Embryology Flashcards
What is DNA?
Transmits genetic code to the next generation
Unit of heredity
What is RNA?
Copies the code from DNA (transcription) and translates it into amino acids
Point between DNA and amino acid production
What are the differences between DNA and RNA?
DNA is double stranded and RNA is single stranded
DNA has thymine as a base and RNA has uricil
DNA has one less oxygen molecule than RNA
What nerve, muscle, and skeletal structure develop from the 1st branchial arch?
Trigeminal
Tensor tympani
Incus and malleus
What nerve, muscle, and skeletal structure develop from the 2nd branchial arch?
Facial
Stapedius
Stapes
What is gastrulation?
The development of the 3 germ layers
Development form a blastocyst to a gastrula
What are the 3 germ layers?
Endoderm, mesoderm, and ectoderm
What develops from the endoderm?
Epithelial lining of the ET
Epithelial lining of GI tract
What develops from mesoderm?
Vascular system (heart, valves)
Bone (ossicles)
Smooth muscle
What develops from ectoderm?
PNS
CNS
Epidermis
Review embryonic development of the inner ear and cochlea
What are 2 similarities of mitosis and meiosis?
Same division phases
Both double number of chromosomes they have before division
What are 2 differences of mitosis and meiosis?
Mitosis produces 2 identical daughter cells and meiosis produces 4 non-identical cells
Mitosis only has one division stage
What are some 1st and 2nd arch syndromes?
Pierre Robins
Stickler
Treacher Collins
What are some main characteristics of 1st and 2nd arch syndromes?
Small/abnormal ear
Small lower jaw
Cleft lip with or without palate
What are epigenetics?
Environmental effects on genes
Most cancers
What is missense non-conservative mutation?
A point mutation where it changes the amino acid that is supposed to go there
Doesn’t do a similar function
What is transcription?
Exact copy of the code
What is translation?
Translating code into amino acids
Cochlear hair cells once fully differentiated, remain in the _______ phase of the cell cycle?
G0
What is a point mutation that prematurely codes for a stop codon?
Nonsense mutation
Genetic crossing over in _______ prevents children form being clones of parents
Prophase 1
What are the stop codons?
UAA
UAG
UGA
Which neural tube defect contains remnants of all three germ layers?
Dermoid cyst
What is the primary function of meiosis?
Combining genetic material from egg and sperm to prevent offspring from being clones of parents
Providing haploid number of chromosomes to germ cells
Does meiosis 2 end with 4 daughter cells with 46 chromosomes?
No, they are haploids
Does DNA structure allow for replication and affords protection against DNA loss and damage?
Yes
What do sperm not contribute? Why?
Mitochondria
Shed cytoplasm
Is a zygote a diploid?
Yes
What does the ET develop from?
The first pharyngeal pouch
What does the EAM develop from?
The first pharyngeal groove
What does the pinna develop from?
Auricular hillocks
What does the inner ear develop form?
Otic placode of the ectoderm
What are adenine and guanine?
Purines (two ring)
What are cytosine and thymine?
Pyramidines (one ring)
What are differences between AD and AR?
AR requires a copy of 2 identical genes
AD has vertical transmission
AR is impacted by consanguinity
AR traits have a 25% chance of being passed down, and AD have a 50% chance
What is an eve gene?
A mitochondrial gene
What is homozygous/
2 identical alleles for one gene
What is genomic imprinting?
Phenotype of a mutation is determined or impacted by who it was passed by
Prader willi - paternal
Angelman - maternal
What is a phenocopy?
An environmental trait that mimics a genetic trait
Hair loss from chemo is a phenocopy of alopecia
For an offspring to inherit an AR condition, does the parent need to be an obligate carrier?
Yes
What is complementary mating?
Not the same deafness gene
Hearing children
What is huntington’s disease an example of?
Genetic anticipation and allele expansion
Does x-linked transmission have male to male transmission?
No
Do chromosomal abnormalities typically adversely affect several different systems and structures?
Yes
Do most people with an unequal number of chromosomes demonstrate growth deficits and intellectual disability?
Yes
Should genetic testing be performed on individuals with multiple malformations and an unknown diagnosis?
Yes
What are the acrocentric chromosomes?
13, 14, 15, and 22 (look up)
What is an aneuploidy?
Abnormal chromosome numebr
What is a pleiotropy?
Multiple phenotypical effects
What is the founder effect?
Genetic conditions more common in a culture that in the general population
What is nullisomic condiiton?
Lethal
WHat is multifacotrial inheritance?
Sporadic gene mutaiton
What is hemizygous?
Sex chromosomes for males
Different chromosomes entirely
What are connexin proteins?
Gap junction proteins that control channels in the cochlea and throughout the body
What is the most common connexin gene mutation
35 del
Is connexin AD or AR?
AR
What are two psychosocial and ethical issues with genetic testing?
Not well regulated, no one is policing discrimination that could come from this testing
This is the only medical testing that can tell you things about family members, privacy issue
What are three ways an extra copy of chromosome 21 can be inherited?
Nondisjunction
Translocation
Mosaicism
What is turner syndrome?
Monosomy of sex chromosomes
Female phenotype
Intellectual disability
Infertility
Ear infections common
X
What is klinefelter’s syndrome?
Trisomy of sex chromosomes
Male phenotype
Low to normal intellect
SNHL common
Infertility
XXY
What transmission does ushers syndrome have and what is a common characteristic other than HL?
AR
Retinitis pigmentosa
Hunter syndrome
X-linked
Chronic diarrhea (megacolon)
Waardenburg
AD
Different colored eyes
Upper limb abnormalities
Stickler
AD
Joint characteristics
Charcot-marie tooth
AR
Sensory and motor nerve degeneration
Achondroplasia
AD
Normal sized trunk and short limbs
NF2
AD
Bilateral vestibular schwannoma
NF1
AD
Cafe au lait spots and tumors on skin
Osteogenesis imperfecta
AD
Bone fragility
JLNS
AR
Long QT syndrome
Mondini malformation of the inner is common associated with what condition?
