1. Laws of Heredity
Pranabjyoti
Das
12/08/13
Pranabjyoti Das
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2. Mendel’s Laws of
Heredity
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Pranabjyoti Das
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3. Pages from Mendel’s Notebook…
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4. What is heredity?
The passing on of
characteristics (traits)
from parents to offspring
Genetics is the study of
heredity
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5. Mendel used peas...
They reproduce sexually
They have two distinct,
male and female, sex cells
called gametes
Their traits are easy to
isolate
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6. Mendel crossed them
Fertilization - the uniting
of male and female
gametes
Cross - combining gametes
from parents with
different traits
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7. Questions
What did Mendel cross?
What are traits?
What are gametes?
What is fertilization?
What is heredity?
What is genetics?
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8. What Did Mendel Find?
He discovered different
laws and rules that explain
factors affecting heredity.
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9. Rule of Unit Factors
Each organism has two
alleles for each trait
– Alleles - different forms of
the same gene
– Genes - located on
chromosomes, they control
how an organism develops
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10. Rule of Dominance
The trait that is observed
in the offspring is the
dominant trait (uppercase)
The trait that disappears
in the offspring is the
recessive trait (lowercase)
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11. Law of Segregation
The two alleles for a trait
must separate when
gametes are formed
A parent randomly passes
only one allele for each
trait to each offspring
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Pranabjyoti Das
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12. Law of Independent
Assortment
The genes for different
traits are inherited
independently of each
other.
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13. Questions...
How many alleles are there
for each trait?
What is an allele?
How many alleles does a
parent pass on to each
offspring for each trait
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14. Questions...
What do we call the trait
that is observed?
What case (upper or lower)
is it written in?
What about the one that
disappears?
What case is it written in?
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15. Phenotype & Genotype
Phenotype - the way an
organism looks
– red hair or brown hair
genotype - the gene
combination of an organism
– AA or Aa or aa
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16. Heterozygous & Homozygous
Heterozygous - if the two
alleles for a trait are
different (Aa)
Homozygous - if the two
alleles for a trait are the
same (AA or aa)
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Pranabjyoti Das
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17. Dihybrid vs Monohybrid
Dihybrid Cross - crossing
parents who differ in two
traits (AAEE with aaee)
Monohybrid Cross crossing parents who
differ in only one trait
(AA with aa)
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18. Questions...
What is the phenotype?
What is the genotype?
What is homozygous?
What is heterozygous?
What is monohybrid
crossing?
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19. 12/08/13
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