Introduction
About Drosophila
Genome of Drosophila
Life cycle
Differentiation
Development of Drosophila
* Embryonic development
* Dorsal -ventral and
* Anterior posterior development
* Body segmentation
* Homeotic gene
Conclusion
Reference
Welcome to the world of Homeotic genes. In this presentation I talk about the interesting history behind homeotic genes as to how it was discovered. Also, the various deformities in Drosophila related to mutations in homeotic genes and the characteristics of homeotic genes. I also talk about hox genes in humans and their function.
Introduction
About Drosophila
Genome of Drosophila
Life cycle
Differentiation
Development of Drosophila
* Embryonic development
* Dorsal -ventral and
* Anterior posterior development
* Body segmentation
* Homeotic gene
Conclusion
Reference
Welcome to the world of Homeotic genes. In this presentation I talk about the interesting history behind homeotic genes as to how it was discovered. Also, the various deformities in Drosophila related to mutations in homeotic genes and the characteristics of homeotic genes. I also talk about hox genes in humans and their function.
A chart showing the fate of each part of an early embryo, in a particular blastula stage is called fate maps. It is done because the correct interpretation of gastrulation is impossible without the knowledge of the position which are the presumptive germinal layers (Ectoderm, Mesoderm and Endoderm) occupy in blastula.
Fate mapping is a method used in developmental biology to study the embryonic origin of various adult tissues and structures. The "fate" of each cell or group of cells is mapped onto the embryo, showing which parts of the embryo will develop into which tissue. When carried out at single-cell resolution, this process is called cell lineage tracing. It is also used to trace the development of tumors.
The SPECIAL - GIANT CHROMOSOMES which are very transcriptionally active DNA, where loops of DNA emerging from an apparently continuous chromosomal axis are coated with RNA polymerase.
Comparatively much larger than polytene chromosomes.
Highly significant for scientific analysis especially regarding gene amplification.
Basics of Undergraduate/university fellows
Nucleosome model of chromosome is proposed by ROGER KORNBERG (son of Arthur
Kornberg) in 1974.
It was confirmed and crystalised by P. Oudet et al., (1975).
Nucleosome is the lowest level of Chromosome organization in eukaryotic cells.
Nucleosome model is a scientific model which explains the organization of DNA and
associated proteins in the chromosomes.
Nucleosome model also explains the exact mechanism of the folding of DNA in
thenucleus.
It is the most accepted model of chromatin organization.
DNA is tightly packed in the nucleus of every cell. DNA wraps around special proteins called histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes.
DNA packaging is crucial because it makes sure that those excessive DNA are able to fit nicely in a cell that is many times smaller.
The DNA in bacterial cells are either circular or linear. To accommodate the size of bacterial cell, supercoiled DNA are folded into loops with each loop resembles shape of bead-like packets containing small basic proteins that is analogous to histone found in Eukaryotes.
Maternal effects are the influences of a mothers genotype on the phenotype of her offspring. It results from the asymmetric contribution of the female parent to the development of zygotes.
In terms of chromosomal genes, both male and female parents contribute equally to the zygote. The female parent contributes to the zygotes initial cytoplasm and organelles. Sperm rarely contribute anything other than chromosomes. Therefore zygotic development begins within a maternal medium and hence the maternal cytoplasm directly affects zygotic development.
cell lineage , cell fate - diverse class of cell fate, cell fate in plant meristem, mammalian development cell fate, nutritional effects on epigenetics, epigenetics of plants,
control of cell fate.
A complementation test (sometimes called a "cis-trans" test) can be used to test whether the mutations in two strains are in different genes. By taking an example of Benzer's work, complementation has been explained.
Polytene chromosome with respect to historical basis, occurrence, structural organisation, bands and inter bands, puff are briefly stated for basic idea.
You may find this interesting understand the reason behind the gaint structure of these chromosomes.
This study material is a compilation of various sources such as text books, website etc...