CHARGE
Most likely syndrome for:
A 12 year old male with severe bilateral SNHL. He was recently diagnosed with hematuria and born with cataracts. Two older first cousins (a male and a female) are similarly affected. These are children of his maternal aunt who also is hearing impaired and has kidney problems. His mother has SNHL and is undergoing kidney failure. Hi father has normal hearing and no ocular or renal problems.
Alport syndrome, x-linked
Most likely:
A 5 year old girl with severe bilateral SNHL. The family is mourning for their 15 year old son who died of a sudden heart attack. That child was born with profound bilateral SNHL. They have another child, a 10-year-old son, who has normal hearing and is in apparent good health. the parents are second-cousins and deny any knowledge of other family members with a history of hearing loss
JLNS
Adele and David, both of whom are hearing, have scheduled an eye appointment for their 16 year old son. He is hard of hearing and has weak eyesight. Hearing loss and vison have become worse, and he can barely see at night
Usher type 2
AR
Susanne, a 4-year-old diagnosed with mixed hearing loss 3 years ago, which is not progressive. She also has prehelical pits with no other facial anomalies. Previous CT scan revealed a mondini malformation. Unsteady on her feet. Dad is wearing bilateral HA for a congenital HL. Dad’s brother, a maternal uncle, and mother were all born wiht or devleoped a hearing loss early in life and had polycystic kidneys.
BOR
AD
Gabrielle, a 15-year-old, who has severe to profound unilateral SNHL since birth. She has gray hair. She also has abnormally thick eyebrows and eyes are laterally displaced. She mother and maternal grandfather are both wearing bilateral hearing aids and have a white forelock.
Waadrenburg type 1
AD
What are two characteristics seen in norries but not ushers?
X linked recessive inheritance
Seizures
AD inheritance. Abnormalities developing from first arch. Fish-like mouth and frequent dental anomalies. Moderate to severe CHL with normal mental status. Normal vision but absent lower lashes.
Treacher collins
AD with weak penetrance. Delayed onset genetic condition. CHL or mixed loss due to post-embryonic remodeling of otic capsule. Preponderance of young white females affected.
Otosclerosis
AD. Premature closure of structures. CHL or mixed hearing loss. Normal intellect. Marked cranial/facial anomalies including maxillary hypoplasia and bulging eyes.
Crouszons
Possible multifactorial inheritance associated with sporadic gene mutations. Incomplete development/absence of ear, nose, mandible, and/or internal organs typically on one side of the face/body. Deafness/blindness in one or both ears/eyes.
OAV syndrome
One of the most common AR neurodegenerative disorder, caused primarily by GAA codon triplet repeat expansion of the FXN gene. Chronic, slowly progressieve neuropathy with diminished tendon reflexes and babinski sign. Uncoordinated voluntary movements. Pre-adolescent onset
Friedrichs ataxia
Is hurler AD or AR?
AR
What is hurler syndrome characterized by?
Course facial features
What is the differential diagnosis for JLNS?
Ward Romano syndrome
What is a biotinidase deficincy?
Treatable and preventable with biotin supplements
Is the connexin protein only expressed in the auditory system?
No
What is the deaf community generally accepting of?
Usher
Will 100% of individuals with NF2 have intellectual disability?
No
Routine blood, urine tests, and x-rays are generally unhelpful in established a genetic cause for hearing loss. What is something a urine test would be helpful in determining?
Alport syndrome
What is the differential diagnosis for NF2?
Vestibular schwannoma
What is the differential diagnosis for usher?
Norrie
What is the differential diagnosis for alport?
BOR
What is the differential diagnosis for pendred?
DFNB4
What does the OtoSCOPE genetic panel do?
Test for both AD and AR conditions
Comprehensive genetic sequencing
Tests for GJB2 and GJB6 connexin genes
Tests for both ushers and pendred
T/F: The most common AD syndromic HL is waardenburg
True
T/F: The most common AR syndromic HL is connexin
False
T/F: For a couple with an AD condition, the risk of having an affected baby is 50%. Their first child was born deaf, therefore, their second child will be hearing.
False
T/F: Generally, non-syndromic autosomal dominant HL is postlingual while non-syndromic autosomal recessive HL is prelingual
True
T/F: According to current laws, insurance companies cannot use genetic info to deny coverage
True
But its not being mandated or monitored
What is linguistic homogamy?
What is x-inactivation?
A form of germ cell mosaicism
What is population bottleneck?
Reduction in population size that enhances the effect of gene drift
What is chimerism?
Presence of 2 sets of DNA
What is Robertsonian translocation?
Common in acrocentric chromosomes
What is waardenburg type IV?
Deafness/profound HL, pigmentary disturbances, and megacolon
What is DFNX?
Perilymphatic gusher with stapes fixation
What is norrie syndrome?
X linked
Congenital cataracts
Progressive SNHL
Seizures
Psychiatric disorder
Blindness
What is the most common non-syndromic deafness and hearing loss in humans?
GJB2/GJB6 gene mutations
What does consanguinity do?
Promotes increased expression of AR traits
What is charcot-marie tooth?
Progressive neurodegenerative disease with polyneuropathy and associated auditory neuropathy
What is aminoglycoside-induced deafness?
Hearing loss is secondary to administration of antibiotics for serious infectious conditions such as tuberculosis
Not dose dependent
What condition has 80% of sporadic mutations and prevent ossification of cartilage to bone especially in long bones of arms and legs?
Achondroplasia
What is balanced polymorphism?
