SectionIIF

Question 1

What is the karyotype for trisomy 18? What is the common name?

Answer 1

-47XY +18

–edwards syndrome

Question 2

What is a distinctive abnormality in Edwards syndrome?

Answer 2

-distinctive overlapping fingers with a clenched fist

Question 3

What is the karytype and common name of trisomy 13?

Answer 3

• 47XY +13
• Patau syndrome

Question 4

What are the characteristic signs of Patau syndrome?

Answer 4

• oral-facial clefts, micropthamia, postaxial polydactylyl
• severe CNS, heart and renal disorders as well

Question 5

What is the karyotype and clinical features of Turner syndrome?

Answer 5

• 45 X
• webbed neck, broad chest and shoulders, female, heart defects.

Question 6

What is the karytype and common findings of Klinefelter syndrome?

Answer 6

• 47XXY, 48XXXY, 49XXXXY
• Tall and long limbs (more X means more SHOX gene= longer limbs)
• Gynecomastia (more X= more girlyness)
• small testes, sparse body hair

Question 7

When is Klinefelter syndrome typically diagnosed?

Answer 7

-After puberty when abnormal development is noticed

Question 8

What is the karyotype and characteristics of Trisomy X?

Answer 8

• 47XXX
• relitively benign, possible sterility and menstrual irregularity

Question 9

What is the karyotyoe and characteristic of 47XYY syndrome?

Answer 9

• 47XYY
• Taller than average male with possible IQ reduction

Question 10

What is the basis of high resolution banding?

Answer 10

• involves staining during prophase or early metaphase when the chomosome are more extended
• allows for the detection of less obvious abnormalities

Question 11

What makes FISH unique?

Answer 11

• It is not necessary to stimulate cells to divide
• commonly used to detect fetal chomosomal abnormalities.

Question 12

What is the use of comparative genomic hybridization?

Answer 12

• used to detect the loss or duplication of whole chromosomes.
• cannot detect balanced rearrangements

Question 13

How many chromosomes do euploid cells have?

Answer 13

-multiples of 23

Question 14

How many chrmosomes does a diploid/haploid/triploid cell have?

Answer 14

• diploid 46 (2n)
• Haploid 23 (1n)
• triploid 69 (3n)

Question 15

What are the definitions of polyploidy and aneuploidy?

Answer 15

• polyploidy: complete set of extra chromosomes
• Aneuploidy: cells containing missing or additional chromosomes (NOT a multiple of 23)

Question 16

What is the most common cause of an aneuploidy?

Answer 16

-nondisjunction in meiosis

Question 17

Why are monosomies more sever than trisomies?

Answer 17

-the body can tolerate an excess of genetic material much better than it can tolerate a lack of it.

Question 18

What is the most common cause of anueploidy in trisomy 21?

Answer 18

-Maternal nondisjunction

Question 19

What is the survival rate for edwards syndrome (trisomy 18)

Answer 19

-50% a few weeks, 5% make it to a year

Question 20

What is the survival rate for Pateau syndrome?

Answer 20

-Similar to Edwards, 5% at a year

Question 21

What is the correlation between maternal age and nondisjunction?

Answer 21

• incidence of nondisjunction rises with increased age
• after age 45 1/25
• for trisomy 21, 18, 13

Question 22

Haploinsufficiency in what gene causes the short stature in Turner’s syndrome?

Answer 22

-The SHOX gene (paternal sex chromosome)

Question 23

What is characteristic of an unbalanced rearrangement?

Answer 23

-gain or loss of chromosomal material

Question 24

What is characteristic of a balanced rearrangement

Answer 24

-no loss or gain of genetic material (mutal exchange or movement)

Question 25

What occurs in a reciprocal translocation? What can this lead to in offspring?

Answer 25

• genetic material is mutually exchanged
• in the offspring, the normal chromosome of one homologous pair, and the derivative (portion containing the translocation) of another can be passed down

–>this can lead to a partial trisomy or monosomy.

Question 26

What occurs in a robertsonian translocation?

Answer 26

-the short arms of two nonhomologous chromosomes are lost and the long arms then fust at the centromere

Question 27

What is the effect of a robetsonian translocation?

Answer 27

• the translocation may have no effect on the carrier becuase they still contain a full complement (they are 45 but the short arm that was lost typically contains no genetic material)
• however, the offspring of these individuals may inherit and extra or missing arm of a chromosome.

Question 28

What two kinds of segregation can happen in an individual with a robertsonian translocation?

Answer 28

• alternate segregation: offsrping chromosomally normal or have a balanced translocation with normal phenotype (think alternate with ALTERNATE generations becuase the next generation will have a mutation)
• adjacent segregation: gametes are unbalanced

Question 29

What is the difference between a terminal deletion and a interstitial deletion?

Answer 29

• Terminal deletion: single break occurs at the end of a chromosome and the tip is lost
• Intersitial deletion: two breaks and the material in between is lost.

Question 30

What is uniparental disomy?

Answer 30

When one parent contributes two copies of a chromososme and the other parent contributes none

Question 31

What are some examples of microdeletions?

Answer 31

• Prader-Willi
• Angelman
• Wolf-Hirschhorn
• Williams
• WAGR

Question 32

Describe pericentric and paracentric inversions.

Answer 32

• pericentric: the breaks occus on each side of the centromere
• Paracentric- both breaks occur in one arm.

Question 33

What are isochromosomes?

Answer 33

-Two copies of one arm