Z
Z (or z or Z score):The standard normal probability density function calculated by the formula:
Z ?1
s ??????2p
p e àeY àm T2=2s 2
where Y is the normal variate,π?3.14159and e ?2.71828,μis the mean and σis the standard deviation.The z values are generally read from statistical tables.Z indicates the height of the ordinate of the curve and thereby the density of the items.?standard deviation ,?normal distribution ,?confidence inter-vals ,?F distribution Z
Buffer :Na 2HPO 4.7H 2O 0.06M,NaH 2PO 40.04M,KCl 0.01M,MgSO 4.7H 2O 0.001M,β-mercaptoethanol 0.05M,pH 7.Do not autoclave it.
Z Chromosome :Refers to the sex chromosome present in both sexes of a species with heterogametic females (thus comparable to the X chromosome).Males are ZZ and females are WZ.?W chromosome ,?sex determination
Z Disc (Z-disk):?sarcomere
Z Distribution :A statistical device for testing the significance of the differences between correlation coefficients in case the null hypothesis is not r =0.The relation of z to r has been elaborated by R.A.Fisher as z =(1/2)[l n(1+r)?l n(1?r)]and its
standard error as s z ?1
?????????
en à3T
p :For routine calcula-tions,tables are available in statistical textbooks.?covariance for correlation coefficient
Z DNA (zig-zag DNA):A relatively rare left-handed double helix that may be formed in the short (8–62bp)regions of alternating purines and pyrimidines (ATGTGTGT,GCATGCAT).The polyGC.polyGC sequences are most favorable for B →Z transition.In some species CA/TG repeats are most conducive for Z DNA formation.Alternating purine-pyrimidine tracts may also modulate the transcription in a plus or minus direction.Base sequences near the tran-scription starting point favor the formation of Z DNA and it may stimulate transcription.Nucleosomes are not formed in the Z DNA tract,thus facilitating the access of transcription factors.In some genes,however,such as in the constitutive nucleolin gene,Z DNA in the promoter downregulates transcription.Vaccinia virus is no longer lethal in mice if the Z DNA binding site is lost.Four families of proteins bind to the crystal structure of Z DNA:ADAR1,an editing enzyme,LM1,an interferon inducible
protein,E3L,a pox virus virulence factor and an orthologue of PKR,interferon-induced protein ki-nase.Z DNA occurs in a dynamic state;it is formed and then it can revert to the B form of the DNA.There is a transition point between the common B and Z DNA forms (see Fig. Z1). The handedness changes abruptly from left to right by a sharp turn of the phosphate backbone.At the transition point an adenine (A0)and thymine (T0),respectively,are extruded as shown by the crystal structure (Ha SC et al 2005Nature [Lond]437:1183).B-Z DNA conformational polymorphism is optically detectable on single-walled carbon nanotubes in whole blood,tissue and within living mammalian cells (Heller DA et al 2006Science 311:508).The figure shows space-filling models (modified after Dickerson RE et al 1982Science 216:475).In mammals,Z DNA forming sequences induce a high level of chromo-somal instability by generating double-strand breaks and large deletions.These deletions at the Z DNA may raise the incidence of certain cancers by increased transcription (Wang G et al 2006Proc Natl Acad Sci USA 103:2677).In bacteria,the Z DNA related deletions are short.
Z DNA B DNA
Figure Z1.The heavy black line represents the sugar-phosphate backbone
An alternating deoxycytidine-deoxyguanosine dinucleotide repetitive sequence [d(CG)n ]can poten-tiate transcription in yeast when placed approximate-ly three helical turns (28bp)upstream of the cytochrome c 1(CYC1)TATA box.Transcriptional activation by the d(CG)9repeat sequence depends on
Z DNA 2129
Z
the Z conformation.The activation is core promoter-specific and most effective when situated 28bp or below upstream of the TATA box.Changing the distance between the d(CG)9repeat sequence and the TATA box modulates the extent of activation.Linker-DNA region is formed at the Z DNA structure with two flanking nucleosomes.Z DNA creates an open chromatin state at the promoter by displacing nucleosomes from its environs and establishing the boundaries of its neighboring nucleosomes (Wong B et al 2007Proc Natl Acad Sci USA 104:2229).?DNA types ,?ADAR ,?RNA editing ,?nanotech-nology ;Liu R et al 2001Cell 106:309;Rothenburg S et al 2001Proc Natl Acad Sci USA 98:8985;Rich A,Zhang S 2003Nature Rev Genet 4:566.
