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TLS Online TPP Program

#Question id: 5141

Which of the following statement not describe the concept of morphogenetic gradient?

#Unit 5. Developmental Biology

  1. Three genes involved in determining the proximal-distal axis of the drosophila’s leg. In the third instar leg disc, the center of the disc secretes the highest concentration of two paracrine factors Wingless and Decapentaplegic. High concentrations of these paracrine factors induce expression of the Distal-less gene. Moderate concentrations induce the expression of the dachshund gene, and lower concentrations induce the expression of the homothorax gene.

  2. Once inside the oocyte, bicoid mRNA attaches to dynein proteins that are maintained at the microtubule organizing center (the slower growing “minus end”) at the anterior of the oocyte. About 90% of the bicoid mRNA is localized to the anterior 20% of the embryo, with its concentration peaking at 7% egg length.

  3. In the anterior region, Bicoid protein prevents translation of the caudal message to specify head and thorax structures, while in the posterior region, nanos protein prevents translation of the hunchback message to specify abdomen.

  4. In the frog Xenopus laevis the specification of different mesodermal cell types by activin. At high concentrations, activin induced expression of the goosecoid gene to specify dorsal most structures, at slightly lower concentrations of activin the same tissue activated the Xbra gene and was specified to become muscle. At still lower concentrations, these genes were not activated, and the “default” gene expression instructed the cells to become blood vessels and heart.

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TLS Online TPP Program

#Question id: 5645

#Unit 5. Developmental Biology

A reproductive difference between sea urchins and humans is ________.
TLS Online TPP Program

#Question id: 5646

#Unit 5. Developmental Biology

In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below. Treatments:

A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads

B: S. purpuratus sperm mixed with beads containing no ERB1 protein

C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads

D: S. franciscanus sperm mixed with beads containing no ERB1 protein

 Based on the description of the experiment, which of the treatments would be considered a "control" treatment for S. purpuratus sperm binding?
TLS Online TPP Program

#Question id: 5647

#Unit 5. Developmental Biology

Use the following information to answer the question. In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein

that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below. Treatments:

A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads

B: S. purpuratus sperm mixed with beads containing no ERB1 protein

C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads

D: S. franciscanus sperm mixed with beads containing no ERB1 protein

Based on the data in the graph, which of the following conclusions is supported?
TLS Online TPP Program

#Question id: 5648

#Unit 5. Developmental Biology

Use the following information to answer the question. In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below. Treatments:

A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads

B: S. purpuratus sperm mixed with beads containing no ERB1 protein

C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads

D: S. franciscanus sperm mixed with beads containing no ERB1 protein

 What is a broader implication from the observations of the experiment?
TLS Online TPP Program

#Question id: 5649

#Unit 5. Developmental Biology

From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?
TLS Online TPP Program

#Question id: 5650

#Unit 5. Developmental Biology

Thalidomide, now banned for use as a sedative during pregnancy, was used in the early 1960s by many women in their first trimester of pregnancy. Some of these women gave birth to children with limb and organ deformities, suggesting that the drug most likely influenced ________.