CH 29 Flashcards
1
Q
what is inheritance?
A
passing of genes and traits from one generation to the next
2
Q
what is genetics?
A
study of genes and inheritance
3
Q
what is genetic counselling?
A
medical branch of study that tests, detects fetal abnormalities, and provides advice accordingly
4
Q
what is a genotype?
A
combination of genes
5
Q
does every human have the same genotype?
A
No, all humans have the same set of genes but each person may differ by the sequence of those genes
6
Q
what are alleles?
A
genes that encode the same protein product but differ in sequence, they are alternate versions of genes
7
Q
what is a phenotype?
A
physical and observed expression of a particular trait/genotype
8
Q
why do genotypes determine one’s phenotype?
A
central dogma of biology
(genes → RNA → proteins)
9
Q
how many alleles per gene do humans have?
A
humans are diploid so they have two maximum alleles per gene (1 from dad, 1 from mom)
10
Q
what are dominant alleles?
A
alleles that need only one copy to be expressed
11
Q
what are recessive alleles?
A
alleles that need two copies to be expressed
12
Q
what is autosomal inheritance?
A
alleles are found on non-sex chromosomes and can be inherited to offspring
13
Q
what are homozygotes?
A
individuals with two of the same alleles
14
Q
what are heterozygotes?
A
individuals with two different alleles
15
Q
who do homozygotes for a dominant disease allele usually die in utero?
A
100% of proteins coded by the alleles are of disease variant, no functional copies made
16
Q
why are individuals who express the traits of a dominant disease usually heterozygotes for that allele?
A
50% of proteins coded by the gene are functional, and that is enough for normal functioning
17
Q
why are most disease alleles carried on the X chromosome?
A
there are very few genes on the Y chromosome
18
Q
what sweeps secondary oocytes down the uterine tubes?
A
cilia on the mucosa of the uterine tubes
19
Q
when is pregnancy most likely to occur?
A
if intercourse occurs within 3-day window of ovulation
20
Q
what moves sperm through uterine tubes?
A
their flagellum, and peristaltic contractions of the uterine tubes
21
Q
describe the path of sperm to fuse with the oocyte
A
corona radiata → zona pellucida → plasma membrane of oocyte → cytoplasm of oocyte
22
Q
why can’t sperm fertilize oocyte within hours after coitus?
A
they must undergo capacitation
23
Q
what is capacitation?
A
changes to sperm’s plasma membrane and increased flagellar whipping due to conditions of the vagina
24
Q
what happens to the plasma membrane of the sperm during capacitation?
A
anything besides phospholipids and glycolipids from membranes are stripped for easier fusion with the oocyte plasma membrane
25
how does the sperm go through the corona radiata and zona pellucida?
sperm releases acrosomal enzymes that digest them, flagellar motility pushes the sperm into the secondary oocyte further
26
what is ZP3?
a protein on the zona pellucida that is a receptor for a sperm plasma membrane
27
what happens when a sperm-ZP3 complex binds oocyte plasma membrane receptors?
an acrosomal reaction is triggered, and the acrosome releases digestive enzymes that digests the surrounding zona pellucida
28
what happens when the plasma membranes of the sperm and oocyte fuse?
the newly fertilized ovum is depolarized
29
which ion enters the cytoplasm after depolarization of the newly fertilized ovum?
calcium, through the the opening of VGCCs
30
what does depolarization of the fertilized egg do?
intracellular Ca2+ triggers exocytosis of secretory vesicles that **block ZP3 receptors** and crystallize zona pellucida
31
what is a slow block to polyspermy?
the process of blocking ZP3 receptors and crystallizing the zona pellucida to prevent multiple sperm fusing with the oocyte
32
why is slow block to polyspermy important? what would happen if every egg were fertilized by multiple sperm?