Z Inactivation :The Z chromosome of birds has the same role in sex determination as the X chromosome in mammals yet its genes are not inactivated in homogametic individuals.?dosage compensation ;Kuroda Y et al 2001Chromosome Res 9:457.Z
Linkage :Refers to genes syntenic
in
the
Z chromosome.?X-linked
Z Ring :Same as Fts Z ring.?tubulin
Z RNA :This left-handed molecule may occur in double-stranded RNA and is similar to Z DNA.?Z DNA ,?ADAR ;structure and origin:Placido D et al 2007Structure 15:395.
Z Scheme :An additional (zig-zag)scheme to generate enough ATP by photosynthesis.Through a two-step process (photosystem I and II)an electron passes from water but there is not enough energy in a single quantum of light to energize the electron directly and
efficiently all the way from PS II to the top of PS I and make NADP +.The leftover energy makes pumping H +possible across the membranes to capture some light energy for synthesizing ATP.The redox state of plastoquinone regulates the transcription of genes encoding the reaction center proteins of both photosystem I and II.?photosystems ;Prince RC 1996Trends Biochem Sci 21:121;Allen JF 2003Science 299:1530;Allen JF,Martin W 2007Nature [Lond]445:610,see Fig.Z2.Z Score :?Z
z Value :The natural logarithm of the ratio of two estimated standard deviations.?variance
ZAG (Zn-α2-glycoprotein):Though this resembles MHC class I heavy chain molecules,it is different because it cannot bind β2-microglobulin.It occurs in the majority of body fluids and is apparently involved in inducing fat loss in adipocytes.It accumulates in breast cancer cells and other cells in serious distress (cachexia).?MHC ,?HLA ,?obesity ;Kennedy MW et al 2001J Biol Chem 276:35008.
Zanier-Roubicek Syndrome :?ectodermal dysplasia ,?hypohidrotic
ZAK (zipper sterile-αmotif kinase):A mixed lineage kinase (MLK)in signal transduction.
ZAP-70(zeta-associated protein 70):A cytosolic protein tyrosine kinase expressed only in T cells and natural killer cells.By binding to phosphorylated ζ-chains of the CD3T cell antigen-receptor complex,it assists in the activation of T cells.Its defect may lead to severe combined immunodeficiency.ZAP-70tyrosine kinase signals to the CXCR4chemokine receptor
Light
H 2O
1.0
R e d u c t i o n p o t.
?1.6P680
Protons
Splitting Mn complex
O 2 + 2H +
Pheophytin
Electron acceptor Photosystem I
Photosystem II Plastocyanin
Light
Fd oxidoreductase
Phyllochinone NADP NADPH
Ferredoxin (Fd)P680?
P700?
Quinone B
Plastoquinone A
Cytochrome complex
P700
cycling
Figure Z2.Z Scheme of photosystems
2130Z Inactivation
Z
and thus regulates the migration of T lymphocytes.It seems to be involved in arthritis in mice.?SHP-1,?CD3T cell,?CXCR,?killer cell,?immunodefi-
ciency,?tyrosine kinases,?retroviral restriction factors;Ottoson NC et al2001J Immunol 167:1857;Sakaguchi N et al2003Nature[Lond] 426:454,crystal structure:Deindl S et al2007Cell 129:735.
ZBP1(Zipcode binding protein):?mRNA migration Zea mays(L.):?maize
Zeatin(6[4-hydroxy-3-methyl-cis-2-butenylamino]pu-rine):Refers to a cytokinin plant hormone.In Agrobacterium T-DNA-located ipt gene encodes an isopentenyl transferase that mediates the synthesis of transzeatin and isopentenyl adenosine.In plant tissue culture media it is a commonly used alternative to kinetin,benzylamino purine or isopentenyl adeno-sine.?plant hormones
Zebra:Equus quagga2n=44;it can form hybrids with both horses(Equus caballus,2n=64)and donkeys (2n=62).Equus grevyi,2n=46(see Fig.Z3);Equus zebra hartmanniae,2n=32.The Zebra duiker (Cephalophus zebra,2n=58)is not a member of the Equidae family but is the male member of a bovine
species.
