C M Y K

SCIENCE KOLKATA WEDNESDAY 14 MARCH 2012 10 water is not in the direction of the wave, it is transverse. In light, the wave is really one of electrical and magnetic effects that rise and fall, Meiosis & Mendel not in the direction of the beam of light, but in Meiosis & Mendel A close look the transverse plane. A close look tapan kumar maitra dwells on the AA cclloossee llooookk And here they are different even from the waves on water – the water moves only up and backbone of classical genetic analysis down and the electrical and magnetic effects can be in any direction in the plane that is at right angles to the beam of light. THE Mendelian laws of genetics form the backbone of Now with certain substances, when a beam of classical genetic analysis; the basic tool is the light passes through them, the electromagnetic inheritance test, in which phenotypes produced by pairs aaaatttt rrrreeeefffflllleeeeccccttttiiiioooonnnn effects are transmitted only in one plane, and the of alleles are followed through successive generations. In light that comes through is weakened, but richer haploid organisms such as Neurospora, 1:1 ratios are in the selected plane of transmission. Light like regularly observed for single pairs of alleles, and the this is called polarised light. If such light is again phenotypes of all genes are directly observed. In diploid movement. A sound wave is a progression of shone on the same material, but turned at right organisms such as the garden pea used by Mendel, the How earth appears from afar may help detect life in compressions and rarefactions of air, set up by a angles, then the light will not pass! A certain phenomena of phenotypic dominance and recessiveness distant worlds, says s ananthanarayanan vibrating object and detected by creating the amount of polarisation also takes place when are encountered, and the familiar 3:1 ratio for single same vibrations in another object, like a eardrum light reflects off a surface, depending on the pairs of alleles, and the 9:3:3:1 ratio for two independent or a microphone diaphragm. The variations in angle of incidence. This is the reason that alleles, are customarily observed. density are, hence, in the same direction as the Polaroid lenses can cut the glare on a sunny day Mendel was aware THERE has been interest in getting a good earthlight that shines on the moon reflects off motion of the wave. But it is different in light – by controlling the amount of reflected light of the role of eggs external view of earth so that we are better the lunar surface and can be detected, albeit waves, and the movement is like the waves on that it allows to pass. and sperm in equipped with what to look for when scanning faintly, by sensitive, large-diameter telescopes on the surface of a pond. Sterzik and colleagues report in the journal fertilisation but for “earth-like” planets around distant stars. earth. The light detected is then not transmitted In these waves, the water bobs up and down, Nature that they used the 8.2 metre Very Large quite unaware Pictures taken from satellites are not good light but reflected light from earth, and it would setting up a similar movement of water, in Telescope in Chile to analyse the polarisation of meiosis as enough and we need a little more perspective — carry not only the effect of the atmosphere but expanding circles, but the movement of the spectrum of earthshine reflected back from the it is known a picture from the moon is not bad. In 2009, a moon. They found that the linear polarisation of today, a fact group in Tenerife, Spain, managed pictures of light scattered by air molecules, aerosols and that only earth’s transmission spectrum, or the light that cloud particles and also by reflection was a more serves to emphasise the passes through our planet’s atmosphere, as seen Partial shade sensitive measure of distribution of atmospheric on the moon. But Michael F Sterzik, Stefano gases or land/water/vegetation features than remarkable ingenuity he displayed Bagnulo and Enric Palle, in Chile, the UK and usual spectroscopy. The results, for the earth, in analysing the problem of again in Tenerife have looked at aspects of show unusual abundance gases like oxygen and character inheritance. It reflected earthlight that shines on the moon to methane, which are themselves bio-signatures, remained to relate the abstract identify features that could indicate the presence Full shade or indicators of life systems. Sun Earth factor, or gene, to some cellular structure. This was done of life! There is also a sharp increase in long by Sutton, Boveri and de Vries in 1902-1904, shortly The last decade has been fruitful in finding wavelength reflection, which indicates the after Mendel’s laws had been rediscovered. The following planets that, we hope, resemble earth, in orbit presence of vegetation. The