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Embryology > formation of zygote > Flashcards

formation of zygote Flashcards

1
Q

fertlization

A

combining male and female gametes to form a cell called a zygote

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2
Q

zygote

A

single cell created by the union of 2 gametes prior to undergoing cleavage

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3
Q

gamete

A

haploid germ cell that can fuse with another germ cell

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4
Q

spermatogenesis

A

development of male gametes or spermatozoa (spermatozoon)

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5
Q

oogenesis

A

development of female gametes or ova (ovum)

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6
Q

conceptus

A

the product of conception at any point between fertilization and birth; includes embryo or fetus & its membranes)

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7
Q

gametogenesis common theme

A

mitosis to create primitive germ cells

primary gametes undergo meiotic cell division; diploid cells to haploid cells

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8
Q

spermatogenesis average duration

A

60 days

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9
Q

spermatocytogenesis

A

spermatogonia divide by mitosis forming primary spermatocytes (2n)

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10
Q

sustentacular cells

A

interposed between primary spermatocytes and spermatogonia

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11
Q

what create the blood-testis barrier

A

tight junctions on the spermatogonia side of cells

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12
Q

what is the function of the blood-testis barrier

A

protect developing gamete from immune system attack

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13
Q

1st meiotic division produces what in male gametes

A

2 secondary spermatocytes (1n)

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14
Q

2nd meiotic division produces what in male gametes

A

2 spermatids (1n) from each spermatocyte; 4 total spermatids

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15
Q

what is spermiogenesis

A

development of spermatids into spermatozoa and its release into seminiferous tubules

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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
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17
Q

acrosome formation

A

cap formed by golgi apparatus

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18
Q

midpiece formation

A

mitochondria to drive tail motion

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19
Q

flagellum formation

A

begins at centriole

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20
Q

how is cytoplasm reduced

A

engulfed by sustentacular cells or sertoli cells

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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

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22
Q

mature spermatozoon are stored in what

A

tail of epididymis 1-2 weeks

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23
Q

how long is sperm viable in female reproductive tract

A

48 hours

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24
Q

oogenesis begins when?

A

during fetal development, but is not complete until fertilization

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25
Q

primary oocytes divide by _____ forming ____

A

mitosis; primary oocytes (2n)

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26
Q

when does mitosis of primary oocytes end

A

shortly after birth

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27
Q

1st meiotic division begins and primary oocyte arrests at ____

A

prophase 1

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28
Q

development and cellular division resumes once _____ is reached

A

sexual maturity

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29
Q

puberty

A

follicular development

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30
Q

ovulation

A

complete 1st meiotic division

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31
Q

fertilization

A

complete 2nd meiotic division

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32
Q

what is the zona pellucida

A

non-cellular membrane (protein meshwork) formed around primary oocyte

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33
Q

zona pellucida is formed by what

A

proteins secreted by oocyte and granulosa cells during follicular development

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34
Q

role of proteins of zona pellucida

A
  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
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35
Q

estrous cycle timing coincides with

A

ovulation (when the female allows the male to mate)

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36
Q

what are the stages of the estrous cycle

A 
follicular phase (proestrus and estrus)
luteal phase (metestrus and diestrus)
anestrus
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37
Q

proestrus

A

follicles begin to grow

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38
Q

estrus

A

sexually receptive

maturation of follicle and ovulation

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39
Q

metestrus

A

corpra lutea develop and mature

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40
Q

diestrus

A

corpra lutea active, maintained, without pregnancy eventually regresses (major determinant of cycle length)

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41
Q

anestrus

A

period of rest in estrous cycle

no follicles develop

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42
Q

seasonal cycles

A

regulated by amount of day light via pineal gland and melatonin

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43
Q

bitch type of estrous cycle

A

nonseasonal monoestrus

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44
Q

queen type of estrous cycle

A

seasonal, spring-early fall; polyestrus

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45
Q

mare type of estrous cycle

A

seasonal, spring; polyestrus

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46
Q

doe, nanny type of estrous cycle

A

seasonal, fall polyestrus

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47
Q

ewe type of estrous cycle

A

seasonal, fall polyestrus

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48
Q

sow type of estrous cycle

A

nonseasonal; polyestrus

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49
Q

secondary oocyte resume of 1st meiotic division is ____ driven

A

hormone

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50
Q

most species resume just prior to _____

A

ovulation

51
Q

what species occurs post ovulation?

A

dog and mare

52
Q

what is a primary oocyte surrounded by epithelial cells called

A

a follicle

53
Q

during the resume of 1st meiotic division, what happens to the follicle?

A

oocyte enlarges, follicle enlarges and develops fluid filled space, zona pellucida thickens

54
Q

after first meiosis is completed, both cells are within the _____

A

zona pellucida

55
Q

secondary oocyte (1n) receives _____

A

most cytoplasm

56
Q

1st polar body (1n) receives _____

A

minimal cytoplasm

57
Q

secondary oocyte begins 2nd meiotic division and arrests at _____

A

metaphase II

58
Q

Ovulation releases what?

A

ovum (secondary oocyte and 1st polar body surrounded by zona pellucida and corona radiata) from follicle

59
Q

what are the effects of fertilization

A 
restore diploid (2n) chromosome number
allow for species variation
determine chromosomal sex (xx or xy)
60
Q

what is the location of fertilization

A

ampulla of uterine tube (typically ampulla/isthmus junction)

61
Q

capacitation of spermatozoa involves

A

biochemical/physiological modification of spermatozoa within female reproductive tract

62
Q

capacitation of sperm begins in the ___

A

uterus

63
Q

capacitation of sperm is complte when?

A

when spermatozoa reach isthmus of uterine tube

64
Q

capacitation enables spermatozoa for what?

