Lethals and mutations in poultry

1. Lethals and mutations in poultry
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2. Introduction
Lethal gene : a gene that in some conditions may
prevent development or cause the death of an
organisam or its germ cells – called also lethal
factor, lethal mutant, lethal mutation.
Over 100 chicken mutant loci have been shown to
have lethal effects.
Lethal action may occur during the incubation or at
various times during later life.
Lethality may be obligate or dependent upon
environmental factors(facultative).
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3. Forms of lethal traits:
 Based on inheritence and degree of lethality lethal traits are
grouped as following:
1. Dominant gene with obligate recessive lethal action.
2. Obligate semilethal trait.
3. Facultative lethal trait.
4. Post hatch obligate lethal.
5. Autosomal recesssive obligate embryonic lethal.
6. Sex linked obligate embryonic lethal.
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4. Dominant traits with obligate recessive lethal
action.
 In this homozygotes are too abnormal to develop and hatch.
 Heterozygotes though abnormal,are viable.
Trait Gene symbol
Ear-tufts Et, et
flightless Fl, fl
creeper Cp, cp
Cornish lethal Cl, cl
Ametapodia Mp, mp
White wing Ww, ww
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5. EAR TUFTS
 Observed in south american
araucana breed.
 Epidermal appendages
project from sides of head in
the vicinity of ear opening.
 Expression of trait varies
widely. unilateral or bilateral,
size, peduncle projection,
attachment, external ear
opening is quite irregular in
shape and external auditory
canal reduced or absent.
 Prenatal mortality of
heterozygotes is about 20-
42%,
 Post hatch mortality is also
observed.
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6. Flightless
 The condition were flight feathers, tail feathers and other
large feathers had shaft defect causing break when
subjected to pressure.
 These feathers are irregular in length and some even broken
by one month age.
 Shafts are very rough and scaly.
 Homozygous state is lethal and 67% of homozygotes did not
survive upto 4 weeks age.
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7. creeper
 The main feature of the heterozygous
creeper is the shortness of its
extremities.
 This condition belongs to the class of
skeletal abnormalities known as
achondroplasia or chondroplasty.
 Tarsometatarsus of longbones is
reduced.
 The heterozygote creeper can be
identified embryonicaly at 6 days of
incubation indicating endochondral
ossification is defecient.
 Homozygote embryos die within 3 days
of incubation(cessation of growth due
Cp gene praventing formation of
vascular system).
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8. Cornish lethal
 Observed in short legged the
tibiotarsus and tarsomatetarsus
were markedly shortened, and the
fibula was overly developed such
that it extends lower end of tibia
where it fuses with tibial
epiphysis.
 Homozygous condition are lethal
at the end of incubation.
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9. Obligate Semi Lethal Traits
 Traits of this type are either dominant or recessive and their time
of lethel action is usually during embryonic life and may also
occur later.
 The proportion of survivng depend upon environment or
modifying gene.
 Lethality between 50% and 100% then this type of trait is reffered
to semi lethal.
 When lethality less than 50% it is called subvital.
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10. trait Gene symbol Trait Gene symbol
Albinisam a,A Rumpleness Rp,rp
Extended black E,e Recessive
polydactyly
po-2,Po-2
Wooly wo,Wo Multiple trait
semi lethal
psp,Psp
Sex linked naked n,N shankless shl,Shl
Icthyosis dehy,Dehy Micromelia-hays mm-H,Mm-H
Scleroderma sd,Sd Sex-linked
wingless
wl,Wl
Naked neck Na,na Cleft palate polygeneic
Apterylosis Ap,ap Superneumary
ribs
polygenic
Ottawa naked nk,Nk Sex-linked
nervous
dissorder
sln,Sln
Edema ed-1,Ed-1,ed-2,
Ed-2
tripsy tip,Tip
Short mandible sm,Sm micropthalmia mi,Mi
Short upper neck su,Su Micropthalmia-3,4 mi-3,Mi-3
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11. Albinisam
 Melanins represent the most
widespread classes of natural
pigment.
 Two main types eumelanin and
pheomelanin.
 It is characterized by a deficit in
the production in melanin and
by the partial or complete
absence of pigment in the skin,
hair and eyes.
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12.  Hen-day egg production of albinos was greater than that of non
albinos in the 4-wk periods between 52 and 60 wk .
 From 28 to 60 wk of age, partial correlation coefficients
between P4 and egg production, and E2 and egg weight were
significant for albino hens but not for non albinos and age and
P4 concentrations were negatively correlated for both albinos
and non albinos .
 Pre ovulatory levels of P4 in albino hens were higher than those
in non albinos.
 Plasma E2 was higher in albinos than in nonalbinos 5 h before
ovulation (P < 0.05).
 These data suggest that increased egg production of albino
hens is associated with differences in P4 and E2
metabolism.sss
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13. NAKED NECK
 These birds either lack tuft of feathers
on the ventral side of the neck above
the crop or it is reduced to just a few
pin feathers or small feathers.
 The feather tracts are absent or
reduced.
 The reduction is less in heterozygotes
than in homozygotes.
 This results in bare skin becomes
reddish, particularly in males as they
approach sexual maturity.
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14. SHORT MANDIBLE
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15. EXTENDED BLACK
 Condition related to
distribution of black
melanin.
 Extended black observed
on the dorsal side.
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16. RUMPLESS
 A skeletal mutant observed
in white leghorns.
 Commonly known as roach
back among poultry men.
 Abnormality of caudal
skeleton .
 In embryonic development
it was found that the tail
vertebrae were absent.
