The introns in pre-tRNA vary in length from 14 to 60 bases and only single intron is found in each pre-tRNA transcript A pre-tRNA intron is excised in one step  Finally, hydrolysis of GTP and ATP is required to join the two tRNA halves generated by cleavage on either side of the intron.

TLS Online TPP Program

#Id: 1043

#Unit 5. Developmental Biology

The positional information needed to construct a limb has to function in a three-dimensional coordinate system:

Proximal-distal axis

Anterior-posterior axis

Dorsal-ventral axis

TLS Online TPP Program

#Id: 1044

#Unit 5. Developmental Biology

The limb bud is regionalized into 3 functional domains

1. Progress zone

2. Zone of polarizing activity

3. Apical ectodermal ridge

TLS Online TPP Program

#Id: 1045

#Unit 5. Developmental Biology

The highly proliferative mesenchyme that fuels limb bud growth is known as the progress zone mesenchyme

TLS Online TPP Program

#Id: 1046

#Unit 5. Developmental Biology

Fgf10 is the major active factor in the PZ.

TLS Online TPP Program

#Id: 1047

#Unit 5. Developmental Biology

The cells found within the most posterior region of the progress zone constitute the zone of polarizing activity.

TLS Online TPP Program

#Id: 1048

#Unit 5. Developmental Biology

Sonic hedgehog, is the major active factor in the ZPA.