Week 2 Random Flashcards
Timing of migration of Primordial germ cells (PGCs)
2nd week: formed in epiblast
3rd week: move to the wall of the yolk sac
4th week: migrate to the developing gonads
5th week: arrive in the gonads then meiosis In the mouse, ~100 PGCs leave the yolk sac →6-7 rounds of mitotic multiplication →4000 enter the primitive gonads
Fate of misdirected PGCs
Die or Form Teratomas
Stages of formation of gametes
1) Movement of PGC to gonads
2) Mitosis in gonads (overproduction followed by density mechanism) in oogonia divide only during development, and in males spermatogonia divide during development and puberty
3) Meiosis
4) Structural and Functional maturation of Eggs and Sperm Oogenesis and Spermatogenesis
Oogenesis
2 million primary oocytes present in the ovaries at birth, only ~40,000-survivie until puberty.
400 (1 per menstrual cycle) are ovulated. Primary oocytes remain in prophase and do not finish their first meiotic division before puberty is reached.
At puberty, one activated primary oocyte produces two haploid cells asymmetric cell division The first polar body The secondary oocyte
The secondary oocyte arrests in metaphase II and is ovulated If penetrated by sperm the second oocyte completes meiosis II, One large ovum (the functional gamete) A tiny second polar body
Describe spermatogenesis
Spermatogonia (diploid)
Spermatocytes (enter meiosis)
Spermatids (haploid)
->spermiogenesis-> during which they acquire a tail (flagellum) and an acrosome that develops from the Golgi body
Sperm
Spermiogenesis:
- formation of acrosome (penetration enzymes)
- condensation of nucleus
- formation of neck, middle piece, and tail
- shedding of most of the cytoplasm that is phagocytized by Sertoli cells
Spermiation
Excess cytoplasm and is released into the lumen of the seminiferous tubule
How Kareotype is done
Leukocyte are isolated, propagated, and toxin are injected Cells are squashed on microscope slide Lightly treated with protease to unwind DNA Stained with Geimsa (non-specific) stain- (total 850 bands; about 50/csome)
Position of centromere
Metacentric (middle) submetacentric- towards one end acrocentric - at the end
p vs q
p is short arm q is long arm 7p22.2 46,XY,inv(9).(p11q12)
FISH
fluorescence in situ hybridization Specific nucleotide probes abeled with fluorescent dyes can be hybridized to the solated chromosomes or nuclei on microscope slides and nalyzed by fluorescence microscopy.
Types of probes in FISH
Locus specific (label single gene or region) Centromeric probe (labels a specific pair of chromosomes at their centromere) Chromosome painting probe (paint entire chromosome)
Two preps for FISH
Metaphase nuclei: visualize chromosome structure Interphase nuclei: determine number
SKY
Spectral Karyotiping FISH with different colors Use in cancer treatment
Why chromosomal studies are important
Confirmation/determination of diagnosis Prognosis Treatment Monitoring disease – disease progresion and relapse
Microarray SNP
This analysis is designed to look for imbalances across the genome using SNP (Single Nucleotide Polymorphism) based technology. The SNP microarray testing has probes that can detect imbalances related to hundreds of common Balanced or low level mosaic chromosome changes will not be identified with this technology
Use of Cell Free Fetal DNA
- Maternal age 35 years or older at delivery - Fetal ultrasonographic findings indicating an increased risk of aneuploidy - History of a prior pregnancy with a trisomy - Positive test result for aneuploidy, including first trimester, sequential, or integrated screen, or a quadruple screen. - Parental balanced robertsonian translocation with increased risk of fetal trisomy 13 or trisomy 21. - 10-15% DNA in mother blood is free fetal DNA - The goal of the test is very specifc trisome 13, 18, 21, XO, XXY
false positive false negative
Type 1 error, 1-accuracy Type 2 error, 1-sensitivty
Balanced / Unbalanced abnormalities of chromosomes
Duplications Inversions Inertions Isochromosomes
der(14;21)
Chromosome derived from 14 and 21
Balanced Translocations types
Reciprocal translocation Parts of chromosomes are exchanged Can result in mutations at break points or can be unaffected. Problems with segregation at gametogenesis Robertsonian translocation- centric fusion of two chromosomes. No lost coding sequences, carrier unaffected. Problems with segregation at gametogenesis.
