9 mendelian

7/25/2019 9 Mendelian

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Principles of Genetics-Inheritance

Mendels lawsGenetics crossings

Dominance relationshipGene linkage and polyploidy

Basic patterns of human inheritancePedigree analysis


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Gregor Mendel German-Polish Worked with bees and peas hose peas because

! lear characters ! "hort generation time ! #asy to keep $rue breeding ! "elf pollination o%er many

generations gi%e same %ariety asparent

&ydridi'ation ! Mating of ( true breeding parents


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Mendels #)periment **+ &ybridi'ation of ( true breed ,Purple White+(+ .* ! /ll purple0+ .( ! 0 purple ! * white

-) / gene can e)ist in more than one form1-) 2rganisms inherit two alleles for each trait1-) When gametes are produced ,by meiosis+3 allele

pairs separate lea%ing each cell with a single allelefor each trait1-) When the two alleles of a pair are di4erent3 one is

dominant and the other is recessi%e1


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Mendels 5aws *

"egregation ! ( alleles for a heritablecharacter

segregate duringgamete

formation and endup in

di4erent gametes


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Mendels 5aw (

Dominance !

* trait is controlled by ( hereditary6factors73which e)ist in ( forms3 *

dominant andanother recessi%e


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Mendels #)periment (


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Mendels 5aw 0

Independent assortment ! #ach pair of alleles segregates

independently of each other pairof allelesduring gamete formation ,if genes

locatedon di4erent chromosomes+


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$est rossing

ross of * test organism with *dominant trait with a homo'ygoterecessi%e for trait / down multiplegenerations

If recessi%e trait seen in /89indi%idual3 then hetero'ygous3otherwise homo'ygous


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Dominance

"imple traits controlled by * gene Gene e)ist in ( allelic types ! Dominant

and

recessi%e Dominant allele co%ers the e4ect of

recessi%e allele &etero'ygote Dominant trait &omo'ygote Dominant : recessi%e trait


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5aw of Probability3 MendelianInheritance3 Punnett s;uare

Punnett s;uare ! Diagram which predict all the probableoutcomes in cross breeding

5aw of probability ! hance of an e%ent occuring Multiplication rule !

Probability of ( things happening in * organism whichis chromosomally separate < multiplication ofprobability of each occurance

/ddition rule

hance of any * mutually e)clusi%e trait occurring iscalculated by addition


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Gene 5inkage

When genes are located closetogether on chromosome3assortment during gamete formationnot independent

#g ! ystic =brosis and color %isiongene on

chromosome >


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Polyploidy

/ddition of number of chromosome sets in anorganism

- #g ! $riploidy3 tetraploidy

&umans ! Miscarriage Plants ! Many ? /utopolyploids ! "ame species - /llopolyploids ! Di4erent @@ 5omatia tasmanica ! $riploid3 %egetati%e

reproduction @@ $riticale ! Wheat rye $etraploid


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Degree of Dominance

omplete ! * dominant o%er another

Incomplete ! ( allele a4ectphenotype in sameway

odominance ! /4ect phenotype indi4erent

ways


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omplete

$ongue curling .ree ear lobe

Widows peak Brown pigment ! Iris3 hair11 &itchhikers thumb

11111


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Incomplete Dominance : PolygenicInheritance

"kin color - Go%erned by many genes with dominant

and recessi%e alleles3 combination of it

determines skin color- Auantitati%e3 each gene contributes

di4erently

- Protein ! Melanin - Genes control melanin and cell acti%ity - Multiple genes


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odominance : Multiplealleles

Blood group and rhesus !- /3 B3 2 and /B phenotype3 rhesus : -%e ,D+

- Determined by ( alleles3 /:a and B:b3 rhesus

D:d ,most common+ - Program addition of speci=c carbohydrates

onto membrane & antigen - If both dominant / and B are present3 both

e)pressed in di4erent ways3 not mi)ede4ect


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Pleiotropy

Multiple e4ect : gene #)ample phenylketonuria gene!

@ Phenylalanine hydro)ylase! Phenylalaninie $yrosine @ Mental retardation3 abnormal

growth3multiple organ damage


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#pistasis

Gene e4ect a4ected by other gene #g ! Dog ( genes

-- Bb ,determine black:brown hair+ -- #e ,determine deposition ofpigment+

"upposed C!0!0!* rule broken


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Pedigree /nalysis

Measure of pattern of inheritance ofa speci=c trait3 in a family line

ses diagram with !Generation row ,&ori'ontal+

Blood relations %ertical


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&aemophilia

E linked recessi%e ause bleeding issues

/ ! .actor FIII B! .actor IE "ymptoms ! Intracranial

haemorrhage3 bleeding into knees,knee pain+


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Genetic Disorders

Fariable onset3 some cause death ystic .ibrosis ! @ $hick mucus3 blocks lungs pancreas

secretion @ 5ife e)pectancy ! H @ aused by recessi%e mutation

@ Pre%ented by carrier testing %ia geneticscreening

@ arried by recessi%e allele


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Phenylketonuria @ ecessi%e3 unable to digest phenylalainine3

accumulates in body @ Phenylalanine ! .or brain de%elopment3

thus sick -@ Impeded neural de%elopment @ Gene ! nknown Breast cancer @ Gene present but in phenotype later @ B /* and ( mutations3 cause ine4ecti%e

gene transcription and translation@ .amily studies to determine chance


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&untingtons Disease

5ate onset &untington gene produce &tt protein ontains trinucleotide repeat se;uence13

randomly may increase or decrease "usceptible indi%iduals ! Increase3 cause

m&tt production Disease

- Dominant diseaseJJ - ause ner%ous system damage and

twitching mo%ement

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