Introduction,In some fungi ,true sexual cycle comprising of nuclear fusion and meiosis is absent.
These fungi derive the benefits of sexuality through a cycle know as parasexuaL cycle.
First Reported by- Gudio Pontecorvo and J.A.Roper(1952)
Parasexual cycle was reported in
Aspergillus nidulans,the imperfect stage of Emericella nidulans.
Since then parasexual cycle has been discovered not only in several members of Deutromycetes but also in fungi belonging to Ascomycetes and Basidiomycetes.
DEFINETION - Parasexuality is defined as a cycle in which Plasmogamy, Karyogamy and Meiosis [Haploidization] take place in sequence but not at a specified time or at specified points in the life cycle of an organism.
Generally parasexual cycle occurs in those fungi in which true sexual cycle does not take place.
Parasexualcycle also know as Somatic recombination. PASEXUALITY ALSO REPORTED IN SOME ORGANISMS- Aspergillus nigar, Penicillium crysogenum, STEPS OF PARASEXUAL CYCLE - 1) ESTABLISHMENT OF HETEROKARYOSIS, 2) Formation of Heterozygous DIPLOIDS, 3) occasional mitotic crossing-over during multiplication of diploid nuclei, 4)occasional haplodization through aneuploidy , COMPARISION BETWEEN SEXUAL AND PARASEXUAL CYCLE, IMPORTANCE OF PARASEXUALITY, C0NCLUSION
Heterothallic species have sexes that reside in different individuals. . The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.
A chemical substance that is produced in one portion of an organism and moves by diffusion or transport to another portion of same individual or to other individual of same species where it induce specific response is called a hormone.
Heterothallic species have sexes that reside in different individuals. . The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.
A chemical substance that is produced in one portion of an organism and moves by diffusion or transport to another portion of same individual or to other individual of same species where it induce specific response is called a hormone.
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
Detail about Basidiomycetes.In this detail about its Ecosystem Relationship,Symbiotic Relationships,General characters,Basidiospores,Life cycle and its Fruiting body.
Contact Email: mzeeshan_93@yahoo.com
Introduction :
Mycorrhizae are mutualistic symbiotic associations formed between the roots of higher plants and fungi.
Fungal roots were discovered by the German botanist A B Frank in the last century (1855) in forest trees such as pine.
In nature approximately 90% of plants are infected with mycorrhizae. 83% Dicots,79% Monocots and 100% Gymnosperms.
Convert insoluble form of phosphorous in soil into soluble form.
Parasexual cycle was first introduced by Guido Pontecarvo and Roper in dueteromycete members. In this sexual reproduction is absent. It is a cycle in which their is no specific time for lasmogamy, karyogamy and meiosis. They derive their sexual benefits from parasexuality.
importance of this cycle can be seen in industrial process, new and better strain,analysis of genetic and physiological processes of perfect and imperfect. it is also successful in genetic control of pathogenecity and host range in fusarium species.
HETEROKARYOSIS AND PARASEXUALITY IN FUNGI.pdfSaloniJoshi20
HETEROKARYOSIS AND PARASEXUALITY IN FUNGI- AD. MYCOLOGY -PLANT PATHOLOGY
The term heterokaryons (hetero=dissimilar, karyons=nuclei) has been defined as the coexistence of genetically-different nuclei in a single cell.
The phenomenon was discovered by Hansen and Smith (1932) in Botrytis cinerea.
FORMATION OF HATEROKARYOSIS
1. Mutation,
2. Anastomosis
3. Inclusion of dissimilar nuclei
FUNGAL PERASEXUALITY
One such novel alternative to sexual reproduction was discovered in fungi (Aspergillus nidulans) by Pontecorvo and Roper in 1958. This they named as the parasexual cycle.
STEPS OF PARASEXUAL CYCLE:
Establishment of Heterokaryosis,
Formation of heterozygous diploids,
Occasional mitotic crossing-over, during multiplication of the diploid nuclei, and
Haplodization through aneuploidy.
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
Detail about Basidiomycetes.In this detail about its Ecosystem Relationship,Symbiotic Relationships,General characters,Basidiospores,Life cycle and its Fruiting body.