Balanced vs. Unbalanced chromosomal rearrangements chraracteristic and types
Usually lethal 1) Spontaneous new mutation 2) Unbalanced inheritance from balanced rearrangements
Reciprocal translocation
Balanced chromosomes exchange
chromosomal studies can help with
Diagnosis (confirmation/determination) Prognosis Recurrence Risk
Amniocentesis
a prenatal diagnosis of chromosomal abnormalities and fetal infections, and also used for sex determination in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amniotic sac surrounding a developing fetus, and the fetal DNA is examined for genetic abnormalities
Cordocentesis
highly specialized prenatal test in which a sample of the baby’s blood is removed from the umbilical cord for testing
Cytogenetics techniques
1) Karyotyping
2) FISH
3) Microarray SNP Analysis
4) Cell free fetal DNA in Maternal Plasma
How does FSH effect ovary?
Production of estrogen
What are the functions of Estrogen?
Proliferation of endometrium
Thinning of the cervical mucus
Stimulate pituitary to secrete LH
LH surge at mid-cycle-> ovulation
Stimulate progesterone production
What cells that produce estrogen in female in ovary?
granulosa and thecal cells
What are LH surge effects?
completion of meiosis I -> preovulatory follicle; arrested in metaphase of meiosis II: 3hrs before ovulation
On ovarian surface:
LH↑→Collagenase↑→Digestions of fibers around the follicle
LH↑→Prostaglandin↑→muscular contraction
What are cells and their function in Corpus lueteum?
Lutean cells: granulosa cells, thecal cells
Progesterone + Estrogen (turns uterine into secretion phase)
How long does it take for an egg to go from ampulla to uterine lumen?
3-4 days
Where does the fertilization occur?
At the ampula of uterine tube
What secretes hCG?
syncytiotrophoblast
When does the corpus luteum stop to produce progesterone?
nProgesterone production until the end of 4th month: trophoblastic secretion of progesterone becomes adequate.
Name three phases of fertilization
Phase I: penetration of the corona radiata
Phase II: penetration of zona pellucida
Phase III: Fusion of the oocyte ad sperm cell membranes
What is Capacitation?
(wash the sperm by folliciular tubule): Maturation of sperm in female reproductive tractà Removal of the glycoprotein coat and seminal plasma proteins from the sperm plasma membrane (Important for IVF invitro fertiliation and IUI)
What is Acrosome reaction?
Release of enzyme by sperm to dissolve zona pellucida (ZP)
What events are triggered by entry of sperm to an egg?
Cortical and zona reactions: to prevent polyspermy (forming cortical granules)
Oocyte completes meiosis II
Egg is activated
What are Blastomeres?
2-, 4-, 8-cell stages, cells →smaller and smaller
What are the results of fertilization?
Restoration of diploid number of chromosomes
Sex determination (at fertilization)
Initiation of cleavage ge:en-US’>Cell free fetal DNA in Maternal Plasma
How does Blastocyst integrate in uterus?
ZP degenerates → uterine fluid penetration → Blastocele (cavity) formation
Inner cell mass → embryoblast
outer cell mass → trophoblast, epithelial wall
What are the three epithelial layers in endometrium?
Compact layer, spongy layer, and basal layer
Contraceptive methods:
Barrier
Hormone-based
IUD nRU-486 (mifepristone): potent progesterone antagonist nSurgery: Vasectomy & tubal ligation
trophoblast differentiation
Week 2 Day 8
Cytotrophoblast (mononucleated) migrate in the Syncitotrophoblast region and lose connection
Syncytiotrophoblast (multinucleated without border)
When and how embroyblast differentiate?
Week 2 Day 8
Hypoblast layer (adjacent to blastocyst cavity)
Epiblast layer (adjacent to the amniotic cavity)
When and where does the amniotic cavity form?
Week 2 Day 8
Surrounded by epiblast cells
When and what makes amniotic memberane?