Enjoy the process of Learning
Thank you
Molecular Mechanism Of Sex Determination In Drosophila.pptxnpppandey100
Drosophila is one of first organism to be studied genetically : due to it’s small size, short life cycle, high reproductive rate, and ease of culture.
The fruit fly Drosophila melanogaster has eight chromosomes: three pairs of autosomes and one pair of sex chromosomes.
Thus, it has inherited one haploid set of autosomes and one sex chromosome from each parent.
In Drosophila, sex determination is achieved by Genic balance mechanism (given by Calvin Bridges , 1926)i.e. a balance of female determinants on the X chromosome and male determinants on the autosomes.
Ratio of X chromosomes: haploid sets of autosomes (X:A) determine the sex.
X chromosome = Female producing effects
Autosomes = Male producing effects
Y Chromosome= Fertility factor in male required for sperm
formation but not in sex determination
Sex Determination in Drosophila involves the following events:-
1.ESTABLISHMENT OF X:A RATIO
2.CONVERSION OF X:A RATIO INTO A MOLECULAR SIGNAL
3.DIFFERENTIAL ACTIVATION OF Sxl GENE
4.DIFFERENTIAL REGULATION OF TRANSFORMER (Tra) GENE
5.ACTION OF Dsx- THE SWITCH GENE OF SEX DETERMINATION
6.PRODUCTION OF MALE OR FEMALE
• Establishment of X:A ratio involves interaction between proteins that are encoded by several X-linked genes and proteins encoded by several autosomal genes.
• X-linked genes are also called numerator genes. e.g. (sisterless; sis) sis-a ,sis-b ,sis-c, runt.
• Autosomal genes are also called denominator genes. e.g. daedpan(dpn), extramacrochaetae (emc).
• In XX embryo – Denominator proteins < Numerator protein.
Output -> Embryo Follow Female Pathway
• In XY embryo – Denominator proteins > Numerator protein
Output -> Embryo Follow Male Pathway
2. CONVERSION OF X:A RATIO INTO A MOLECULAR SIGNAL
Sis protein homodimer formed only in XX female, that binds to the early promoter (PE) of sex-lethal (sxl) gene and transcribe early Sxl m-RNA.
Sxl protein is synthesised from early Sxl m-RNA.
Sxl is the master regulator of the sex determination pathway in Drosophila.
A chart showing the fate of each part of an early embryo, in a particular blastula stage is called fate maps. It is done because the correct interpretation of gastrulation is impossible without the knowledge of the position which are the presumptive germinal layers (Ectoderm, Mesoderm and Endoderm) occupy in blastula.
Fate mapping is a method used in developmental biology to study the embryonic origin of various adult tissues and structures. The "fate" of each cell or group of cells is mapped onto the embryo, showing which parts of the embryo will develop into which tissue. When carried out at single-cell resolution, this process is called cell lineage tracing. It is also used to trace the development of tumors.
The SPECIAL - GIANT CHROMOSOMES which are very transcriptionally active DNA, where loops of DNA emerging from an apparently continuous chromosomal axis are coated with RNA polymerase.
Comparatively much larger than polytene chromosomes.
Highly significant for scientific analysis especially regarding gene amplification.
Basics of Undergraduate/university fellows
Nucleosome model of chromosome is proposed by ROGER KORNBERG (son of Arthur
Kornberg) in 1974.
It was confirmed and crystalised by P. Oudet et al., (1975).
Nucleosome is the lowest level of Chromosome organization in eukaryotic cells.
Nucleosome model is a scientific model which explains the organization of DNA and
associated proteins in the chromosomes.
Nucleosome model also explains the exact mechanism of the folding of DNA in
thenucleus.
It is the most accepted model of chromatin organization.
DNA is tightly packed in the nucleus of every cell. DNA wraps around special proteins called histones, which form loops of DNA called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin. Chromatin in turn forms larger loops and coils to form chromosomes.
