11/6 8-9a Chromosomal Abnormalities II

Question 1

Two major types of chromosomal structural abnormalities

Answer 1

Balanced and Unbalanced

Question 2

3 types of balanced chromosomal structural abnormalities

Answer 2

Inversions, reciprocal translocations, Robertsonian translocations

Question 3

4 types of unbalanced chromosomal structural abnormalities

Answer 3

Deletions, duplications, isochomosomes, marker (ring) chromosomes

Question 4

Balanced structural abnormalities have normal or abnormal complement of chromosomal material?

Answer 4

Normal, leading to normal phenotypic presentation

Question 5

Unbalanced structural abnormalities have normal or abnormal complement of chromosomal material?

Answer 5

Abnormal

Question 6

2 types of inversions (balanced chromosomal structural abnormality)

Answer 6

Pericentric and paracentric

Question 7

Structural rearrangements require what kind of DNA break?

Answer 7

Two double stranded DNA breaks

Question 8

What type of abnormality is shown here: 46, XX inv(5)(p12q14)

Answer 8

Pericentric inversion on chrom 5 from p12 to q14, in a female with 46 chromosomes

Question 9

4 types of gametes resulting from pericentric inversion

Answer 9

1 normal, 2 duplication/deletion, 1 inversion

Question 10

What does “pericentric” refer to in pericentric inversion?

Answer 10

Inversion that includes the centromeric DNA sequences

Question 11

What is the meiotic structure with two chromosomes called?

Answer 11

Bivalent

Question 12

What is the meiotic structure with three chromosomes called?

Answer 12

Trivalent

Question 13

What is the meiotic structure with three chromosomes called?

Answer 13

Quadravalent

Question 14

4 types of gametes resulting from paracentric inversion

Answer 14

1 normal, 1 deletion/duplication, dicentric, 1 deletion/duplication, acentric, 1 inversion

Question 15

Likelihood of parent with paracentric inversion producing live offspring with unbalanced chromosomal content?

Answer 15

Essentially zero, any potential fertilization would likely lead to spontaneous abortion.

Question 16

What type of abnormality is shown here: 46, XY inv(3)(q22q24)

Answer 16

Paracentric inversion on chrom 3 from q22 to q24, in a male with 46 chromosomes

Question 17

What type of abnormality is shown here: 46, XX t(3;21)

Answer 17

Reciprocal translocation between chromosomes 3 and 21, in a female with 46 chromosomes

Question 18

3 segregation patterns during meiosis of reciprocal translocation carriers

Answer 18

Alternative, Adjacent-1, Adjacent-2

Question 19

2 types of gametes produced by an alternate segregation of reciprocal translocation carriers

Answer 19

1 normal, 1 balanced

Question 20

Type of gametes produced by an adjacent (-1, -2) segregation of reciprocal translocation carriers

Answer 20

Unbalanced

Question 21

Partial trisomy and partial monosomy result after fertilization of a wt gamete with gamete produced from what type of segregation with reciprocal translocations?

Answer 21

Adjacent-1 or -2

Question 22

Balanced reciprocal chromosome translocations of chromosomes 9 and 22 can lead to what type of leukemia?

Answer 22

Chronic Myelogenous Leukemia or CML

Question 23

CML involves reciprocal translocations of which two chromosomes?

Answer 23

Chromosomes 9 and 22

Question 24

What is the name of chromosome 22 after its reciprocal translocation with chromosome 9?

Answer 24

Philadelphia chromosome

Question 25

What are the two components of the fusion gene resulting in chronic myelogenous leukemia?

Answer 25

BCR (breakpoint cluster region) on chromosome 22 and ABL on chromosome 9

Question 26

Why is ABL called an proto-oncogene?

Answer 26

Its reciprocal translocation onto chromosome 22 creates a fusion gene with BCR that can lead to chronic myelogenous leukemia (CML)

Question 27

What type of abnormality is shown here: 46, XX t(9;22)(q34;q11.2)

Answer 27

Reciprocal translocation between chromosomes 9 and 22 at the q34 and q11.2 regions, in a female with 46 chromosomes

Question 28

What disease is likely to occur with this abnormality: 46, XX t(9;22)(q34;q11.2)

Answer 28

Chronic myelogenous leukemia or CML

Question 29

What type of abnormality does the Philadelphia gene arise from?

Answer 29

Reciprocal translocation between chromosomes 9 and 22

Question 30

What type of translocation involves acrocentric chromosomes losing their short arms?

Answer 30

Robertsonian translocation

Question 31

What occurs in a Robertsonian translocation?

Answer 31

Fusion of long arms of two acrocentric chromosomes, with deletion of the short arms

Question 32

Is a Robertsonian translocation balanced or unbalanced?

Answer 32

Balanced, because there are 5 acrocentric chromosomes in the human karyotype, which all contain repetitive satellite DNA and copies of rRNA. Loss of 2 short arms can be compensated for

Question 33

What type of abnormality is shown here: 45, XY, der(14;21)(q10;q10)

Answer 33

Robertsonian translocation between chromosomes 14 and 21 at origin of the long arms (q10), in a male with 45 chromosomes

Question 34

Why does Robertsonian translocation result in 1 less chromosome?

Answer 34

2 acrocentric chromosomes fuse, deleting the short arms and forming one chromosome with the two long arms

Question 35

What type of abnormality and disease is shown here: 45, XY, der(14;21)(q10;q10) +21

Answer 35

Down syndrome due to Robertsonian translocation

Question 36

How many different gametes can be produced by a parent with Robertsonian translocation?

Answer 36

6

Question 37

What proportion of the gametes produced by a parent with Robertsonian translocation (45, XY, der(14;21)(q10;q10)) are viable?

Answer 37

3/6 or half

Question 38

Of the viable gametes produced by a parent with Robertsonian translocation (45, XY, der(14;21)(q10;q10)) , what proportion would have a normal phenotype?

Answer 38

2/3, one normal, one balanced

Question 39

Of the viable gametes produced by a parent with Robertsonian translocation (45, XY, der(14;21)(q10;q10)) , what proportion would have an abnormal phenotype? What would that be?

Answer 39

1/3, Down syndrome