Week 2 Day 8
Amnioblast (epiblast cells that adjacent to the cytotrophoblasts)
What are lacunae? How do they form? Where do they appear? When do they appear?
Week 2 Day 9
Vacuoles fuse in syncytiotrophoblast
What types of cells are present in hypoblast and epiblast during Day 9?
Epiblast – columnar
Hypoblast – cuboidal
What is fibrin coagulum?
A plug that seal the outer layer of endometrium after the embryo implants in uretus.
When does the lacuna becomes continous with sinusoids?
Week 2 Day 11-12
What is the name of a layer that surrounds Secondary yolk sac?
What is the name of a layer that surrounds amniotic cavity and chorionic cavity?
When do they appear?
Week 2 Day 11-12
Extraembryonic splanchnic mesoderm.
Extraembryonic somatic mesoderm.
What is the name of the cavity that is surrounded by extrasomatric membrane?
Chorionic caivty
What are the extension of cytotrophoblast called?
When and where do they grow?
Week 2 Day 13
Primary villi
They grow in syncytiotrophoblast
When and where does the secondary yolk sac come from?
Week 2
It pinches off from the primitive sac.
Also called definitive yolk sac.
What is the exocoelomic cavity?
What is the chorion composed of
Week 2
Extraembryonic somatic mesoderm
syncytiotrophoblast
cytotrophoblast
What is name that connects embryo to the chorion and what does it become?
Week 2
Connecting Stalk
Umbilical cord
Decidua reaction
Week 2 Day 11
Endometrium cells become polyhedral and prepare for implantation.
Which chromosomes regulate embryoblast?
Which chromosomes regulate trophoblast?
Female
Male
What types of cells are in epiblast?
Pluripotent.
What is the first site of hematopoesis?
Primary Yolk Sac
beta-hCG uses
Early pregnancy tests
Detecting may have hCG levels low. In normal pregnancy, hCG levels double every 2-3 days.
What forms extraembyronic mesoderm?
What does this extraembryonic mesoderm become?
Migration of epiblasts
Splanchnic mesoderm
Somatic mesoderm
Utero-placental circulation
Maternal blood lacunae form in the endometrium by invasion of syncytiotrophoblast + Chorionic villi = EARLY PLACENTA
Blood starts flowing in the trophoblast.
What are the two components of future planceta?
Endometrium and chorion
Oocyte maturation inhibitor
Inhibits progression of oocytes from birth
Small peptide
Stages in egg development
PRIMODIAL FOLLICE
cells become cuboidal and produce stratified epithelium of granulosa cells =
PRIMARY FOLLICLE
theca folliculi (stromal cells) separates it from connective tissue
zona pellucida (layer of glycoproteins on the surface of the oocyte, ofrming the zona pellucida)
inner cells become theca interna and outer into theca externa (fibrous capsule)
Antrum develops between granulosa cells
Cumulus oophorus forms around egg
MATURE GRAAFIAN FOLLICLE
What is the name of the cell formed by Cleavage?
Blastomere
Morula
16 cell ball
Composed of inner and outer cell mass
The inner cell mass give rise to the embryo proper
The outer cell mass give rise to the trophoblast which contributes to placenta
Blastula
Uterine fluid enters between cells
Blastocele forms
Cells of the inner cell are called embryoblast and outer cell mas trophoblast
Zona pellucida dissapears
L selectin mediate carbohydrate binding
When does the gastrulation begin?
What is gastrulation?
Week 3
Formation of all three germ layers: ectoderm, mesoderm, and endoderm
What are three components of primitive streak?
Node, Pit, and Groove
Where does the primitive streak go from and to?
From Cloacal membrane (anus) to Buccopharyngeal membrane (mouth).
Ovulation steps
Meiosis II is initiated
3 hours before ovulation arrested in methaphase
surface of ovary bulge
stigma (avascular spot) appear
LH increases collagenase activity
Prostaglandin levels also increase
Cumulus oophorus breaks free
Some of the cumulus oophorus cells then rearrange themselves around the zona pellucida to form the corona radiata.
Where are epiblast and hypoblast fused?
Buccopharyngeal membrane (mouth) and cloacal membrane (anus)
What does the gastrulation form?