analysis indicates the facts indicate that the behaviour of the Mendelian genes around distant stars. A planet that has no light of separate contribution of clouds and ocean and is Moon in inheritance is mirrored in the behaviour of the its own, of a distant star, is not visible from earth, Reflected sensitive to even 10 per cent changes in visible chromosomes in fertilisation and meiosis. as the glare of the mother star prevents any light Light through earth’s vegetation. The results, they say, “represent a Fertilisation in both plants and animals involves the reflected light from the planet from being seen. Moon orbit atmosphere benchmark for the diagnostics of atmospheric union of maternal and paternal nuclei, providing a While the first method to detect planets was, composition, mean cloud height and surface of means for the union of parental characteristics in the hence, through the slight wobble that they create exoplanets”. offspring. The contribution of the sperm consists in the position of the mother star, which affects Transmitted light Christoph U Keller or Leiden University, The primarily of nuclear materials; so the sperm nucleus is the colour of the light it emits, a more effective Netherlands, adds in a commentary that the source of all paternal genetic contributions. It is the way has been with planets that pass between the measuring yet another property of the reflected genetic equivalent of the egg nucleus, despite the fact star and earth and cause a minute dip in the light Lunar night light could more sensitively indicate the presence bathed in that egg and sperm differ radically in size and received. With some refinement, it should also of life. An effect of reflection or passing through morphology. be possible to detect the effect that the gasses in earthlight some substances, by polarised light, is that the Meiosis provides for a reduction in the number of the planet’s atmosphere have on the light that electrical and magnetic components of light chromosomes in the egg and sperm, with fertilisation passes very near the planet’s surface. To be ready Back-reflection waves be put “out of step”. When this happens, restoring the somatic number in the zygote. The somatic, to draw conclusions from these effects, it was of from the moon the plane of polarisation keeps changing, in a or diploid, chromosome number is therefore made up of interest to see what effect earth had on light Light Earthshine spiral manner, as the wave moves on and this is two equivalent haploid sets of chromosomes, one of from the sun, as the light grazed earth and reflected called circular polarisation. maternal and the other of paternal derivation. Every passed on into space. by the earth While crystal structures or plates made from chromosome has a mate with which it is linearly and The Tenerife experiment was conducted from such materials can be created to turn the plane genetically homologous. during a lunar eclipse, where the moon is dark of polarisation, it is found that living tissue A mechanism for the segregation of the maternal and as earth’s shadow is upon it, but there is still uniformly causes circular polarisation in only paternal derivatives of every chromosome pair is some light that has passed through earth’s the Earth one sense, that is right-handed or left-handed. provided through the process of synapsis. The two atmosphere. This light, which dimly illuminates Finding handedness in circular polarisation of members of every pair synapse in meiotic prophase, separate from each other, and pass to opposite poles at the eclipsed moon, also reflects back to earth sun light reflected by an exoplanet would then point and the reflected light was examined for Reflected a finger to living materials! anaphase, and thus are incorporated into the nuclei of indicators of the components of earth’s light different gametes. atmosphere. Sure enough, analysis in the visible The writer can be contacted at If we substitute “genes” or “alleles” for “chromosomes” and infra-red region showed signs of ozone, [email protected] in the above statements, we are describing the water, carbon dioxide and methane and also of also the effect of reflection by different surfaces, inheritance and transmission of Mendelian factors. The calcium and of some gases arising from human like the clouds, the sea, rocks or plants. first critical demonstration of the relationship of a particular character to a particular chromosome was that activity. And so, there is interest in refining the The main effect in the case of transmitted light Plane of one wave effect of earth’s known gases on transiting was that the gasses through which the light involving sex determination. Although chromosomes now Plane of known to be sex or X chromosomes were first found, in sunlight so that we can make sense out of similar passed absorbed