Freethought & Rationalism Archive

Quetzal · 03-19-2003, 02:34 AM

Quote:

Originally posted by malookiemaloo
Why is it then that in the UK here we see international soccer players who have sons who also become internationals/

m

Because out of a population of n individuals, some will become soccer players. IOW, a purely stochastic component.

In addition, whereas the son who becomes a soccer player may inherit a few physical attributes associated with soccer players (improved eye-hand coordination, balance, etc), there is no genetic endowment that insures someone will become a soccer player. Consider all the people who are soccer players who have sons who DON'T become soccer players.

Third, you are ignoring the social component. In many societies, children are influenced strongly in choice of career or profession by the career or profession of their parents. If soccer playing is a career that the father enjoyed, it stands to reason that he will encourage his son to follow in his footsteps.

Fourth, beyond a very limited suite of physical (i.e., inheritable) traits, most of what makes someone an international-class soccer player is drive, determination, and training or other non-inheritable, extrinsic traits.

Finally, the suite of traits that make someone a good soccer player can be inherited from people who are not, nor ever have been, soccer players. Consider the number of soccer players whose parents weren't soccer players.

I'm sure others can come up with more reasons. These were just a few off the top of my head.

(edited for clarity)

ps418 · 03-19-2003, 06:25 AM

I have an RNA question that i've been pondering. Several, actually.

How quickly does/can RNA transcription take place? Sure there's bound to be a range, depending on what's happening at promotor region, and the availability of base pairs. But is it possible to say in general how many transcripts are produced per unit time per gene? Does anyone know?

Also, how long is the life of an RNA trascript inside the cell, before the transcript is broken down? Again, Im sure there's a range of RNA lifespans, depending on various things, but I'm looking for a general idea. And how quickly can translation occur?

Patrick

MortalWombat · 03-19-2003, 08:44 AM

Quote:

Originally posted by ps418
I have an RNA question that i've been pondering. Several, actually.

How quickly does/can RNA transcription take place? Sure there's bound to be a range, depending on what's happening at promotor region, and the availability of base pairs. But is it possible to say in general how many transcripts are produced per unit time per gene? Does anyone know?

Pretty complex answer. It depends on the gene, organism, stage of development, tissue, lots of factors. I don't know the average rate offhand.

Quote:

Also, how long is the life of an RNA trascript inside the cell, before the transcript is broken down? Again, Im sure there's a range of RNA lifespans, depending on various things, but I'm looking for a general idea. And how quickly can translation occur?

Again, depends on the gene. Actually, it also depends on the type of organism. Bacteria, for example, do not have a nucleus, so transcription and translation are coupled, and in many cases degradation starts occurring right away as well. While in eukaryotes, translation doesn't occur until the RNA is transported into the cytoplasm.

As far as eukaryotic mRNA turnover, which is what I'm more familiar with, you might try starting here:

Quote:

Nature Reviews Molecular Cell Biology 2, 237 -246 (2001)

THE CAP-TO-TAIL GUIDE TO MRNA TURNOVER

Carol J. Wilusz, Michael Wormington & Stuart W. Peltz

Preface

The levels of cellular messenger RNA transcripts can be regulated by controlling the rate at which the mRNA decays. Because decay rates affect the expression of specific genes, they provide a cell with flexibility in effecting rapid change. Moreover, many clinically relevant mRNAs � including several encoding cytokines, growth factors and proto-oncogenes � are regulated by differential RNA stability. But what are the sequence elements and factors that control the half-lives of mRNAs?

Summary

Messenger RNA abundance is determined by balancing transcription and RNA decay. mRNA stability can be rapidly modulated to alter the expression of specific genes thereby providing flexibility in effecting changes in patterns of protein synthesis.
An evolutionarily conserved mRNA-degradation pathway is initiated by the removal of the 3' poly(A) tail. This disrupts the translation initiation complex and provides degradative enzymes with access to the 5' cap and remaining RNA body.
The intimate relationship between mRNA decay and translation is further indicated by the ability of translation-initiation factors and proteins that bind the poly(A) tail to protect the mRNA from degradation. Moreover, evidence shows that inhibiting translation elongation promotes mRNA stabilization
The turnover of mRNAs is also regulated by cis-acting elements that either promote or inhibit their decay. The most prevalent is the A+U-rich element (ARE), found in the 3'untranslated region (3' UTR) of mRNAs encoding many important growth control proteins. ARE-binding proteins affect mRNA stability, translation and subcellular localization. Other elements found in the 5' UTR and coding regions also modulate transcript stability.
Several signalling pathways are implicated in triggering changes in stability of specific mRNAs. One example is the interleukin-2 mRNA, which is stabilized by the c-Jun amino-terminal kinase (JNK) signalling pathway through JNK-responsive elements in its 5'UTR.
A strong link between translation and RNA turnover is also shown by nonsense-mediated decay, which ensures that mRNAs containing premature stop codons are degraded.

You might also want to check out Chapter 5 of Benjamin Lewin's Genes VII, which deals with mRNA.

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03-19-2003, 06:25 AM	#12
ps418 Veteran Member Join Date: Mar 2001 Location: Louisville, KY, USA Posts: 1,840	I have an RNA question that i've been pondering. Several, actually. How quickly does/can RNA transcription take place? Sure there's bound to be a range, depending on what's happening at promotor region, and the availability of base pairs. But is it possible to say in general how many transcripts are produced per unit time per gene? Does anyone know? Also, how long is the life of an RNA trascript inside the cell, before the transcript is broken down? Again, Im sure there's a range of RNA lifespans, depending on various things, but I'm looking for a general idea. And how quickly can translation occur? Patrick

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