A

fertilization

65
Q

what occurs for spermatozoa to enter ovum

A

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
Q

2nd meiosis of seconary oocyte continues within

A

zona pellucida (may be helpful to draw all steps on one sheet)

67
Q

mature oocyte

A

(1n) most cytoplasm with pronucleus

68
Q

2nd polar body (1n)

A

minimal cytoplasm

69
Q

fusion of pronuclei to zygote

A

spermatozoon nucleus enlarges forming pronucleus
non-nuclear portions of spermatozoon degenerate
pronuclei migrate toward each other and nuclear membranes are lost
zygote! (2n)

70
Q

semen evaluation includes

A

numbers of sperm (number needed to reach and penetrate zona pellucida; takes several!)
morphology of sperm

71
Q

ability to reach ova involves

A

tail morphology

72
Q

ability to penetrate zona pellucida involves

A

tail morphology and acrosome

73
Q

progressively motile sperm means

A

sperm that swim in a straight line

74
Q

what must you have for AI?

A

healthy sperm and knowing when fertile period of female is (estrous cycle)

75
Q

healthy sperm

A

can survive outside body and can be “re-introduced” to body (female tract)

76
Q

what is required for embryo transfer?

A

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
Q

evaluation of stage and quality of embryo includes

A

morula to blastocyst stages most hardy

looking for degeneration of blastomeres and loss of embryo form

78
Q

in vitro fertilization involves what

A

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
Q

somatic cells

A

diploid cells of the body

80
Q

autosomes

A

chromosome that is not a sex chromosome; pairs same in both genders; number vary with species

81
Q

sex chromosomes (allosome)

A

chromosomal pair that differs in form, size and behavior, differs between males and females; 1 pair

82
Q

alleles

A

different forms of a gene

83
Q

gene mutations

A

changes in DNA sequence (autosomal, x linked, y linked)

84
Q

dominant mutations

A

relationship between alleles of a gene, shows phenotype when present

85
Q

recessive mutations

A

relationship between alleles of a gene, requires both genes in an individual to have same allele for related phenotype to be expressed

86
Q

epigenetics

A

heritable changes in gene expression without a change in DNA sequence

87
Q

epigenetics includes

A

dna methylation
chromatin remodeling
x inactivation
gene silencing

88
Q

dna methylation

A

methylation of cysteine residue(s), represses transcription [dna can be expressed at higher or lower levels; usually lower]

89
Q

chromatin remodeling

A

dynamic modification of chromatin structure (histones binding) that regulates gene expression

90
Q

x inactivation

A

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
Q

what is a barr body

A

the inactivated x chromosome

92
Q

gene silencing

A

regulating gene expression in transcription or translation; silencing reduces expression (prevent from being turned into a protein)

93
Q

genomic imprinting

A

subset of autosomal genes where one copy is turned off in a parent of origin dependent manner

94
Q

imprinting occurs where

A

in either the ova or sperm

95
Q

only gene of ___ is expressed

A

non-imprinted origin

96
Q

types of imprints include

A

covalent (dna or histone methylation)

noncovalent (dna-protein or DNA-RNA interactions)

97
Q

requires nuclear enzymatic machinery to maintain what

A

parental epigenetic mark throughout cell cycle

98
Q

stem cells

A

undifferentiated cell that can differentiate into a specialized cell type and divide by mitosis

99
Q

embryonic stem cells

A

inner cell mass of blastocyts; pluripotent to ectoderm, mesoderm, or endoderm

100
Q

adult stem cells

A

progenitor cells found in adult tissues

101
Q

what is the chromosomal theory of inheritance

A

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
Q

abnormalites of chromosomes can be ___ or ____

A

numerical or structural

103
Q

how are abnormalities of chromosomes ID’d

A

few are born alive; often seen as infertility or early embryonic loss

104
Q

embryonic loss in equine due to abnormal chromosomes

A

15-24%

105
Q

embryonic loss in cattle

A

45-65%

106
Q

embryonic loss in sheep

A

20-30%

107
Q

embryonic loss in swine

A

30-50%

108
Q

mule

A

cross between a femal horse and a male donkey

109
Q

hennie

A

cross between a female donkey and a male horse

110
Q

common abnormalities for either cross

A

abnormal chromosome pairing (horse 32pr; donky 31pr)
few to no mature sperm
most oogonia die when enter meisosis
foalings are rare

111
Q

every mule or hinney has a unique bray often acomination of a

A

whinney and a bray

112
Q

trisomy 21 (downs syndrome) is caused by

A

3 chromosomes of #21 (triplication of gene)

113
Q

what are the range of possible effects of trisomy 21

A

specific alleles present in a given individual

variable penetrance- other factors besides allele impact outcome of expression

114
Q

what is the most common cause of human birth defects

A

trisomy 21

115
Q

what is the most common abnormal chromosome number

A

trisomy 21

116
Q

trisomy 21 have problems with _____ development

A

body and brain (mental retardation and developmental delay)

may have heart defects, hypothyroidism or celiac disease

117
Q

what is triple x syndrome

A

3 sex chromosomes, 3-Xs

118
Q

triple x occurs in

A

primarily in humans, occurs rarely in domestic

119
Q

signs of triple x syndrome

A
  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
Q

XXY (Kleinfelter syndrome)

A

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
Q

XO (Turner’s Syndrome)

A

1 sex chromosome, 1x

122
Q

XO have what phenotype

A

phenotypic female

123
Q

reproductive organs of XO

A

hypoplastic ovaries, small uterus and under developed external genitalia; Delayed puberty

124
Q

XO occurs in

A

horse, pig, dog, cat

Embryology (18 decks)

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