Daughter molecules

Dinardo S, Voelkel K, Stemglanz R 1984 DNA topoisomerase II mutant of Saccharomyces cerevisiae. topoisomerase II is required for segregation of daughter molecules at the termination of DNA replication. Proc Natl Acad Sci USA 81 2616-2620... 

Implicit in the functioning of the Watson-Crick DNA model is the idea that the strands of a DNA molecule must separate and new daughter strands must be synthesized in response to the sequence of bases in the mother strand. This is called semiconservative replication. Still, conservative replication, in which both strands of a daughter molecule are newly synthesized, could not be ruled out by consideration of the structure of DNA alone. 

When the two strands of the DNA double helix are separated, each can serve as a template for the replication of a new complementary strand. This produces two daughter molecules, each of which contains two DISA strands with an antiparallel orientation (see Figure 29.3). This process is called semiconservative replication because, although the parental duplex is separated into two halves (and, therefore, is not "conserved" as an entity), each of the individual parental strands remains intact in one of the two new duplexes (Figure 29.8). The enzymes involved in the DlsA replication process are template-directed polymerases that can synthesize the complementary sequence of each strand with extraordinary fidelity. The reactions described in this section were first known fiom... 

The Watson and Crick hypothesis for DNA replication proposed that each strand of DNA is used as a template for the production of one of the daughter DNA molecules. Thus the result of replication would he that one strand of DNA is present in each daughter molecule of DNA. This is a semi-conservative mechanism of replication. A simplified diagram of replication is shown in Fig. S.AIO however, the replication patterns are different in bacteria and in eukaryotes. 

If DNA replication were dispersive, each strand of each daughter molecule would have had an intermediate density in the experiment. The fact that after one generation, one strand of the DNA still had the same density as the parental (l5N) DNA served to further corroborate the conclusion that DNA replication is semiconservative. 

Semiconservative replication refers to the conservation of just one half of the parental DNA structure when it undergoes replication to give two daughter molecules. Thus, in Fig. 16-1, each chain of the parental DNA acts as a template and remains intact through the doubling process. 

To find the average energy transferred to the electronic-vibrational molecular degrees of freedom, it is necessary to know the distribution of the probabilities of formation of the daughter molecule in different final states. This energy is of the same order of magnitude as the expected value of the neutrino rest mass, and at attained energy resolutions must be, naturally, taken into account in the reduction of the experimental (3 spectrum. 

R jm and Rq" are the equilibrium configurations of the nuclei of the parent molecule (RT) in the electron state m and of the daughter molecule (RHe)+ in the electron state n, respectively. Shown in Fig. 1 are the electron terms and the vibrational wave functions of the parent and the daughter molecules together with the transition nuclear density function... 

Similarly, for the probability of the daughter molecule remaining in the ground electron state we obtain... 

The matrix elements between functions E(K) and overlap integrals of the MO of the parent and the daughter molecules. These matrix elements are easily calculated using the mathematics developed in the paper by Kaplan and Rodimova (1973). However, since a few dozen of such elements arise, we do not present the corresponding expressions here. Let us write down only one of them ... 

The vibrations and rotations of the daughter molecule may be excited owing both to the jump in the charge of the radioactive nucleus and to the recoil momentum of the latter. The electron excitations are due only to the jump in the charge. 

The excitation probabilities are expressed in terms of determinants of the overlap integrals of molecular orbitals of the parent and the daughter molecules. One must take into account all the elements of the determinant, since the nondiagonal matrix elements are comparable in magnitude with the diagonal ones. 

Probability of Formation of Daughter Molecules in Ground and in Excited... 

The distributions of discrete excitations of daughter molecules versus the excitation energy, W0n = W0n(AE ), are presented in Fig. 4. The excitation energy was calculated according to the well-known formula of Roothaan (1951) for the energy difference of two singlet states... 

In the case of the tritium fi decay, all excitation spectra of daughter molecules are similar. They consist of a principal maximum located in the region of 20-40 eV. This maximum accumulates about half the summary probability of all excitations and corresponds to the one-electron transitions from the L shell into the lower vacant MO. In addition, the spectra... 

The spectrum of / decay, or the (i spectrum, is a distribution of ejection probabilities for the ji electron versus its kinetic energy. As an initial formula for deriviing an expression for the / spectrum we will use Eq. (8). As was mentioned above, the ft decay in a molecule is a multichannel process owing to the fact that both the parent and the daughter molecules may be in different electronic, vibrational, and rotational states. Thus, Eq. (8) should be employed for each channel of the reaction. Using the energy conservation law and the factorization of the matrix element, Eq. (12), we obtain the following expression for the probability of ft decay in the channel 0 n ... 

Considering that the average excitation energy of the daughter molecule A (RHe+) is determined as... 

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