Figure Z3.Equus grevyi
ZEBRA(Zta):A non-acidic activator protein of the lytic cycle of the Epstein-Barr virus;it promotes the assembly of the DA complex(TFIID-TFIIA)of transcription factors.?transcription factors,?open transcription complex,?DA
Zebrafish(Brachydanio rerio,2n=50):A3–4cm tropical freshwater fish;the genome size is about 2×109bp(see Fig.Z4).It is easy to breed and becomes sexually mature in2–3months(4generations/year).
The embryogenetic pattern is laid down in12hours,
and it is well suited for the analysis of developmental pathways and cell lineages in this small vertebrate. Hundreds of eggs are laid externally.The embryos are transparent and permit observation of gastrulation, development of the brain and heart,etc.Haploids survive for several hours and mutants are available.
About600genes involved in its development have
been identified,and in1998a3350cM map of3.3cM resolution became available.The zebrafish genome has extensive homology to that of humans.?EP,?meda-
ka,?GloFish;Fishman MC1997Methods Cell Biol
52:67;Detrich HW III et al1999(Eds.)The ebrafish: Biology.Academic Press;radiation hybrid map: Geisler R et al1999Nature Genet23:86;Hukriede
NA et al1999Proc Natl Acad Sci USA96:9745; Woods IG et al2000Genome Res10:1903;Shin JT, Fishman MC2002Annu Rev Genomics Hum Genet
3:311;hemetopoiesis:de Jong JLO,Zon LI2005Annu
Rev Genet39:481;human disease model:Lieschke GJ, Currie PD2007Nature Rev Genet8:353;http://zebra.
https://www.doczj.com/doc/dd14771956.html,;https://www.doczj.com/doc/dd14771956.html,/ZFIN/;https://www.doczj.com/doc/dd14771956.html,;
https://www.doczj.com/doc/dd14771956.html,/fishscop/;http://www.tigr.
org/tdb/tgi.shtml;https://www.doczj.com/doc/dd14771956.html,;http://zf-espresso.tue bingen.mpg.de
.
Figure Z4.Zebrafish
Zebu(Bos indicus):2n=60.?Santa Gertrudis cattle
Zein:A prolamine protein in maize(homologous to gliadin in wheat)that may account for up to50%of
the grain proteins.It does not have high nutritional
value(and is therefore undesirable)because of the
low lysine and tryptophan content.It is deposited in
zein bodies at the place of synthesis.In the high-
lysine maize varieties(opaque,floury)prolamines
are very low and non-prolamine proteins increase.
?high-lysine corn,?glutenin
Zeitgeber:A rhythmic external signal for the circadian change.?circadian rhythm
Zeitnehmer:An internal signal for rhythmicity in response to the zeitgeber or even in its absence.
?circadian rhythm,?zeitgeber
Zeitnehmer2131
Z
Zellweger Syndrome(ZS):A brain-liver-kidney(cere-brohepatorenal)recessive disease involving human chromosome7q11.12-q11.13;but over a dozen other loci may have similar effects.The basic defect is due to peroxisome anomalies.?microbodies,?neuro-muscular diseases,?chondrodysplasia punctata,?cataract,?pseudo-Zellweger syndrome
Zero,Absolute:The minimum lowest temperature; Kelvin0°=Celsius?273.15°.
Zero Time Binding:Refers to the status of reassociation of two single-strand palindromic DNAs at the beginning of an annealing kinetics experiment.These are the fastest reassociating fractions because they are repeats and are close to each other.?c0t curve zeste(z,chromosome1.10of Drosophila):The protein kinase product apparently alters the chromatin structure and affects the expression of w,Ubx,dpp by attaching to their promoters.Its action bears similarity to Polycomb.The zeste-white3complex regulates the spindle attachment to the cortical actin.?w locus,?Polycomb;McCartney BM et al2001 Nature Cell Biol3:933.