- slow block to polyspermy prevents every sperm trying to fuse w/ oocyte
- too many chromosomes is fatal for an embryo
33
what is syngamy?
the fusion of the female and male pronuclei to form a single diploid nucleus
(**different from fertilization**)
34
what structures are found upon fertilization?
- large ovum w/ female pronuclei
- second polar body
- male pronuclei
35
what is cleavage?
rapid mitotic division of the zygote after ~24 hours post fertilization
36
how is cleavage different from normal mitotic divisions?
it increases the number of cells without a significant increase in size
37
when is a morula formed?
~4 days after fertilization
38
what is a morula?
solid mass of cells formed through cleavage of a zygote
39
what is uterine milk?
glycogen-rich fluid formed by the uterus that enters zona pellucida of a morula and rearranges its cells, forming a blastocyst cavity
40
what is a blastocyst cavity?
uterine milk-filled pouch
41
what does formation of a blastocyst cavity mean for the morula
the morula is now a blastocyst
42
what are the two parts of a blastocyst?
- embryoblast
- trophoblast
43
what is the embryoblast?
inner cell mass in the blastocyst that gives rise to embryo
44
what is the trophoblast?
outer cell mass of the blastocyst that forms fetal portion of the placenta
45
what happens to the blastocyst on the 5th day after fertilization?
blastocyst secretes an enzyme that digests through zona pellucida and it hatches out the hole
46
what is implantation?
blastocyst implanting on the endometrium of the uterus, with the embryoblast oriented towards endometrium
47
when does implantation occur?
7 days after fertilization
48
why does the embryoblast orient itself toward the endometrium in implantation?
to be closer to nutrients provided by the endometrium
49
what are some histological changes to the endometrium and blastocyst during implantation?
endometrium becomes more vascularized, endometrial glands enlarged, blastocyst is engulfed in endometrial tissue
50
what happens to the trophoblast 8 days after fertilization?
- trophoblast differentiates into two layers
- secretes enzymes that liquefy the endometrium for nourishment
- secretes hCG, preventing CL degeneration
51
what happens to the embryoblast 8 days after fertilization?
embryoblast differentiates into two layers
52
what is the bilaminar embryonic disc?
flat disc structure formed from the two layers that came from the embryoblast
53
what is the amniotic cavity?
cavity formed by the cells of the bilaminar embryonic disc containing amniotic fluid
54
what is the function of amniotic fluid?
cushions and protects the fetus during pregnancy, absorbs shock, moisturizes the fetus
55
where does amniotic fluid come from?
- filtered from maternal capillaries
- fetal urine
56
why does the umbilical vesicle shrink as development progresses?
its nutrient-providing function is replaced by the placenta
57
what are the functions of the umbilical vesicle?
- nourishes embryo during week 2/3
- forms first blood cells
- contains primordial germ cells of the developing fetus
- cushions embryo and prevents dessication
58
what two structures sandwich the bilaminar embryonic disc 8 days after fertilization?
- amniotic cavity
- umbilical vesicle
59
when does the chorion develop?
~12 days post-fertilization, the two layers of the trophoblast develop into the chorion
60
what does the chorion eventually become
the fetal portion of the placenta
61
what are the functions of the chorion?
- Secretes proteins that block maternal antibody production
- Secretes hCG
- Promotes the production immuno- suppressing T lymphocytes in endometrium
62
what is the chorionic cavity?
cavity formed by inner layer of chorion fusing with inner cell layer
63
what is the connecting stalk?
layer of cells that connect bilaminar embryonic disc to the trophoblast, eventually becomes the umbilical cord
64
when does the connecting stalk form?
