Dihybrid Crosses

Mendel crossed varieties of peas that differed in two characteristics—that is, he performed dihybrid crosses.

TLS Online TPP Program

#Id: 1040

#Unit 5. Developmental Biology

The first visible sign of limb development is the formation of bilateral bulges called limb buds.

1. limb bud  is 

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#Id: 1041

#Unit 5. Developmental Biology

The cells that make up the limb bud are derived from the 

1. posterior lateral plate mesoderm

2. adjacent somites

3. bud’s overlying ectoderm

TLS Online TPP Program

#Id: 1042

#Unit 5. Developmental Biology

Limb field - All the cells are capable of forming a limb on their own.

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#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