Zeugopodium:Corresponds to the radius,the ulna,the tibia and the fibula.
ZFX(human chromosome Xp22.3-p21.2):This Zinc finger protein similar to Zfy was believed to be responsible for feminization of some XY individuals and gondal dysgenesis.It is not a primary sex determining protein.ZFX escapes inactivation in humans but not in mice.It controls pluripotency of stem cells.?pluripotency;Palmer MS et al1990Proc Natl Acad Sci USA87:1681.
ZFY(zinc finger Y,Yp11.3):A sequence in the Y chromosome assumed to be involved in the matura-tion of testes or sperm.A729bp intron located immediately upstream of the Zinc finger exon shows no or ery little sequence variation in worldwide human samples.?Zinc finger,?ZFX Zidovudin:?AZT
zif:?NGFI-A
Zig-Zag Inheritance:?criss-cross inheritance
Zig-Zag Model of Chromosome Fiber:Radiation-induced DNA breaks revealed fragment sizes of 78bases,which corresponds to one turn of the DNA around the nucleosome.Additional peaks between 175and450bases reflect the relative position of the nearest neighbor nucleosomes.Calculations and other considerations seem to support a zig-zag model of the chromatin fiber rather than a simple helical
model(Rydberg B et al1998J Mol Biol284:71).?solenoid
Zinc Finger Nucleases:These are limited-specificity nucleases that can recognize certain DNA sequences and cause small deletions at selected targets.The Zn fingers prefer guanine-rich tracts,particularly 5′-GNN-3′triplets.Each nuclease unit may have three fingers and each grabs one triplet,i.e.,a total of nine bases.The dimeric structure of the nuclease cleaves both strands in a tract lying between the G-rich sequences(see Fig.Z5).Non-homologous end-joining may follow the double-strand breaks and thus somatic and germ line mutations may occur.Zinc finger nu-cleases are associations of the Zinc finger with,e.g.,a FokI restriction endonuclease(target GGATG(N)9/13) and can thus be targeted to specific mammalian genes (Porteus MH2006Mol Ther13:438)or can be used to repair specific defective genes in plants by targeted homologous recombination(Wright DA2005Plant J 44:693).?non-homologous end-joining,?gene ther-apy;Bibikova M et al2002Genetics161:1169; Miller JC et al2007Nature Biotechnol25:778.
Figure Z5.Diagram of a dimeric(A and B)zinc-finger endonuclease and its mode of cleavage(at the green lines)of DNA.The subunits recognize of the DNA sequence by the green shaded square domain.The zinc-fingers bind to the G-rich repeats.(Modified after Bibikova M et al2002Genetics161:1169)
Zinc Fingers:These are binding mechanisms of tran-scription factors and other regulatory proteins contain-ing tandemly repeated cysteine and histidine molecules and they fold in a“finger-like”fashion cross-linked to Zn.They contain other highly conserved amino acids—phenylalanine(F),leucine(L)and tyrosine(Y). Some Zinc finger proteins bind the RNA to the DNA. About0.7%of the proteins in budding yeast and the nematode Caenorhabditis elegans contain Zn finger motifs;in yeast most commonly2/molecule and in Caenorhabditis up to14/https://www.doczj.com/doc/dd14771956.html,ing DNA microarray designs,putative Zn finger transcription factor binding sites can be identified.By designing new Zinc finger motifs,specific regulation of gene expression is possible(Reynolds L et al2002Proc Natl Acad Sci USA100:1615).Zinc is an essential
2132Zellweger Syndrome Z
element for life and it is a cofactor for several enzymes.?hormone receptor,?DNA-binding protein domains,?microarray hybridization,?acrodermatitis entero-pathica,?ZFY,?RING finger,?binuclear Zinc cluster,?Cys4receptor,?GA TA,?LIM;Rubin GM et al2000Science287:2204;Bulyk ML et al2001 Proc Natl Acad Sci USA98:7158;Pabo CO et al 2001Annu Rev Biochem70:313;binding tools:http:// https://www.doczj.com/doc/dd14771956.html,/mb/barbas/zfdesign/zfdesignhome. php;Zn finger protein design:http://bindr.gdcb.iastate. edu/ZiFiT/.