DNA packaging is crucial because it makes sure that those excessive DNA are able to fit nicely in a cell that is many times smaller.
The DNA in bacterial cells are either circular or linear. To accommodate the size of bacterial cell, supercoiled DNA are folded into loops with each loop resembles shape of bead-like packets containing small basic proteins that is analogous to histone found in Eukaryotes.
Maternal effects are the influences of a mothers genotype on the phenotype of her offspring. It results from the asymmetric contribution of the female parent to the development of zygotes.
In terms of chromosomal genes, both male and female parents contribute equally to the zygote. The female parent contributes to the zygotes initial cytoplasm and organelles. Sperm rarely contribute anything other than chromosomes. Therefore zygotic development begins within a maternal medium and hence the maternal cytoplasm directly affects zygotic development.
cell lineage , cell fate - diverse class of cell fate, cell fate in plant meristem, mammalian development cell fate, nutritional effects on epigenetics, epigenetics of plants,
control of cell fate.
A complementation test (sometimes called a "cis-trans" test) can be used to test whether the mutations in two strains are in different genes. By taking an example of Benzer's work, complementation has been explained.
Polytene chromosome with respect to historical basis, occurrence, structural organisation, bands and inter bands, puff are briefly stated for basic idea.
You may find this interesting understand the reason behind the gaint structure of these chromosomes.
This study material is a compilation of various sources such as text books, website etc...
Enjoy the process of Learning
Thank you
Molecular Mechanism Of Sex Determination In Drosophila.pptxnpppandey100
Drosophila is one of first organism to be studied genetically : due to it’s small size, short life cycle, high reproductive rate, and ease of culture.
The fruit fly Drosophila melanogaster has eight chromosomes: three pairs of autosomes and one pair of sex chromosomes.
Thus, it has inherited one haploid set of autosomes and one sex chromosome from each parent.
In Drosophila, sex determination is achieved by Genic balance mechanism (given by Calvin Bridges , 1926)i.e. a balance of female determinants on the X chromosome and male determinants on the autosomes.
Ratio of X chromosomes: haploid sets of autosomes (X:A) determine the sex.
X chromosome = Female producing effects
Autosomes = Male producing effects
Y Chromosome= Fertility factor in male required for sperm
formation but not in sex determination
Sex Determination in Drosophila involves the following events:-
1.ESTABLISHMENT OF X:A RATIO
2.CONVERSION OF X:A RATIO INTO A MOLECULAR SIGNAL
3.DIFFERENTIAL ACTIVATION OF Sxl GENE
4.DIFFERENTIAL REGULATION OF TRANSFORMER (Tra) GENE
5.ACTION OF Dsx- THE SWITCH GENE OF SEX DETERMINATION
6.PRODUCTION OF MALE OR FEMALE
• Establishment of X:A ratio involves interaction between proteins that are encoded by several X-linked genes and proteins encoded by several autosomal genes.
• X-linked genes are also called numerator genes. e.g. (sisterless; sis) sis-a ,sis-b ,sis-c, runt.
• Autosomal genes are also called denominator genes. e.g. daedpan(dpn), extramacrochaetae (emc).
• In XX embryo – Denominator proteins < Numerator protein.
Output -> Embryo Follow Female Pathway
• In XY embryo – Denominator proteins > Numerator protein
Output -> Embryo Follow Male Pathway
2. CONVERSION OF X:A RATIO INTO A MOLECULAR SIGNAL
Sis protein homodimer formed only in XX female, that binds to the early promoter (PE) of sex-lethal (sxl) gene and transcribe early Sxl m-RNA.
Sxl protein is synthesised from early Sxl m-RNA.
Sxl is the master regulator of the sex determination pathway in Drosophila.
