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BIO |! 351 |! Exam |! 3 |! with |! precise |!
detailed |! solutions
When |! and |! where |! are |! cardioprogenitors |! specified? |! - |! Correct |! answer |! ✔Cardioprogenitors |! are |! specified |! during |! early |! embryogenesis |! in |! the |! splanchnic |! mesoderm, |! which |! is |! derived |! from |! the |! lateral |! plate |! mesoderm, |! and |! is |! known |! as |! the |! cardiogenic |! field |! or |! cardiogenic |! mesoderm. What |! does |! the |! primary |! heart |! field |! form? |! - |! Correct |! answer |! ✔The |! primary |! heart |! field |! forms |! the |! initial |! scaffold |! and |! eventually |! the |! ventricle. |! The |! secondary |! heart |! field |! continues |! to |! create |! cells |! and |! forms |! all |! the |! other |! structures. What |! is |! the |! splanchnic |! mesoderm? |! - |! Correct |! answer |! ✔The |! splanchnic |! mesoderm |! is |! the |! layer |! that |! forms |! the |! circulatory |! system |! and |! the |! future |! gut |! wall. |! Cardiogenic |! cells |! are |! also |! formed |! from |! this |! layer. Where |! does |! cardiac |! primordia |! arise |! from? |! - |! Correct |! answer |! ✔The |! splanchnic |! mesoderm. What |! is |! linked |! to |! the |! ventral |! closure |! of |! the |! embryo? |! - |! Correct |! answer |! ✔Migration |! of |! the |! cardiac |! primordia |! an |! formation |! of |! the |! linear |! heart.
What |! is |! induced |! by |! rapid |! growth |! of |! the |! neural |! tube |! and |! somites? |! - |! Correct |! answer |! ✔Ventral |! closure. What |! is |! the |! heart |! defect |! Dextrocardia? |! - |! Correct |! answer |! ✔This |! is |! where |! the |! heart |! lies |! on |! the |! right |! side |! of |! the |! thorax |! because |! it |! looped |! to |! the |! wrong |! side. What |! other |! defect |! can |! cause |! the |! heart |! to |! be |! looped |! the |! wrong |! way? |! - |! Correct |! answer |! ✔Situs |! inversus, |! which |! causes |! complete |! asymmetry |! of |! all |! organs |! within |! the |! body. What |! is |! the |! heart |! defect |! Heterotaxy? |! - |! Correct |! answer |! ✔This |! is |! where |! the |! heart |! is |! located |! on |! the |! right |! side |! of |! the |! chest |! instead |! of |! the |! left |! side. |! This |! is |! random |! and |! usually |! fatal. How |! are |! the |! chambers |! of |! the |! heart |! created |! after |! looping? |! - |! Correct |! answer |! ✔Endocardial |! cushions |! form |! on |! the |! dorsal |! and |! ventral |! walls |! of |! AV |! canal, |! which |! then |! meet |! and |! separate |! the |! AV |! canal |! into |! the |! right |! and |! left |! channels |! and |! act |! as |! primitive |! valves |! for |! the |! heart. How |! can |! malformations |! of |! the |! endocardial |! cushions |! affect |! the |! heart? |! - |! Correct |! answer |! ✔This |! can |! lead |! to |! atrial |! and |! ventricular |! septal |! defects, |! abnormal |! transposition |! in |! the |! great |! vessels, |! and |! defects |! often |! associated |! with |! craniofacial |! defects.