Zinc Knuckle(Zf-CCHC):A Zn-binding motif com-monly found in the nucleocapsids of retroviruses (e.g.,HIV)and in regulatory proteins of diverse eukaryotes.Its sequence is CX2CX4HX4C where X can be different amino acids.These protein motifs are involved in binding RNA or single-strand DNA.(See Le Thuy et al2001Mol Cell Biol21:8346).
Zinc Ribbon Fold(CXXC(H)-15/17-CXXC):This is present in diverse binding proteins.?binding proteins,?transcription factors
Zinc Ring Finger:?RING finger
ZIP1,ZIP2:Protein factors that mediate phosphoryla-tion of potassium ion channels by protein kinase C.?protein kinase,?ion channel
Zipcode:?mRNA migration
Zipper Domain:Refers to part of dimeric DNA-binding proteins where the two subunits are held together by repeating amino acid residues;in the other parts the subunits are separated from each other.?leucine zipper
Zoidogamy:In this fertilization takes place by motile antherozoids.?siphonogamy
Zollinger-Ellison Syndrome(Wermer syndrome MEN 1):A multiple endocrine adenomatosis(neoplasia) encoded in human chromosome11q13.?adenoma-tosis multiple endocrine
Zona Pellucida:A yolky layer around the mammalian egg.Zona pellucida domains are present in dauer larvae of nematodes and mechanotransducers in Drosophila and are involved in other functions.The domain~260amino acids have eight conserved cysteines near the carboxyl end and are often glycosylated.?fertilization[animals],?vitelline layer,?egg,?dauer larva,?mechanosensory genes; Jovine L et al2002Nature Cell Biol4:457;Jovine L et al2005Annu Rev Biochem74:83. Zonoskeleton:This includes the scapula,the clavicle and the hip bones.Zonula Occludens:A tight cell junction mediated by ZO proteins associated with a210–255kDa membrane-
tied guanylate kinase.?MAGUK,?ELL;Meyer TN
et al2002J Biol Chem277:24855.
Zoo Blot:Southern hybridization experiments with probes derived from a variety of different species to
test potential homologies.(See Rijkers T,Ruther U
1996Biochim Biphys Acta1307:294).
Zoo FISH:Fluorescent in situ hybridization maps for several species to study the evolutionary relations of
their chromosomes.?FISH
Zoonosis(zoonotic infection):Animal pathogens trans-
ferred to humans(by e.g.,grafts,food)may lead to
the development of new human diseases under natural conditions.?grafting in medicine,?acquired immunodeficiency,?xenotransplantation,?Dengue fever,?Ebola virus,?Pox Virus,?West Nile Virus,
?sleeping sickness,?influenza,?SARS,?ence-phalopathies,?mycobacteria,?plague,?laboratory safety;Weiss RA1998Nature Med4:391.
Zoospore:This is a motile(swimming)spore.
Zootype Hypothesis:According to this,HOX-type homeobox genes are present in all metazoa.?home-
otic genes
ZP1,ZP2,ZP3:Refer to zona pellucida glycoproteins.
?fertilization,?zona pellucida
ZPA(zone of polarizing activity):Determines the anterior/posterior differentiation of the limbs and is located behind AER in the limb bud.?AER,?limb
bud
ZPK:Denotes a leucine zipper protein kinase.?DNA-binding protein domains
ZPR:Refers to zinc finger protein binding to the epidermal growth factor receptor.?zinc fingers,
?EGFR
Zta:?ZEBRA
Zuotin:Z DNA and tRNA binding protein of yeast.It
has structural homology with DnaJ and is functional-
ly related to the mammalian chaperone MIDA1, required for cellular growth.?chaperones,?DnaK,
?MIDA1;Braun EL,Grotewold E2001Mol Biol
Evol18:1401.
Zwischenferment:?G6PD
Zwitterion:A dipolar ion with separated positive and negative poles.
