Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 1
Autosomal and X-linked inheritancein practical animal breeding
Ákos Maróti-Agóts
Univ.Vet.Med.Budapest
Department of Animal Breeding and GeneticsMendelian Genetics
•Foundation of modern genetics•Augustinian friar and abbot of St.
Thomas' Abbey in Brno•Classic genetics, transmission genetic•Studied segregation of traits in the garden pea (Pisum sativum) beginning in 1854•Mendel was “rediscovered” in 1902
Gregor Johann Mendel (1822-1884)
Classic genetics– inheritance of qualitative traits –Mendel’s laws.
• single major genes (alleles), monogenic traits
• environmental factors rarely have any influence on the phenotype
• the trait is present or not, e.g. cattle colour (red-black), horned or polled etc.
• segregation of the traits during crosses, free and independent combinations
Generations:P = parental generationF1 = 1st filial generation, progeny of the P generationF2 = 2nd filial generation, progeny of the F1 generation (F3 and so on)
Crosses:Monohybrid cross = cross of two different true-breeding strains (homozygotes) that differ in a single trait.
Reciprocal cross = sexes for the two strains are reversed (and if the results are the same, trait is not sex-linked).
Dihybrid cross = cross of two different true-breeding strains (homozygotes) that differ in two traits.
*Genetics etiquette - female conventionally is written first
Mendelian GeneticsMendelian Genetics Some basic terminology 1.gene/locus: DNA sequence which determines a trait
[A locus]allele: variant form of a gene ‘allele for black, allele for red’
[A, a ]phenotype: an individual’s ‘appearance’ for a particular trait [red, black]genotype: which pair of alleles an individual carries at a particular locus
[AA, Aa, aa]
phenotype ≠ genotype!homozygous: a genotype where both alleles are the same [AA, aa]
heterozygous: a genotype where the alleles are different [Aa]
dominant: one copy of the allele is sufficient to express the phenotype [AA = Aa → ‘A’ phenotype]
recessive: two copies of the allele are necessary to express the phenotype[aa → ‘a’ phenotype]
Mendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Some basic terminology 2.
Mendelian Genetics
•Homozygosity in parents: the two members of a gene pair (allelesresponsible for a trait) segregate (separate) from each other in the formation of gametes (eggs or sperm).
•Half the gametes carry one allele, and the other half carry the other allele (A or a).
Alleles for a trait are then "recombined" at fertilization, producing thegenotype for the traits of the offspring.
Homozygosity in parents
Mendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Some basic terminology 3.Pp – uniform, polled cow
P –polled , dominant
p – horned, recessive
Gametes?: P p
Mendelian Genetics
PpBb – uniform polled, black cow
P – polled , dominant p – horned, recessive
B – black, dominant b – red, recessive
PB Pb pB pbGametes?:
Mendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Gametes
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 2
Mendelian Genetics
I. Uniformity and reciprocity: monohybrid crossing, homozygous parents, F1 generation genotype and phenotype uniform, independently of thegender of dominant or recessive parent
•Punnett Square: parental gametes P1 (B) x P2 (b)
homozygous red Holstein (bb) homozygous black (BB)Holstein cow/dam X bull/sire
BBbb
Mendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Mendel I.P: BB x bb
F1:
B B
b
b
Punnett Square B B
B B
b b
b b
Result F1: fenotype and genotype 4 x Bb = 100% Bb
Allele-freqences: 4/8=0,5 A 4/8=0,5 a
Mendelian Genetics
•F1 generation: each calf BLACK and HETEROZYGOUS (Bb)
F (black) allele is dominant phenotype and genotype UNIFORM
Mendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Mendel I.
• Reciprocity : pure homozygous parental lines F1 generation uniformity: gender indifferent
(dominant, recessive parent: ♂, ♀)
Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Reciprocity Mendelian Genetics Mendel II.
II. Segregation of Characteristics in F2 generation• Crossing F1 generation (heterozygous (Bb) black Holstein-Friesian cattle)
P: BB x bb
F1: Bb x Bb
B b
B
b
Punnett Square
B b
B b
B B
b b
F2: 1xBB, 2xBb, 1xbb = 25% BB, 50% Bb, 25%bb
F2:
F2 genotype: 1 homozygous black (BB), 2 heterozygous black (Bb) 1 homozygous red (bb),
F2 phenotype:3 black and 1 red cattle
Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Mendel II.
