Genes that control coat color in mammals represent some of the best early examples of genes with multiple alleles exhibiting different phenotypes. A classic example is the C gene in hamsters. Three of the known alleles of this gene are C, c^a and c^k. Each supplies a different amount of black pigment to the coat hair. The phenotypes of three different homozygous strains are as follows.

would mate the true-breeding  c^a c^a  hamsters to the true-breeding c^k c^k  hamsters to produce heterozygous  c^a and c^k  F1 progeny. Crosses and their interpretation that would have allowed geneticists to come to the conclusion that c^a and c^k were likely to be alleles of the same using the concept that alleles of the same gene will be tightly linked. What will be the ratio of F2 hamster;

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#Question id: 15301

#Unit 5. Developmental Biology

Initially, the morula does not have an internal cavity. However, during a process, cavitation, the trophoblast cells secrete fluid into the morula to create a blastocoel, these 

membranes of trophoblast cells contain_______?

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#Question id: 15302

#Unit 5. Developmental Biology

FOXP1 is a transcription factor which stimulate the production of Oct4 and Nanog and establish pluripotency. Which of the following statements are correct regarding to the mechanism of alternative splicing of FOXP1. 

A. There are two isoforms of the FoxP1 protein, One is the product of an mRNA spliced to include a particular exon, 18b, while the other splicing variant carries exon 18a.

B. When alternative splicing generates a form including exon 18b in place of 18a, the resulting isoform (FOXP1-ES) binds to a different DNA sequence and thus controls expression of a different set of genes.

C. The protein encoded by the exon 18b– carrying mRNA is called FOXP1-ES it fails to stimulate expression of OCT4 and NANOG and instead actives genes that promote differentiation. 

D. The exon 18a– containing form encodes FOXP1 itself, and this has the opposite effect: this activates genes that promote dedifferentiation, and thus stimulates iPS cell formation.

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#Question id: 15303

#Unit 4. Cell Communication and Cell Signaling

Neurofibromatosis, a benign tumor of the sheath cells that surround nerves, is caused by

a.  Loss of both alleles of NF1

b.  Mutation in RAS GAP-type protein

c.  A single mutant NF1 allele

d.  Mutation in SRC protein

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#Question id: 15304

#Unit 4. Cell Communication and Cell Signaling

An activating mutation of one of the two alleles of a proto-oncogene converts it into an oncogene, This can occur by EXCEPT

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#Question id: 15305

#Unit 4. Cell Communication and Cell Signaling

The multi-hit model, which proposes that multiple mutations are needed to cause cancer, which of the following is incorrect regarding to this model?

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#Question id: 15306

#Unit 4. Cell Communication and Cell Signaling

The transformation of a normal cell to a cancer cell is accompanied  by the loss of function of one or more tumor‐suppressor genes. High‐throughput sequencing studies have identified hundreds of genes that are implicated as tumor suppressors in humans. Some of the better characterized genes;

Gene	Primary tumor	Proposed function
i) APC	Colorectal	Binds β ‐catenin acting as transcription factor
ii) BRCA1	Breast	DNA repair
iii) MSH2, MLH1	Melanoma, pancreatic	p16: Cdk inhibitor ARF: stabilizes p53
iv) E‐Cadherin	Breast, colon	Cell adhesion molecule
v) INK4a	Colorectal	Mismatch repair
vi) NF1	Neurofibromas	Activates GTPase of Ras

Choose incorrect matching regarding tumor‐suppressor genes/primary tumor/proposed functions;