light at particular frequencies, the other an insect, in 1891, it was not until 1901-1902 that a data from a distant planet. which are characteristic of the gases. Analysis of particular chromosome was actually shown to possess a the spectrum of the light then showed the sex-determining role. Reflected light frequencies where there was absorption and, This stemmed from the observation that two types of The other kind of external view of earth is by hence, the presence of the gases. In the case of sperm are produced in equal numbers by an XO male its reflected light, like the light we see coming reflected light also, there is the effect of (one X chromosome as opposed to two in an XX female), from the moon. Here again, a handy observation absorption, as the light does pass through Propagation and that the two sexes are produced in equal numbers. post is the moon, not in eclipse but in a quarter atmosphere, but there is also the effect of The two types of sperm differ only in that one type has moon position. The dark part of the moon, reflection. an X chromosome while the other lacks one; so the X where it is “night”, is then bathed in reflected Apart from frequency, which is a property that chromosome must be influential in determining the sex light from earth, as earthlight, corresponding to light waves share with sound waves, light has of the offspring. The egg receives a single X chromosome moonlight, which we have on earth. And this another property of the direction of periodic as the result of chromosome segregation; whether the resulting zygote will be male or female is determined by impact on water shortages somewhere Britain’s water footprint was felt out- the type of fertilising sperm. else.” side the UK. It remained for Morgan and Bridges to demonstrate, in His warning backs up analysis by the Ashok Chapagain, the WWF’s senior a classical series of studies, that a particular gene was to AA hhaarrdd,,ddrryy ffuuttuurree Royal Academy of Engineering, which water adviser, said, “Water scarcity affe- be found in a particular chromosome. Morgan had found that Britain and other developed cts at least 2.7 billion people in 201 shown that the transmission of white, a recessive eye countries depended heavily on import- river basins for at least one month a colour in Drosophila melanogaster, depended on which ing hidden or “virtual” water from year. International trade and the global- sex carried the allele initially. For example, if a white- As global bodies gather in Marseilles to is threatening global development places prone to droughts and short- isation of the supply chain... make wat- eyed male is crossed with a homozygous red-eyed goals and will exacerbate inequality ages. In a 2010 report, the academy er scarcity a global issue.” female, the F1 flies of both sexes are red-eyed, the F2 discuss water supplies, sarah morrison between countries, sectors and regions. estimated that two-thirds of all water But the need is not expected to lessen. females are all red-eyed, and F2 males are red and reports on the waste that will create a thirsty Managing Water under Uncertainty and that Britain needed came embedded in Increasingly, underground water sour- white-eyed in equal numbers. With the sexes being Risk shows that while 86 per cent of the imported food, industrial products and ces have been tapped to respond to produced in equal numbers, this gives a normal 3:1 ratio world by 2050 population in developing regions are clothes such as cotton. In 2008, a study growing demand and, under what the of the eye colours but with the added qualification that expected to have improved access to published by the conservation group, UN report called a “silent revolution”, the white-eyed flies are always male. When the safe drinking water by 2015, there are WWF, found that about 60 per cent of this process has tripled over the past 50 reciprocal cross is made, using a white-eyed female and years. Transnational land acquisi- a red-eyed male, the F1 males are white-eyed and the F1 THE world is wasting water on a gramme run by the OECD, said the tion, where countries acquire females red-eyed. In the F2 generation, half the males truly colossal scale, according to the world was experiencing a water “cri- land outside their jurisdiction to and female are white-eyed and the other half red-eyed. United Nations, and more than 80 per sis”. He added, “More people in cit- get access to water, has risen from This type of inheritance paralleled the transmission of cent of the used water is neither col- ies now don’t have access to water 20 million hectares in 2009 to the X chromosome; Bridges showed conclusively that the lected nor treated — the equivalent to than back in 1980. In developing more than 70 million today. gene white was located on the X chromosome. When the planet leaving the taps full on and