ch 12- reproduction Flashcards
binary fission
unicellular organisms
prokaryotes
mitochondria
chloroplasts
DNA replicated and migrates to ends of cells and SEPTUM forms
Budding
DNA replicated and deposited into bud
hydra and yeast do this
what does regeneration
hydra and planaria and fungi
parthogenesis
Unfertilized egg develops to a
viable organism (e.g., honeybees exhibit
haplodiploidy (males haploid, females diploid)).
spermiogenesis
final stage of spermatogenesis
haploid spermatids differentiate into mature motile spermatozoa (mature sperm cells)
NO CHANGE IN AMOUNT OF GENETIC MATERIAL
spermatogenesis
is the formation of mature
spermatozoa from spermatogonium. In this process,
diploid germ cells (spermatogonium) become haploid
gametes (spermatozoa).
produces four spermatids
seminiferous tubules
of testes are the site of
spermatogenesis (sperm production) and
contain:
● Sertoli cells: Surround and nourish sperm.
Produce inhibin (inhibits FSH - negative
feedback).
● Spermatogenic cells: Produce spermatozoa.
what activates sertoli cells
FSH
where are not mature sperm tranpsorted
from the seminiferous tubules to the epididymis via peristalsis
the epididymis is a duct around the testes
here the sperm are stored and matured
where does sperm go after the epididymis
Sperm moves through vas deferens (group of tubules) to ejaculatory duct (where vas deferens meets seminal vesicles) which propels sperm into
urethra and leads to ejaculation out of penis as semen (sperm + accessory gland secretions).
sperm parts
● Head: Contains nucleus and acrosome.
● Midpiece: Mitochondria (ATP production).
● Tail: Long flagellum (microtubules) to propel sperm.
seminal vesicle
accesory gland
Secrete fructose (nutrients to
produce ATP), viscous mucus (cleans and
lubricates urethra), and prostaglandins (causes
urethral contractions which propels sperm).
prostate gland
Alkaline secretions (basic) to
counteract uterine acidity.
accessory gland
bulbourethral gland
Viscous mucus (cleans and
lubricates urethra).
accessory gland
blastocyst
fertilized egg
what produces estrogen and progesterone
ovary
oogenesis steps
- Many oogonia produced, majority die via
apoptosis, small fraction remain and differentiate
to primary oocytes (begin meiosis but are
arrested in prophase I until puberty). - At puberty: one egg per month ovulates,
completing meiosis I, which produces a large
secondary oocyte (arrested in meiosis II during
metaphase II) and a polar body. - If fertilization occurs: meiosis II is completed.
- At the end of meiosis II: 2-3 polar bodies
(non-viable) and 1 oocyte (viable, contains majority
of cytoplasm, mitochondria, and nutrients for
fetus) are produced.
when is meiosis I and II completed for eggs
I- puberty during ovulation one egg per month
-also produces polar body
II- after fertilization
-2-3 polar bodies by the end of meiosis II
FSH
Follicle stimulating hormone (FSH): Stimulates
follicles in the ovary to develop and production
of estrogen and progesterone.
● Follicles are fluid filled sacs on the ovaries that contain an immature egg (arrested at meiosis I). The corpus luteum is a temporary endocrine structure formed by the dominant follicle after ovulation of the egg.
LH
Stimulates ovulation
of egg, corpus luteum formation, which produces
estrogen and progesterone. The ovulated egg is
released from a dominant follicle to complete
meiosis I.
birth control pills
release
synthetic estrogen and progesterone, inhibiting
GnRH production during the menstrual cycle through
negative feedback and thus preventing the
menstrual cycle from causing ovulation.
temp dependent sex determination pattern 1 and 2
● Some reptiles determine their sex in
development not by chromosomes, but by
temperature.
○ Pattern I development results in males in
cold temperatures, and females in warm
temperatures (eg, turtles).
○ Pattern II development results in females
in low and high temperatures, and males
in intermediate temperatures (eg,
crocodiles).
factors influencing development- apoptosis
Programmed cell death is important for
normal development of the fetus (eg,
removing webbing between fingers) and
adults (preventing cancer).
factors influencing development- egg cytoplasm determinant
If egg cytoplasm is unevenly distributed
(creating animal and vegetal poles), an axis is created, influencing how the embryo divides during cleavage.
factors influencing development- homeotic genes
master controller
homeotic genes
homeobox
hox genes
master controller
turns different gene
expressions on/off.
homeotic genes
decide which part of the
embryo develops into what structures.