In |! an |! developing |! embryo |! heart |! (day |! 21), |! name |! what |! each |! part, |! from |! anterior |! to |! posterior, |! will |! eventually |! form |! in |! a |! mature |! heart |! (newborn). |! - |! Correct |! answer |! ✔From |! top |! to |! bottom: |! Aortic |! sac, |! conotruncal, |! right |! ventricle, |! left |! ventricle, |! right |! atrium, |! left |! atrium, |! atrioventricular |! (AV) |! valve What |! defect |! results |! from |! failure |! of |! the |! septum |! to |! separate |! the |! ventricle? |! - |! Correct |! answer |! ✔Ventricular |! Septal |! Defect |! (VSD). |! This |! leads |! to |! mixing |! of |! arterial |! and |! venous |! blood |! occurs |! in |! both |! outflow |! tracts |! but |! especially |! in |! the |! pulmonary |! artery. What |! genes |! regulate |! the |! formation |! of |! a |! 4-chambered |! heart? |! - |! Correct |! answer |! ✔Tbx5, |! which, |! in |! mammals, |! is |! initially |! expressed |! in |! the |! entire |! ventricular |! primordial |! heart |! field |! and |! then |! later |! becomes |! restricted |! to |! the |! right |! atrium |! (RA), |! left |! atrium |! (LA), |! and |! left |! ventricle |! (LV). What |! does |! restricting |! Tbx5 |! expression |! lead |! to? |! - |! Correct |! answer |! ✔This |! leads |! to |! formation |! of |! the |! right |! ventricle |! in |! a |! four-chambered |! heart. |! If |! expression |! is |! not |! restricited, |! a |! three-chambered |! heart |! is |! created. Where |! do |! the |! septa |! that |! separate |! the |! truncus |! arteriosus |! into |! the |! pulmonary |! artery |! and |! aorta |! form |! from? |! - |! Correct |! answer |! ✔They |! form |! from |! cells |! of |! the |! cardiac |! neural |! crest. How |! does |! formation |! of |! the |! lung |! bud |! begin? |! - |! Correct |! answer |! ✔The |! lung |! bud |! begins |! as |! an |! outpouching |! from |! the |! foregut, |! forming |! the |! esophagus |! and |! trachea.
What |! is |! the |! homologous |! structure |! of |! lungs |! in |! the |! teleost |! (fish)? |! - |! Correct |! answer |! ✔The |! swim |! bladder What |! are |! some |! potential |! outcomes |! in |! lung |! bud |! development |! defects? |! - |! Correct |! answer |! ✔Separation |! of |! the |! trachea |! and |! esophagus |! does |! not |! occur |! correctly. |! This |! means |! the |! two |! are |! either |! attached |! in |! some |! way |! of |! the |! tube |! of |! each |! does |! not |! fully |! form. What |! order |! [from |! first |! created |! to |! last |! created] |! does |! branching |! morphogenesis |! occurs? |! - |! Correct |! answer |! ✔Trachea, |! bronchi, |! bronchioles, |! alveolar |! sacs How |! many |! lung |! bud |! lobes |! are |! created |! in |! humans? |! In |! a |! mouse? |! - |! Correct |! answer |! ✔For |! humans, |! there |! are |! five |! total: |! 2 |! left |! lobes |! and |! 3 |! right |! lobes. |! For |! a |! mouse, |! there |! are |! also |! five: |! 1 |! left |! lobe |! and |! 4 |! right |! lobes. What |! are |! the |! purposes |! of |! Type |! I |! and |! Type |! II |! alveolar |! cells? |! - |! Correct |! answer |! ✔Type |! I |! alveolar |! cells |! flatten |! and |! enable |! greater |! gas |! exchange. |! Type |! II |! regenerate |! or |! form |! Type |! I |! cells. What |! progenitor |! cells |! do |! each |! of |! these |! create? |! Basal |! cells? |! Clara |! cells? |! Type |! II |! cells? |! - |! Correct |! answer |! ✔Basal |! Cells |! = |! Bronchi |! Progenitor |! Cells Clara |! Cells |! = |! Brionchiole |! Progenitor |! Cells Type |! II |! Cells |! = |! Alveolar |! Progenitor |! Cells