12 days post-fertilization
65
what is gastrulation?
major cell migration and differentiation occuring in the third week of development
66
what is the product of gastrulation?
embryo now consists of three primary germ layers that give rise to all tissues in the newborn
67
what is the primitive streak?
shallow groove on the dorsal surface of the bilaminar embryonic disc that divides the disc into a head, tail, left, and right sides
68
what is the primitive node?
bulbous projection at the head end of the primitive streak
69
what happens to the cells at the primitive streak during gastrulation?
they invaginate and break off
70
what is the endoderm?
innermost cells formed from gastrulation
71
what is the mesoderm?
middle layer of cells formed from gastrulation
72
what is the ectoderm?
outermost layer of cells formed from gastrulation
73
what does the endoderm give rise to?
Epithelial lining of digestive canal and respiratory systems, other organs
74
what does the mesoderm give rise to?
muscles, bones, CT, peritoneum
75
what does the ectoderm give rise to?
epidermis of skin, nervous system
76
what is induction?
process of one developing tissue secreting chemicals that initiates the differentiation of neighbouring cells into tissues
77
what is an example of induction
Mesodermal cells of primitive node form hollow tube from head to tail called notochordal process at 16 days
78
what is the notochordal process?
hollow tube from head to tail found 16 days post-fertilization
79
what is the notochord?
the notochordal process becomes a solid mass by 22-26 days post-fertilization
80
what does notochord formation induce?
development of the vertebral bodies and nucleus pulposus
81
what extraembryonic membrane does the umbilical vesicle eventually form?
the allantois
82
what is the function of the allantois?
- early production of blood
- early formation of blood vessels
- eventually helps form the urinary bladder
83
what is neurulation?
the process of forming the neural groove, neural plate, neural folds, and neural tube
84
how is the neural groove formed?
formation of the notochord induces overlying ectodermal cells to migrate, forming the neural groove over the notochord
85
what is the neural plate?
the entire ectodermal structure overlying the notochord
86
how are neural folds formed?
ectodermal ridges on either side of the neural groove become more prominent
87
how is the neural tube formed?
as the neural folds become more prominent, they eventually fuse to form the neural tube
88
what structures does the neural tube give rise to?
- brain
- spinal cord
89
what must happen to the neural tube for the brain and spinal cord to properly develop?
the neural tube must close?
90
what are neural tube defects?
incomplete closure or other malformations of the neural tube and resulting structures
e.g. spina bifida, anencephaly
91
what is anencephaly?
most severe manifestation of a neural tube defect
- cranial bones fail to develop
- embryonic brain structures contact amniotic fluid and degenerate
92
what dietary suppplement reduces the risk of neural tube defects
folic acid (vit B9)
93
what are somites?
cube-shaped structures formed from migration and clustering of mesodermal cells adjacent to notochord and neural tube
94
what do somites eventually give rise to?
all CT, including bone, muscle tissue
95
what week post-fertilization does angiogenesis begin?
at week 3
- begins in umbilical vesicle, connecting stalk, and chorion, *outside of embryo*
96
how do mesodermal cells form into blood vessels
mesodermal cells differentiate into hemangioblasts → angioblasts → blood islands
- spaces in blood islands form lumen of blood vessels
97
what week post-fertilization does blood begin to form inside the embryo?
at week 5
- blood begins to form inside embryo's liver
- supplemented at week 12 in forming spleen, RBM, thymus
98
from what mesodermal tissue does the heart form from?
cardiogenic mesenchyme
99
when does the heart begin to form?
at day 18-19
100
how does the heart differentiate into system of tubes, eventually forming the atria and ventricles?
**induction signals from endoderm** signal the heart to differentiate into the system of tubes
101
at what week post-fertilization does the heart begin to beat?
week 3
102
what are chorionic villi?
finger-like projections of the trophoblast into the endometrium
103
at what week post-fertilization do chorionic villi form?
at week 2
104
at what week post-fertilization do the chorionic villi become vascularized and connect to the embryonic heart?
at the end of week 3
105
what happens at the chorionic villi?
maternal blood bathes the chorionic villi, allowing for exchange between maternal and fetal blood at the intervillous spaces
106
do maternal and fetal blood mix?
no
107
what are some substances that can cross the placenta?