An idea which helps to know about both male and female sex hormones known as androgens, estrogens and progesterones and the differences between them. And basic information regarding sexual functionality helps us to know their necessity in our body
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
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.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
1. MOLECULAR MECHANISM OF
SEX DETERMENITION IN
DROSOPHILA & HUMAN
A Seminar On:
Presented by-
Sambit Kumar Dwibedy
PG 2nd Year
Semester Roll No-03
2. CONTENTS
1.Introduction
2.Sex Chromosomes & Sex Determination
3.Different Mechanisms Of Sex Determination
4.Sex Determination In Drosophila
a. X:A Ratio Mechanism
b. Molecular Mechanism
5.Sex Determination in Human
a. Chromosomal Basis
b. Molecular Mechanism
6.Conclusion
?
3. INTRODUCTION
• The word SEX is derived from the Latin word sexus meaning
separation.
• Sex is the morphological ,physiological & behavioral difference
observed among egg producing organism and sperm producing
organism.
4. WHAT IS SEX DETERMINATION?
It refers to the hormonal, environmental and genetical
especially molecular mechanism that make an organism
either male or female.
6. DIFFERENT SEX DETERMINATION SYSTEM
1.Chromosomal Basis Of Sex Determination
2.Genic Determination Of Sex
3.Cytoplasmic Sex Determination
4.Genic Balance Theory
5.Haplodiploidy Mechanism
6.Environmental Sex Determination
7. SEX DETERMINATION IN DROSOPHILA
• Sex in Drosophila is determined by Genic Balance Mechanism.
• Ratio of X chromosomes: haploid sets of autosomes (X:A)
• X chromosome = Female producing effects
• Autosomes = Male producing effects
• Y Chromosome= Fertility factor in male
• X:A ratio
Female = 1.0 (2X:2n)
Male = 0.5 (1x:2n)
0.5 < X:A < 1.0 = intersex
10. MOLECULAR MECHANISM OF SEX DETERMINATION IN DROSOPHILA
Sex Determination in Drosophila involves the following events:-
1.ESTABLISHMENT OF X:A RATIO
2.CONVERSION OF X:A RATIO INTO A MOLECULAR SIGNAL
3.DIFFERENTIAL ACTIVATION OF Sxl GENE
4.DIFFERENTIAL REGULATION OF TRANSFORMER GENE
5.ACTION OF Dsx- THE SWITCH GENE OF SEX DETERMINATION
6.PRODUCTION OF MALE OR FEMALE
11. ESTABLISHMENT OF X:A RATIO
• Establishment of X:A ratio involves interaction between proteins that
are encoded by several X-linked genes and proteins encoded by
several autosomal genes.
• X-linked genes are also called numerator genes. e.g. sis-a ,sis-b ,sis-c,
ran.
• Autosomal genes are also called denominator genes. e.g. dpn, emc
• The denominator gene encode denominator proteins which
antagonize numerator proteins.
• In XX embryo – Denominator proteins < Numerator protein
→Embryo Follow Female Pathway
• In XY embryo – Denominator proteins > Numerator protein
→Embryo Follow Male Pathway
13. CONVERSION OF X:A RATIO INTO A MOLECULAR SIGNAL
1.Sxl is the master regulator of the sex determination pathway.
2.In XX Drosophila Sxl is active during the first 2 hours of after
fertilization.
3.Sxl gene transcribe a distinct embryonic type m-RNA from the
promoter PE.
4.The early Sxl m-RNA are processed and translated into SXL protein.
5.After a few divisions , transcription starts from PM promoter instead of
PE.
6.Transcription from PM promoter is also initiated in XY embryos.
14. DIFFERENTIAL ACTIVATION OF Sxl GENE
1.If SXL protein is already available (i.e.,from early translation) the sxl pre-
mRNA is spliced to form the functional female specific message.
2. This encodes a functional protein of 314 amino acids.
3.In wild type Drosophila with one X chromosome & 2 sets of autosomes, Sxl
gene is transcribed from the late promoter. In absence of early SXL protein, the
RNA splicing does not exclude the male specific exon in the m-RNA.
4. The resulting RNA encodes a non-functional peptide as the male specific
exon contains a translation termination codon (UGA) after amino acid 48.