What |! is |! the |! embryological |! origin |! of |! the |! lens? |! - |! Correct |! answer |! ✔Head |! surface |! ectoderm: |! the |! lens |! forms |! from |! the |! optic |! placode, |! which |! is |! a |! thickening |! of |! the |! head |! surface |! ectoderm If |! Microphthalmos |! is |! genetic, |! in |! which |! of |! the |! following |! genes |! would |! you |! most |! likely |! expect |! to |! find |! a |! mutation? |! - |! Correct |! answer |! ✔RX, |! which |! is |! required |! for |! induction |! of |! the |! eyes If |! you |! notice |! the |! colchlea |! is |! missing |! in |! the |! inner |! structure |! of |! a |! mouse |! ear, |! what |! would |! you |! expect |! of |! the |! mouse? |! - |! Correct |! answer |! ✔Deafness |! because |! the |! cochlea |! is |! needed |! to |! receive |! auditory |! vibrations. What |! is |! the |! embryological |! origin |! of |! the |! cochlea |! and |! semicircular |! canals |! (inner |! ear)? |! - |! Correct |! answer |! ✔Head |! surface |! ectoderm: |! both |! of |! these |! structures |! are |! formed |! by |! involution |! of |! the |! otic |! placode, |! which |! is |! a |! thickening |! of |! the |! head |! surface |! ectoderm What |! is |! myopia |! and |! hyperopia |! and |! how |! common |! are |! each? |! - |! Correct |! answer |! ✔Myopia |! is |! nearsightedness |! and |! is |! prevalent |! in |! 25% |! of |! the |! population |! [50% |! of |! medical |! students]. |! Hyperopia |! is |! farsightedness |! and |! is |! prevalent |! in |! 5% |! of |! the |! population. What |! gene |! is |! required |! for |! vertebrate |! retina |! development? |! - |! Correct |! answer |! ✔Rx |! genes
What |! is |! Microphthalmos? |! - |! Correct |! answer |! ✔Microphthalmos |! is |! a |! developmental |! disorder |! of |! the |! eye |! that |! literally |! means |! small |! eye. |! One |! or |! both |! eyes |! may |! be |! involved. |! This |! is |! caused |! by |! a |! mutation |! in |! the |! RX |! gene. What |! are |! the |! steps |! in |! the |! formation |! of |! the |! optic |! sulcus, |! vesicle, |! and |! cup? |! - |! Correct |! answer |! ✔1. |! The |! optic |! sulcus |! forms |! in |! the |! forebrain |! during |! neurulation.
- |! The |! optic |! vesicle |! begins |! to |! form |! on |! day |! 22 |! before |! the |! cranial |! neurophore |! has |! closed. |!
- |! By |! day |! 24, |! the |! optic |! vesicles |! lie |! adjacent |! to |! the |! surface |! ectoderm.
- |! During |! the |! 5th |! week, |! the |! optic |! vesicle |! invaginates |! to |! become |! the |! optic |! cup, |! and |! the |! choroidal |! fissure |! forms |! on |! the |! inferior |! surface |! of |! the |! optic |! cup |! and |! stalk. How |! and |! when |! is |! the |! lens |! pit |! created? |! - |! Correct |! answer |! ✔The |! lens |! pit |! is |! created |! during |! week |! 5 |! when |! the |! lens |! placode |! invaginates., |! which |! eventually |! pinches |! off |! to |! form |! a |! lens |! vesicle. When |! are |! the |! choroid |! and |! sclera |! formed? |! - |! Correct |! answer |! ✔The |! choroid |! and |! sclera |! are |! formed |! during |! the |! 5th |! to |! 7th |! week |! of |! development |! when |! the |! mesenchyme |! surrounds |! the |! developing |! eyeball |! (optic |! globe). How |! are |! the |! eyelids |! formed? |! - |! Correct |! answer |! ✔The |! upper |! and |! lower |! eyelids |! form |! from |! folds |! of |! surface |! ectoderm. |! They |! fuse |! together |! by |! the |! end |! of |! the |! 8th |! week |! and |! separate |! again |! between |! the |! 5th |! and |! 7th |! months.
