Chromosomal abnormalities (M1B1)

Question 1

what’s the most common birth defect?

Answer 1

Turner’s syndrome

Question 2

what is the to the technique that produces an image of an individual’s chromosomes?

Answer 2

karyotype

Question 3

what is ploidy?

Answer 3

The number of sets of chromosomes in a cell or an organism.

ex. haploid means one set and diploid means two sets.

Question 4

monoploid > n
haploid > n
diploid > 2n
euploid > 2 or more eg. 2n, 3n 4n etc.

triploid and up is both euploid and polypoid

Answer 4

…

Question 5

a condition in which the cells of an organism have more than two paired (homologous) sets of chromosomes is called?

Answer 5

polyploid

rarely occurs in humans, although it occurs in some tissues (especially in the liver)

Question 6

what is aneuploid?

Answer 6

is an abnormal number of chromosomes such as having a single extra chromosome (47), or a missing chromosome (45)

Question 7

what is the difference between aneuploidy and polyploidy?

Answer 7

• Aneuploidy refers to a numerical change in part of the chromosome set
• polyploidy refers to a numerical change in the whole set of chromosomes

Question 8

Aneuploid (not good) karyotypes are given names with the suffix -somy (rather than -ploidy, used for euploid karyotypes), such as trisomy and monosomy.

Answer 8

…
trisomy is when a person has three of a particular chromosome, instead of the usual two. monosomy is when they just have one chromosome instead of the usual two.

Question 9

The most well-known trisomy is?

Answer 9

trisomy 21, or Down syndrome

Question 10

what are autosomes and sex chromosomes?

Answer 10

autosomes are the 22 similar chromosomes between both genders while sex chromosomes which is 23 is XX for female and XY for male

Question 11

what is genotype and phenotype?

Answer 11

• genotype is the set of genes the individual carries

- phenotype is the external appearance of an individual as determined by his genotype

Question 12

what is non-disjunction?

Answer 12

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution

Question 13

When a person has more than one type of chromosomal makeup, that is called?

Answer 13

Mosaicism

(In Down syndrome, mosaicism means that some cells of the body have trisomy 21, and some have the typical number of chromosomes)

Question 14

causes of down syndrome?

Answer 14

• Meiotic nondisjunction - 95% (trisomy 21)
• Unbalanced translocation- 4% b/w 21 and 13,14,15
• Mosaicism due to mitotic non dysjunction-1%

Question 15

infants who have trisomy 18 (edward syndrome) usually die by the age of? what are the symptoms?

Answer 15

• 2 months

- Mental retardation, congenital heart defects, low set ears, flexion of fingers

Question 16

infants who have trisomy 13 usually die by the age of? what are the symptoms?

Answer 16

• 3 months

- mental retardation, holoprosencephly(when the face doesn’t fully close), congenital heart defects

Question 17

cause of klinefelter’s syndrome? who does it affect? symptoms?

Answer 17

-Nondisjunction of XX
homologue
-males only
-Sterility, testicular atrophy, hyalinization of seminiferous tubules, gynecomastia (having boobs)

Question 18

no. of chromosomes? causes of turner syndrome? who does it affect?

Answer 18

-45 X karyotype
-females
-Structural abnormalities of X chromosome, One X chromosome is
missing, Mitotic nondisjunctiom

Question 19

structural abnormalities occur when the chromosome’s structure is altered, this can take several forms like?

Answer 19

Translocation, deletion or duplication of

chromosomes

Question 20

two main types of translocations?

Answer 20

Reciprocal and Robertsonian

Question 21

what are the differences between Reciprocal and Robertsonian translocation?

Answer 21

•reciprocal translocation, two different chromosomes have
exchanged segments with each other.
•Robertsonian translocation, an entire chromosome attaches to another at the centromere

Question 22

chromosomal deletions are caused by?

Answer 22

environmental factors

Question 23

cause of cri-du-chat syndrome? symptoms?

Answer 23

• Partial deletion of chromosome 5

- High pitched cat like cry, a small head size , low birth weight, mental retardation and congenital heart disease

Question 24

why do cri-du-chat patients have cat like cry?

Answer 24

larynx of the child is improperly

developed.

Question 25

cause of angelman’s syndrome? symptoms?

Answer 25

• Microdeletion of long arm of chromosome 15

- Mentally retarded, Cannot speak, Prolonged periods of laughter

Question 26

causes of prader-willi syndrome? symptoms?

Answer 26

-Microdeletion occurs on long arm of
chromosome 15
-Obesity, Mental retardation, Hypogonadism, Cryptorchidism

Question 27

causes of fragile X? who does it affect? symptoms

Answer 27

-caused by a break or weakness on the
long arm of the X chromosome
-males affected more than females
-the 2nd most common inherited cause of mental retardation, large ears, prominent jaw and pale blue irises

Question 28

what is tripolar in abnormal mitotic figures?

Answer 28

are three radiating spokes coming out from a center hub; it looks like a little Mercedes sign

Question 29

what are the difference normal hands and hands of down syndrome?

Answer 29

normal hands have 2 creases while DS has 1 called simian crease