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TLS Online TPP Program

#Question id: 7121

How do the endodermal cells of the sea urchin embryo carry out gut formation during gastrulation?

#Unit 5. Developmental Biology
  1. They move inside the blastocoel, and form the skeletal structures that will support the adult animal.
  2. They move into the blastocoel as mesenchyme and crawl ventrally, to mark the location of the future mouth.
  3. Changes in cell shape initiate the invagination; convergent extension extends the sheet of cells into the blastocoel, and finally, filopodia make contact with the future mouth region and pull the tip of the gut to that point.
  4. They enter the interior of the embryo through the dorsal lip of the blastopore and, through a combination of cell movements and convergent extension, form the gut.
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TLS Online TPP Program

#Question id: 800

#Unit 1. Molecules and their Interaction Relevant to Biology

Following table lists the two major forms of DNA duplexes, conformation of base attached to the sugar and the nature of major and minor grooves.

DNA duplex

Properties

(A)  A form

(i) Syn conformation of the base to sugar

(B)  B form

(ii) Anti conformation of the base to sugar

 

(iii) Wide major groove

 

(iv) Narrow major groove

 

(v) Wide minor groove 

 

(vi) Narrow minor groove 

 

(vii) C-3’ endo sugar puckering

 

(viii) C-2’ endo sugar puckering

TLS Online TPP Program

#Question id: 801

#Unit 1. Molecules and their Interaction Relevant to Biology

Identify the type of DNA from the structures given below and match the correct form with its characteristics described.
TLS Online TPP Program

#Question id: 802

#Unit 1. Molecules and their Interaction Relevant to Biology

A single-stranded DNA molecule contains 40 nucleotides with equal amounts of A, C, G, and T. This DNA strand can combine with a complementary DNA strand to form a double-stranded DNA molecule. Which is a possible sequence and structure for this DNA molecule?
TLS Online TPP Program

#Question id: 803

#Unit 1. Molecules and their Interaction Relevant to Biology

A single-stranded DNA molecule contains 40 nucleotides and has the sequence 5’-(GA)20-3’. When this single strand binds to a complementary DNA strand to form a B-DNA structure,
TLS Online TPP Program

#Question id: 804

#Unit 1. Molecules and their Interaction Relevant to Biology

With respect to microRNAs, which, if any, of the following statements, is false?

a) A microRNA normally works by binding to perfectly complementary sequences within an RNA transcript, usually an mRNA.

b) Like the great majority of mRNAs an miRNA is usually produced as a larger precursor RNA that is capped and has a 3’ poly(A) tail.

c) The precursor miRNA undergoes different types of post-transcriptional cleavage by endoribonucleases that are specific for double-stranded target sequences.

d) A nuclear endoribonuclease called dicer cleaves the miRNA precursor so that it forms a stem-loop RNA.
TLS Online TPP Program

#Question id: 804

#Unit 1. Molecules and their Interaction Relevant to Biology

With respect to microRNAs, which, if any, of the following statements, is false?

a) A microRNA normally works by binding to perfectly complementary sequences within an RNA transcript, usually an mRNA.

b) Like the great majority of mRNAs an miRNA is usually produced as a larger precursor RNA that is capped and has a 3’ poly(A) tail.

c) The precursor miRNA undergoes different types of post-transcriptional cleavage by endoribonucleases that are specific for double-stranded target sequences.

d) A nuclear endoribonuclease called dicer cleaves the miRNA precursor so that it forms a stem-loop RNA.