What |! is |! Connexin |! 26? |! - |! Correct |! answer |! ✔Connexin |! 26 |! (kDalton) |! = |! Gap |! Junction |! protein |! Beta |! 2 Connexin |! 26 |! is |! expressed |! in |! the |! supporting |! cells |! of |! the |! ear |! and |! is |! required |! for |! normal |! K+ |! homeostasis. Pharyneal |! arches |! 1 |! & |! 2 |! form |! which |! part |! of |! the |! ear? |! - |! Correct |! answer |! ✔The |! pinna |! (external) |! ear. What |! are |! some |! congenital |! defects |! of |! the |! pinna? |! - |! Correct |! answer |! ✔Auricular |! Tags |! and |! Malformations |! of |! the |! outer |! ear. The |! optic |! placode |! develops |! into |! the |! adult |! ___________ |! while |! the |! otic |! placode |! develops |! into |! the |! adult |! __________. |! - |! Correct |! answer |! ✔lens, |! cochlea/semicircular |! canals What |! cells |! in |! the |! central |! nervous |! system |! form |! the |! blood-brain |! barrier |! that |! protects |! the |! brain |! from |! chemicals |! in |! the |! bloodstream? |! - |! Correct |! answer |! ✔Astrocytes ___________ |! produce |! myelin |! in |! the |! central |! nervous |! system |! myelination |! while |! __________ |! produces |! it |! in |! the |! peripheral |! nervous |! system. |! - |! Correct |! answer |! ✔Oligodendrocytes, |! Schwann |! cells A |! developing |! embryo |! is |! treated |! with |! a |! toxin |! that |! completely |! disrupts |! all |! neuromuscular |! junction |! development. |! What |! stage |! of |! muscle |! development |!
would |! be |! blocked |! by |! this |! treatment? |! - |! Correct |! answer |! ✔Formation |! of |! secondary |! myotubes. |! Formation |! of |! secondary |! myotubes |! requires |! innervation |! at |! the |! neuromuscular |! junctions. |! The |! previous |! steps |! do |! not |! required |! this |! innervation. Which |! structures |! derives |! from |! the |! neural |! crest |! and |! regulate |! the |! "fight |! or |! flight" |! stress |! response? |! - |! Correct |! answer |! ✔Sympathetic |! chain |! ganglion Which |! progenitor/stem |! cell |! populations |! leads |! to |! the |! formation |! of |! Clara |! cells? |! - |! Correct |! answer |! ✔brionchiole |! progenitor |! cells When |! Tbx5 |! is |! expressed |! in |! both |! the |! left |! and |! right |! ventricle |! in |! the |! mouse, |! what |! results? |! - |! Correct |! answer |! ✔3-chambered |! heart Because |! the |! lung |! bud |! is |! derived |! from |! the |! foregut, |! primordial |! lung |! bud |! defects |! can |! lead |! to |! malformation |! of |! what |! structures? |! - |! Correct |! answer |! ✔trachea/esophagus Between |! five |! and |! seven |! weeks, |! the |! optic |! globe |! is |! surrounded |! by |! mesenchyme |! and |! forms |! the |! ___________________________. |! - |! Correct |! answer |! ✔choroid |! and |! sclera A |! baby |! is |! born |! with |! a |! mutation |! in |! the |! Rx |! gene. |! Which |! of |! the |! following |! defects |! would |! you |! expect |! the |! newborn |! to |! have? |! - |! Correct |! answer |! ✔microphthalmia
What |! is |! white |! and |! grey |! matter? |! - |! Correct |! answer |! ✔White |! matter |! is |! myelinated |! regions |! of |! the |! brain |! that |! look |! white. |! Grey |! matter |! are |! areas |! of |! the |! brain |! with |! many |! neuronal |! cells |! bodies |! that |! look |! gray. Does |! myelenation |! increase |! or |! decrease |! as |! you |! get |! older? |! - |! Correct |! answer |! ✔Increases |! as |! you |! get |! older |! with |! brain |! almost |! fully |! myelinated |! by |! the |! age |! of |! 20. What |! cells |! line |! the |! neuroventricles? |! - |! Correct |! answer |! ✔Ependymal |! cells What |! regulates |! differentiation |! at |! the |! neural |! tube |! lumen? |! - |! Correct |! answer |! ✔Notch |! signaling What |! is |! the |! importance |! of |! notch |! signaling |! in |! regards |! to |! neuron |! development? |! - |! Correct |! answer |! ✔1. |! suppresses |! neuronal |! & |! oligodendrocyte |! differentiation
- |! promotes |! astrocyte |! differentiation A |! loss |! of |! Notch |! signaling |! leads |! to |! too |! many |! neurons. What |! is |! the |! importance |! of |! Robo/Slit |! proteins |! in |! regards |! to |! regulation |! of |! midline |! crossing |! by |! neurons? |! - |! Correct |! answer |! ✔Without |! the |! action |! of |! Slit |! protein, |! located |! in |! the |! midline, |! the |! neurons |! all |! cluster |! near |! the |! midline |! and |! do |! not |! form |! the |! bilateral |! neuronal |! columns. |! Slit |! activates |! Robo1 |! which |! then |! blocks |! the |! ability |! to |! of |! the |! growth |! cone |! to |! respond |! to |! Netrin. |! Robo3 |! blocks |! Robo1 |! expression |! and |! the |! growth |! cone |! can |! respond |! to |! Netrin.