F2: Phenotype 3:1
F2: Genotype 1:2:1
Autosomal monohybrid cross - dominant – recessive inheritance
https://www.youtube.com/watch?v=UwB5L-v-krE
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 3
Autosomal monohybrid cross-dominant–recessive inheritance
Question No02: HYPP disease
Hyperkalemic periodic paralysis or HYPP is a non lethal, autosomal-dominantgenetic disease.
Symptoms: Muscle trembling, prolapse of the third eyelid, generalized weakness‚ dog-sitting’, complete collapse, death
H – normal allele H’ - HYPP mutant-allele
HH- healty HH’ – carrier HYPP H’H’ – HYPP
P: HH x H’H’
Question: Pheno- ( healthy / ill ) and genotype in F2 generation?(Punnett square for F1 and F2 generation)
P: HH x H’H’
F1:H’ H’
H
H
H H
H H
H’ H’
H’ H’
Result:
100% HH’- HYPP, carrier
F2: HH’ x HH’
H H’
H
H’
H H
H’ H’
H H’
H H’
Result:
25% HH – healthy
50% HH’- HYPP, carrier
25% H’H’- HYPP
Autosomal monohybrid cross-dominant–recessive inheritance
> Human dominant-recessive traits
•hitchhiker's thumb and straight thumb (dominant)
recdom
• attached ear lobes and free ear lobes (dominant)
• clockwise whorl (dominant), counterclockwise whorl
•left thumb crossing right (dominant), and right thumb crosses right (rec)
III. Law of independent assortment: two or more alleles at different loci (di-, tri-and polyhybrid crosses)
free and independent segregation of genes new combinations (genotype, phenotype) (mendelian orinterchromosomal recombination)
- reciprocity!- in reality: only in case of general population of animals, according to the lawof averages
Mendelian GeneticsMendelian Genetics Mendel II.Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Mendel III.
Mendelian Genetics
Pure homozygous parental lines - dihybrid cross - dominant-recessive inheritance
Polled black PPBB Horned red ppbbP – polled, dominant X p – horned, recessiveB – black, dominant b – red, recessive
F1?: PpBb
Mendelian GeneticsMendelian Genetics Mendel II.Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Dihybrid cross
♂
♀PB Pb pB pb
PB PPBB PPBb PpBB PpBb
Pb PPBb PPbb PpBb Ppbb
pB PpBB PpBb ppBB ppBb
pb PpBb Ppbb ppBb ppbb
Mendelian Genetics Dihybrid cross
Phenotypical segregation ratio:9:3:3:1
Mendelian GeneticsMendelian GeneticsMendelian Genetics Mendel II.Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Dihybrid cross
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 4
horned
red
F2 generation: 4 different phenotypes9 different genotypes
9 : 3 : 3 : 1PPBB PPbb ppBb ppbbPPBb Ppbb ppBBPpBBPpBb
polledblack
polledred
horned black
fenotypes
genotypes
phenotypes
Mendelian Genetics Dihybrid cross
Recombinant!
Mendelian GeneticsMendelian GeneticsMendelian Genetics Mendel II.Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Dihybrid cross
• ppbb
ppbb
P_bb P_B_
ppbb
P_bb
P_bb
ppB_
• Figure 2 : Two traits (black/white and short/long hair, with black and short dominant) show a 9:3:3:1 ratio in the F2 generation. (S=short, s=long, B=black, b=white hair)(1) Parental generation. (2) F1 generation. (3) F2 generation.Results : 9x short black hair, 3x long black hair, 3x short white hair, 1x long white hair.
black/white and short/long hair (black and short dominant)
S=short s=long
B=black b=white hair
(1) Parental generation
(2) F1 generation
(3) F2 generation
Results: 9x short black hair
3x long black hair
3x short white hair
1x long white hair
F2 generation: 9:3:3:1
Dihybrid cross, dominant - recessive INTERMEDIATE inheritance - monohybrid cross- Lack of dominance: in the heterozygous organism both alleles of a loci are expressed in the phenotype- Heterozygous phenotype: intermediate characteristic, different from bothparents
Mosaic effect:
The original characteristic of bothparents appears in the phenotype of theheterozygotes, e.g. roan shorthorncattle (a coat with red and white hair)
Compromise effect: intermediatecharacteristic, phenotype of parentsappears in the descendant not, e.g. Blue Andalusian (crossing black and white individuals → bluish chickens)
Robert CollingCharles Colling
The Durham Ox was famous for its
massive size with contemporary
estimates ranging between over 1700kg!