- oxygen
- nutrients
- gases
- drugs
- some toxins
108
how do substances cross the placenta?
they may pass across the epithelial tissues of the chorionic villi and into fetal capillaries
109
what blood vessels run through the umbilical cord?
fetus's umbilical artery and umbilical vein
110
which vessel found in the umbilical cord runs toward the fetal heart?
the umbilical vein
111
what do the umbilical vein and umbilical artery form from?
mucoid connective tissue from the allantois
112
what happens during the fourth week of development?
- rapid organogenesis
- embryo folds from a disc to a cylinder with C-shaped curve
- primitive digestive canal forms
- primitive lens and ear bud forms
- limb buds form
113
what happens during the fifth week of development?
brain grows rapidly, head is larger than trunk by end of week 6
114
what happens during the sixth week of development?
- limbs lengthen and straighten
- heart now contains four chambers
115
what happens during the seventh week of development?
- digits form but are webbed
- tail begins to straighten
116
what happens during the eighth week of development?
- tail disappears
- digits fully formed and separated
- external genitals are formed
- embryo now looks human
117
what is the fetal period?
- from week 9 to birth
- rapid growth
- only a few new structures appear
- fetus is more resilient to microbial infection, drugs, radiation compared to embryo
- 50% of birth weight will be added in the last 2.5mo
118
what are teratogens?
chemical/physical agents that affect development
119
what is fetal alcohol spectrum disorder?
facial malformations, neurological dysfunction due to alcohol consumption during pregnancy
120
what is ectopic pregnancy?
embryo implants outside the uterus
121
what are some prenatal diagnostic tests?
- fetal ultrasonography
- amniocentesis
- chorionic villus sampling
- maternal alpha-fetoprotein sampling
122
what is fetal ultrasonography?
- sound waves passed over abdomen and reflected back by fetal tissues and converted into a sonogram
- can detect gross malformations
- noninvasive procedure
123
what is amniocentesis?
withdrawal of amniotic fluid and testing of fetal cells and fluids
- can detect some genetic disorders
- can determine sex
- invasive procedure
124
what is chorionic villus sampling?
sampling of chorionic tissue, doesn't penetrate all the way into the cavities
- detects similar things as amniocentesis
- can detect some genetic disorders
- can determine sex
125
what is maternal alpha-fetoprotein sampling?
- alpha-fetoprotein should decrease in maternal blood after week 16
- high levels after week 16 **may indicate neural tube defect**
126
When can you expect to be able to detect a heartbeat from the developing embryo/fetus?
week 3
127
what are some changes that occurs to the mother during pregnancy?
- Weight gain
- Lordosis
- CO increases 1.2-1.3x b/c SV increases 1.3x
- increased appetite but decreased motility
- increased GFR and urination frequency
- changes to skin pigmentation
- increased elasticity of vagina
128
why does weight gain occur during pregnancy?
due to fetal development and the accumulation of fluids, including preparation for lactation
129
why does lordosis occur during pregnancy?
to compensate for growing abdomen in the anterior
130
why does CO increase during pregnancy?
to service the placenta as well as fetal tissues
131
why does increased appetite but decreased motility in the digestive canal occur during pregnancy?
increased appetite to service growing fetus, decreased motility to ensure maximum absorption
132
why does increased GFR occur during pregnancy?
permits removal of maternal AND fetal wastes
133
why is there increased frequency of urination during pregnancy?
- there is increased GFR and increased pressure from fetus in uterus on the urinary bladder
- ensures frequent removal of maternal AND fetal wastes
134
what controls changes to the mother during pregnancy?
hormones
135
what secretes hormones in the first 3-4months of pregnancy?
corpus luteum
136
why does the corpus luteum secrete estrogen and progesterone in the first 3-4 months of pregnancy?
to prevent shedding of the functional and compact layers of the endometrium and to prepare mammary glands for lactation
137
what secretes hormones starting from the 3rd month of pregnancy?
the placenta
138
what is the function of relaxin?
it loosens all ligaments, especially at pubic symphysis and sacroilial and sacrococcygeal joints
- helps relax cervic before birth
139
what is human chorionic somatomammotropin?
hormone that probably prepares mammary glands for lactation, also seems to regulate both maternal and fetal metabolism during development
140
what is the function of corticotropin releasing hormone from the placenta?
