Study Questions 10 Flashcards
. What organ systems are greatly affected by amphibian metamorphosis? Briefly describe changes in these systems between larval and adult forms. What is initiating those changes?
All organ systems are affected by amphibian metamorphosis
· Changes in systems between larval and adult forms
· Initiation > thyroid hormones thyroxine (T4) and triiodothyronine (T3)
Locomotory Apoptosis of tail
Respiratory Change in haemoglobin (water to air oxygen supply)
Circulatory Aortic arch, jugular vein -> carotid arch, systemic arch, cardinal veins
Nutritional Long spiral gut to short gut, change in jaws
Nervous Develop nicitating membrane, loss of lateral line system, change in retina photo pigment expression
Excretory Ammonia –> urea
Integuement Change in dermis, epidermis, glands
. How would you define ‘regionally specific development programs’ (=organ specific programmed response)? Give an example.
Regionally specific development programs, or organ specific programmed response, is the differences in tissue responses and timing to the expression of derivatives of thyroid hormones (tissue may differentiate or degenerate)
· Organ specific -> transplant tail into tail region = both apoptose, transplant eye cup into tail region = only tail apoptose (programmed response)
· Example – T3, T4 hormones instruct limb bud muscles to grow and tail muscles to undergo apoptosis
What are the four major regeneration mechanisms? Briefly (one sentence) describe each of them.
Epimorphosis – amputation cause dedifferentiation of cells and formation of undifferentiated mass of cells (blastema) which re-specifies into lost part of body (e.g. salamander limb)
· Morphallaxis – regeneration via repatterning/rearrangement of existing structures with little new growth (hydra repattern after loss of limb to reform)
· Compensatory Regeneration – differentiated cells divide to form cells similar to itself but maintain differentiated functions and therefore do not come from stem cells or dedifferentiated adult cells (liver) (intermediate form of regeneration)
· Stem-cell mediated Regeneration – regrowth of certain organs or tissues lost (e.g. bone marrow replace blood cells, hair)
Salamanders can reconstruct a complete limb, if necessary. Which parts of the limb are getting reconstructed after amputation? How do we call this type of regeneration?
· Reconstruction of missing parts of limb after amputation
· Epimorphosis regeneration of proximal to distal limb portion
Describe the process of limb regeneration in salamander.
. Amputation
ii. Plasma clot form
iii. Surrounding epidermis cover wound to form wound epidermis (no scar tissue)
iv. Wound epidermis proliferate into apical epidermal cap (AEC) – prevent scar formation v. Under AEC dedifferentiation and proliferation form regeneration blastemal vi. Cells undergo respecification to form new structures
. What are the similarities between apical ectodermal ridge and apical epidermal cap? What are the differences? (Define both of them first.)
Apical Ectodermal Ridge
· produced in limb formation of embryogenesis
· area underneath is progress zone (constant proliferation, determine distal part + what limb developed)
· proximal to distal formation
· secrete fgf8 for PZ proliferation maintenance -prevents early cartilage formation
· induced by fgf10
· important for limb bud formation
· signalling centre
· maintain mesenchyme proliferation for proximal distal growth
· expression of molecules that make AP axis
· interact w/ protein that make AP DV axes for differentiation coordination
Apical Ectodermal Cap
· produced in limb regeneration
· area underneath known as regeneration blastema
· stimulate growth of blastema by release fgf8 (P563)
· maintains zone dedifferentiation and proliferation
· prevents early cartilage formation
· requires fgf10, fgf8, shh
· fgf2 for angeiogenesis
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· roximal to distal respecification
- What is the role of nerves in salamander’s limb regeneration?
· Nerves release factors that drive proliferation of blastema cells from AEC
o Glial growth factor?
o Newt anterior gradient protein – allow blastema cells proliferate
Explain the following statement: Blastema is heterogeneous population of restricted progenitor cells.
The cell population in the blastema retain their specification and there are multiple kinds of cells
· Old Dermis and skeleton cells can only give rise to dermis or skeleton
· Old Muscle, Schwann and epidermis cells can only become new muscle, Schwann and
epidermis
· Restricted Progenitors are not fully undifferentiated and are not multipotential
● Progenitors have a restricted set of redifferentiation fates (blastema retain specification)
- What are the major steps in mammalian liver compensatory regeneration?
I. Removal of liver lobe
II. Metalloproteases digest ECM to separate/loosen hepatocytes
III. Lipopolysaccharides activate non-hepatocytes to secrete Paracrine factors to induce hepatocytes to re-enter cell cycle
IV. Stellate cells release hepatocyte growth factor (HPF) and TGF-beta
A. HPF activated by metalloproteases
V. Proliferation of remaining tissue
A. Hepatocytes, bile duct, kupffer, endothelial, Ito cells divide
VI. All cell types retain identity (no dedifferentiation occurs)
- Define maximum life span. Define maximum life expectancy.
Maximum life span – maximum number of years a member of species has been known to survive (not expected to live this long)
· Life expectancy – span of time you expect to live
- What are the consequences of an increase in a human life span?
Causes of death changed
o Heart attack and cancer deaths increase
o Infection, parasite deaths decrease
o Increasing prevalence of gray hair, sag skin, stiff joins, loss muscle mass/strength,
fertility issue, memory loss
· Senescence due to illness
. List a few causes of aging that we mentioned in class?
Wear AND Tear and genetic instability > change in chromatin structure, enzyme defects,
reduced DNA repair
· Oxidative Damage – reactive oxygen species damage tissue, DNA
· Mitochondrial DNA – higher chance mutation b/c more replication going on and more exposure to reactive oxygen species, no histones for protection, less repair mechanisms
· Mutations that cause Premature Aging Symptoms – early aging from Hutchinson-Gilford progeria syndrome
- Briefly describe the differences between three types of IVF we talked about in class.
Gamete Intrafallopian Transfer GIFFT
● sperm injected into oviduct at ovulation
● sperm don’t have to travel
● internal fertilization
● at least one fallopian tube open
● used when cervical/immunological factors hinder sperm
Zygote Intrafallopian Transfer ZIFT
● fertilization in dish, zygotes placed in fallopian tube not uterus
● external fertilization
● fertilization confirmation
Intracytoplasmic Sperm Injection ICSI
● single sperm injected into egg cytoplasm
● remove egg from ovary, place fertilized egg into uterus
● use when low viable sperm count
- From the table below choose three genes encoding human transcription factors involved in embryonic development and discuss briefly the consequences their mutations would have during embryogenesis (this question will be on the exam!).
● Androgen Receptor - Androgen Insensitivity Syndrome – mutation alter RNA longevity, no uterus but have vagina, testes don’t descend (sterile)
● Estrogen Receptor – growth regulation problems, sterility
● SRY – male sex reversal to female
What are the possible consequences of mutation in a regulatory part of a gene? In an intron? In a sequences which will be transcribed into 5’ and 3’ UTRs of the mRNA? In a coding sequence? Would you be able to give one example for each of these mutations?
Mutation in regulatory part of gene can have large effect on protein the gene codes for
· Mutation in intron can result in
o new splice site, convert intron to exon
o remove splice site, change exon
o change affinity of splice site for specific splice factors
· Mutation in 5’ UTR of mRNA =
o change translation efficiency
o form new start codon which extends N-terminus
o remove original start codon = shorten N-terminus
· mutation in 3’ UTR of mRNA =
o alter mRNA stability for binding sites of miRNA or regulatory proteins
o affect mRNA trafficking by mutation of location sequences
· coding region
o result in point mutation
o introduce premature stop codon