○ This is carried out through regulating the
formation of the body axes and body
structures in the proper location during
early embryonic development.
homeobox
is a common DNA sequence
homologous across organisms that contains
homeotic genes.
hox genes
are a subset of homeotic genes
that are responsible for anterior-posterior
(head-to-tail) position of body parts during
development.
ovoviviparity
Offspring develops in eggs that
hatch within the mother’s body. There is no
placental connection, the embryos rely on the yolk
sac in the egg. This is common in some snakes and
amphibians.
viviparity
Offspring develops inside the mother’s
body and are nourished via a placental
connection. Most common in mammals.
oviparity
Offspring develops in eggs that hatch
outside of the mother’s body. There is no placental
connection between the mother and the eggs.
Common in birds, fish, and reptiles.
what happens during the follicular phase
Hypothalamus releases
Gonadotropin Releasing Hormone (GnRH) →
anterior pituitary releases LH and FSH → FSH
binds to the ovaries and induces follicles to
develop → developing follicles release estrogen
→ endometrium thickens → rapid LH spike →
ovulation.
what happens during ovulation
Ovulation (egg is released from
Graafian follicle) → fimbriae on oviduct catches
egg, cilia sweep egg into oviduct → egg travels
down oviduct (awaiting sperm fertilization).
what happens during the luteal phase
Follicle develops into the corpus
luteum (maintained by FSH and LH) → corpus
luteum produces progesterone and some
estrogen → uterine lining thickens (prepares for
implantation).
what happens if no implantation occurs
LH and FSH levels
drop (due to hypothalamus and pituitary
inhibition by increased progesterone and
estrogen) → corpus luteum can no longer be
maintained → progesterone and estrogen
levels drop (hypothalamus and pituitary are not
inhibited anymore) → endometrium sloughs off
(menstruation) → cycle repeats.
what happens if implanatation occurs
Outer layer of placenta
produces human chorionic gonadotropin
(hCG) → maintains corpus luteum →
progesterone and estrogen levels maintained
→ endometrium remains (no menstruation).
hCG
hCG can be given to women during fertility
treatment to trigger ovulation and enhance
progesterone release.
lactation and childbirth
positive feedback loops
● Lactation: Infant suckling increases prolactin
production which causes lactation (milk
production) and further increases infant suckling.
Oxytocin releases milk (milk let down reflex).
● Childbirth: Oxytocin induces contractions which
push the baby out of the womb. The baby
pushes against a nerve in the cervix that signals
the hypothalamus and pituitary to release more
oxytocin.
what are the negative feedback loops in reproduction
● The hypothalamus releases GnRH causing the
pituitary to release FSH and LH which increase
testosterone levels. High testosterone levels
inhibit the hypothalamus from releasing GnRH,
lowering FSH and LH and testosterone.
● The same occurs with estrogen and
progesterone in the menstrual cycle.
where does fertilization occur
in the oviduct
female egg components
Outermost layer, corona radiata, nourishes
developing egg. Underneath is the vitelline layer
(known as the zona pellucida/jelly coat in mammals),
made of glycoproteins. Plasma membrane is under
the zona pellucida.
capacitation
Another maturation step for
sperm prior to fertilization. Triggered by
secretions in uterine wall and occurs in the
oviduct. Destabilizes sperm plasma membrane
proteins and lipids resulting in:
● Preparation of sperm tip for acrosomal
reaction.
● Increased calcium permeability causing a
hyperactive state (flagella beats harder,
sperm swims faster).
acrosomal reaction
reaction: Recognition process
between sperm and egg before fusion. Ensures
same-species fertilization. Sperm goes through
the corona radiata to reach zona pellucida.
Actin from sperm binds to ZP3 protein of egg’s
zona pellucida (mutual recognition). Membranes
of sperm head and acrosome fuse, releasing
hydrolytic acrosomal enzymes (hydrolases)
to digest zona pellucida and allow sperm to fuse
with plasma membrane of egg (fertilization).
polyspermy block
prevents polyploidy by inhibiting polyspermy (multiple sperms penetrating egg)
fast block
slow block
fast block
occurs first when sodium ions
diffuse into the egg, depolarizing its
membrane and prevents sperm binding.
slow block
Gradual, long-lasting occurs
second. Calcium ions released in egg
stimulate cortical reaction (exocytosis of
cortical granules). Cortical granules make
the vitelline membrane (jelly coat)
impenetrable and stimulate proteases to
separate the vitelline membrane from
plasma membrane.
mitochondrial DNA
is inherited from the mother
cleavage
is rapid cell division without changing the
total mass of cells. The subsequently smaller cells
resulting from cleavage are called blastomeres.
axis of cleavage types
● Radial cleavage: cells aligned in vertical axis
(eg. deuterostomes).
