Download mutation and recombination as one nucleotide pair

REVIEWS
CELL HEREDITY.
CELL
HEREDITY. By
By R.
R. Sagar
Sagar and
and F.
F. J.
J. Ryan.
Ryan. New
New York:
York: John
John Wiley
Wiley and
and Sons.
Sons. 1961.
1961.
Pp. 411. 60s.
The biochemist seeking to understand the relevance of Genetics to his
subject is not, in general, prepared to work his way through the breeding
of pea plants and Drosophila before he gets to the one-gene-one-enzyme
hypothesis. It is to the biochemists and biophysicists that the present book
will be of most value.
Dr Sager and Professor Ryan begin, not with Mendel, but with the
structure of RNA and DNA, and with the evidence from work on transforming principle, bacteriophage and plant viruses, that the nucleic acids
are hereditary determinants. The one-gene-one-enzyme hypothesis and
the problem of coding nucleic acids to determine protein structure both
make their appearance in the first chapter. The authors go on to consider
the experimental characteristics of mutation and discuss the properties
that the gene must have to explain these characteristics. Throughout the
book much emphasis is placed on work carried out with microorganisms
the life cycles of Chlamdomonas
Chlamdomonas and
and J*Ieurospora
J'Ieurospora are
are made
made use of to explain
recombination and chromosome mapping, and the genetics of bacteria
and bacteriophage are dealt with in considerable detail.
One of the most important sections is that in which the authors discuss the
nature of the gene with particular
particular reference
reference to
to its
its fine structure as revealed
by work with bacteriophage and other systems. Of special interest to
biochemists is the evidence supporting the identification of the unit of
mutation and recombjnatjon
recombination as one nucleotide pair. Extensive use is
made of this concept in the chapter devoted to the chemical nature of
mutation.
Non-chromosomal genes are considered at some length. The authors
discuss the inheritance of organelles such as chioroplasts
chloroplasts and mitochondria
and also of characters
characters such
such as
as streptomycin
streptomycinresistance
resistanceininChlamydomonas
Chlamdomonas
and male sterility in maize, which are apparently not associated with any
visible cell structure.
The relationship between genes and protein structure is examined in a
chapter on the mechanisms of gene action. Recent work carried out on
the structure of the different hmogIobins
hmoglobins is used to illustrate the hypothesis
that mutations are expressed as altered amino acid sequences. The authors
also discuss possible mechanisms for allelic complementation.
In a section on genetic control of cell integration the authors pay
particular attention to protein and nucleic acid synthesis. It is perhaps a
little surprising in a book which is otherwise so up to date that no mention
is made of the work of Weiss, Hurwitz and others on the enzymic synthesis
of RNA which requires the presence of DNA.
In the final chapter the authors summarise current theories on the
nature and transmission of hereditary materials, the mechanisms of recombination and of gene action. The book ends on a speculative note with a
discussion of the possible ways
ways in
in which
which the
the first
first self-replicating
self-replicatingorganic
organic
systems might have originated.
Most of the terms used are explained but the reader who is not already
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REVIEWS
familiar with the subject may occasionally find the going
going rather
rather heavy.
heavy.
The diagram illustrating pachytene pairing in a translocation heterozygote
is particularly difficult to understand. However, apart from such minor
points, to anyone who wishes to catch up on the most exciting advances
that have been made in molecular biology and genetics in the last few
years, this book can be strongly recommended.
J. T. 0. KIRK.
GENETICS ON THE POPULATION LEVEL. By Marianne Rasmusson. Acta Zoologica,
Stockholm. Svenska
Stockholm.
SvenskaBokförlaget.
Bokforlaget. Pp.
Pp. 192.
192.
The author's intention has been to collect the theorems and fundamental
principles on which population genetics is founded and present them in a
compressed and mathematically simple way. Few would dispute the need
for a book which achieves these aims.
Genetics on the Population Level which is in many ways an elementary
version of Falconer's Quantitative Inheritance, can be divided into four sections.
The first, of 28 pages, introduces those principles of Mendelian genetics
which are required in subsequent chapters. The second, of 93 pages, is
devoted to population genetics. In this the author derives the HardyWeinberg law, describes the approach to equilibrium under random mating
and the estimation of gene frequencies both algebraically and with the aid
of simple numerical models. She then describes the forces operating to
change the population such as mutation, selection and migration. This
section is completed by a simplified version of Wright's and Malécot's
treatment of the effects of inbreeding, drift and assortative mating. Again
the treatment is algebraic, relieved only by an account of the rather dubious
lineage of the Ptolemies and a complex pedigree taken from a Swedish
herd book.
which deals
deals with biometrical
biometrical genetics,
The third section,
section, of
of 40
40 pages,
genetics,
pages, which
opens with a discussion of the relationship between genotype and phenotype for quantitative characters. The author then disposes of the notoriously
difficult problem of scales and scaling tests in one page. The partitioning
of variation between additive and dominance components using a regression
technique is laboriously pursued using simple numerical models all based
on single gene
gene differences.
differences.In
Incontrast
contrastshe
shequotes
quotesthe
therelevant
relevantformuhr
formul
for many alleles and many loci with the barest of illustrations and comments.
The effect of linkage is ignored and epistasis is discussed only in terms of
numerical models. Unfortunately, her whole treatment of biometrical
genetics is unbalanced by the author's belief that it cannot
cannot be
be applied
applied to
to
situations where there are unequal gene frequencies and genotype-environment interactions.
The last section, of 22 pages, is devoted to practical difficulties encountered
in two problems of population genetics, namely, the genetic effect of
ionising radiation on human populations and selection for quantitative
characters. This section could have done much to counteract the paucity
of illustrative material in the sections devoted to the derivation of formul.
But it is not presented in this way. While the discussion of these two
problems is interesting it does not illustrate the methods of population and
biometrical genetics nor does the relevance of these methods to the two
problems emerge.