Chromosomal disorder

Question 1

By 1890, it was known that one human chromosome did not always have a partner, and in 1905 Wilson and Stevens extended this observation by establishing the pattern of human sex chromosomes. What is this chromosome?

Answer 1

X chromosome

Question 2

By 1890s, it was believed that there were ____, including one X chromosome, in each male somatic cell and ____, including two X chromosomes, in each female cell.

Answer 2

47 chromosomes; 48 chromosomes

Question 3

In 1923, this chromosome was discovered which leads to the belief that both sexes have 48 chromosomes.

Answer 3

Y chromosome

Question 4

Joe Hin Tijo and Albert Levan refuted that both sexes have 48 chromosomes in 1956 when they showed the normal human chromosome number to be ____.

Answer 4

46

Question 5

In 1959, the first chromosomal disease in humans disease in humans is discovered. What chromosomal disease is this?

Answer 5

Trisomy 21

Question 6

The development of ____ in 1970 markedly increased the ability to resolve small chromosomal aberrations.

Answer 6

Chromosomal banding

Question 7

The development of chromosomal banding in 1970 markedly increased the ability to resolve small ____.

Answer 7

chromosomal aberrations

Question 8

____ refers to alternating light & dark regions along the length of a chromosome, produced after staining with a dye.

Answer 8

Chromosome banding

Question 9

A ____ is defined as the part of a chromosome that is clearly distinguishable from its adjacent segments by appearing darker or lighter with the use of one or more banding techniques

Answer 9

Band

Question 10

The number of chromosomal abnormalities has increased further with the development of improved techniques including various ____ methods and ____.

Answer 10

Fluorescence in situ hybridisation (FISH); comparative genomic hybridisation (CGH)

Question 11

____ is a laboratory technique for detecting & locating a specific DNA sequence (i.e. gene) on a chromosome.

Answer 11

Fluorescence in situ hybridization (FISH)

Question 12

The technique relies on exposing chromosomes to a small DNA sequence called a probe that has a fluorescent molecule attached to it.

Answer 12

Fluorescence in situ hybridization (FISH)

Question 13

____ is a technique that permits the detection of chromosomal copy number changes w/o the need for cell culturing.

Answer 13

Comparative genomic hybridisation (CGH)

Question 14

In this technique, the green to red fluorescence ratio measured along the chromosomal axis represents loss or gain of genetic material in the tumour at that specific locus.

Answer 14

Comparative genomic hybridisation (CGH)

Question 15

In Comparative genomic hybridisation (CGH), areas on the chromosome, or spots on the array, that are more green than average are present in ____ in the test sample; those that are more red than average are ____ in the test sample.

Answer 15

extra copies; deleted

Question 16

In 1970, how many chromosomal disorders have been discovered?

Answer 16

20

Question 17

By 1990 more than ____ different chromosome abnormalities had been described, in addition to many normal variants

Answer 17

600

Question 18

The increased resolution of the more recently developed techniques such as ____ has led to greater difficulties in differentiating between the increasingly numerous normal & abnormal chromosomal variants.

Answer 18

array CGH

Question 19

Examples of databases for submicroscopic chromosome variants.

Answer 19

DECIPHER (Sanger institute); Database of Genomic Variants (Toronto)