How |! do |! Robo/Slit |! proteins |! regulate |! midline |! crossing |! by |! neurons? |! - |! Correct |! answer |! ✔Slit |! activates |! Robo1 |! which |! then |! blocks |! the |! ability |! to |! of |! the |! growth |! cone |! to |! respond |! to |! Netrin. |! Robo3 |! blocks |! Robo1 |! expression |! and |! the |! growth |! cone |! can |! respond |! to |! Netrin. |! Once |! past |! the |! midline, |! Slit |! once |! again |! blocks |! the |! ability |! of |! the |! growth |! cone |! to |! respond |! to |! Netrin. What |! defect |! can |! a |! mutation |! in |! the |! Robo3 |! protein |! cause? |! - |! Correct |! answer |! ✔Scoliosis What |! happens |! during |! the |! first |! wave |! of |! myotube |! formation? |! - |! Correct |! answer |! ✔The |! first |! wave |! occurs |! through |! a |! nearly |! simultaneous |! fusion |! of |! existing |! myoblasts |! to |! form |! primary |! myotubes. What |! happens |! during |! the |! second |! wave |! of |! myotube |! formation? |! - |! Correct |! answer |! ✔Fetal |! myoblasts |! fuse |! asynchronously |! to |! form |! secondary |! myotubes, |! which |! is |! initiated |! at |! the |! site |! of |! neuromuscular |! junctions |! formation |! of |! primary |! fibers. |! Basically, |! innervation |! is |! required |! for |! secondary |! myotube |! formation. Where |! do |! cells |! of |! the |! peripheral |! and |! autonomic |! nervous |! systems |! form |! from? |! - |! Correct |! answer |! ✔The |! neural |! crest, |! which |! is |! derived |! from |! the |! dorsal |! neural |! tube |! that |! migrates |! outward. Where |! are |! Schwann |! cells |! created |! from? |! - |! Correct |! answer |! ✔The |! cranial |! and |! trunk |! neural |! crest
How |! are |! PGCs |! specified? |! - |! Correct |! answer |! ✔proximal |! posterior |! epiblast |! cells |! -> |! fragilis |! expressed |! in |! epiblast |! cells |! -> |! Blimp1 |! expression |! in |! half |! the |! cells |! -> |! stella |! is |! then |! all |! expressed |! in |! the |! cells |! that |! become |! PGCs How |! do |! PGCs |! migrate |! to |! the |! gonads? |! - |! Correct |! answer |! ✔E7.0: |! leave |! the |! posterior |! primitive |! streak, |! enter |! the |! endoderm E9.0: |! Enter |! the |! hindgut |! and |! migrate |! dorsally |! E10.0: |! exit |! hindgut |! and |! enter |! the |! genital |! ridges E11.5: |! Enter |! the |! developing |! gonad |! (they |! proliferate |! while |! migrating |! to |! about |! 2500-5000 |! PGCs) How |! do |! PGCs |! know |! where |! to |! migrate? |! - |! Correct |! answer |! ✔Stem |! cell |! factor |! is |! secreted |! by |! cells |! along |! the |! route |! of |! migration-necessary |! for |! maintenance |! of |! PGCs. BMP4 |! and |! BMP8b |! are |! secreted |! from |! extraembryonic |! ectoderm |! at |! E7.0. |! In |! response |! to |! these |! factors, |! competent |! cells |! at |! the |! posterior |! of |! the |! embryo |! will |! __________. |! - |! Correct |! answer |! ✔become |! primordial |! germ |! cells In |! testis |! development, |! what |! do |! the |! testis |! cords |! become? |! - |! Correct |! answer |! ✔The |! seminiferous |! tubules. |! PGCs |! will |! induce |! the |! epithelial |! cells |! to |! become |! Sertoli |! cells |! that |! will |! secrete |! anti-Mullerian |! hormone |! (AMH), |! which |! degrade |! the |! Mullerian |! ducts |! found |! in |! female |! gonads.