Contact Email: mzeeshan_93@yahoo.com
Introduction :
Mycorrhizae are mutualistic symbiotic associations formed between the roots of higher plants and fungi.
Fungal roots were discovered by the German botanist A B Frank in the last century (1855) in forest trees such as pine.
In nature approximately 90% of plants are infected with mycorrhizae. 83% Dicots,79% Monocots and 100% Gymnosperms.
Convert insoluble form of phosphorous in soil into soluble form.
Parasexual cycle was first introduced by Guido Pontecarvo and Roper in dueteromycete members. In this sexual reproduction is absent. It is a cycle in which their is no specific time for lasmogamy, karyogamy and meiosis. They derive their sexual benefits from parasexuality.
importance of this cycle can be seen in industrial process, new and better strain,analysis of genetic and physiological processes of perfect and imperfect. it is also successful in genetic control of pathogenecity and host range in fusarium species.
HETEROKARYOSIS AND PARASEXUALITY IN FUNGI.pdfSaloniJoshi20
HETEROKARYOSIS AND PARASEXUALITY IN FUNGI- AD. MYCOLOGY -PLANT PATHOLOGY
The term heterokaryons (hetero=dissimilar, karyons=nuclei) has been defined as the coexistence of genetically-different nuclei in a single cell.
The phenomenon was discovered by Hansen and Smith (1932) in Botrytis cinerea.
FORMATION OF HATEROKARYOSIS
1. Mutation,
2. Anastomosis
3. Inclusion of dissimilar nuclei
FUNGAL PERASEXUALITY
One such novel alternative to sexual reproduction was discovered in fungi (Aspergillus nidulans) by Pontecorvo and Roper in 1958. This they named as the parasexual cycle.
STEPS OF PARASEXUAL CYCLE:
Establishment of Heterokaryosis,
Formation of heterozygous diploids,
Occasional mitotic crossing-over, during multiplication of the diploid nuclei, and
Haplodization through aneuploidy.
Sex and sexuality are very common words in biology but para-sexuality is a little bit uncommon, several organisms in general and fungi in particular have the pleasure of sexuality to bring variations by beside sex. This PPT explores the beauty of para-sexuality for the academic fraternity.
Introduction, Types-somatic and germinal; Mechanism of meiotic crossing oversynapsis, duplication of chromosomes, breakage and union, terminalization;
Cytological basis of crossing over - Stern’s experiment in Drosophila; Creighton
and McClintock’s experiment in Maize; Crossing over in Drosophila, Construction
of genetic maps in Drosophila - two point and three-point crosses; Interference and
coincidence.
Abnormalities 0f mitotis By KK Sahu SirKAUSHAL SAHU
INTRODUCTION
WHAT IS MITOSIS
PHASES OF CELL CYCLE AND MITOSIS
SOURCE & REASON OF ABNORMAL MITOSIS
EFFECTS OF ABNORMAL MITOSIS
ABNORMALITIES OF MITOSIS IN PLANTS
ABNORMALITIES OF MITOSIS IN ANIMALS & HUMAN BEINGS
FACTORS RESPONSIBLE FOR MITOTIC ABNORMALITY
ADVANTAGES & DISADVANTAGES OF ABNORMAL MITOSIS
CONCLUSION
REFERENCE
What is Genome,Genome mapping,types of Genome mapping,linkage or genetic mapping,Physical mapping,Somatic cell hybridization
Radiation hybridization ,Fish( =fluorescence in - situ hybridization),Types of probes for FISH,applications,Molecular markers,Rflp(= Restriction fragment length polymorphism),RFLPs may have the following Applications;Advantages of rflp,disAdvantages of rflp, Rapd(=Random amplification of polymorphic DNA),Process of rapd, Difference between rflp &rapd
Introduction- PTERIDOPHYTES
Pteridophytes in the broad interpretation of the term are vascular plants (plants with xylem & phloem) that reproduce & disperse via spores, because they produce neither flowers nor seeds, they are refered to as CRYPTOGAMS.
The 305 genera & 13,000 species of pteridophytes found throughout the world.
