<< Chapter < Page Chapter >> Page >

Scientists of the early 1900's recognized that if the tetranucleotide model was correct, then DNA could not differ sufficiently among species to explain the incredible diversity of heritable differences. From the biochemical perspective, proteins were a superior candidate because they were known to be both incredibly diverse and physically associated with DNA in the nucleus.

From the cell biology and genetics perspective, however, evidence continued to accumulate that DNA was responsible for heredity. One particularly significant discovery, published in 1944 by Oswald T. Avery, Colin MacLeod, and Maclyn McCarty, provided very strong evidence that DNA was responsible for inducing heritable changes in a species of bacteria (Avery et al., 1944).

While momentous in hindsight, Avery et al.’s discovery was not particularly illuminating to the generally protein-focused biochemistry community. The biochemist Erwin Chargaff, however, reacted differently. As he later wrote, Avery et al.’s results

...almost abruptly, appeared to foreshadow a chemistry of heredity and, moreover, made probable the nucleic acid character of the gene. It certainly made an impressionon a few, not many, but probably on nobody a more profound one than on me. For I saw before me in dark contours the beginning of a grammar of biology. (Chargaff, 1971, p.639)

The intellectual impact of Avery et al’s work was such that Chargaff abandoned all prior research (or completed it quickly) and refocused the efforts of his entire lab on the question of DNA. As he wrote in 1971,

I started from the conviction that, if different DNA species exhibited different biological activities, there should also exist chemically demonstrable differencesbetween deoxyribonucleic acids. From the very beginning I drew an analogy to the proteins in assuming that the biological activity of the nucleic acid probably restedon the sequence specificity of its constituents–on the order in which the four different nucleotides were arranged in the macromolecule–rather than on the occurrence of new, as yet unrecognized constituents. (Chargaff, 1971, p.639)

Chargaff’s nearly 'insurmountable’challenge was to develop an analytical technique to precisely and reliably quantify the nucleotide composition of DNA. Such a tool would allow him to test the idea that DNA of different species differed in nucleotide composition. Such a result would be consistent with Chargaff’s proposition, inspired by Avery et al.’s work, that DNA is biologically active, its biological activity differs among species (in that it is responsible for their different heritable phenotypes) and that its activity is conferred by the particular sequence of nucleotides.

Let’s consider what insights the ability to quantify the relative amounts of A, T, G and C provide in relation to both the tetranucleotide model and Chargaff’s proposition above.

1. Reconsider the tetranucleotide model .

a. If DNA is composed of serially repeated tetranucleotides and you precisely measure the relative quantities of A, T, C and G in an organism’s DNA, what do you expect to find? Why? Please explain.

b. If DNA is composed of tetranucleotides and you compare the relative quantities of A, T, C and G (for example, the ratios of A to G or T to C) among species what would you expect to find? Why? Please explain.

2. Now consider Chargaff’s hypothesis. If DNA is biologically active, its biological activity differs among species and its activity stems from the particular sequence of nucleotides, what would you expect to find if you precisely measure the relative quantities of A, T, C and G in a variety of species and compare them? Why? Please explain.

    Works cited

  • Avery, O.T., C.M. MacLeod, and M. McCarty. 1944. Studies on the chemical nature of the substance inducing transformation of Pneumococcal types. The Journal of Experimental Medicine. 79: 137-159.
  • Chargaff, E. 1971. Preface to a grammar of biology. A hundred years of nucleic acid research. Science. 172:637-642.

Questions & Answers

An investment account was opened with an initial deposit of $9,600 and earns 7.4% interest, compounded continuously. How much will the account be worth after 15 years?
Kala Reply
lim x to infinity e^1-e^-1/log(1+x)
given eccentricity and a point find the equiation
Moses Reply
12, 17, 22.... 25th term
Alexandra Reply
12, 17, 22.... 25th term
Akash
College algebra is really hard?
Shirleen Reply
Absolutely, for me. My problems with math started in First grade...involving a nun Sister Anastasia, bad vision, talking & getting expelled from Catholic school. When it comes to math I just can't focus and all I can hear is our family silverware banging and clanging on the pink Formica table.
Carole
find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
Leonardo Reply
How do i figure this problem out.
how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Discovering the chemical structure of dna. OpenStax CNX. Sep 21, 2007 Download for free at http://cnx.org/content/col10457/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Discovering the chemical structure of dna' conversation and receive update notifications?

Ask