Lactate dehydrogenase (LDH) can exist as various tetrameric isozymes. Extracts from different rat tissues were run on a nondenaturing polyacrylamide gel and stained for LDH activity, as shown below. Standard tetramers of M subunits (M4) and H subunits (H4) were run alongside the tissue extracts. Which of the following is the subunit composition of the isozyme running at position 2 ?

#Question id: 7764

#Unit 5. Developmental Biology

Cellular senescence may have evolved to protect organisms against cancer. Instead of dividing out of control, the cells die. Cellular senescence appears to be regulated by several tumor suppressor genes, especially p53.what is the most appropriate reason behind this,

1) Transcription factor p53 is thought to suppress tumorigenesis by causing cell arrest and senescence in response to short telomeres, DNA damage, and viral or external signals to divide

2) This factor can stop the cell cycle, cause cellular senescence in rapidly dividing cells, instruct genes to initiate cellular apoptosis, and activate DNA repair enzymes.

3) Induction of apoptosis or cellular senescence by p53 always beneficial.

#Question id: 7765

#Unit 5. Developmental Biology

The enzyme complex or gene that maintains telomere integrity is________, which acts as an antisenescence complex. Mice and humans with its deficiencies age prematurely (Mitchell et al. 1999). Overexpressing or reactivating it in senescent cells extends longevity in mice without increasing cancer,

#Question id: 7766

#Unit 5. Developmental Biology

The relationship between shortened telomeres and stem cell depletion has been seen in degenerative diseases such as mouse muscular dystrophy,

I) When____ is activated by damaged telomeres, DNA replication halts, and if the repair doesn’t work, apoptosis is initiated. If the cell is a stem cell or some other rapidly replicating cell, this will reduce the numbers of cells produced, and the lack of stem cells will produce an “aged” phenotype.

 II) When ____ is activated by damaged telomeres, DNA replication halts, repair do its work, apoptosis is inhibited. If the cell is a stem cell or some other rapidly replicating cell, this will increase the numbers of cells produced, and then these cells will produce an “aged” phenotype.

 Choose correct gene name with right statement

#Question id: 7767

#Unit 5. Developmental Biology

How can evolution select for phenotypes that postpone reproduction or sexual maturity?” There is often a trade-off between reproduction and maintenance, and in many species reproduction and senescence are closely linked. Recent studies of mice, Caenorhabditis elegans, and Drosophila suggest that there is a conserved genetic pathway that regulates aging and that it can indeed be selected for. This pathway involves the response to insulin and insulin-like growth factors, Name of these transcription factors are

#Question id: 7768

#Unit 5. Developmental Biology

The insulin signaling pathway inhibits the synthesis of the Foxo transcription factor proteins that would otherwise increase cellular longevity. Downregulation of the insulin signaling pathway has several other functions, choose right one

#Question id: 8287

#Unit 9. Diversity of Life Forms

The following phylogeny shows six living species (a-f) and five ancestral (now extinct) species (#1-5). If the phylogeny had been developed on the basis of similarities in bone structure, which of the following predictions would you make in terms of the structure of a particular enzyme?