The pteridophyte includes Clubmosses,SPike-mosses, Quilworts,Horsetails,Ferns.
FERNS -Adiantum (Maiden-hair fern)
(Family-Pteridaceae)
A.pedatum, A. raddianum(Delta-maiden hair),
Asplenium, (FAMILY-ASPLENACEAE)- Asplenium nidus
(Birds nest fern),
Blechnum, (family-blechnaceae) , Cyrotomium, (family-dryopteridaceae), Davalia, (family-davalliaceae), Doryopteris
(family-pteridaceae), Nephrolepis,(family-lomariopsidaceae) -N. biserrata furcans, N. exallata mucosa, Pityrogramma
(family-pteridaceae), P.calomelanos (silver fern), P.chrysophylla (golden fern), Platycerium family-polypodiaceae
P. bifurcatum, P.willinckii (silver staghorn),Polypodium(family-polypodiaceae), Polystichum (family-dryopteridaceae),Pteris
(family- pteridaceae), CONCLUSION
Introduction -Remote means – far away ; Sensing means – believing or observing or acquiring some information.
Remote sensing means acquiring information of things from a distance with sensors. (without touching the things)
Sensors are like simple cameras except that they not only use visible light but also other bands of the electromagnetic spectrum such as infrared, microwaves and ultraviolet regions.
Distance of Remote Sensing, Definition of remote sensing - Remote Sensing is:
“The art and science of obtaining information about an object without being in direct contact with the object” (Jensen 2000).
India’s National Remote Sensing Agency (NRSA) defined as : “Remote sensing is the technique of deriving information about objects on the surface of the earth without physically coming into contact with them.”
Remote Sensing Process, - (A) Energy Source or Illumination.
(B) Radiation and the Atmosphere.
(C) Interaction with the Target.
(D) Recording of Energy by the Sensor.
(E) Transmission, Reception, & Processing.
(F) Interpretation and Analysis.
(G) Application.
Remote sensing platforms , History of Remote Sensing, Applications of remote sensing - In Agriculture, In Geology, Applications of National Priority.
INTRODUCTION -
The source of sugar can be stems or underground roots.
Two principle source of sugar are Sugarcane & sugar beet.
Also called as industrial plants
The sources of storage sugars are;
Stems- Sugarcane, Sugar maple
Roots- Beets, carrots
Flowers- palm
SUGARCANE (Saccharum officinarum)
SYSTEMATIC POSIYION –
Class- Liliopsida
Order- Poales
Family- Poaceae
Genus- Saccharum
Species- officinarum
Vernacular name- Ganna
Botanical & ecological description of sugarcane, SUGARCANE GROWING REGIONS, Cultivation of sugarcane, Processing of sugarcane, Uses of sugarcane
Sugar beet (Beta vulgaris) - SYSTEMATIC POSITION-
Family-Amaranthaceae
Genus- Beta
Species- vulgaris
Vernacular name- chukandar
Cultivation of Sugar beet, harvesting of Sugar beet, Processing of sugar extraction from Sugar beet, By-products of Sugar beet, Uses of sugar beet,
PALMYRA PALM- Manufacture OF Jaggery
Sweet potato (Ipomoea batatas) -
SYSTEMATIC POSITION-
Class - Magnoliopsida
Order- Solanales
Family-Convolvulaceae
Genus –Ipomoea
Species- batatas
USES OF SWEET POTATO,
Stevia rebaudiana- USEs OF STEVIA
Other sugars, Importance of sugar
Environmental management: Introduction and scopeRashmi Yadav
What is Environment ? The sum total of all surroundings of a living organism, including natural forces & other living things which provide conditions for development & growth as well as of danger & damages.
INTRODUCTION, Environmental management ,DEFINITION – “Environmental management system refers to the management of an organization's environmental programs in a comprehensive, systematic, planned and documented manner. It includes the organizational structure, planning & resources for developing, implementing and maintaining policy for environmental protection.”