countries, especially, there is a trem- To illustrate the political, tech- making a cross between a white-eye female and a red- the plugs out. endous economic and human cost nical and financial solutions to eyed male, he noted the appearance of exceptional This and other equally worrying real- to this.” the world’s water problems, a 400 individuals, whose genotype was such as to suggest a ities will be presented this week to aro- Since 1900, more than 11 million square-metre Vilage of Solutions failure of the usual type of inheritance of the X und 35,000 people from 180 countries people have died because of drought, will be built inside the Water chromosomes. Thus, in an F1 population that should have contained only red-eyed females and white-eyed at the World Water Forum, a gathering according to the UN, and more than Forum this year, housing a school, males, there appeared an occasional white-eyed female held every three years, which will hear two billion have been affected by it library, town hall, factory and or red-eyed male, with the exceptional females occurring the most disturbing reports yet on the — more than any other physical haz- bank. Different funding mec- with a frequency of one in 2,500. The frequency of state of the world’s rivers, lakes and ard. The OECD is calling for “urgent hanisms and technologies will be exceptional males was about one in 1,200. aquifers. reform” of water management and explained. LV Morgan discovered, in 1922, a strain of Drosophila Demand for water is expected to suggests using economic instru- However, the forum, organised melano gaster that apparently gave 100 per cent non- increase by 55 per cent over the next ments, such as taxation, tariffs and by the French government, the disjunction. As in the case of Bridges’ exceptional four decades, according to a new study transfers, to encourage greater “wat- World Water Council and the City individuals, the daughters appeared to receive both X to be presented at the forum in France. er efficiency”. of Marseille, where it is being held, chromosomes from their mother, and the sons a single X Framing the Water Reform Challenge, Olcay Unver, coordinator of the has been criticised for being mer- chromosome from their father. Examination of the from the Organisation for Economic United Nations World Water Assess- still nearly one billion people without ely a “talking shop”. chromosomes of the female showed two X Cooperation and Development (OEC- ment, said it would be a “game-chang- such access and, in cities, the num- Said Daniel Yeo, WaterAid’s senior chromosomes attached to each other in the D), points out that rapid urbanisation, er” if the world could tackle environ- bers are growing. policy adviser for water security, “They neighbourhood of their centromeres, with the result that climate change and the altering global mental challenges without using water- Water management can no longer will have the big debates there, but it’s they always passed to the same pole. The AY economy are putting growing pressures wasting technologies such as biofuels. be seen as a local issue, said Unver; it not where change happens. The real chromosome is present in these females, and it on supplies. In around 40 years’ time, “Water underpins all aspects of devel- had to be treated as a global one. situation is that dirty water kills more segregates from the joined X chromosomes. Evidence more than 40 per cent of the world’s opment,” he said. “It is the only medi- “Water is not only what we drink, kids in sub-Saharan Africa than tuber- that the random assortment of two pairs of alleles population — 3.9 billion people — are um through which all crises can be what we wash with, or what we use to culosis, malaria and Aids combined. (Mendel’s second law) is paralleled by the random likely to be living in river areas in the jointly addressed. It should be seen as irrigate; it is also embedded in the We have the technology to change assortment of paired chromosomes was provided by grip of a severe “water-stress”. The UN an explicit element in any decision- products that we eat, consume and this; what we need is the political will Carothers in 1913. warns this could also be felt in parts of making framework.” use,” he said. “This gives us a totally and the internal capacity to deliver it Europe, affecting up to 44 million peo- Unver is lead author of a UN report up different perspective to water — it is in developing countries.” The writer is associate professor and head, Department ple by 2070. for publication that warns that unprece- subject to trade policies, and one nat- Olcay Unver: Water management can of Botany, Ananda Mohan College, Kolkata Anthony Cox, head of a water pro- dented growth in the demand for water ion, or one corporation, can have an no longer be seen as a local issue. The Independent, London

C M Y K