- stimulates anterior pituitary gland to make and release ACTH
- may serve as "clock" for when pregnancy ends
- pregnant women with high levels of CRH through pregnancy tend to deliver prematurely; women with low levels tend to deliver late
141
what does ACTH do in the fetus during labour?
binds cells in fetus's suprarenal cortex to make and release cortisal and DHEA
142
what does DHEA do in the placenta during labour?
placenta converts DHEA into estrogens
143
what do estrogens made from DHEA in the placenta do during labour?
estrogens cause myometrium to increase the expression of oxytocin receptors in their plasma membranes, also stimulates gap jxn formations btwn myometrial fibres for better and more rapid communication (helps overcome effects of progesterone which inhibits uterine contractions)
- also stimulates production of enzymes in cervix that degrade collagen fibres, relaxing cervis to permit dilation
144
what does oxytocin released from posterior pituitary do during labour?
oxytocin binds uterus to stimulate contractions
145
what does relaxin do during labour?
assists in dilating cervix and preparing pelvis for delivery
146
what is the stimulus for the labour feedback loop?
fetal head sits on internal os
- may be faciliated by rupture of the amniotic sac
147
what are the receptors for the labour feedback loop?
**stretch receptors in cervix** sense stretching from pressure of fetal head, sending nerve impulses to hypothalamus
148
what is the control centre for the labour feedback loop?
**hypothalamus**, which synthesizes and secretes oxytocin in to the blood
149
what are the effectors for the labour feedback loop?
oxytocin binds receptors on **myometrium**, stimulating forceful and frequent contractions
150
what is the net physiological response for the labour feedback loop?
fetus continues exit from uterus into vagina, stretching cervix even more
151
Kathy is breastfeeding her infant and is experiencing what feel like early labor pains. What is causing these painful feelings? Is there a benefit to them?
As part of the feedback mechanism for lactation, oxytocin is released from the posterior pituitary. It is carried to the mammary glands where it causes milk to be released into the mammary ducts (milk ejection). The oxytocin is also transported in the blood to the uterus, which contains oxytocin receptors on the myometrium. The oxytocin causes contraction of the myometrium, resulting in the painful sensations that Kathy is experiencing. The uterine contractions can help return the uterus back to its prepregnancy size.
152
Jack has hemophilia, which is a sex-linked blood-clotting disorder. He blames his father for passing on the gene for hemophilia. Explain to Jack why his reasoning is wrong. How can Jack have hemophilia if his parents do not?
Sex-linked genetic traits, such as hemophilia, are present on the X chromosomes but not on the Y chromosomes. In males, the X chromosome is always inherited from the mother, and the Y chromosome from the father. Thus, Jack’s hemophilia gene was inherited from his mother on his X chromosome. The gene for hemophilia is a recessive gene. His mother would need two recessive genes, one on each of her X chromosomes, to be hemophiliac. His father must carry the dominant (nonhemophiliac) gene on his X chromosome, so he also would not have hemophilia.
153
Alisa has asked her obstetrician to save and freeze her baby’s cord blood after delivery in case the child needs a future bone marrow transplant. What is in the baby’s cord blood that could be used to treat future disorders in the child?
The cord blood is a source of stem cells, which are unspecialized cells that have the potential to specialize into cells with specific functions. The hope is that stem cells can be used to generate cells and tissues to treat a variety of disorders. It is assumed that the tissues would not be rejected since they would contain the same genetic material as the patient—in this case Alisa’s baby.