Definitive Endoderm
The Intraembryonic Mesoderm
Trilaminar Embryo
What happens if primitive streak does not dissapear?
It forms a sacrococcygeal tumor (in newborn)
Direction of mesoderm differentiation
Cranial to caudal
Layers of mesoderm
Axial Mesoderm
Paraxial Mesoderm (somitomeres and somites)
Intermediate Mesoderm (urogentical system)
Lateral Plate Mesoderm (body wall)
Mesodermal contribution to the chorion (chorion)
Prechordal plate
Sets the limit for the cranial migration of notochordal cells
Induces formation of the forebrain
What are the results of the notochord formation?
- formation is a series of steps involving fusing with the endoderm
- defines primary axis, gives embryo some rigidity
- induces formation of vertebral column
- induces neuroectoderm to form neural plate
- persists as the nucleus pulposus in the intervertebral disc until early childhood. Likely replaced by connective tissue
3rd Week - Week of Threes
- 3 parts to the primitive streak - groove, pit, node
- 3 directions imparted by the primitive streak: dorsal-ventral, right-left, cranial-caudal
- 3 definitive germ layers - ectoderm, mesoderm, endoderm
- 3 types of villi - primary, secondary, tertiary
2nd Week - Week of Twos
- 2 trophoblastic layers - cytotrophoblast and syncytiotrophoblast
- 2 layers from the inner mass - epiblast and hypoblast
- 2 yolk sacs - primary and secondary
- 2 extraembryonic mesoderms - splanchnic and somatic
- 2 future cavities - chorionic and amniotic
- 2 components of the placenta - endometrium and chorion
- 2 clinical uses of betahCG
What causes neurulation?
What will the neural plate form?
Prechordal plate and notochord induce neural plate formation in the overlying ectoderm.
Neural plate differentiates to neuroectoderm that forms the brain and spinal cord (CNS) during the embryonic period?
What is the difference between primary, secondary, and tertiary stem villi?
Primary –cytotrophoblastic core covered by a synctial layer
Secondary – mesoderm layer, followed by cytotrophoblast, and then synctiotrophoblast
Tertiary villus – when blood vessels differentiate from mesoderm
When tertiary villi form, which side contacts the embryo and which side contacts the baby.
Syncitotrophoblast covers vessels in villia
Cytotrophoblast contacts endometrium
Composition of bilaminar embryonic disk.
Epiblast and hypoblast.
Prochordral plate
Week 2
Fusion of epiblast and hypoblast that will become mouth.
What are some of the different types of genes expressed?
Housekeeping genes
Specialized genes
Finely tuned genes
Normal vs. Diseased gene expression
What type of proteins remodel chromatin?
ATP-dependent chromatin remodeling complexes
What is The code-reader complex?
It is a scaffold protein bound to multiple proteins that recognize the chromatin modifications.
Types of miRNA
Small nuclear RNA (snRNA) - mRNA processing
Small nucleolar RNA (snoRNA) – rRNA processing
Small cytoplasmic RNA (scRNA) – range of function
microRNAs (miRNAs) – post-transcriptional gene-silencing
Whare are the functions of TFs
TFIID = TBP + TAFS
TFIIB = recognize BRE element
TFIIF = stabolize interaction TBP/TFIIB
TFIIE = attacts TFIIH
TFIIH = unwinds DNA; phosphorylateion CTD; releases RNA pol from the promtoter
What are enzymes involved in mRNA editing?
Phosphatase
Guanyl transferase
Methyl transferase
Alternative Splicing mechanisms
Exon skipping
Mutually exclusive exons:
Alternative 5’ donor site:
Alternative acceptor site:
Intron retention:
“Cryptic splice site” - a site whose sequence resembles an authentic splice site and which might be selected instead of the authentic site during aberrant splicing
Domainds of TFs
DNA-binding domain (DBD).
Dimerization domain
Activation domain.
HOX genes
They control the fundamental architectural plan of the developing embryo.
They are 180 bp long genes, coding for 60 (180 ÷ 3) amino acid long proteins.
