Mutations/Chromosomal abnormalities

Question 0

Male pt shows high forehead, large ears, long face and prominent jaw. Pt additionally has learning disabilities. Further physical exam shows large testes, conn. tissue weakness and mitral valve prolapse

Answer 0

Fragile X syndrome

Question 1

Triplet repeat expansion in the X chromosome

Answer 1

Fragile X syndrome

Question 2

47 XXY

Answer 2

Klinefelter syndrome

Question 3

Although females have another X to compensate for X link recessive disorders, which condition still can have features show in the female?

Answer 3

Fragile X syndrome
Female carrier can show the characteristic facial features which include high forehead, large ear, long face and prominent jaw

Question 4

Pt presents with mild learning disability, reduce IQ, and exhibits self obsessed behavior. What karotype do you expect?

Answer 4

47 XXY

Question 5

Pt with reduced IQ and gynecomastia. How would you treat?

Answer 5

pt is XXY

treat with testosterone starting in puberty

Question 6

Conditions seen more commonly with increasing maternal age?

Answer 6

Klinefelter syndrome

Down syndrome

Question 7

You notice short arms on chromosomes are lost in FISH test. whats going on?

Answer 7

Robertsonian translocation

Question 8

Acrocentric chromosome

Answer 8

centrosome is on the end

Question 9

Two acrocentric chromosomes combine and lose their satellite arms. what happens to those arms in Robertsonian translocation?

Answer 9

those arms contains redundant rRNA, no harm there

usually considered functionally balanced since no genetic information is lost

Question 10

When can issues arise with Robertsonian translocations?

Answer 10

Issues can arise during chromosome segregation in meiosis I

Question 11

With pachytene quadrivalents, how many outcomes can there be?

Answer 11

6 possible 
normal, balanced or unbalanced 
1 normal 
1 carrier 
4 unbalanced

Question 12

what are the two situations that result in Down syndrome

Answer 12

Robertsonian Translocation to 14/21 and 21

or Trisomy 21 from non disjunction in maternal meiosis I

Question 13

You deliver a baby and it sounds like a cat!!! Whats wrong with his chromosomes?

Answer 13

deletion in terminal portion of chromosome 5

Question 14

Duchenne muscular dystrophy

Answer 14

microdeletion on X chromosome (Xp21)

Question 15

How do unbalanced insertions occur?

Answer 15

if material has moved within the same chromosome complement then one has a duplication and other is now missing that region
so technically, its an insertion and deletion

Question 16

pericenteric inversion

Answer 16

involves the centromere

genes flip around the centromere

Question 17

paracenteric inversions

Answer 17

gene swap happens in the arms

Question 18

2 or more genetically distinct cell lines derived from more than one zygote

Answer 18

Mixoplody - chimerism

Question 19

2 or more cell lines that differ in genetic constitution that are derived from a single zygote

Answer 19

Mixoploidy - Mosaicism

accounts for 1-2% of Down syndrome

Question 20

how frequent are chromosomal abnormalities in mature oocytes?

Answer 20

25%

Question 21

____ of all spermatozoa contain chromosomal abnormalities

Answer 21

10%

Question 22

Meiosis definition

Answer 22

process of nuclear division marking the final stage of gamete formation

Question 23

how does meiosis differ from mitosis?

Answer 23

mitosis results in 2 daughter cells, each diploid
meiosis halves the number creating 4 haploid gametes

meiosis only in the final stages of gamete formation

occurs in 2 distinct cell division events (I and II)

Question 24

Meiosis I starts with and ends with?

Answer 24

starts with diploid cell with replicated and condensed chromosomes (XX)
ends with haploid cells with pairs of sister chromatids (X) and (X)

Question 25

Meiosis II starts with and ends with?

Answer 25

starts with haploid cells with pairs of sister chromatids (X) and (X)

ends with four haploid cells with individual chromosomes ( I ) ( I ) ( I ) ( I )

Question 26

homologous recombination

Answer 26

also called Cross-over

allows genetic variation in resulting offspring

Question 27

what must occur for homologous recombination to occur?

Answer 27

chromosomes must synapse to form a bivalent (pair) for meiotic recombination to occur

errors in this process are a frequent cause of chromosomal abnormalities - translocations and inversions

Question 28

Example numerical of chromosomal abnormality

Answer 28

Aneuploidy
which is loss or gain of one or more chromosomes

Polyploidy - addition of one or more complete haploid complements

Monosomy - loss of a chromosome

Question 29

What is an example of a structural chromosome abnormality?

Answer 29

these are rearrangements resulting from chromosome breakage and subsequent reunion in different configuration
includes translocations, inversions, deletions, and insertions

Question 30

Trisomy 21 most frequently occurs from

Answer 30

non disjunction in the maternal meiosis I

Question 31

Non disjunction in Meiosis I results in

Answer 31

two disomic gametes and two nullisomic gametes

Question 32

Non disjunction in Meiosis II results in

Answer 32

1 Disomic gamete
1 Nullisomic gamete
2 normal monosomic gametes

Question 33

XXX is an example of ? and what the are symptoms?

Answer 33

polyploidy
no overt symptoms but there is a mild reductio in IQ and oppositional behavior
due to maternal non disjunct in meiosis I

Question 34

what would you suspect of a patient showing a reduction in IQ and emotional immaturity with FISH karotype showing chromosome evident of a paternal non disjunction in meiosis II

Answer 34

XYY male

YY never split during gamete formation

Question 35

Pt shows neck webbing and puffy extremities. You notice short stature for her age and normal intelligence but unusual social skills. What symptoms would you expect her to have later in life?

Answer 35

She is XO, has turner syndrome

she would have ovarian failure and narrowing of the aorta later in life

Question 36

Does the inheritance of the X in Turner syndrome make any difference to the offspring?

Answer 36

yes, paternal X Turner pts show higher social cognition skills

Question 37

45 X

Answer 37

Turner syndrome

Question 38

In reciprocal translocations, when do issues usually arise?

Answer 38

during chromosomal segregation in meiosis I

Question 39

If fragments exchanged in reciporal translocation are relatively equal then

Answer 39

there are generally no deleterious effects in the CARRIER

Question 40

Reciprocal translocation

Answer 40

breakage of at least 2 chromosomes and exchange of fragments

Question 41

Reciprocal translocations in Meiosis I

Answer 41

cannot form bivalents due to translocation forming a pachytene quadrivalent where each chromosome aligns with homologous material

Question 42

Pachytene Quadrivalents

Answer 42

pattern of segregation determines is the haploid is normal, balanced or unbalanced.
Normal (1/6)
Balanced (1/6)
Unbalanced (4/6)

Question 43

Microdeletion on chromosome 15 (15q11-13) results in

Answer 43

Prader Willi syndrome or Angleman

Question 44

Angelman Syndrome

Answer 44

deletion on maternal chromosome 15

Question 45

Prader Willi syndrome

Answer 45

deletion of paternal chromosome 15

Question 46

You deliver a floppy baby who wont eat. Years later, mother brings in an overweight toddler showing learning disabilities. What could be the condition?

Answer 46

Angelman or Prader Willi syndrome

Question 47

What is Prader willi/ Angelman an example of?

Answer 47

Imprinting - this is where the gene/region shows different expression depending on parent of origin
this is believed to be due to differences of methylation of DNA

Question 48

Angelman syndrome characterized by

Answer 48

inappropriate laughter, ataxia and severe learning disabilities