Post on 18-Dec-2015
4.3 THEORETICALGENETICS To be able to define the key terms of
theoretical genetics To describe inheritance patterns using
inheritance diagrams To be able to explain sex linkage
DEFINITIONS
Genotype: the alleles of an organismPhenotype: The characteristics of an organismDominant allele: the allele that gets expressed in heterozygous conditionRecessive allele; the allele that has an effect on the phenotype when present in the homozygous state.Codominant alleles: pairs of alleles that are both expressed when presentLocus: specific position of a gene in a chromosomeHomozygous; having two copies of the same allele.Heterozygous: having two different alleles of a geneCarrier: a person with one recessive faulty allele for a genetic disorderTest cross: testing a suspected heterozygote by crossing with the homozygous recessive
#1 - COMPLETE DOMINANCEP: RR rrF1: Genotype Phenotype Type of Genotype
Rr red heterozygousF1 Cross: Rr RrPunnett Square:
F2: Genotype Phenotype Type of GenotypeRR red homozygousRr red heterozygousRr red heterozygousrr white homozygous
RR Rr
Rr rr
R
r
R r
F2 Genotypic Ratio:1 RR : 2 Rr : 1 rrF2 Phenotypic Ratio:3 red: 1 white
#4 - INCOMPLETE DOMINANCEP: RR rrF1: Genotype Phenotype Type of Genotype
Rr pink heterozygousF1 Cross: Rr RrPunnett Square:
F2: Genotype Phenotype Type of GenotypeRR red homozygousRr pink heterozygousRr pink heterozygousrr white homozygous
RR Rr
Rr rr
R
r
R r
F2 Genotypic Ratio:1 RR : 2 Rr : 1 rrF2 Phenotypic Ratio:1 red: 2 pink : 1 white
#7 - CODOMINANCEP: RR WWF1: Genotype Phenotype Type of Genotype
RW red & white heterozygousF1 Cross: RW RWPunnett Square:
F2: Genotype Phenotype Type of GenotypeRR red homozygousRW red & white heterozygousRW red & white heterozygousWW white homozygous
RR RW
RW WW
R
W
R W
F2 Genotypic Ratio:1 RR : 2 RW : 1 WWF2 Phenotypic Ratio:1 red : 2 red & white : 1 white
#15 - BLOOD TYPINGP: IAi IBiPunnett Square:
F1: Genotype PhenotypeIAIB ABIAi AIBi Bii O
IAIB IAi
IBi ii
IA
i
IB i
#12 - SEX LINKAGE- HAEMOPHILIAP: XHY XHXh
Punnett Square:
F1: Genotype Phenotype Sex Type of GenotypeXHXH normal F homozygousXHXh carrier F heterozygousXHY normal M hemizygousXhY hemophilia M hemizygous
XHXH XHXh
XHY XhY
XH
Y
XH Xh
#8 - COMPLETE DOMINANCEP: yyrr YYRRF1: Genotype Phenotype Type of Genotype
YyRr yellow/round heterozygousF1 Cross: YyRr YyRrPunnett Square:
F2: Genotype Phenotype9 Y_R_ yellow/round3 Y_rr yellow/wrinkled3 yyR_ green/round1 yyrr green/wrinkled
yR
yr
YR
Yr
YYRR YYRr YyRR YyRr
YYRr YYrr YyRr Yyrr
YyRR YyRr yyRR yyRr
YyRr Yyrr yyRr yyrr
YR Yr yR yr
PEDIGREESExample:You are a normal female (homozygous). Both of your parents are normal. Your younger brother is normal and your older brother has hemophilia.
You!
XHXh XHY
XHYXhY XHXH