Gametogenesis and Fertilization Flashcards
formation and development of specialized sex cells (haploid) through meiosis
gametogenesis
gametogenesis in males
spermatogenesis
gametogenesis in females
oogenesis
problems with gametogenesis result in chromosome abnormality disorders - types?
numerical, structural
explain the process of spermatogenesis
Spermatogonia (diploid, x23 pairs single chromatid chromosomes, one autosome pair and one sex link pair) in the testis undergoes DNA replication to become a primary spermatocyte (diploid, x23 pairs double chromatid chromosomes). This daughter cell undergoes a meiotic division in which DNA is replicated to create 2 secondary spermatocytes (haploid, x23 double chromatid chromosomes). They each will undergo another meiotic division but DNA is not replicated to become 4 spermatids (haploid, x23 single chromatid chromosomes). To become a mature sperm, they will undergo a process called spermiogenesis.
explain the process of oogenesis
Primary oocyte (diploid, x23 pairs double chromatid chromosome) is located in the ovary. It is wrapped in primary follicular cells which will continue to grow around the primary oocyte. The zona pellucida will form between the primary oocyte and the follicular cells. After the first meiotic division, the antrum will separate the secondary oocyte (haploid, x23 double chromatid chromosomes) in mature follicles and an outer layer of follicular cells. The first polar body is also now present. After the second meiotic division, a second polar body is present in the oocyte, which is surrounded by the corona radiata to allow for sperm to enter and begin fertilization.
describe DNA molecules in humans
46 chromosomes, 22 homologous autosome pairs and 1 sex-linked pair
XX
female sex link
XY
male sex link
paired strand of nucleotides (base pairs)
DNA
chromosomes are composed of …
DNA molecules
coding sequence on a chromosome of nucleotide base pairs for protein production
genes
paired DNA molecules aka double chromatid chromosomes
diploid
single DNA molecule aka single chromatid chromosome
haploid
each molecule in a diploid pair is called a
chromatid
only occurring in gametes, this is a process of 2 divisions without an intervening period of DNA replication
meiosis
what is the state of the gamete prior to the first meiotic division?
diploid # of chromosomes (23 pairs of single chromatid chromosomes), 22 autosomes and 1 sex-linked that originate from one chromosome from each parent
DNA is replicated (x2 to x4) to form diploid # of chromosomes (23 pairs of double chromatid chromosomes)
what occurs during the first meiotic division?
reduction division (x4 to x2) and the formation of haploid # of chromosomes (23 single chromatid chromosomes)
what occurs during the second meiotic division?
separation of chromatids, reduction division (x2 to x1), formation of haploid # of chromosomes (23 single chromatid chromosomes)
errors in morphogenesis, not all of which are clinically significant; human birth defects
congenital anatomic abnormalities
____ of newborns have single minor anomalies
14%
____ of newborns have clinically significant anomalies
3%
____ of newborns have major multiple defects, causing ____ of infant deaths
0.7%, 20%
abnormal shape, form or position due to mechanical stress
deformation
abnormal organization of cells into tissues; non-specific and affects several organs
dysplasia
structural abnormalities of any type, including malformation and disruption
congenital anomaly
intrinsically abnormal development (i.e., genetic etiology)
malformation
extrinsically-induced abnormal developement (i.e., environmental etiology)
disruption
study of causes, mechanisms, patterns of abnormal development with genetic and environmental factors
teratology
malformations cause ____ of anomalies, ____ of those with known causes
1/3, 85%
chromosomal abnormalities are common in malformation - types?
numerical, structural
failure to disjoin; disproportionate # of chromosomes of DNA distributed to daughter cells during meiosis, resulting in too many or too few chromosomes
nondisjunction
nondisjunction is a type of which anomaly?
malformation (structural or numerical)
meiosis is dependent upon … of chromosomes or DNA to daughter cells
equal distribution
types of numerical chromosome abnormalities
turner syndrome, trisomy of autosomes, trisomy of sex chromosomes
describe turner syndrome
45,X (missing a sex-link chromosomes) only occurring in female phenotype
trisomy 18 =
edward’s syndome
trisomy 13 =
patau syndrome
trisomy 21 =
down syndrome
describe some physical characteristics of an individual with trisomy 21 (down syndrome)
mental deficiency, brachycephaly, flat nasal bridge, upward slant to palpebral fissures, protruding tongue, simian crease, clinodactyly of 5th digit, congenital heart defect
describe some physical characteristics of an individual with klinefelter syndrome
XXY
tall, long lower limbs, gynecomastia, intellectual defects, aspermatogenesis
trisomy of sex chromosomes
not detected until puberty
may be ‘normal’ in appearance
types of structural chromosome abnormalities
translocation, deletion, duplication, inversion, nucleic acid substitutions on DNA
transfer of one piece of a chromosomes to a nonhomologous chromosomes
translocation
which structural chromosome abnormality is associated with a number of cancers?
