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

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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

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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

Lab - Mendelian & X linked 09/10/2019

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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Ákos Maróti-Agóts 10

– 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!