02 Passage of Info from Parent to Offspring

1. Inherited Change and Inherited Change and
Gene TechnologyGene Technology
The passage of information The passage of information
from parent to offspringfrom parent to offspring
ALBIO9700/2006JK

2. •Locus – Locus – position on the chromosome position on the chromosome
in which the gene residesin which the gene resides
*plural: loci*plural: loci
•Alleles – Alleles – a particular variety of the a particular variety of the
same gene same gene
ALBIO9700/2006JK

3. •HomozygousHomozygous – 2 identical alleles of a – 2 identical alleles of a
genegene
•Heterozygous Heterozygous – 2 different alleles of a – 2 different alleles of a
genegene
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4. •GenotypeGenotype – alleles possesed by an – alleles possesed by an
organismorganism
•PhenotypePhenotype – observable – observable
characteristics/physical traits of an characteristics/physical traits of an
organism (resulting from interaction organism (resulting from interaction
between genotype and environment)between genotype and environment)
ALBIO9700/2006JK

5. •Dominant Dominant – when effect on the phenotype of a – when effect on the phenotype of a
heterozygote is identical to its effect in a heterozygote is identical to its effect in a
homozygotehomozygote
•RecessiveRecessive – only expressed when no dominant – only expressed when no dominant
allele is presentallele is present
•CodominantCodominant – both alleles have an effect on – both alleles have an effect on
the phenotype of a heterozygous organismthe phenotype of a heterozygous organism
ALBIO9700/2006JK

6. Genetic Diagram (monohybrid Genetic Diagram (monohybrid
crosses)crosses)
•Let N be the dominant allele for normal pigment.
•Let n be the recessive allele for albino.
Parent phenotype Heterozygous Normal Parent phenotype Heterozygous Normal Heterozygous Heterozygous
NormalNormal
Parent genotype  Parent genotype  Nn Nn X X
Nn Nn
Gametes Gametes NN nn
NN nn
Possible offspring Possible offspring
genotype genotype NN NN Nn Nn Nn Nn
nn nn
Offspring phenotype Normal Normal Normal Offspring phenotype Normal Normal Normal
AlbinoAlbino
Ratio of phenotypeRatio of phenotype 3 normal : 1 albino3 normal : 1 albino
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7. ALBIO9700/2006JK
NNNN
NormalNormal
NnNn
NormalNormal
NnNn
NormalNormal
nnnn
AlbinoAlbino
Genotypes of parentGenotypes of parent
Genotypes Genotypes
of parentof parent
N nN n
NN
nn
Ratio of phenotypeRatio of phenotype 3 normal : 1 albino3 normal : 1 albino

8. Genetic Diagram (dihybrid crosses)Genetic Diagram (dihybrid crosses)
•Let A be the dominant allele for purple stem and a
recessive green
•Let D be the dominant allele for cut leaves and d
recessive smooth
Parent phenotype Heterozygous HeterozygousParent phenotype Heterozygous Heterozygous
Parent genotype  AaDd Parent genotype  AaDd X AaDd X AaDd
Gametes Gametes ADAD AdAd aDaD
adad
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9. ALBIO9700/2006JK
AADD
Purple,
cut
AADd
Purple,
cut
AaDD
Purple,
cut
AaDd
Purple,
cut
AADd
Purple,
cut
AAdd
Purple,
smooth
AaDd
Purple,
cut
Aadd
Purple,
potato
AaDD
Purple,
cut
AaDd
Purple,
cut
aaDD
Green,
cut
aaDd
Green,
Cut
AaDd
Purple,
cut
Aadd
Purple,
smooth
aaDd
Green,
Cut
aadd
Green,
smooth
Genotypes of parentGenotypes of parent
GenotypeGenotype
s of s of
parentparent
AD Ad aD adAD Ad aD ad
ADAD
AdAd

aDaD

adad
Ratio of phenotypeRatio of phenotype 9 purple,cut:3 purple,smooth:3 green,cut:1 green,smooth 9 purple,cut:3 purple,smooth:3 green,cut:1 green,smooth

10. •Sex linkageSex linkage – related to genes that are – related to genes that are
carried on an X chromosome but not on a carried on an X chromosome but not on a
Y chromosomeY chromosome
•CodominanceCodominance??
•Multiple allelesMultiple alleles – the existence of 3 or – the existence of 3 or
more alleles of a gene (eg. determination more alleles of a gene (eg. determination
of A, B, and O blood groups)of A, B, and O blood groups)
ALBIO9700/2006JK

11. Test CrossesTest Crosses
•Involves crossing an organism showing Involves crossing an organism showing
the dominant phenotype with one which is the dominant phenotype with one which is
homozygous recessive to find out if the homozygous recessive to find out if the
dominant genotype is hetero- or dominant genotype is hetero- or
homozygous.homozygous.
ALBIO9700/2006JK