Characteristics of environmental management, Two main standards- BS7750,ISO 14001, Schemes of environmental management- Eco management and Audit schemes(EMS), Why have an EMS? Scope of environmental management, Importance of environmental management, Role of remote sensing in environmental management
Introduction,Definition, Cycling elements, Types of biogeochemical cycle- Gaseous cycle and sedimentary cycle Nitrogen cycle, steps of Nitrogen cycle- Nitrogen fixation, Nitrification, Assimilation Ammonification, and Denitrification and ecological function of nitrogen, use of nitrogen cycle phosphorus cycle, steps of phosphorus cycle, biological functions of phosphorus cycle and other functions of phosphorus and conclusion
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
2. INTRODUCTION
In some fungi ,true sexual cycle comprising
of nuclear fusion and meiosis is absent.
These fungi derive the benefits of sexuality
through a cycle know as parasexuaL
cycle.
4. Parasexual cycle was reported in
Aspergillus nidulans,the imperfect stage of
Emericella nidulans.
Since then parasexual cycle has been discovered
not only in several members of Deutromycetes
but also in fungi belonging to Ascomycetes and
Basidiomycetes.
So,far it has not been rported in Phycomycetes
fungi.
5. Parasexuality is defined as a cycle in which
Plasmogamy, Karyogamy and Meiosis
[Haploidization] take place in sequence but not at a
specified time or at specified points in the life cycle of
an organism.
Generally parasexual cycle occurs in those fungi in
which true sexual cycle does not take place.
Parasexualcycle also know as Somatic recombination.
DEFINETION
6. PASEXUALITY ALSO REPORTED IN
SOME
ORGANISMS
• Aspergillus niger
• Aspergillus
fumigatus
• Aspergillus oryzae
• Aspergillus sojae
Pontecarvo et al
[1952]
Stromnaes and
Garber [1963]
Ishitani [1956]
Ishitani et al
[1957]
ORGANISM
S
11. • The various steps of the parasexual cycle has
been worked out in detail for Aspergillus
nidulans ,Aspergillus nigar and Penicilium
chrysogenum .
• In A . nidulans which serves as the typical
example, the parasexual cycle occurs in the
following four steps;
STEPS OF PARASEXUAL
CYCLE
12.
13. • The presence of haploid nuclei of dissimilar genotypes
in the same cytoplasm is a pre-requisite for
recombination.
• This is achieved by heterokaryosis which is bought
about by-
I. Mutation
II. Anastomosis
Between hyphae of different origin.
This step is equal to plasmogamy of sexual
reproduction.
ESTABLISHMENT OF HETEROKARYOSIS
16. The nuclear fusion between dissimilar nuclei
result in formation of heterozygous diploid
nuclei or zygotes a rare event, occuring at the
rate of one in a million.
• Fusion between identical nuclei to occur.
• But since the homozygous diploid nuclei thus
formed ultimatly give rise to non –
recombinant haploid nuclei
17. Such fusion have no genetic
relevence.
The heterozygous nuclei, which
are fairly stable, by multiplication
and staring out through conidia
give rise to diploid thalli.
The diploid colonies are
recognized by-
20. • When measured the DNA content of haploid
and diploid spore suspension of the
A.nidulans and A.fumigatus.
• As result of their lower amount of total DNA
per cell.
• This work demonstrates that the use of flow
cytometry is a very rapid, simple and accurate
method.
21. • To distinguish diploid and haploid spores in
Aspergillus species ,this technique could be
also applied to parasexual analysis in other
filamentous fungi, especially in those species
of industrial interest where sexual crosses are
unavailable,
(i.e-Penicillum chrysogenum, A.niger,
A.oryzae, etc).
22. • This is typical of parasexual phenomenon ,and
obviously the prolonged diploid phase, involving
repeated nuclear division enhance the chances
of mitotic crossing-over.
23. • This is the most important or key event in
parasexual cycle.
• It is during this step that genetic
recombination take place,
• Crossing over during mitosis is rare
phenomenon, first noticed in Fruit Fly by stern
in 1936.
occasional mitotic crossing-over
during multiplication of diploid
nuclei
24. • In A. nidulans mitotic crossing-over occurs
rarely, with a frequency of 10-2 per nuclear
divison.
• Intrestingly enough, in some fungi , like
Penicillium chrysogenum and Aspergillus
niger,it is as frequent as during meosis.