ZygDNA:It has been reported that0.1to0.2%of
the eukaryotic DNA may not be replicated until
ZygDNA2133
Z
late leptotene?zygotene.This delayed replication involves dispersed4–10kb stretches and it has been assumed that these segments(ZygDNA)code for genes with products aiding chromosome pairing.It is assumed that a leptotene(L)lipoprotein is involved in the delayed replication.(L)?meiosis;Hotta Y et al 1985Cell40:785.
Zygomeres:Refer to hypothetical initiators of chromo-some pairing in the DNA.
Zygomorphic:A structure of bilateral symmetry,like a snapdragon flower(see Fig.Z6
).
Figure Z6.Zygomorphic.Courtesy of Dr.Z.Schwarz-Sommer
Zygonema:Denotes the chromosome at the zygotene stage.?meiosis,?zygotene stage
Zygosis:Twins can be identical(monozygotic,MZ)or non-identical(dizygotic,DZ).The distinction is not always simple because dizygotic twins(like any siblings)may show several identical features,de-pending on the genetic constitution(consanguinity) of the parents.If the probability of monozygosis between twins with identity in a genetic marker is designated as P(A1/B)where A1and B are different markers and the probability of the twins being either dizygotic or erroneously assumed to be monozygotic is:1?P(A1/B).The calculation may be based on the formula:
PeA
1=BT?1
1t?Q?L
where Q is the dizygotic:monozygotic proportion in
the population(DZ/MZ),and L=likelihood ratio of
the conditional probabilities for DZ and MZ twins
would be identical for a particular genetic condition.
The conditional probabilities that if one of the twins is
of a particular dominant type,the second would also
be of the same type at dizygosis is0.5–1.0,and at
monozygosis1.0.In the case of recessive markers,
these probabilities are0.25and1.0,respectively.The
probabilities also depend on the genetic constitution
of the parents.Recessive markers may be expressed
only if both parents carry that particular allele.If
either of the parents is homozygous for a domi-
nant marker,then both twins must carry that
marker,irrespective of zygosity.L can be computed
as L?P?DZ
P?MZ
L1×L2…L n where P?DZ
P?MZ
is the empirical
probability of the DZ:MZ proportions in the general
population,and L1×L2…L n are the conditional
probabilities for the genetic markers1to n used,
either0.25or1.0.Further complications may arise if
either the penetrance or expressivity of the markers
varies.The DZ:MZ proportions may vary generally
from0.65:0.35to0.70:0.30but are somewhat
different in various ethnic groups,depending on the
age of the mother,the use of fertility drugs and
artificial insemination,etc.DNA markers,either by
RFLP or the PCR method of typing,can better
resolve the problem than using blood types or other
genetic analyses.?conditional probability,?likeli-
hood,?RFLP,?PCR,?DNA fingerprinting,?twin-
ning,?monozygotic,?dizygotic,?concordance,
?discordance
Zygosity:?zygosis
Zygospore:This is formed by the fusion of two spores or
two multinucleate gametangia.?heterothallism,
?homothallism,?gametangia
Zygote:A cell resulting from the union of two gametes
of opposite sexes.?gamete
Zygotene Stage:This stage of meiosis occurs when the
homologous chromosomes(supposedly)begin to
synapse.The pairing usually begins at the termini and
proceeds toward the centromeric region.At this stage
the synaptonemal complex is detectable by electro-
nmicroscopy.The intimate bivalent pairing appears to
be a requisite for chiasma formation as well as for
genetic recombination(see Fig.Z7).?meiosis,
?chiasma,?synaptonemal complex,?association
point,illustration after K.Bela^r:
2134Zygomeres Z
Figure Z7.Zygotene
Zygotic Combinations:?Punnett square,?allelic com-binations
Zygotic Gene:During embryo development this gene is involved in the early control of differentiation in contrast to the maternal effect genes,which are transcribed from the maternal genome and their product is transfused to the embryo.?maternal effect genes,?morphogenesis
Zygotic Gene Activation:After fertilization there is a transition from maternal to zygotic control of development.This process in mouse begins after G2 of the one cell embryo(Schultz RM1993Bioessays 15:531).In humans it seems to be somewhat delayed.