The Durham Ox was a Shorthorn bred
here, in the Bright Water area, in 1796.
Example: shorthorn cattle: white (WW) and red (RR) individuals cross roan (RW) calves
INTERMEDIATE inheritance - monohybrid cross
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 5
Monohybrid segregation and intermediate hereditary -color transmission with the Shorthorn cattle
white/
red
W W
R RW RW
R RW RW
xP: red x white(reciprocity!)
F1: roan(uniformity!)
F1: roan
F1-gametes
1 homozygote red (RR)2 heterozygote roan (RW)1 homozygote white (WW)
(segregation!)
F2: Geno- and phenotype
1:2:1
P: FFBB X ffbb
F1: FfBbModerate frizzle plumage, beige eggshell(uniformity!)
F: frizzle flow
f: normal plumage
B: brown eggshell
b: white eggshell
Dihibrid keresztezés – intermedier öröklésmenet – interkromoszómális rekombináció
Dihybrid segregation and INTERMEDIATE hereditary –interchromosomal recombination
F2 generation FfBb x FfBb
♂
♀
FB Fb fB fb
FB FFBB FFBb FfBB FfBb
Fb FFBb FFbb FfBb Ffbb
fB FfBB FfBb ffBB ffBb
fb FfBb Ffbb ffBb ffbbF2 generation:
• 9 different genotypes
• 9 different phenotypes
• segregation ratio: 1:2:1:2:4:2:1:2:1
Dihybrid segregation and INTERMEDIATE hereditary –interchromosomal recombination
https://www.youtube.com/watch?v=-IRi1GLYob8
During meiosis, when homologous chromosomes are paired together, there are points along the chromosomes that make contact with the other pair. This point of contact is deemed the chiasmata, and can allow the exchange of genetic information between chromosomes. This further increases genetic variation.
AB, ab
recombinant Ab, aB type.
Intrachromosomal recombination: crossing over
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 6
Intrachromosomal recombination: crossing over, linkage Polled versus Horned : linkage
•Polled is the name for the absence of hornsin cattle, sheep and goats
•Polled is an autosomal dominant trait in cattle.• The gene causing the absence of horns is at the top of cattle chromosome 1. the exact gene is yetunknown.
• Based on this information, several DNA markers near the gene, called "linked" markers, can be used to test for homozygosity of polled in an individual
• if suitable family members are also available!
• Five DNA markers seem to be close enough (microsatellites)
•Three of these have been designed so that they can be analyzed in a single test, called multiplex PCR.
•If we know the whole family, we can make pairs from microsatellites and polledorhorned informations allele•If we have made pairs from linked alelles of microsatellite allel and polled
allele we can follow the inheritance of polled gene
Intrachromosomal recombination: crossing over
The Genome Sequence of Taurine
Cattle: A Window to Ruminant
Biology and Evolution
The Bovine Genome Sequencing and Analysis Consortium,* Christine G. Elsik,1 Ross L. Tellam,2 Kim C. Worley
Intrachrom. recombination: crossing over, gene mapping
• 2x 42 min +5 min break
• Tormay pass: Univet2017
• https://www.socrative.com/apps.html
• Room number: ENGGENETIK• first ARS!! →→
Socrative Dihybrid cross: dominant-recessive and intermediate inheritance
nn nN NN hh hH,HH
dominant-recessiveintermediatehorned polled„normal” earshort ear medium
F1=?
F2=? (Geno- and Phenotypes)
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F1: HhNn
F1-gametes?:
HN, Hn, hN, hn
F2:
6 different phenotype
9 different genotype
Dihybrid cross: a dominant-recessive and an intermediate inheritanceDihybrid cross: dominant-recessive and intermediate inheritance
• Manx cat: carrying „Mx” semidominant lethal gene - heterozygous (Mxmx) – viable kitten, special characteristic – tailless cats
• Homozygous embryos (MxMx) – embryonic lethal - intrauterine death, absorption
• Viable offspring: heterozygous tailless cats (Mxmx), or homozygous,fully tailed cats not carrying the lethal allele combination (mxmx)
Mendelian Genetics
Manx tailless cat
Mendelian GeneticsMendelian Genetics Mendel II.Mendelian GeneticsMendelian GeneticsMendelian GeneticsMendelian Genetics Some basic terminology 2.Mendelian GeneticsMendelian Genetics Exception
• Crossing heterozygous cats :F2 generation 2:1 ratio
Manx tailless cat
Exeption: lethal genes
Mx mx
Mx Mx Mx Mx mx
mx Mx mx mx mx
Phetotype 1:2
Genotype 1:2
Intrauterine absorbtion
F1: Mxmx x Mxmx
F2:
- Mendelian laws are not strictly true
- reciprocity?