15. Mechanism of sxl Splicing
1. In male the m-RNA is spliced in a manner that yields 8 exons and the termination
codon is within exon no 3.
2. In female, RNA processing yields only 7 exons and the male specific exon 3 is spliced
out as a large intron.
16. DIFFERENTIAL REGULATION OF TRANSFORMER GENE
1.The expression of tra gene is controlled by SXL protein.
2.Tra gene is transcribed into pre-tra mRNA.
3.tra pre-mRNA is spliced alternatively to create a female specific
mRNA and a non specific mRNA.
4.Male specific tra mRNA contains a termination codon in the
second exon.
5.This exon is not utilized in female specific m-RNA.
6.Female specific tra RNA is translated into a functional TRA protein.
7.But in male TRA protein is not synthesized.
17.
18. Dsx- THE SWITCH GENE OF SEX DETERMINATION
1.Doublesex gene is an autosomal gene that can produce 2 different proteins
through alternate splicing of its m-RNA.
2.A gene named tra 2 produce TRA 2 protein in both male and female.
3.Dsx gene produce pre dsx mRNA.
4.If the TRA & TRA 2 both are present, the dsx transcript is processed in a
female specific manner and produces DSXF protein.
5.In absence of TRA, a male specific transcript is made which encodes DSXM
protein.
19. PRODUCTION OF MALE OR FEMALE
1.DSXF represses the genes required for male development and activates
female specific genes. Ultimately the XX Drosophila develops into a female.
2.DSXM inhibits female traits and promote male traits. Ultimately the XY
Drosophila develops into a Male.
22. MOLECULARE MECHANISM
• Embryos are developed completely neutral for about 2 weeks. Then it follow either male or
female pathway.
• Early embryo has a bipotential gonad.
• The bipotential gonad later can follow one of the 2 alternative pathway and develop into
testes or ovary.
• Normal growth & maintenance of bipotential gonad is regulated by few genes including
EMX2, GATA4,WT1,LHX9 & SF1.
• Male phenotype in human is determined by sry gene.
• This gene is present on the short arm of the Y- chromosome.
• When sry gene is not present as in XX individuals the bipotential gonad follow ovarian
pathway.
• Loss of function of sry results in complete male to female sex reversal.
23. TESTIS PATHWAY
Sry is expressed only in some somatic cells of the bipotential gonad.
Sry gene encodes SRY or TDF protein.(Testis determining factor).
Target gene of SRY in the bipotential gonad is sox9.
Sox9 produce SOX9 protein and induce testis development.
SOX9 activates FGF9 protein.
FGF9 cause some somatic cells of the gonad to differentiate into sertoli cells.
Sertoli cell produce anti-mullerian hormone., which supress the development of
female reproductive tract.
Sertoli cells also induce other somatic cells of the gonad to become leydig cells
Leydig cell secrete male sex hormone testosterone.
This hormone completes the development of testis
24. OVARIAN PATHWAY
In absence of sry expression gonad develops into ovary.
Some somatic cell become follicle cell.
Other somatic cell become theca cell and secrete the female sex
hormone estrogen.
Estrogen completes the development of ovary and contribute in
development of female secondary sexual character.
26. CONCLUSION
Sex is a biological riddle.
Hundreds of theories & mechanisms have discovered regarding
determination of sex. But non of them are satisfactory.
Several things in this field are yet to be discovered.
27. BIBLIOGRAPHY
1.Snustad,P. & Simpsons,M.J.(2003)Principles of genetics 3rd ed.John
Wiley & Sons,Inc.:USA.
2.Sing,B.D.(2003)Genetics2nd ed.Kalyani publisher:Noida.
3.Dobzhansky,T.etal(1973)Principles of genetics.5th ed.TATA McGRAW
hill company ltd:New Delhi
4.Rastogi,V.B.(1984)Elements of genetics.11th ed.Kedar Nath Ram
Nath:Meerut