Wolf an ducts

Anti-Müllerian Hormone (AMH)

Breaks down Mullerian ducts

Dihydrotestosterone (DHT)

Converts to dihydrotestosterone (DHT)

Recombination Errors

Irregular recombination during Prophase II can cause SRY gene to be transferred to the X chromosome; Results in infertile XX males

Gene Mutations – Androgen Insensitivity

Deletion or mutation of Androgen Receptor on X chromosome results in Androgen Insensitivity; Genetic males but phenotypic females

Gene Mutations – Pseudohermaphroditism

XY individuals that have both male and female structures at different times in their lives

Intersex Variations

Innate sexual characteristics that don’t fit medical and social norms for male or female bodies

X Chromosome Dosage Compensation

One X chromosome is switched off; Forms a Barr body, remaining tightly packed

X Chromosome Inactivation

Begins when the zygote is about 32 cells; X Inactivation Centre (Xic) on the X chromosome

Sex-Influenced Traits

Expressed in both sexes, but differently in each

Sex-Limited Traits

Inherited by both sexes, but expressed in only one

Imprinted Genes

Genes whose expression is determined by the parent that contributed them