The document discusses different types of epistatic interactions, including dominant and recessive epistasis where one gene hides the effects of another gene. It provides examples of different epistatic ratios seen in traits like eye color in Drosophila and fruit shape in plants. The types of epistasis covered include dominant, recessive, duplicate recessive genes, and genes with cumulative effects.
Epistasis is a Greek word that means standing over .Bateson used it to describe the masking effect in 1909.
An interaction between a pair of loci in which the phenotype effect of one locus depends on the genotype at the second locus.
Genes whose phenotypes are ;
Expressed,epistatic.
Altered or suppressed hypostatic.
This PPT consists of 15 slides only explaining Pleiotropy. This is a phenomenon when one gene controls more than one trait , the traits may be related .Generally one gene's product acts for many reactions and so can affect more than one trait. Examples can be seen in pea Coloured flower and pigmentation in leaf axil, frizzle trait in chicken, fur colour and deafness in cats,Human pleiotropic traits are PKU,Sickle cell Anaemia. HOsyndrome , p53 gene etc
Epistasis is a Greek word that means standing over .Bateson used it to describe the masking effect in 1909.
An interaction between a pair of loci in which the phenotype effect of one locus depends on the genotype at the second locus.
Genes whose phenotypes are ;
Expressed,epistatic.
Altered or suppressed hypostatic.
This PPT consists of 15 slides only explaining Pleiotropy. This is a phenomenon when one gene controls more than one trait , the traits may be related .Generally one gene's product acts for many reactions and so can affect more than one trait. Examples can be seen in pea Coloured flower and pigmentation in leaf axil, frizzle trait in chicken, fur colour and deafness in cats,Human pleiotropic traits are PKU,Sickle cell Anaemia. HOsyndrome , p53 gene etc
It is the fundamental law of population genetics and provides the basis for studying Mendelian populations ( Mendelian population: A group of sexually inbreeding organisms living within a circumscribed area). It describes populations that are not evolving.
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.
According to Hardy (England,1908) and Weinberg (Germany,1909), gene and genotype frequency of a Mendelian population remain constant generation after generation unless there is selection,mutation,migration or random drift.
Inability of a plant with functional pollen to set seed when self-pollinated.
Hindrance to self-fertilization.
Prevents inbreeding and promotes outcrossing.
Reported in about 70 families of angiosperms including crop species.
Introduction :
Mendel and subsequent workers assumed that a character was governed by a single gene.
But it was later discovered that many characters in almost all the organisms are governed by two or more genes. Such gene affect the development of concerned characters in various ways.
The phenomenon of two or more gene affecting the expression of each other in various ways in the development of a single character of on organism is known as gene interaction.
It is the fundamental law of population genetics and provides the basis for studying Mendelian populations ( Mendelian population: A group of sexually inbreeding organisms living within a circumscribed area). It describes populations that are not evolving.
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.
According to Hardy (England,1908) and Weinberg (Germany,1909), gene and genotype frequency of a Mendelian population remain constant generation after generation unless there is selection,mutation,migration or random drift.
Inability of a plant with functional pollen to set seed when self-pollinated.
Hindrance to self-fertilization.
Prevents inbreeding and promotes outcrossing.
Reported in about 70 families of angiosperms including crop species.
Introduction :
Mendel and subsequent workers assumed that a character was governed by a single gene.
But it was later discovered that many characters in almost all the organisms are governed by two or more genes. Such gene affect the development of concerned characters in various ways.
The phenomenon of two or more gene affecting the expression of each other in various ways in the development of a single character of on organism is known as gene interaction.
Gene interactions occur when two or more different genes influence the outcome of a single trait
Epistasis is a phenomenon in which the expression of one gene depends on the presence of one or more modifier genes.
A gene whose phenotype is expressed is called epistatic.
Lesson 2 of an A Level teaching resource, produced in conjunction with the Charles Darwin Trust, that uses Darwin's work on pigeon breeding and the work of contemporary scientists to explore genetics and evolution.
This second lesson covers the topic of genetics.
The accompanying teacher's notes can be found on our website at www.linnean.org/funkypigeons
Lesson 1 of an A Level teaching resource, produced in conjunction with the Charles Darwin Trust, that uses Darwin's work on pigeon breeding and the work of contemporary scientists to explore genetics and evolution.
This first lesson covers the topics of artificial selection and genetics.