- It does matter, which gender carries the dominant or recessive alleles inpure homozygous form F1 generation can be uniform, but dissimilarphenotypes can occur
- Sex determination →sex chromosomes
- mammals: ♀ XX, ♂ XY
- birds: ♂ ZZ, ♀ ZW !!!
(homogametic and heterogametic sex)
Linked traits
- recessive X-linked alleles expressed in the heterogametic sex HEMIZYGOUS character (XY, ZW)
- gene mutations, diseases – mammals ♂, birds ♀ antimasculine, antifeminine „lady killer gene” lethal gene mutations, recessive – still expressed!
- e.g. mammals: haemophilia (dog, horse, swine), tremor (swine, dog, turkey), Duchenne muscular dystrophy (cat, dog e.g. golden retriever) → mother heterozygouscarrier → male hemizygous offspring 50% affected
Haemophilia in dogcarrier bitch XH Xh x XH Y healthy male
bitch malesXH XH XH Xh XH Y Xh Yhealthy carrier healthy haemophilic
Linked traits – sex linked traits THE HISTORY OF HAEMOPHILIA IN THE ROYAL FAMILIES OF EUROPE British Journal of Haematology, 1999, 105, 25–32
Queen Victoria and Prince Albert withtheir children (1857).
Empress Alexandra at the Tsarevich’sbedside during a haemophiliac crisis in 1912.(Radio Times Hulton Picture Library.)
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 8
Sexing one day old chicks in peak production layer stocks commercial hatcheries: only pullets are raised – sexing needed
Practical usagePossible methods:
1. Vent or cloacal sexing,
Japanese experts
Reciprocal sex-linked crossing:
2. Feathering:
crossing pure lines:
slow (dominant) ♀ and
fast, early (recessive) ♂
(Leghorn cock X
Rhode Island Red hen)
F1: not uniform!
eminence, genital organ
ZSLOW W
Zs ZSLOWZs ZsW
Zs ZSLOWZs ZsW
Sexing of one day chicken - methodes
Plumage colour or markings:
- P: pure parental lines, both sexes
- recessive homozygous ZsZs always the cock!
- dominant hemyzigous ZSWalways the hen!
Sexing of one day chicken - methodes
- gold (yellow) recessive s /silver (white) dominant S
White Wyandotte hen X Rhode Island Red cock
- ZSW x ZsZs
- F1?: NOT UNIFORM!
hen
cock
ZS W
Zs ZS Zs ZsW
Zs ZSZs ZsW
ZS Zs heterozygous silver cockerel
ZsW hemizygous golden pullet
Sexing of one day chicken - methodesPlymouth dom.♀ X Black Leghorn rec.♂
ZBW X ZbZb (B-barred)
day-old cockerels: white dot on
their heads
ZB W
Zb ZB Zb Zb W
Zb ZB Zb Zb W
Marking: barred/solid
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Ákos Maróti-Agóts 9
- reciprocal cross - F1 generation uniform broiler chicken (♀ dominant)
- recessive gene of dwarfism in chicken (dw)
Reciprocal cross-F1 generation uniform broiler chicken(♀ dominant) Reciprocal cross-F1 generation uniform broiler chicken(♀ dominant)
♀
♂
Zdw W
ZDw ZDw Zdw ZDw W
ZDw ZDw Zdw ZDw W
• Dwarf breeding hens (ZdwW) 30% smaller body size – more economical keeping, feeding, more eggs
• Intensive growth cocks (ZDwZDw)• F1 generation: 5% smaller heterozygous (ZDwZdw) cocks and
normal hemizygous (ZDwW) hens
F1 generation
-recessive gene of dwarfism in chicken(dw)
Booroola farm, 1980
– FecB gene on 6th chromosome
– Autosomal dominant
Heterozygous ewes: +1,5 oocyte +1 lamb
Homozygous ewes: +3 oocyte +1,5 lamb
Receptor mutation (BMPR-1B) in ovaries reduced inhibinproduction FSH production increases polyovulation
Desired trait, but lambs need care
Mating with FecB-carrier rams
Autosomal prolificacy gene in sheep - FecB
The Booroola Fecundity (FecB) Gene Maps to Sheep Chromosome 6. Montgomery
– Romney breed
• FecX gene on X chromosome
Heterozygous ewes +0,6 lamb
Granulosa-cells produce less inhibin and 17-β-oestradiol infollicules longer FSH effect polyovulation
Homozygous ewes are infertile
Inhibin and 17-β-oestradiol production is completely blockedinfertility
Heterozygous ewes are desired
Matings with FecX carrier (hemizygous) rams
X-linked prolificacy gene in sheep - FecX
– Some genes are imprinted, meaning that gene expression occurs from only one allele. The expressed allele is dependent upon its parental origin.
