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;

#Question id: 5659

#Unit 5. Developmental Biology

 Following are the statements related to mammalian chaemotaxis .
A. During chaemotaxis, the oocyte and its accompanying cumulus cells secrete molecules that attract only uncapacitated sperm toward the egg during the last stages of sperm migration.
B. These chaemotactic compound are hormone progesterone, which is made by the cumulus cells.
C. Progesterone has been shown to bind to a receptor that activates Ca2+ channels in the cell membrane of the sperm tail, leading to sperm hyperactivity and provides directional cue.
D. Cumulus cells also secrete a substance, CRISP1, that attracts sperm and hyperactivates them through CatSper channels similar as in sea urchins.
Which of  the following statement is incorrect?

#Question id: 5658

#Unit 5. Developmental Biology

 Following events occur during fertilization in mammals.

A. sperm penetrates cumulus layer

B. sperm nucleus delivered into cytoplasm

C. sperm plasma membrane fuses with egg plasma membrane

D. calcium waves

E. enzymes released from acrosome on sperm head enable sperm to penetrate zona pellucida

F. transit through the cumulus or binding to zona pellucida elicits acrosomal reaction in sperm

G. egg completes meiosis and development is initiated

which of the following sequence is correct?

#Question id: 5657

#Unit 5. Developmental Biology

Following statements regarding to the molecular processes of capacitation.

A. The sperm cell membrane is altered by the removal of cholesterol by albumin proteins in the female reproductive tract.

B. Particular proteins or carbohydrates on the sperm surface are lost during capacitation.

C. The membrane potential of the sperm cell becomes more positive as potassium ions leave the sperm. This change in membrane potential may allow calcium channels to be opened and permit calcium to enter the sperm.

D. Calcium and bicarbonate ions are critical in activating cAMP production and in facilitating the membrane fusion events of the acrosome reaction.

E. As a result of cAMP formation, protein phosphorylation occurs. Once they are phosphorylated, some proteins migrate to the surface of the sperm head. One of these proteins is juno, which is critical in sperm-egg fusion.

which one of the following combinations is correct?

#Question id: 5656

#Unit 5. Developmental Biology

What is the cortical reaction, and why is it important?

#Question id: 5655

#Unit 5. Developmental Biology

What is the "acrosomal reaction"?

#Question id: 5654

#Unit 5. Developmental Biology

Two human disorders, Prader-Willi syndrome and Angelman syndrome, occur when a small deletion in a specific region of chromosome 15 is contributed by either the father or mother, respectively. Why does this small deletion not behave as a recessive allele for either syndrome, that is, why is its loss not made up for by the good copy of the region on chromosome 15 contributed by the other parent?