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17. Facultative lethal traits
 These traits are generally not lethal due to direct action of the
mutant gene.
 Though these individuals do not survive well in normal
environment , special effort must be made to provide an
extremely favorable environment to keep mortality minimum.
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18. Trait Gene
symbol
Trai t Gene
symbol
Trait Gene
symbol
Apterylosis Ap, ap Congenital
leg anomaly
cla, Cla Short
mandible
sm, Sm
Sex-linked
naked
n, N Crippling
anomaly
polygeneic Crooked
neck
crn, Crn
Flightless Fl, fl exencephaly polygenic Shankless shl, Shl
Sleepy eye se, Se shaker sh, Sh Blindness,
rods and
cones
rc, Rc
Scaleless sc, Sc Tipsy tip, Tip
Ottawan naked nk, Nk Arched neck polygenic
Wiry wi, Wi gasper ga, Ga
Woolly wo, Wo Micropthalmi
a
mi, Mi
porcupine pc, Pc Blindness, beg, Beg
dactylolysis dac, Dac Blind, Bc, Bc
Short upper
beek
su, Su Retina
dysplasia
rdd, Rdd
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19. SCALELESS
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20. CROOKED NECK
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21. Post hatch obligate lethal traits
 The time of action of this type of obligate lethal is after the
chick has hatched,and it may even be as late as adulthood.
Trait Gene symbol Tr ait Gene symbol
Blistered foot
lethal
bf, Bf Congenital loco Lo, Lo
Stringy st, St Sex-linked
lethal
xl, Xl
Sparrrow head sph, Sph Jittery j, J
Micromelia-hays mum-H, Mm-H Nervous
disorder
hnd, Hnd
Crazy cy, Cy Paroxysm px, Px
Faded shaker Fs, Fs Congenital
tremor
polygenic
Atresia isthmi Aro, aro
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22. embryonic lethal traits
1. Autosomal recessive obligate embryonic lethals:
this embryonic lethal has no effect in the heterozygote but it
is lethal to the homozygote in either early or more often late
embryonic life.
2. sex-linked obligate embryonic lethal:
this type of lethal effects female embryos only.
carrier males are unaffected.
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23. Early embryonic lethals
 These traits are expressed in first few days of embryo
development.
Trait Gene symbol
Recessive white lethal l, L
Blood ring blr, Blr
Early sex linked lethal
barrier
sex, Sex
Prenatal lethal pn, Pn
Ladykiller lk, Lk
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24. BLOOD RING
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25. Polydactylous embryonic lethals
 Diplopodia : having supra neumary digits most of them
during last stage of incubation.
 Split floot : digits are split having and each having
phalanges
 Eupdiplopodia : this is expression of two complete sets of
digits located dorsally to the normal ones this was observed
in white leghorn breeds
 Taploid : a lethal condition were the feet and wings of
embryos with this condition resemble those of a mole.
The length of wing, bone, vertebral column, development of
face is retarded .
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26. Hypodactylous embryonic lethals:
1. Wingless
2. Limbless
3. Stumpy
4. Coloboma : the mutation defect observed in white
leghorn. This condition were the cartilage may be missing,
reduced or deformed.
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27. Facial embryonic lethals:
These are autosomal recessive genes:
 Duck beak and donald duck
 Missing maxillae
 Missing mandible
 Missing upper beak
 Ectrodactyly : missing of entire pre maxilla and palatine
process, in homozygous condition feet and leg defects also
observed. embryos die between 17-20 days incubation.
 Perocephaly : malformations of head.
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28. Miscellaneous embryonic lethals
 Stickines (sy)
 Open breast syndrome (obs)
 Dorking lethal (dl)
 Crooked neck dwarf (cn)
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29. FEATHER MUTATIONS
 Fray (fr) - autosomal recessive (affects mostly wing flights & tail
feathers)
 Flightless (F1) - autosomal dominant (affects mostly wing flights
& tail feathers)
 Alopecia - autosomal recessive (affects mostly remiges &
rectrices)
 Dysplastiv remiges (dr) - (affects remiges & rectrices, -extreme
cases wing coverts)
 Hypoplasia of tail feathers (Hy) - autosomal dominant (affects tail
feathers, resembles rumplessness, but vertebrae normal) Found
in Ingie Fowl.
 Matted Down - polygenic trait
 Ragged Wing (rw) - autosomal recessive (affects wing flights)
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30.  Porcupine (pc) - autosomal recessive (spiny quills)
 Ropy (ropy) - autosomal recessive (sticky down, adults - large
wing feathers, sometimes body feathers - roughness)
 Stringy (st) - recessive (down feathers stringy, very high mortality
rate)
 String-2 (st-2) - autosomal recessive (down sticky, adults - most
barbules were absent from wing & tail feathers)
 Sunsuit (sn) - autosomal recessive (down wiry & sticky, adults -
extremities bare of feathers, body better covered)
 Wiry (wi) - autosomal recessive (down sticky & lacked barbs on
distal halves. Adults - mostly wiry barbs of wing flights & tail
feathers).
 Wooly (wo) - autosomal recessive (shortened down- semi-
naked, slick shiny feet. Adults - feathers abnormal in structure,
rough & incomplete).
 Wing Patch - expression limited to males, may possibly be linked
to the lavender locus.
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31. FRIZZLE SILKY FEATHERS
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32. HARD FEATHERS SOFT FEATHERS
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33. BRACHYDACTYLY
 The shorter outer toe trait
has been given the
mutation name:
Brachydactyly - By gene
(autosomal incomplete
dominant)
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34. THANK YOU
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