formation of zygote Flashcards
1
Q
fertlization
A
combining male and female gametes to form a cell called a zygote
2
Q
zygote
A
single cell created by the union of 2 gametes prior to undergoing cleavage
3
Q
gamete
A
haploid germ cell that can fuse with another germ cell
4
Q
spermatogenesis
A
development of male gametes or spermatozoa (spermatozoon)
5
Q
oogenesis
A
development of female gametes or ova (ovum)
6
Q
conceptus
A
the product of conception at any point between fertilization and birth; includes embryo or fetus & its membranes)
7
Q
gametogenesis common theme
A
mitosis to create primitive germ cells
primary gametes undergo meiotic cell division; diploid cells to haploid cells
8
Q
spermatogenesis average duration
A
60 days
9
Q
spermatocytogenesis
A
spermatogonia divide by mitosis forming primary spermatocytes (2n)
10
Q
sustentacular cells
A
interposed between primary spermatocytes and spermatogonia
11
Q
what create the blood-testis barrier
A
tight junctions on the spermatogonia side of cells
12
Q
what is the function of the blood-testis barrier
A
protect developing gamete from immune system attack
13
Q
1st meiotic division produces what in male gametes
A
2 secondary spermatocytes (1n)
14
Q
2nd meiotic division produces what in male gametes
A
2 spermatids (1n) from each spermatocyte; 4 total spermatids
15
Q
what is spermiogenesis
A
development of spermatids into spermatozoa and its release into seminiferous tubules
16
Q
what are the developmental changes that occur during spermiogenesis
A
acrosome formation (golgi apparatus) midpiece formation (mitochondria aggregate proximal region of tail) flagellum formation (centrioles migrate to a pole) reduction excess cytoplasm
17
Q
acrosome formation
A
cap formed by golgi apparatus
18
Q
midpiece formation
A
mitochondria to drive tail motion
19
Q
flagellum formation
A
begins at centriole
20
Q
how is cytoplasm reduced
A
engulfed by sustentacular cells or sertoli cells
21
Q
what spermiation
A
release of spermatozoa into lumen of seminiferous tubule; initially spermatozoa have a small cytoplasmic droplet of excess cytoplasm which is lost or shed
22
Q
mature spermatozoon are stored in what
A
tail of epididymis 1-2 weeks
23
Q
how long is sperm viable in female reproductive tract
A
48 hours
24
Q
oogenesis begins when?
A
during fetal development, but is not complete until fertilization
25
primary oocytes divide by _____ forming ____
mitosis; primary oocytes (2n)
26
when does mitosis of primary oocytes end
shortly after birth
27
1st meiotic division begins and primary oocyte arrests at ____
prophase 1
28
development and cellular division resumes once _____ is reached
sexual maturity
29
puberty
follicular development
30
ovulation
complete 1st meiotic division
31
fertilization
complete 2nd meiotic division
32
what is the zona pellucida
non-cellular membrane (protein meshwork) formed around primary oocyte
33
zona pellucida is formed by what
proteins secreted by oocyte and granulosa cells during follicular development
34
role of proteins of zona pellucida
1. species specific receptors for spermatozoa (can be fooled; horse vs. donkey)
2. protect from immune system "attack"
3. protect from pathogen "attack"
4. absence or dysfunction result in decrease fertility and/or early embryonic loss
35
estrous cycle timing coincides with
ovulation (when the female allows the male to mate)
36
what are the stages of the estrous cycle
```
follicular phase (proestrus and estrus)
luteal phase (metestrus and diestrus)
anestrus
```
37
proestrus
follicles begin to grow
38
estrus
sexually receptive
| maturation of follicle and ovulation
39
metestrus
corpra lutea develop and mature
40
diestrus
corpra lutea active, maintained, without pregnancy eventually regresses (major determinant of cycle length)
41
anestrus
period of rest in estrous cycle
| no follicles develop
42
seasonal cycles
regulated by amount of day light via pineal gland and melatonin
43
bitch type of estrous cycle
nonseasonal monoestrus
44
queen type of estrous cycle
seasonal, spring-early fall; polyestrus
45
mare type of estrous cycle
seasonal, spring; polyestrus
46
doe, nanny type of estrous cycle
seasonal, fall polyestrus
47
ewe type of estrous cycle
seasonal, fall polyestrus
48
sow type of estrous cycle
nonseasonal; polyestrus
49
secondary oocyte resume of 1st meiotic division is ____ driven
hormone
50
most species resume just prior to _____
ovulation
51
what species occurs post ovulation?