translocation
part of a chromosome is lost
deletion
example of deletion
cri du chat syndrome (deletion on chromosome 5)
example of duplication
fragile X syndrome (CGG triplet repeated 200 times on FMR1 gene of X chromosome)
what does fragile x syndrome affect and what does it cause?
development of synapses
most common cause of mental disabilities
structural chromosome abnormality that does not usually cause malformation
inversion
example of nucleic acid substitution on DNA, specifically on fibroblast growth gene
achondroplasia
describe nucleic acid substitutions
spontaneous
error in replication
error during DNA repair
chemical or radiation induced
describe achondroplasia
Originating from a mutation during spermatogenesis, the fibroblast growth factor receptor gene 3 has a mutation. This abnormality is autosomal dominant.
primitive sex cells that undergo mitotic division
spermatogonia
cells that undergo reduction division
primary spermatocytes
cells that divide to form 4 haploid spermatids
secondary spermatocytes
spermiogenesis
transformation of spermatids into spermatozoa
where is sperm stored?
epididymis
ductus deferens experiences ____ ____ to transport sperm, in which fluid is added by seminal vesicles, prostate, and bulbourethral glands
peristaltic contractions
transport of sperm to urethra, a sympathetic response
emission
expulsion from urethra
ejaculation
in regard to ejaculate, how many sperm are there?
200-600 million deposited, 200 million survive
alteration of membrane proteins due to an acrosome reaction
capacitation
proliferate by mitotic division in early fetal life
oogonia
describe the components of the primary oocyte
It is formed before birth and doesn’t complete its first meiotic division until adolescence. This is when the primordial follicle develops into the primary follicle during puberty. It also contains the zona pellucida.
describe the components of the primary follicle
contains primary oocyte and theca folliculi (interna and externa)
describe the components of the secondary follicle
antrum (with follicular fluid), primary oocyte, cumulus oophorus
how long is the menstrual cycle?
28 days
describe the menstrual phase
4-5 days
sloughing off of the functional layer of the endometrium
describe the proliferative phase
9 days
growth of ovarian follicles stimulated by estrogen secretion
proliferation of endometrium
describe the luteal phase
13 days
formation, function, and growth of the corpus luteum
describe the ischemic phase
no pregnancy
ischemia, venous stasis, detachment of endometrium
when does menopause occur?
48-55 years old
ovulation is triggered by what?
surge in luteinizing hormone ~ mid cycle
when is secondary oocyte expelled? when does it form? what does it form?
ovulation
after 1st meiotic division
first polar body
formed by the walls of theca interna and ovarian follicle
corpus luteum
function of corpus luteum
secrete progesterone, stimulates change in endometrium
scar on ovary as a remnant of ovulation
corpus albicans
3 main female reproductive organs
uterus, uterine tube, ovaries
describe the parts of the uterus
body (fundus, isthmus, layers), cervix
layers of the body of the uterus
perimetrium, myometrium, endometrium
qualities of the endometrium
compact, spongy, basal lining
describe the parts of the uterine tube
horns, ampulla
describe oocyte transport from the ovary to the uterus
fimbriated end of uterine tube approximates ovary, fimbriae sweep secondary oocyte into uterine tube, uterine tube peristalsis occurs to move oocyte into uterus
describe the process of fertilization
In the ampulla, sperm passes through the corona radiata and undergoes a zonal reaction to penetrate the zona pellucida. Plasma membranes of the sperm and oocyte fuse, and the oocyte will undergo its second meiotic division and expel the second polar body. The male pronucleus and ootid will form, coming together to create a zygote
describe the cleavage of the zygote
Repeated mitotic divisions of blastomeres that occurs in the uterine tube and will compact, forming a morula with an inner cell mass and outer cell layer
embryoblast will become …
embryo
trophoblast will become …
embryonic placenta
the inside of the morula that is present ~ day 4
blastocyst cavity
thin outer layer of blastocyst
trophoblast
describe the attachment to the endometrium
~ day 6, there are changes in trophoblast which creates the cytotrophoblast and syncytiotrophoblast, which has projects that push into the endometrium. This creates a hypoblast layer on the surface of the blastocyst cavity, becoming the primitive endoderm
describe dizygotic twins
This hereditary occurance originates from 2 zygotes and the fertilization of 2 oocytes. There are 2 amnions and 2 chorions, one around each fetus.
describe monozygotic twins
Fetuses that are the same sex and genetically identical. This occurs through division of embryoblast into 2 embryonic primordia in blastocyst stage. They have separate amniotic sacs but a common chorionic sac and placenta.
embryologists describe stages of development starting at date of fertilization to date of birth (266 days/38 weeks)
fertilization age
clinicians describe stages of development starting at date of onset of last menstrual period to date of birth (280 days/40 weeks)
gestational age
weeks 0-8 fertilization age
weeks 0-10 gestational age
embryonic period
weeks 9-38 fertilization age
weeks 11-40 gestational age
fetal period
