Chromosomal Aberrations

Question 1

false about adrenoleukodystrophy
A. X linked genetic disorder that occurs primarily in male
B. Disorder of peroxisomal fatty acid beta oxidation
C. Accumulation of very short chain fatty acids in tissues
throughout the body

Answer 1

C - very long dapat

Question 2

enumerate 3 most severely affected sites @ adrenoleukodystrophy

Answer 2

myelin in the CNS
adrenal cortex
Leydig cells in the testis

Question 3

location of main mutation @ adrenoleukodystrophy

Answer 3

Long arm of Chromosome X region 28

Question 4

False about meiosis
A. daughter cells are diploid
B. at prophase I, tetrads are formed from homologous chromosomes
C. problems here would lead to genetic mutations

Answer 4

A - haploid dapat any daughter cell

Question 5

main cause of aneuploidy

Answer 5

nondisjunction (or non-separation) during meiosis 1

results in N+1, N+1, N-1, N-1) or meiosis 2 (results in N+1, N-1, N, N

Question 6

False about Monosomy
A. missing chromosome perturbs the overall gene balance in the chromosome set
B. missing chromosome allows any deleterious recessive allele on the single chromosome to be hemizygous and thus to be directly expressed phenotypically
C. Down Syndrome is an example of this

Answer 6

C - Down syndrome is trisomy. Example ng monosomy is Turner Syndrome (X0)

Question 7

Which is mismatched?
A.Klinefelter syndrome : XXY
B.Patau syndrome: Trisomy 12
C.Edward’s Syndrome: Trisomy 18

Answer 7

B - Patau syndrome is trisomy 13

Question 8

harelip and rocker bottom feet present at __
A.Klinefelter syndrome : XXY
B.Patau syndrome: Trisomy 13
C.Edward’s Syndrome: Trisomy 18

Answer 8

B

Question 9

Faunlike ears present at __
A.Klinefelter syndrome : XXY
B.Patau syndrome: Trisomy 13
C.Edward’s Syndrome: Trisomy 18

Answer 9

C

Question 10

identify the aneuploidy: Epicanthal folds, flat nasal bridges, upslanting palpebral fissures, midface hyperplasia, small mouths, cleft or high arched palates, delayed or absent teeth or enamel defects

Answer 10

48 XXXX

Question 11

two ways for aberrations in chromosome structure to occur: enumerate

Answer 11

1. Total amount of genetic information in the chromosome can change
2. Genetic material may remain the same, but is rearranged

Question 12

False about deletions
A. Deletions revert even if DNA is gone
B. Effect of deletion depends on what was deleted
C. Human disorders caused by large chromosomal
deletions are generally seen in heterozygotes since homozygotes usually die

Answer 12

A - irreversible sila

Question 13

identify this chromosomal aberration & classify its type:
Affected individuals have underdeveloped vocal chords, wide set eyes, small head and jaw, moderate to severe mental health problems, very short

Answer 13

Cri-du-Chat syndrome

deletion

Question 14

Tandem duplications are said to be adjacent to one another. Differentiate reverse tandem from terminal tandem.

Answer 14

Reverse tandem result in genes arranged opposite
order of original.
 Terminal tandem are duplications at the end of a
chromosome

Question 15

(1) What exactly happens in MECP2 Duplication Syndrome?

(2) What is MECP2 responsible for?

Answer 15

(1) Extra copy of MECP2 gene is caused by a
duplication of genetic material in the long (q) arm
of the X chromosome
(2) MECP2 – responsible for normal function of
nerve cells

Question 16

False about MECP2 Duplication Syndrome
(A) Almost exclusively in females
(B) Characterized by moderate to severe
intellectual disability
(C) Weak muscle tone in infancy, feeding
difficulties and poor or absent speech.
(D)Some affected individuals experience loss of previously acquired skills (developmental regression)

Answer 16

(A) - almost exclusively in males dap at

Question 17

identify the chromosomal aberration:Results when a chromosome segment excises and
reintegrates oriented 180o from original orientation

Answer 17

inversion

Question 18

Differentiate pericentric from paracentric inversion

Answer 18

Pericentric Inversion – includes centromere
 Paracentric Inversion – does not include
centromere

Question 19

Which is false?
A.Inversion has same effect on homozygote & heterozygote.
B.Linked genes are often inverted together.
C.Gametes produced from pericentric and paracentric
inversions are imbalanced

Answer 19

A

Question 20

Differentiate effect of inversion on homozygote & heterozygote

Answer 20

Homozygote will have normal meiosis
Heterozygote effect depends on whether crossing
over occurs
(1) If no crossing over, no meiotic problem
occurs
(2) If crossing over happens, unequal
conversion may produce serious genetic
consequences

Question 21

Which can happen in a heterozygous paracentric inversion but not in a heterozygous pericentric inversion?
A.One normal gamete
B.One gamete with duplication and deletion
C.One gamete with reciprocal duplication and
deletion
D.Two deletion products

Answer 21

D

A - happens in both
B & C - for heterozygous pericentric inversion only

Question 22

Why do the great majority of inversions have no
phenotypic consequences in a way that alters its
gene expression?

Answer 22

In an inversion, the total amount of genetic information stays the same.

Question 23

(a) alternate name of Angelman Syndrome

(b) in what chromosome is it involved

Answer 23

(a) Happy Puppet Syndrome

b) Involved in chromosome 15q11q13 (regions q11 and q13

Question 24

False about Angelman Syndrome
A. Speech impairment, e and non-verbal communications skills higher than verbal ones
B. ataxia of gait and/or tremulous movement of limbs
C. combination of frequent crying, apparent sad demeanor

Answer 24

C - frequent laughing dapat, and apparent happy demeanour

Question 25

When does translocation occur?

Answer 25

occurs when a segment of one chromosome becomes attached to another

Question 26

What is reciprocal translocation?

Answer 26

Arise from two different mechanisms

a) Chromosomal breakage and DNA repair
(b) Abnormal crossovers (between non-homologous chromosomes

Question 27

Reciprocal translocation leads to
A. change in total amount
B. rearrangement of genetic material

Answer 27

B. hence they are called balanced translocations

Question 28

identify: Most common type of chromosomal rearrangement in humans. transfer of genetic material occurs in only one direction

Answer 28

Robertsonian (unbalanced) Translocations

Question 29

true about Robertsonian translocations
(A)Breaks occur at the extreme end of the short arms of two non-homologous acrocentric chromosomes
(B)The small fragments fuse at their centrometric regions to form single chromosome
(C)The large acrocentric fragments are subsequently lost

Answer 29

A

B - large ang nagffuse
C - small ang nawawala

Question 30

Robertsonian translocations occur only in these 4 chromosomes. enumerate!

Answer 30

13, 14, 15, 21

Question 31

A translocation may happen for follicular lymphoma to occur. What chromosomes are affected in follicular lymphoma?

Answer 31

14 –> 18

Question 32

in follicular lymphoma, what is transferred from chrome 14 to 18? what genes are affected?

Answer 32

IgH enhancer on chromosome 14 transferred to
chromosome 18 altering expression of bcl-2
genes causing follicular lymphoma

Question 33

(a) chromosomes affected in translocation leading to chronic myelogenous leukaemia
(b) what exactly happens?

Answer 33

(a) 9 and 22
(b) Normal bcr1 gene on chromosome 22 fuse with
c-abl gene on chromosome 9 forming bcr1-abl
fusion protein