Quiz 3

After death, in skeletal muscles calcium leaks from sarcoplasmic reticulum into cytoplasm and ATP concentration slowly reduces within 1-4 hours. At what step muscle myosin cycle will be arrested once ATP is no longer available (2-4 hours after death)?

• Myosin-ADP-Pi will not be able to bind actin filament. Muscles will be relaxed.

• Myosin-ADP will not be able to bind actin filament. Muscles remain in contracted state.

• Myosin will not be able to dissociate from actin filament. Muscles remain in contracted state.

• Myosin will not be able to dissociate from actin filament. Muscles will be relaxed.

Protein in skeletal muscle, which binds along the length of actin filaments and prevents the interaction of thin filaments with myosin is

• Tropomyosin
•  a-actinin

• Titin

• ryanodine receptor

• T tubule

Choose a false statement about collagen

• Collagen is the most abundant protein in human body

• Three polypeptide chains of collagen assemble in triple helix

• Collagen is synthesized in the form of procollagen. Proteolytic cleavage of procollagen by proteases is required for the formation of collagen fibrils.

• Collagen is a major component of intermediate filaments in fibroblasts.

Choose all important steps in activation of Cdk1 kinase? Cdk1 needs to.....

• Bind SDKI p21 or p27

• bind cyclin B

• be phosphorylated on Thr 160 by SDK-activating kinase

• be phosphorylated by wee1-kinase

• be dephosphorylated by Cdc25 phosphatase

Fill in the space. Sister chromatids in newly replicated chromosomes are held together by a protein complex called __Cohesin___. During metaphase to anaphase transition this protein complex is proteolytically cleaved by protease named ___separase___

• Securin; separase

• Condensin, separase

• Cohesin; anaphase promoting complex

• Cohesin; caspase

• No correct answer is provided

Fill in space. Checkpoint kinases phosphorylate cdc25. If you activate checkpoint kinases, and transition from G2 to M will be ______. Cdc25 will be _____.

• Activated/delayed

• Activated / speeded up

• Inhibited/delayed

• Inhibited/speeded up

In the following text, alleles associated with dominant phenotypes are indicated by uppercase letters (B, W) and alleles associated with recessive phenotypes are indicated by lowercase letters (b, w). First, you cross brown and Wingless BBww female to the black with normal wings bbWW male. Then you cross F1 BbWw female to a bbww black, wingless male. You count 1200 offspring in the F2 generation. If the wing and the color traits were linked and no homologous recombination occurred during meiosis, how many black wingless flies bbww you count in F2?

Apoptotic caspases are

• Proteases

• E3 ubiquitin ligases

• DNAases (endonucleases)

• Kinases

Mammalian cells become haploid at the end of

• Mitosis

• Meiosis I stage

• Meiosis II stage

What transmembrane proteins mediate cell - extracellular matrix adhesion?

• Integrins Cell-Extracellular matrix adhesion (FA)

• E-cadherins Cell-Cell adhesion, Adherens junctions (AJ)

• Claudins Tight Junctions (TJ)

• Connexins Gap Junctions (GJ)

• Desmocollin and desmoglein Cell-Cell adhesion