The nuclear genome of mammals is 40% G+C and the dinucleotide CG is fivefold less common than statistically expected.

TLS Online TPP Program

#Id: 1034

#Unit 5. Developmental Biology

In birds, primary neurulation generates the neural tube anterior to the hindlimbs.

TLS Online TPP Program

#Id: 1035

#Unit 5. Developmental Biology

In mammals, secondary neurulation begins at the level of the sacral vertebrae of the tail.

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#Id: 1036

#Unit 5. Developmental Biology

Junctional neurulation 

combination of mechanisms involved in both primary and secondary neurulation

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#Id: 1037

#Unit 5. Developmental Biology

Primary neurulation can be divided into four stages:

1. Elongation and folding of the neural plate

2. Bending of the neural plate

3. Convergence of the neural folds

4. Closure of the neural tube

TLS Online TPP Program

#Id: 1038

#Unit 5. Developmental Biology

Anencephaly 

a failure of the anterior (rostral) portion of the embryonic neural tube (anterior neuropore) to close properly.

OR

a failure to close the neural tube allows the forebrain to remain in contact with amniotic fluid and subsequently degenerate.

TLS Online TPP Program

#Id: 1039

#Unit 5. Developmental Biology

Craniorachischisis-combination of anencephaly with a contiguous bony defect of the spine (also without meninges covering the neural tissue –rachischisis)