The accompanying teacher's notes can be found on our website at www.linnean.org/funkypigeons
QUANTITATIVE INHERITANCE - KERNEL COLOR IN WHEATNethravathi Siri
Nilsson-Ehle (1909) and East (1910, 1916) documented first significant evidence of
quantitative inheritance by their individual works in wheat.
Their analysis started from one-locus control which continued to two locus control
and concluded at three-locus control.
Basics of Undergraduate/university fellows
Epistasis is a Greek word that means standing over.
BATESON used term epistasis to describe the masking effect in 1909
The term epistasis describes a certain relationship between genes, where an allele of
one gene hides or masks the visible output or phenotype of another gene.
When two different genes which are not alleles, both affect the same character in such
a way that the expression of one masks (inhibits or suppresses) the expression of the
other gene, the phenomenon is said to be epistasis.
The gene that suppresses other gene expression is known as Epistatic gene.
The gene that is suppressed or remain obscure is called Hypostatic gene
The classical phenotypic ratio of 9:3:3:1 F2 ratio becomes modified by epistasis.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
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Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
2. Introduction
Chemical Interpretation
Kinds of Epistasis
(і) Dominant Epistasis.
(ii) Recessive epistasis
(iii) Duplicate Recessive Genes
(iv) Duplicate Dominant Genes
(v) Duplicate Genes with Cumulative Effect
(vi) Dominant Recessive Interaction
References
3. Epistasis is Greek word meaning standing over.
It was first used in 1909 by Bateson to describe a
masking effect.
An interaction between a pair of loci, in which the
phenotypic effect of one locus depends on the
genotype at the second locus.
Genes whose phenotype are
Expressed-epistatic
altered or suppressed-hypostatic
4. Difference between dominance and
epistasis
Dominance Epistasis
Involves intra-allelic Involves inter-allelic
gene interaction. gene interaction.
One allele hides the One gene hides the
effect of other allele at effect of other gene at
the same gene pair. different gene loci.
5. Chemical interpretation:
A gene is a chemical determiner.
Gene products interact with the environment and
factors such as temperature, light, hormones and
enzymes.
If there is any problem or mutation in the
intermediates, it can lead to another phenotype
and hence disturb the Mendelian ratios.
6.
7. Example
Effects of two genes that function in eye
pigmentation in Drosophila.
The genes are vermilion (v) and cinnabar (cn).
Flies that are mutant for cn lack xanthommatin.
They have bright red eyes because of the
drosopterin.
Mutant v flies also lack xanthommatin but for a
different reason. In these flies the pathway is
blocked because there is no functional V enzyme.
8. Kinds of Epistatic Interactions
In epistasis less than four phenotypes appear in F2.
(і) Dominant Epistasis. (12:3:1)
(ii) Recessive epistasis.(9:3:4)(Supplementary interaction)
(iii) Duplicate Recessive Genes (9:7) (Complementary
Genes)
(iv) Duplicate Dominant Genes. (15:1)
(v) Duplicate Genes with Cumulative Effect (9:6:1)
(vi) Dominant Recessive Interaction (13:3)
9. Dominant Epistasis. (12:3:1)
Dominant allele (eg.,A) of one gene hides the effect of allele
of another gene (eg., B) and expresses itself phenotypically.
The B allele (hypostatic) will be expressed only when gene
locus A contains two recessive (aa) alleles.
Thus, the genotype AA BB or Aa Bb and AA bb or Aa bb
produce the same phenotype
genotype aa BB or aa Bb and aa bb produce two additional
phenotype.
This type of dominant epistasis modifies the classical ratio of
9:3:3:1 into 12:3:1
10. Epistatic Hypostatic Phenotypic
alleles alleles Expression
aa bb b
aa BB, Bb B
AA, Aa Bb, Bb, bb A
11. Example:
Studied in summer squash (Cucurbita pepo)
Common fruit colors-white,yellow &green
White (W) is dominant over colored squash
Yellow (Y) is dominant over green squash
Pure breeding white fruited variety is crossed
with the double recessive green variety,F1
hybrids are all white
When the hybrids are selfed-white, yellow
&green fruited plants arise in the ratio of 12:3:1
12. The effect of
dominant gene ’Y’ is
masked by the
dominant gene ’W’
(epistatic gene)
P WWYY X wwyy ♂/♀ WY Wy wY wy
(white) ↓ (green) WY WWY WWY WwY Ww
Y y Y Yy
F1 WwYy
Wy WWY WWyy WwYy Wwy
(white) (selfed) y y
F2 wY WwY WwYy wwYY wwY
White:Yellow:Green Y y
wy WwYy Wwyy wwYy wwy
12 : 3 : 1 y
13. Recessive epistasis. (9:3:4)
(Supplementary interaction)
Recessive allele (aa) of one gene locus hides the
effect of another gene locus (BB, Bb or bb) and
expresses itself phenotypically.