dog and mare
52
what is a primary oocyte surrounded by epithelial cells called
a follicle
53
during the resume of 1st meiotic division, what happens to the follicle?
oocyte enlarges, follicle enlarges and develops fluid filled space, zona pellucida thickens
54
after first meiosis is completed, both cells are within the _____
zona pellucida
55
secondary oocyte (1n) receives _____
most cytoplasm
56
1st polar body (1n) receives _____
minimal cytoplasm
57
secondary oocyte begins 2nd meiotic division and arrests at _____
metaphase II
58
Ovulation releases what?
ovum (secondary oocyte and 1st polar body surrounded by zona pellucida and corona radiata) from follicle
59
what are the effects of fertilization
```
restore diploid (2n) chromosome number
allow for species variation
determine chromosomal sex (xx or xy)
```
60
what is the location of fertilization
ampulla of uterine tube (typically ampulla/isthmus junction)
61
capacitation of spermatozoa involves
biochemical/physiological modification of spermatozoa within female reproductive tract
62
capacitation of sperm begins in the ___
uterus
63
capacitation of sperm is complte when?
when spermatozoa reach isthmus of uterine tube
64
capacitation enables spermatozoa for what?
fertilization
65
what occurs for spermatozoa to enter ovum
pass between cells of corona radiata (motility driven, some enzymes)
binds receptors on zona pellucida
penetrate zona pellucida (acrosome and motility driven)
fusion of cell membranes of spermatozoon and secondary oocyte
66
2nd meiosis of seconary oocyte continues within
zona pellucida (may be helpful to draw all steps on one sheet)
67
mature oocyte
(1n) most cytoplasm with pronucleus
68
2nd polar body (1n)
minimal cytoplasm
69
fusion of pronuclei to zygote
spermatozoon nucleus enlarges forming pronucleus
non-nuclear portions of spermatozoon degenerate
pronuclei migrate toward each other and nuclear membranes are lost
zygote! (2n)
70
semen evaluation includes
numbers of sperm (number needed to reach and penetrate zona pellucida; takes several!)
morphology of sperm
71
ability to reach ova involves
tail morphology
72
ability to penetrate zona pellucida involves
tail morphology and acrosome
73
progressively motile sperm means
sperm that swim in a straight line
74
what must you have for AI?
healthy sperm and knowing when fertile period of female is (estrous cycle)
75
healthy sperm
can survive outside body and can be "re-introduced" to body (female tract)
76
what is required for embryo transfer?