They contain the so-called “homeodomain” consisting of a DNA-binding Helix1-Helix2-Helix3 motif (A). Helix3 occupies the major groove of DNA, while the N-terminal arm binds to the minor groove (B).
Effects of ubiquitin
Monoubiquitylated = Histone regulation
Multiubiquitylated = Endocytosis
Polyubiquitylated = DNA Repair; Degradation
What is the tag that directs proteins to lysosome?
What is the tag of ER resident proteins?
mannose-6-phosphate
KDEL
Functions of Amino Acids
a) Proteins
b) Hormones
c) Co-enzymes
d) Nucleotides
e) Alkaloids
f) Cell wall polymers
g) Antibiotics
h) Neurotransmitters
Top three molecules by mass in the body
Water
Protein
Fat
Modifications in amino acids
–Hydroxylation (proline, lysine)
–Esterification (serine, threonine, tyrosine) •Acetylation •Phosphorylation
–Disulfide bonds (cysteine → cystine)
–Methylation (lysine, histidine, glutamate)
–Carboxylation (glutamate)
10 Essential amino acids
These Ten Valuable Amino acids Have Long Preserved Life In Man.
Threonine Tryptophan
Valine Arginine*
Histidine* Leucine
Phenylalanine Lysine
Isoleucine Methionine*
(Tryosine can be made from Phenylalanine)
Name the
5 carbon ring
6 carbon ring
Furanose
Pyranose
What type of transport occurs at nuclear porest?
Gated transport
How do molecules enter nucleus
<5kDa diffusion
>60kDa active transport
RAN transport
Cargo binds to the carrier (Nuclear Import Receptor).
Carrier enters the nucleus, releases protein, and binds to RAN-GTP
Carrier enters cytoplasm and GTP is hydrolyzed and RAN released.
NFAT import
(IL2 used during Tcell activation)
NFAT is triphosphorylated
High calcium activates calcineurin (protein phosphatase)
NFAT with calcineurin enters nucleus
Gene activation (IL2 transcription)
Low calcium removes calcineurin from NFAT, and NFAT is phosphorylated and exported
Three secretory pathways
Signal-mediated diversion to lysosomes
Constitutive secretory pathway (e.g. collagen)
Signal-mediated diversion to secretory vessicles (for regulated secretion) (e.g. digestive enzymes)
What is the most abundant protein in mammals
Collagen
16 types but predominant
Collagen structure, assembly
Composed of two identical chains (α1) and an additional chain that differs slightly in its chemical composition (α2)
Each chain contains 1050 amino acids
Collagen are translated as longer precurosrs
Co-translational translocation
Default pathway
Modifications of collagen in ER and golgi
The signal peptide on the N-terminal is dissolved, and the molecule is now known as propeptide (not procollagen).
Hydroxylation of lysines and prolines on propeptide by the enzymes prolyl hydroxylase and lysyl hydroxylase (to produce hydroxyproline and hydroxylysine) occurs to aid crosslinking of the alpha peptides. It is this enzymatic step that requires vitamin C as a cofactor. In scurvy, the lack of hydroxylation of prolines and lysines causes a looser triple helix.
Glycosylation occurs by adding either glucose or galactose monomers onto the hydroxyl groups that were placed onto lysines, but not on prolines. From here the hydroxylated and glycosylated propeptide twists towards the left very tightly and then three propeptides will form a triple helix. This molecule, now known as procollagen (not propeptide) is composed of a twisted portion (center) and two loose ends on either end. At this point the procollagen is packaged into a transfer vesicle destined for the golgi apparatus.
In Golgi,
polymers of sugars are added
Largest capacity organ for protein synthesis
Pancreas
What cell in pancreas produce digestive enzymes?
acinar cells
Examples of enzymes produced in pancreas
Trypsinogens (1, 2, 3)
Chymotrypsinogen (A, B)
α-Amylase
Procarboxypeptidase A (1, 2)
Lipase
Procarboxypeptidase B (1, 2)
DNase
Prophospholipase (I, II)
RNase
Proelastase
Mesotrypsin
How genes for digestive enzymes are regulated?