– Woodland, coopworth breeds
– Maternal genomic imprinting
– In oocytes this gene is inactivated
– +0,25 lamb
Expressed only in daughters of FecX2W rams
Homozygous ewes are not infertile, as the maternal gene is inactive
Genomic imprinting-based prolificacy gene in sheep - FecX2W
– Thoroughbred and quarter horse
– Supposed to be X-linkeddominant
– Homozygotes are infertile
– Environmental factors, flushing(temporary, purposeful elevation in the plane of nutrition around breeding time)
Biovulation
Embrional mortality, abortion, miscarriage, premature birth, lowbirth weight, perinatal mortality, weak performance
Undesirable trait, genetic „disease”
Protection: selection, reproductive care
Twin pregnancy in horse
Galli 2003: A cloned horse born to its dam twin
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– Polygenic quantitative trait: 5., 7., 9., 10., 11., 12., 19., 23. chromosomescontain QTL-s
– QTL: stretches of DNA containing genes that underlie a quantitative trait.
– STH, STHR, IGF and BMP play part
Increase the biosynthesis of steroid hormones
Regulates the growth of the follicules
Frequency of twin pregnancy can be increased from 1-4 % to 25-30 %
Also influenced by: season (spring and autumn)
age (older cows)
nutrition (flushing)
lactational performance (high production)
Twin pregnancy in cattle
– Biovulation
– Chimerism 90 % - anastomoses between the two fetuses’ circulation cell migration
An organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes
Freemartinism, if the calves differ in their sex:
heifer calves are infertile with immature genital organs
Dairy: not desired; beef : desired
Disadvantages: abortion, difficult parturition, premature parturition, placenta retention, perinatal mortality, longer involution, laterconception…..
Twin pregnancy in cattle II.
57
Temple Grandin methodes in Hungary
– Polygenic heredity, h2 low
– 1., 4., 8., 13., 15., 16. chr.
– Negative correlation between prolificacy and meat production
Crossing of prolific maternal and meat producing paternal lines
Oestrogen-receptor gene +0,4 …… +2,3 piglet
Prolactin-receptor gene -0,15 …… +1,8 piglet
Retinol-binding-protein-4 needed for avoidance of abortion
Osteopontin ovulation rate
Haemopoetin nutrition of fetuses
Low h2, selection is not efficient
Environmental effects
Reproductive traits in swine
– Tropical, subtropical breeds are more resistant
– But: they have many undesired traits
– Resistance of tropical breeds is based on:
– Regulation of the level of metabolism
– Egress of heat by sweat and by regulation of skin vessels
– Slick hair (dominant) – reflection
– HSP70 – Genetic adaption of the cells
Heat resistence genes in cattle
Intramuscular fat (marbling) improves beef quality
– SNP: single nucleotide polymorphism
– Diacilglicerin-acetiltranszferáz:
– Tiroglobulin: marbled (timin)
marbling, milk fat%
– Leptin: marbling
– Kappa-kazein:cheese
– Lizozim: mastitis-resistence
– Genomic selection!
– The whole genome of sires is known
– Selection based on genetic markers, which are in linkage withQTLs
QTL-s of beef quality and milk production in cattle
Lab - Mendelian & X linked 09/10/2019
Ákos Maróti-Agóts 11
Thank you for your attention!