supraovulation of donor female
fertlization of ova either by natural cover, AI, or in vitro
collection of embryos
synchronization of recipient female's estrus cycle to donor
77
evaluation of stage and quality of embryo includes
morula to blastocyst stages most hardy
| looking for degeneration of blastomeres and loss of embryo form
78
in vitro fertilization involves what
collection of oocytes (supraovulation and surgical or post-mortem)
in vitro maturation of oocytes
in vitro fertilization of oocytes (capacitated sperm, intracytoplasmic sperm injection [ICSI])
In vitro culture of zygote to approptiate stage and hormonal timing of recipient for successful implantation (blastocyst)
79
somatic cells
diploid cells of the body
80
autosomes
chromosome that is not a sex chromosome; pairs same in both genders; number vary with species
81
sex chromosomes (allosome)
chromosomal pair that differs in form, size and behavior, differs between males and females; 1 pair
82
alleles
different forms of a gene
83
gene mutations
changes in DNA sequence (autosomal, x linked, y linked)
84
dominant mutations
relationship between alleles of a gene, shows phenotype when present
85
recessive mutations
relationship between alleles of a gene, requires both genes in an individual to have same allele for related phenotype to be expressed
86
epigenetics
heritable changes in gene expression without a change in DNA sequence
87
epigenetics includes
dna methylation
chromatin remodeling
x inactivation
gene silencing
88
dna methylation
methylation of cysteine residue(s), represses transcription [dna can be expressed at higher or lower levels; usually lower]
89
chromatin remodeling
dynamic modification of chromatin structure (histones binding) that regulates gene expression
90
x inactivation
maintains normal level of gene expression in females
one x chromosome (maternal or paternal) inactivated
inactivates majority of genes on the chromosome
occurs in blastocyt, occurs in random fashion
91
what is a barr body
the inactivated x chromosome
92
gene silencing
regulating gene expression in transcription or translation; silencing reduces expression (prevent from being turned into a protein)
93
genomic imprinting
subset of autosomal genes where one copy is turned off in a parent of origin dependent manner
94
imprinting occurs where
in either the ova or sperm
95
only gene of ___ is expressed
non-imprinted origin
96
types of imprints include
covalent (dna or histone methylation)
| noncovalent (dna-protein or DNA-RNA interactions)
97
requires nuclear enzymatic machinery to maintain what
parental epigenetic mark throughout cell cycle
98
stem cells
undifferentiated cell that can differentiate into a specialized cell type and divide by mitosis
99
embryonic stem cells
inner cell mass of blastocyts; pluripotent to ectoderm, mesoderm, or endoderm
100
adult stem cells
progenitor cells found in adult tissues
101
what is the chromosomal theory of inheritance
traits of an individual are determined by specific genes on chromosomes inherited from the dam and sire. Gnes on the same chromosome tend to be inherited together and so are known as linked genes
102
abnormalites of chromosomes can be ___ or ____
numerical or structural
103
how are abnormalities of chromosomes ID'd
few are born alive; often seen as infertility or early embryonic loss
104
embryonic loss in equine due to abnormal chromosomes
15-24%
105
embryonic loss in cattle
45-65%
106
embryonic loss in sheep
20-30%
107
embryonic loss in swine
30-50%
108
mule
cross between a femal horse and a male donkey
109
hennie
cross between a female donkey and a male horse
110
common abnormalities for either cross
abnormal chromosome pairing (horse 32pr; donky 31pr)
few to no mature sperm
most oogonia die when enter meisosis
foalings are rare
111
every mule or hinney has a unique bray often acomination of a
whinney and a bray
112
trisomy 21 (downs syndrome) is caused by
3 chromosomes of #21 (triplication of gene)
113
what are the range of possible effects of trisomy 21
specific alleles present in a given individual
| variable penetrance- other factors besides allele impact outcome of expression
114
what is the most common cause of human birth defects
trisomy 21
115
what is the most common abnormal chromosome number
trisomy 21
116
trisomy 21 have problems with _____ development
body and brain (mental retardation and developmental delay)
| may have heart defects, hypothyroidism or celiac disease
117
what is triple x syndrome
3 sex chromosomes, 3-Xs
118
triple x occurs in
primarily in humans, occurs rarely in domestic
119
signs of triple x syndrome
1. tall stature
2. microcephaly (small head)
3. epicanthial folds (vertical skin folds that may cover medial canthus of eye)
4. Delayed development (motor, speech, language)
5. learning disabilities
6. Infertility
120
XXY (Kleinfelter syndrome)
3 sex chromosomes, 2 Xs; 1-y
Presence of Y= male-determining genes and phenotype
abnormal spermatogenesis and hypoplastic testes due to extra X
Dogs, Cats
121
XO (Turner's Syndrome)
1 sex chromosome, 1x
122
XO have what phenotype
phenotypic female
123
reproductive organs of XO
hypoplastic ovaries, small uterus and under developed external genitalia; Delayed puberty
124
XO occurs in
horse, pig, dog, cat