Zygotic Induction:Usually the integratedλprophage is inherited as an integral gene of the bacterial chromosome.However,when a lysogenic Hfr cell carryingλis crossed to a non-lysogenic F?recipient, the prophage leaves the chromosomal position (induction)and becomes an infectious vegetative phage after replicating to about100–200particles. After zygotic induction,only the markers transmitted before the position of the prophage has changed are recovered in the recombinants.Zygotic induction does not occur if the F?cells are lysogenic, irrespective of whether or not the Hfr is lysogenic. The F?recipient is immune to superinfection by freeλphage and it cannot support the vegetative develop-ment of the chromosomalλphage transmitted by the Hfr donor.This indicates that the F?cytoplasm carries an immunity substance or a repressor.?lysogeny,?Hfr,?F?,?lysogenic repressor,?lambda phage; Hayes W1965The genetics of bacteria and their viruses.Wiley,New York.
Zygotic Lethal:A genetic factor that permits the function of the gametes but kills the zygote.The two systems presented here occur in the plant Oenothera,which carry translocation complexes. Letters printed in gray indicate lack of zygote
formation(see Figures Z8and Z9)?translocation,
?complex heterozygote,?translocation[in animals],
?Oenothera
Zymogen:An inactive enzyme precursor.?regulation
of enzyme activity
Zymogram:Electrophoretically separated isozymes are identified in the electrophoretic medium(starch, agarose)by supplying a chromogenic substrate
in situ and this reveals the position of the functionally
active enzyme bands.?electrophoresis,?isozyme Zymolase:This hydrolyzes1→3glucose linkages such
as those existing in yeast cell walls;it is not an exactly defined mixture of proteins extracted from Athro-bacter luteus.
Zymosan:A cell wall extract with a variety of components interfering with the C3complement.
?complement;Ohki K et al2001Immunol Cell Biol
79:462.
Zymotype:This is an electrophoretically determined pattern of enzymes(proteins)which is characteristic
of individuals or group of individuals.?isozymes,
?electrophoresis,?zymogram
F
e
m
a
l
e
g
a
m
e
t
e
s
Figure Z9.Gametic lethal factors A and B are unable
to form selfed zygotes and only the heterozygous embryos are viable.Only the female can contribute viable
B gamete and the male produces viable A gametes
Male gametes
F
e
m
a
l
e
g
a
m
e
t
e
s
Figure Z8.In zygotic lethality only the heterozygotes are
viable and both types of homozygotes are lethal
Zymotype2135
Z
2136Zymotype
Historical vignettes
“I have a rather strange feeling about our DNA
structure.If it is correct,we should obviously follow
it up at a rapid rate.On the other hand it will at the
same time be difficult to avoid the desire to forget
completely about nucleic acid and to concentrate on
other aspects of life.”(JD Watson’s letter to Max
Delbrück on March22,1953.Quoted after HF
Judson1979The Eighth Day of Creation.Simon and
Schuster,New York,p.229)
Evelyn Witkin(2002)in reminiscing about the
pre-Watson and Crick and Hershey and Chase era at
the Cold Spring Harbor Laboratory writes(Annu.
Rev.Microbiol.56:1):
“Although Avery et al(1)had demonstrated in
1944that the genetic material is DNA,the
prevailing attitude at Cold Spring Harbor had been
respectful skepticism.Some suggested that the
transforming DNA in their experiments had acti-
vated genetic information already present or
somehow caused a directed mutation.Others
believed that the minuscule trace of protein still
contaminating the DNA was the active agent.
Delbruck declared DNA to be a“stupid”molecule,
incapable of carrying genetic information.”
In1962Francis Harry Compton Crick,James
Dewey Watson and Maurice Hugh Frederick Wilkins
were jointly awarded the Nobel Prize in Physiology or
Medicine“for their discoveries concerning the
molecular structure of nucleic acids and its signifi-
cance for information transfer in living material”.
In1969the Nobel Prize in Physiology or
Medicine was shared by Max Delbrück,Alfred D
Hershey and Salvador Luria.
Z