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thank you for your time, I have still not made myself clear sorry, I will readdress the question more properly shortly!

Hi; I understand that we have a pair of chromosome in each set, not identical as each derives fom a different parent. when a cell "decides" to code for a particular protein, say from number 1 in the set, what determins the decison which of the 2 to code from in producing the protein? Thanks Martyn sorry, this derived from homework but is not a homework question

thanks for this, sorry my question wa snot more clear given the starting point of the question, 25,000 genes, 3.20E+9 nucleotides and the need to use stretch of DNA in each gene as a unique identification tag, I don't understand I don't understand the maths, where does 4.0E+5 and 10.0E+3 come from? In particular the 4.0E+5 and why is it important to remember that and 10.0E+3? Thanks

From my very basic understanding the question seems to relate to the baisc concept of shell content; the responses sem to indicate that (as is frequently the case) there is more to things than the basic. if so an elaboration of the "space between" explanations, not shells, would be very helpful please!

Hi, I'm martyn, very old, 61 and teaching myself, or trying so to do, genetics et al using "Molecular Biology, The Cell", I guess I am goimg to need some help!

the question was "to use a stretech of the human DNA genome (25k) as a unique identification tag what length of DNA sequence would you use?" The answer is below. I am struggling to figure out where the exponents and bases came from? "For calculations such as these, it is useful for purposes of estimation to remember that 4 5 =103 (4n produces the series: 4, 16, 64, 256, 1024; thus, 45 = 1024 =103) and that (1/4)5 ≅ (1/10)3. Hence, 4 different nucleotides can generate 1024 different DNA sequences, each 5 nucleotides long. Similarly, an 8- nucleotide DNA sequence can provide enough diversity to tag 25,000 genes, there being 4 8 or 65,536 possible 8-nucleotide sequences. . "