● Spiral cleavage: misaligned cells, deviate
from axis (eg. protostomes).
determinate vs indeterminate cells
● Determinate (or mosaic) cleavage:
Blastomeres have decided fate.
● Indeterminate (or regulative) cleavage:
Blastomeres do not have pre-set fate. Cells
that result from indeterminate cleavage are
totipotent.
holoblastic vs meroblastic cleavage
evenness of division
● Holoblastic cleavage: Throughout entire
embryo, evenly divides embryo, in animals
with little yolk (eg. humans, sea urchins).
○ Exception: Frogs have lots of yolk and
also undergo holoblastic cleavage that is
uneven (exhibit polarity).
● Meroblastic cleavage: Partial cleavage,
embryo not evenly divided, in animals with
lots of yolk (eg. birds, fish, reptiles). Exhibits
polarity with animal pole (active cleavage)
and vegetal pole (mainly yolk, negligible
division).
morule
(ball of blastomeres): Forms at 16-32 cell
stage.
blastula stage
(hollow cavity): Forms at 128 cell
stage. Blastocoel is hollow, fluid filled center.
blastocyst stage
Cells of blastula divide and
differentiate.
cleavage occurs
as fertilized egg travels to the uterus
in the uterus
the fertlized egg is at the blastocyst stage
grastulation
Gastrulation is the formation of a trilaminar embryo. Epiblast cells invaginate inwards through the primitive streak to form three germ layers: endoderm, mesoderm, ectoderm. Embryo is now at the gastrula stage.
As cells invaginate they create an opening called the
blastopore, which forms the gut tube
(archenteron), the center cavity that becomes the
digestive tract.
ectoderm forms
● CNS (brain and spinal cord) and PNS, as well
as neural crest cells and neural ganglia.
● Sensory parts of ear, eye, and nose.
● Epidermis layer of skin, hair, and nails.
● Mammary and sweat glands.
● Pigmentation cells.
● Enamel of teeth.
● Adrenal medulla.
mesoderm forms
● Bone and skeleton.
● Skeletal, smooth, and cardiac muscle.
● Cardiovascular system.
● Gonads.
● Adrenal cortex.
● Spleen.
● Notochord (induces spinal cord formation
from ectoderm).
endoderm forms
● Epithelial lining of digestive, respiratory, and
excretory systems.
● PLTT (Pancreas, Liver, Thyroid and
parathyroid, Thymus).
organogenesis
formation of new organs
neurulation steps
is nervous system development: An
embryo at this stage is known as a neurula.
1. Notochord stimulates ectoderm to thicken, forming the neural plate.
2. Neural plate folds onto itself forming the neural fold / neural groove.
3. Neural fold continues to fold, forming a hollow tube (neural tube).
● Some cells roll off to form neural crest cells (migrate to form teeth, craniofacial bones, skin pigmentation, etc.).
4. Neural tube differentiates into CNS.
● Mesoderm cells (somites) form two masses alongside notochord. Becomes vertebrae and skeletal muscles associated with axial skeleton.
totipotent
Totipotent stem cells can become any cell (eg.
zygote, blastomeres of morula).
pluripotent
stem cells can become any of of the
3 germ layers (eg. ICM cells → embryonic stem
cells).
multipotent
stem cells can only differentiate to
a few cell types of a specific tissue type (eg.
hematopoietic stem cell → many blood cells).
amnion
Amnion: innermost layer, membrane around
embryo secretes amniotic fluid (water cushion,
protecting embryo).
● Amniotes (reptiles, mammals, birds,
marsupials) have an amnion, anamniotes
(amphibians, fish) do not (surrounding water
serves as cushion).
chorion
outermost layer.
● Placental mammals: forms fetal half of the
placenta (platform for exchange of gases,
nutrients, and waste).
● Egg-laying animals: membrane for gas
exchange just underneath egg shell.
allantois
sac that buds off of the archenteron.
Stores waste for disposal.
● Placental mammals: transports waste to
placenta, becomes the umbilical cord, and
in adults forms urinary bladder.
● Egg-laying animals: initially stores uric acid,
later fuses with chorion (helps with gas
exchange).
yolk sac
contains yolk (intraembryonic,
provides nutrients).
● Placental mammals: transient function until
placenta develops. First site of blood cell
formation.
● Egg-laying animals: provides all nutrients for
developing embryo.