What |! does |! testosterone |! induce |! Wolffian |! duct |! to |! differentiate |! into? |! - |! Correct |! answer |! ✔Wolffian |! duct |! differentiate |! into |! the |! epididymis, |! vas |! deferens, |! and |! seminal |! vesicles. In |! ovary |! development, |! what |! happens |! to |! the |! sex |! chords? |! - |! Correct |! answer |! ✔The |! sex |! chords |! degenerate |! and |! proliferation |! of |! epithelial |! cells |! will |! form |! cortical |! cords. The |! Wolffian |! duct |! contributes |! to |! which |! of |! the |! following |! male |! gonadal |! structures? |! - |! Correct |! answer |! ✔vas |! deferens A |! researcher |! is |! studying |! a |! transcription |! factor |! that |! that |! is |! essential |! for |! the |! formation |! of |! the |! mesonephric |! duct. |! Based |! on |! your |! knowledge |! of |! the |! developing |! urogenital |! tract, |! which |! of |! the |! following |! defects |! would |! you |! predict |! that |! you |! will |! find |! in |! mice |! when |! a |! knock |! out |! mutation |! has |! been |! made |! in |! this |! gene? |! - |! Correct |! answer |! ✔Male |! mice |! will |! have |! defects |! of |! their |! vas |! deferens. |! During |! development |! of |! the |! testis |! the |! epigenital |! mesonephric |! tubules |! are |! maintained |! and |! form |! the |! epididymis |! and |! efferent |! ducts. |! If |! this |! factor |! is |! important |! for |! the |! development |! of |! the |! mesonephric |! duct |! then |! these |! structures |! may |! be |! rudimentary |! or |! absent. In |! the |! photomicrograph |! the |! expression |! of |! cyp26b1 |! RA |! is |! degraded. |! What |! does |! the |! male |! female |! genital |! ridge |! expression |! pattern |! mean? |! - |! Correct |! answer |! ✔cyp26b1 |! can |! degrade |! RA |! in |! males In |! the |! developing |! embryo |! ______________ |! induces |! female |! germ |! cells |! to |! enter |! _______________. |! - |! Correct |! answer |! ✔retinoic |! acid; |! meiosis
are |! haploid, |! and |! females |! develop |! from |! fertilized |! eggs |! and |! are |! diploid. |! This |! is |! mainly |! found |! in |! insects |! such |! as |! wasps, |! bees, |! and |! ants. |! The |! unfertilized |! males |! are |! the |! "workers." What |! is |! the |! difference |! between |! Single-locus |! CSD |! (sl-CSD) |! and |! Multi-locus |! CSD |! (ml-CSD)? |! - |! Correct |! answer |! ✔**sl-CSD |! is |! where |! sex |! is |! determined |! by |! multiple |! alleles |! at |! a |! single |! locus. |! They |! are |! female |! if |! they |! carry |! two |! different |! alleles |! (heterozygotes) |! and |! male |! if |! they |! carry |! one |! (hemizygotes) |! or |! more |! (homozygotes) |! copies |! of |! the |! same |! allele. **ml-CSD |! is |! determined |! by |! several |! loci, |! each |! with |! two |! alleles. |! An |! individual |! heterozygous |! at |! any |! of |! these |! loci |! is |! female |! while |! homozygotes |! and |! hemizygotes |! are |! male. What |! determines |! drosophila |! flies |! as |! female |! or |! male? |! - |! Correct |! answer |! ✔Female |! flies |! have |! 