Principles of Heredity

1. Laws of HeredityLaws of Heredity
Pranabjyoti Pranabjyoti
DasDas
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2. Mendel’s Laws of Mendel’s Laws of
HeredityHeredity
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3. Pages from Mendel’s Notebook…Pages from Mendel’s Notebook…
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4. What is What is heredityheredity??
The The passing passing on of on of
characteristics characteristics (traits)(traits)
from parents to offspringfrom parents to offspring
GeneticsGenetics is the study of is the study of
heredityheredity
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5. Mendel used peas...Mendel used peas...
They reproduce They reproduce sexuallysexually
They have two distinct, They have two distinct,
malemale and and femalefemale, sex cells , sex cells
called called gametesgametes
Their Their traitstraits are easy to are easy to
isolateisolate
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6. Mendel Mendel crossedcrossed them them
FertilizationFertilization - the uniting - the uniting
of male and female of male and female
gametesgametes
CrossCross - combining gametes - combining gametes
from parents with from parents with
different traitsdifferent traits
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7. QuestionsQuestions
What did Mendel cross?What did Mendel cross?
What are What are traitstraits??
What are What are gametesgametes??
What is What is fertilizationfertilization??
What is What is heredityheredity??
What is What is geneticsgenetics??
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8. What Did Mendel Find?What Did Mendel Find?
He discovered different He discovered different
lawslaws and and rulesrules that explain that explain
factors affecting factors affecting heredityheredity..
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9. Rule of Unit FactorsRule of Unit Factors
Each organism has two Each organism has two
alleles alleles for each for each traittrait
–Alleles Alleles - different forms of - different forms of
the same the same genegene
–Genes Genes - located on - located on
chromosomes, they control chromosomes, they control
how an organism developshow an organism develops
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10. Rule of DominanceRule of Dominance
The trait that The trait that is observedis observed
in the offspring is the in the offspring is the
dominant trait dominant trait (uppercase)(uppercase)
The trait that The trait that disappears disappears
in the offspring is the in the offspring is the
recessive trait recessive trait (lowercase)(lowercase)
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11. Law of SegregationLaw of Segregation
The two alleles for a trait The two alleles for a trait
must separatemust separate when when
gametes are formedgametes are formed
A parent randomly passesA parent randomly passes
only oneonly one allele for each allele for each
trait to each offspringtrait to each offspring
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12. Law of Independent Law of Independent
AssortmentAssortment
The genes for different The genes for different
traits are traits are inherited inherited
independentlyindependently of each of each
other.other.
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13. Questions...Questions...
How many How many allelesalleles are there are there
for each trait?for each trait?
What is an What is an alleleallele??
How many How many allelesalleles does a does a
parent pass on to parent pass on to eacheach
offspring for offspring for eacheach trait trait
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14. Questions...Questions...
What do we call the trait What do we call the trait
that is that is observedobserved? ?
What What casecase (upper or lower)(upper or lower)
is it written in?is it written in?
What about the one that What about the one that
disappearsdisappears? ?
What What casecase is it written in? is it written in?
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15. Phenotype & GenotypePhenotype & Genotype
PhenotypePhenotype - the way an - the way an
organism organism lookslooks
–red hair or brown hairred hair or brown hair
genotypegenotype - the - the gene gene
combinationcombination of an organism of an organism
–AAAA or or Aa Aa oror aa aa
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16. Heterozygous & HomozygousHeterozygous & Homozygous
HeterozygousHeterozygous - if the two - if the two
alleles for a trait are alleles for a trait are
different different ((AaAa))
Homozygous Homozygous - if the two - if the two
alleles for a trait are the alleles for a trait are the
same same ((AAAA or or aaaa))12/08/13 16Pranabjyoti Das

17. Dihybrid vs MonohybridDihybrid vs Monohybrid
Dihybrid CrossDihybrid Cross - crossing - crossing
parents who differ in parents who differ in two two
traits traits ((AAEEAAEE with with aaeeaaee))
Monohybrid CrossMonohybrid Cross - -
crossing parents who crossing parents who
differ in only differ in only one trait one trait
((AAAA with with aaaa))
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18. Questions...Questions...
What is the What is the phenotypephenotype??
What is the What is the genotypegenotype??
What is What is homozygoushomozygous??
What is What is heterozygousheterozygous??
What is What is monohybrid monohybrid
crossingcrossing??
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