The alleles of B locus express themselves only
when epistatic locus has dominant alleles (eg., AA
or Aa).
This will modify the ratio 9:3:3:1 to ratio 9:3:4
14. Epistatic Hypostatic Phenotypic
alleles alleles Expression
aa BB, Bb, bb a
AA, Aa BB, Bb B
AA, Aa bb b
15. In horses, brown coat color (B) is dominant over
tan (b).
However, how that gene is expressed in the
phenotype is dependent on a second gene that
controls the deposition of pigment in hair.
The dominant gene (C) codes for the presence of
pigment in hair, whereas the recessive gene (c)
codes for the absence of pigment.
16.
17. Duplicate Recessive Genes (9:7)
(Complementary Genes)
Both the genes loci have homozygous recessive
alleles and both of them produce identical
phenotype.
Both dominant alleles are necessary to produce a
different phenotype. e.g.: AABB, AaBB, AaBb, in all
these combinations.
Both the dominant alleles (A and B) are present
and they will produce a different phenotype.
Whereas aaBB or bbAA, in which the other
dominant allele is absent, produces the normal
phenotype.
18. Epistatic Hypostatic Phenotypic
alleles alleles Expression
aa BB, Bb, bb No phenotype
AA, Aa, aa bb production
AA, Aa BB, Bb Phenotype due
to dominant
19. Bateson and Punnett observed that when two
white flowered varieties of sweet pea, Lathyrus
odoratus were crossed, F1 progeny had coloured
flowers. When F1 was selfed, the F2 ratio showed
the presence of both coloured and white flowered
varieties in the ratio 9:7.
In man, deaf mutism is complementary gene
dependent, depending upon two dominant genes A
and B, the presence of both of them is responsible
for normal hearing and speech.
20.
21. In this case dominant alleles on both locus
are required hence wherever A and B both
are present they result into purple effect
masking the white.
This is because A and B alleles modified the
colorless precursor by showing their effects
22.
23. The purple pigment in corn requires that two
enzymes (controlled by two dominant alleles) must
be active for the pigment to form.
Two white varieties of corn showing the genotypes
AAbb and aaBB, will produce a ratio of 9/16 purple
and 7/16 white ears, depending upon the nine
different possible arrangements of the
chromosomes (and alleles) for these
characteristics.
24. Duplicate Dominant Genes. (15:1)
The dominant alleles of both the genes produce the same
phenotypic effect giving the ratio 15:1.
At least one of the dominant allele is necessary for the
phenotypic effect. e.g. AABB, AaBb, Aabb, aaBB, aaBbgive one
phenotype.
In the absence of all the dominant genes (only in case of aabb),
the recessive phenotype will be expressed.
The duplicate genes are also called pseudoalleles
25. Epistatic Hypostatic Phenotypic
alleles alleles expression
aa bb Another
phenotype
aa BB, Bb Same
AA, Aa bb phenotype
AA, Aa Bb, Bb
26. As observed by G.H.Shull, the seed capsules of
Shepherd’s purse (genus Capsella) occur in two
different shapes,
i.e. triangular and top shaped.
When F1 individuals were self crossed, the F2
generation showed plants with triangular and top
shaped capsules in the ratio 15:1
(A and B) would produce plants with triangular-shaped
capsules.
aabb would produce plants with top shaped capsules.F2
phenotypic ratio 15(triangular) 1(Top shaped).
27. P: AABB × aabb
(triangular) (top-shaped)
F1 : AaBb
(triangular)
AB Ab aB ab
AABB AABb AaBB AaBb
AB
(triangular) (triangular) (triangular) (triangular)
AABb AAbb AaBb Aabb
Ab
(triangular) (triangular) (triangular) (triangular)
AaBB AaBb aaBB aaBb
aB
(triangular) (triangular) (triangular) (triangular)
AaBb Aabb aaBb aabb
Ab
(triangular) (triangular) (triangular) (top-shape)
28. Duplicate Genes with
Cumulative Effect. (9:6:1)
Both the dominant non allelic alleles, when present
together, give a new phenotype, but when allowed to
express independently, they give their own
phenotypic expression separately.