The contain pancreas consensus element (PCE)
A transcription factor, PTF-1, present selectively in the exocrine pancreas, binds to this region and is essential for expression of these digestive enzymes.
How do digestive enzymes get diverted to secretory vesicles for regulated secretion?
- Creating a transport vesicle involves assembling a protein coat on the cytosolic face of the budding membrane
- Different protein coats select different cargo
- ** GTP-binding** proteins control both spatial and temporal aspects of membrane exchange
Clathrin coats types
trans-Golgi network - transport to lysozomes
trans-Golgi network - storage in secretory vesicles
plasma membrane - receptor-mediated endocytosis
Clathrin multimers
Triskelions
How digestive enzyme exocytosis is regulated?
By neurohumoral agents
gastrin-releasing peptide (GRP)
cholecystokinin (CCK)
acetylcholine (Ach)
secretin
vasoactive intestinal polypeptide (VIP)
What is the name of the response mediates an adaptive response so that the exocrine pancreas can adjust its machinery to the effects of the stressors and proceed with normal synthetic and transport functions
3 functions
unfolded protein response (UPR)
1) chaperones and foldases
2) activate the ERAD
3) global reduction in translation (except for digestive enzymes)
quality control system for unusable proteins
ER-associated protein degradation (ERAD)
Calnexin function
Ensures that glycosylated proteins are correctly folded.
Describe ERAD
Chaperone cannot fold the protein
Protein is feed through channel to cytoplasm
Protein in ubiquitinated
Proteasome degrades protein
What is central organ tha regualtes level of cholesterol?
Liver
LDL function
Carries cholesterole
apolipoprotein B100 (part of LDL complex) that binds to LDL receptor and signals removal of LDL from ciruclation
Cholesterol function
Membrane permeability
Precursor for the biosynthesis of steroid hormones, bile acids, and vitamin D
Enzymes in lysozome
Nucleases
Proteases
Glycosidases
Lipases
Phosphatases
Sulfatases
Phospholipases
3 pathways to degradation in lysozomes
Autophagy
Phagocytosis
Endocytosis
Types of Coenzymes (Cofactors)
Cosubstrate: associates transiently with the active site of an enzyme
Prosthetic group: associates permanently to the active site of an enzyme
ATP
energy, energy charge, cation
deltaG = -7kcal/mol
Magnesium
Energy charge = ([ATP] + ½ [ADP])/ ([ATP] + [ADP] + [AMP])
Enzymes
AMP + ATP <-> ADP + ADP
XMP + ATP <-> XDP + ADP
XDP + ATP <-> XTP + ADP
Adenylate kinease
Nucleoside monophosphate kinease
Nucleoside diphosphate kinease
X=A,G,U, or C
AH2 + NAD+ –> A + NADH + H+
CH3CH2OH + NAD+ –> CH3CHO + NADH + H+
Dehydrogenase
Alcohol denhydrogenase
Which part of the CoA is reaction?
Sulfhydryl group (-SH)
forms thioester bonds with organic acids
Thioester bond -7kcal/mol
What is the function of S-adenosyl methionine
To carry methyl groups
Converted to S-adenosyl homocysteine after the methyl transfer
Turner Syndrome characteristics
Only monosomy compatible with life
Absence of ovaries
Webbed neck
Lymphedema of the extremities
Skeletal deformities
Broad chest
Widely spaced nipples
Cri-du-chat Syndrome characteristics
Deletion of chromosome #5
cat-like cry
Microcephaly
intelectual disability
congenital heart disease
Miller-Dieker syndrome characteristics
a condition characterized by a pattern ofabnormal brain development known as lissencephaly. Normally the exterior of the brain (cerebral cortex) is multi-layered with folds and grooves. People with lissencephaly have an abnormally smooth brain with fewer folds and grooves.
Angelman’s syndrome
Microdeletion on maternal csome15
Intellectual disability
Cannot speak
Exhibit poor motor development
Prone to unprovoked and prolonged period of laughter
Prader Willi
Microdeletion on paternal csome15
Hypotonia
Obsety
Intellectual disability
Hypogonadism
Undescended testes
Ciclosporin
Calcinurin inhibitor
Reduces immune response