2 |! X |! chromosomes |! and |! so |! have |! twice |! as |! much |! of |! Runt, |! Sisterless-A |! (SisA) |! and |! Scute |! genes |! as |! well |! as |! the |! Unpaired |! signaling |! factor. |! This |! activates |! the |! sxl |! (sex-lethal) |! gene, |! which |! has |! a |! splicer |! Transformer |! gene |! (Tra) |! that |! splices |! sex-specific |! mRNAs. |! Males, |! with |! only |! one |! X, |! do |! not |! have |! a |! sufficient |! amount |! of |! activator |! proteins |! to |! activate |! the |! sxl |! protein. What |! does |! a |! fruitfly |! do |! with |! a |! Y |! chromosome? |! - |! Correct |! answer |! ✔The |! Y |! chromosome |! does |! not |! have |! any |! affect |! on |! sex-determination |! but |! is |! necessary |! for |! spermatogenesis. If |! there |! is |! a |! mutation |! in |! the |! male |! specific |! exon |! of |! sex-lethal |! (sxl) |! that |! removes |! the |! stop |! codon |! what |! sex |! would |! offspring |! be? |! - |! Correct |! answer |! ✔All |! female
What |! evidence |! is |! there |! that |! SRY |! is |! the |! testis |! determining |! factor? |! - |! Correct |! answer |! ✔It |! is |! expressed |! in |! testis |! as |! well |! as |! is |! detected |! in |! XY |! and |! rare |! XX |! males |! but |! are |! absent |! from |! XX |! and |! XY |! females. |! This |! can |! be |! seen |! experimentally |! when |! XX |! females, |! who |! do |! not |! have |! the |! SRY |! and |! lack |! male |! genitals, |! have |! SRY |! expressed. |! This |! creates |! an |! XX |! female |! with |! male |! genitals. What |! are |! some |! other |! genes/factors |! that |! play |! a |! role |! in |! mammal |! sex- determination? |! - |! Correct |! answer |! ✔Sox9 |! and |! Steroidogenic |! factor |! 1 |! (SF-1), |! which |! are |! both |! activated |! by |! the |! presence |! of |! SRY |! gene. |! XX |! individuals |! that |! have |! an |! extra |! copy |! of |! Sox9 |! develop |! as |! infertile |! males |! but |! do |! not |! have |! the |! SRY |! gene. A |! knockout |! of |! sox9 |! was |! made |! using |! a |! Sf-1cre |! and |! floxed |! sox9 |! allele. |! What |! do |! you |! expect |! the |! phenotype |! of |! XY |! mice |! to |! be? |! - |! Correct |! answer |! ✔Female. |! This |! is |! because |! Sox9 |! can |! replace |! SRY |! but |! SRY |! cannot |! form |! testes |! if |! Sox9 |! is |! absent. What |! is |! campomelic |! dysplasia? |! - |! Correct |! answer |! ✔Campomelic |! dysplasia |! is |! a |! severe |! disorder |! that |! affects |! the |! development |! of |! the |! skeleton |! and |! reproductive |! system. |! Individuals |! with |! this |! typically |! are |! short |! in |! stature |! with |! bowing |! long |! bones |! as |! well |! as |! external |! genitalia |! that |! do |! not |! look |! clearly |! male |! or |! clearly |! female |! (ambiguous |! genitalia). What |! does |! Fibroblast |! growth |! factor |! 9 |! (Fgf9) |! do? |! - |! Correct |! answer |! ✔Fgf9 |! necessary |! for |! Leydig |! cells |! to |! proliferate. |! They |! promote |! Sertoli |! cell |! differentiation |! and |! mesonephric |! cell |! migration |! necessary |! for |! testis |! cords |! to |! form.