In the absence of any dominant allele, the recessive
allele is expressed.
29. Epistatic Hypostatic Phenotypic
alleles alleles expression
aa bb Neither a nor b
aa BB, Bb B only
AA,Aa bb A only
AA,Aa Bb, Bb A+B mutually
supplement
30. In pigs S and s are allelic genes;
S giving sandy colour
ss giving white colour.
A non-allelic gene R also gives sandy colour (same
as S) but when both the dominant genes interact
together, they give red colour.
Non-allelic gene does not interact with ss
31. P: SSrr × ssRR
(sand (sandy)
SsRr (red)
F1 :
SR Sr sR sr
SSRR SSRr SsRR SsRr
F2 : SR
(red) (red) (red) (red)
SSRr SSrr SsRr Ssrr
Sr
(red) (sandy) (red) (sandy)
SsRR SsRr ssRR ssRr
sR
(red) (red) (sandy) (sandy)
SsRr Ssrr ssRr ssrr
Sr
(red) (sandy) (sandy) (white)
32. Dominant Recessive Interaction (13:3)
The dominant allele (A), either in homozygous or
heterozygous condition, of one gene and the homozygous
recessive allele (bb) of other gene produces the same
phenotype.
In F2 generation, progenies having A (homozygous or
heterozygous) or bb (homozygous) will not allow the C
gene to be expressed.
Genotype AABB, AABb, AaBb and Aabb produce same
phenotype and the genotype aaBB, aaBb and aabb
produce another but same phenotype.
33. Epistatic Hypostatic Phenotypic
alleles alleles expression
aa Bb, BB, bb a doesn’t
inhabit B or b
AA, Aa Bb, Bb , bb A inhibit B or b
34. In Leghorn fowl, the white colour of feather is
formed by CCII (due to the presence of epistatic
gene I).
Similarly in Plymouth Rock fowl the white
colour of feather is formed by ccii (due to the
absence of dominant C gene).
Therefore C is suppressed by inhibitor gene
both in dominant (I) and recessive (ii) condition.
35. P: CCII × ccii
(White Leghorn) (White Plymouth Rock)
F1 : CcIi
(white)
CI Ci cI ci
CCII CCIi CcII CcIi
CI
(white) (white) (white) (white)
CCIi CCii CcIi Ccii
Ci
(white) (colored) (white) (colored)
CcII CcIi ccII ccIi
cI
(white) (white) (white) (white)
CcIi Ccii ccIi ccii
ci
(white) (colored) (white) (white)
36. Example:
Interaction involves an inhibitory factor which by
itself has no phenotypic effect
But, when present in the dominant form prevents or
inhibits the expression of another dominant gene
eg :.Malvidin in primula flowers
Malvidin is a O-Methylated anthocyanin
responsible for the blue pigments in Primula
polyanthus plant
37. Synthesis of malvidin (blue) is controlled
by gene K
In recessive state(k), malvidin is not
synthesized
Production is suppressed by gene D,
found at completely different locus
D allele is dominant to K allele
38. KKdd x kkDD
(blue) (white)
↓
KkDd
(selfed)
(white)
↓
♂/♀ KD Kd kD kd
KD KKD KKD KkD KkDd
D d D
Kd KKD KKdd KkDd Kkdd
d
kD KkD KkDd kkDD kkDd
D
kd KkDd Kkdd kkDd kkdd
39. KkDd genotype will not
produce malvidin due to
the presence of D allele
Thus, white & blue colored
flowers producing plants
are obtained in the ratio of
13:3
Also known as dominant
40.
41. References:
Hartl,D.L., & Jones,W.E., (1998) “Genetics Principles
and Analysis” ed: 4th Jones and Bartlett Publishers
International London,UK, pp: 19,20,61-63
Miko, I., (2008) Epistasis: Gene interaction and
phenotype effects. Nature Education 1(1)
Richards,J.E. & Hawley, R. S., (2010) “ The human
genome” ed: 3rd Academic Press, pp: 31
Verma,P.S., & Agarwal,V.K., (2004) “Cell biology,
Genetics, Molecular Biology, Evolution and Ecology” ed:
24th S.Chand and Company Ltd,Ram Nagar, New
Delhi. Pp: 45-56