question_answer

Name a disorder, give the karyotype and write the symptoms where a human female suffers as a result of an additional copy of chromosome number 21 (trisomy).

OR

(i) Write the scientific name of the bacterium used by Frederick Griffith in his experiment.

(ii) How did he prove that transforming principle is responsible for transformation of the non-virulent strains of bacteria into the virulent form?

(iii) State the biochemical nature of the transforming principle.

(iv) Give the name of the scientists who proved it.

 

Answer:

In humans, it comes almost as a result of primary non- disjunction of chromosome 21 during egg formation. The defect is associated with a particular small portion of chromosome 21. When the particular chromosome segment is present due to translocation in three copies, instead of two, Down's syndrome occur. Such individuals are aneuploid and have 47 chromosomes.

Characteristic features:

- The affected individual is short statured.

- They have a small rounded head.

- These have an open mouth with protruded tongue.

- Their palm is broad.

- Their physical, psychomotor and mental development is retarded.

OR

(i)   Streptococcus pneumoniae.

(ii)  Griffith conducted an experiment, in which R-strain bacterium was non-virulent and S-strain was virulent.

When a mixture of heat-killed S-strain and live R-strain was injected into the mice, the infection occurred and the mice died. From this experiment, he proved that the live non-virulent strain had been transformed into the virulent strain. This may be due to some transforming principle, from the heat-killed S-strain into the R-strain.

(iii) The transforming principle of Griffith's experiment concludes that DNA acts as the genetic material.

(iv) Avery, Macleod and McCarty.