• Pontecorvo and roper (1952) invoked mitotic
crossing-over to explain the development of new
heterozygous, recombinant haploid nuclei,
which has subsequently also proved
cytologically.
25. • Reciprocal exchanges between homologous
chromosome at the four-strand stage were
observed by Pritchard & Roper (1995) and
Kafer (1961).
• It is charectristic feature of mitotic crossing-
over that the exchange or chiasmata
formation, is confined a single chromosome
pair out of the whole complement of
chromosomes.
26. • In meiosis, the crossing-over n all the occurs
simultaneously in all the chromosomes.
• The subsequent a splitting of chromosomes and
segregation of strands is as it occurs in mitosis .
• Crossing-over followed by segregation of strands
gives homozygosis for all markers
distal to the point of chiasma. Markers
proximal to the point of exchange and markers
on other chromosomes remain heterozygous.
27. • The haploid nuclei give rise to haploid nuclei by
gradual loss of chromosomes during succesive
mitotic divisions .This is called Haplodization .
Meiosis is not involved .
• The haplodization , which occurs at a constant
frequency of 10-3 per nuclear division ,is the
result of Aneuploidy .
occasional haplodization
through aneuploidy
28. During mitotic division , non-disjunction of the
chromatic of one chromosomes pair result in aneuoloid
nuclei which can be represented as (2n-n) i.e haploid
at the end .
The aneuploids are genetically unstable , and ones the
loss of chromosomes has started , the selection favours
the development of fully balance haploid nuclei .
Parasexual cycle closely stimulates the events of th
sexual cycle .
It involves everthings , Plasmogamy ,Karyogamy an
Haplodization , but in modified form and without an
fixed plan with regard to time and space .
29. • Parasexual cycle closely stimulates the events of
the sexual cycle .
• It involves everthings , Plasmogamy
,Karyogamy and Haplodization , but in
modified form and without any fixed plan with
regard to time and space .
• The two processes nevertheless , end with
similar results , i.e give rise to recombinant
haploid nuclei.
30.
31. 1) Nuclear fusion is in
speciallized
structures .
2) Zygote usually
persist one nuclear
generation only .
1) Rare nuclear fusion
in vegitative
structures cells .
1) Zygote persist
through many
mitosis .
SEXUAL CYCLE
PARASEXUAL
CYCLE
32. 3) Recombination by
meiosis crossing-over
in all chromosome
pair, reduction of
chromosome number,
random assortment of
members of each
chromosome pair.
3) Recombination by rare
accidants of mitosis ,
a. Mitotic crossing-over
,at each event usually
confined to one
exchange in singal
chromosome arm.
33. 4) Products of meiosis
readily recognised and
isolated .
b) Haplodization
independent of
crossing-over ,random
assortment of members
of each chromosome
pair.
4) Recombinanant occur
among vegitative cells ,
recognised only by use
of suitable genetic
markers .
34. • Some of the most important antibiotic producing
fungi, like Penicillium chrysogenum
(penicillin) and Acremonium chrysogenum
(cephalosporin), lack sexual reproduction. The
discovery of parasexual phenomenon in them
has provided suitable techniques to obtain
higher antibiotic strains. Some antibiotic
producing fungi in which parasexual genetic
recombination have been established are the
following:
36. • Parasexuality has been known only a laboratry
phenomemon.
• However the result of Ingram(1968) strongly
suggested that it may be widespread in nature.
37. • Through it has been demonstrated only
Ascomycotina,Basidiomycotina and
Deuteromycotina ,there are strong
evidences of its occurrence in some
coenocytic fungi like Phytopthora
cactorum .
• The phenomenon is linked with
heterokaryotic condition ,
38. Which is very frequently encountered in
nature populations.
But every heterokaryotic species may not
necessarity be parasexual.
Thus “The role of parasexuality in the
origin of individuals to be assessed.
39. Introduction to Mycology by- H.C. Dube Third
edition .
An introduction to Mycology – R S Mehrotra . K R
Aneja .
Introduction of Mycology by -Alexopoulos ,Mins
and Blackwell .
Parasexual cycle –Wikipedia the free encyclopedia .