REPRODUCTIVE
BEHAVIOR
Reproductive Behaviors
Sexually dimorphic behaviors:
Courting
Mating
Parental behaviors
Aggressive behaviors
Behaviors are largely shaped by
hormones during fetal development and
after birth
Sexual Development
An individual’s sex is determined by their inherited chromosomes at ovum fertilization by the father
Humans inherit 23 pairs of chromosomes23rdpair are the sex chromosomesXX and XYY chromosome is responsible for development of glands that produce male sex hormones
Chromosomes
Sex Organs
Gonads – testes and ovaries
Produce ova/ sperm and secrete hormones
Development controlled by Sry gene on Y chromosome
Once developed, hormones continue sexual development via
organizational & activational effects
Internal sex organs
Female – fimbriae, fallopian tubes, uterus, & inner 2/3 of
vagina (together called Müllerian system)
Does not require hormonal signal – develops automatically
Male – epididymis, vas deferens, & seminal vesicles (called
Wolffian system)
Only develops if stimulated by hormones produced by testes
Anti-Müllerian hormone – defeminizes
Androgens – steroid hormones signal Wollfian system development &
masculinize
Testosterone & dihydrotestoserone (converted from testosterone)
Internal Sex Organs
Male Reproductive System
Sex Organs During Fetal
Development
AMH
+Androgens
No AMH
No
Androgens
Internal Sex Organs
Genetic Disorders of Internal
Sex Organs
Androgen insensitivity disorder – insensitive
to androgens
Due to genetic mutation on X-chromosome
Prevents formation of androgen receptors
Develop female external genitalia without
corresponding internal sex organs → XY woman
Persistent Müllerian duct syndrome
Due to failure in production of anti-Müllerian
hormone or absence of hormone receptors
In genetic males, masculinization occurs via
androgens, but no de-feminization
Individual has male & female sex organs
Genetic Disorders of Internal
Sex Organs
Turner’s syndrome
A genetic disorder due to loss of X chromosomal
material that affects females primarily
Associated with Dr. Henry Turner who described
several cases in 1938
Characterized by abnormal physical features and
cognitive, social, and behavioral deficits
Prevalence 1: 2500
Heterogeneous disorder
Ranges from mild to severe
Develop into females with corresponding internal
and external characteristics
Lack gonads – no ovaries
Form of TS
Karyotype
Frequency (%)
Description
Monosomy X
Only 1 X Chromosome
45, X
45 – 50
2/3 maternally
derived; occurs
during meiosis
before fertilization
Mosaicism
45, X/ 46, XX or
45, X/ 46, XY,
47, XXX
30
Occurs early in
mitotic cell
division; almost all
are female
Isochromosome
2 short X arms or 2
long arms (arms are
identical)
46, isoXᵐ or 46,
isoXᵖ
10
Occurs during
anaphase when
chromosome
strand divides
transverse
direction, not
axially
Deletions,
rearrangements,
and
translocations
10
Abnormality during
meiotic division
Ring X
Centromere region of X
missing
→
ring
formation
2 - 5
Loss of centromere
causing ring to
form
Characterization of TS
Etiologies
