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What is genetics?
The scientific
study ofheredity
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Gregor Mendel
Born in 1822 inCzechoslovakia.
Became a monk at amonastery in 1843.
Taught biology andhad interests in
statistics.Also studied at theUniversity of Vienna
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Mendel continued
After returning to the
monastery he
continued to teachand worked in the
garden.
Between 1856 and
1863 he grew andtested over 28,000
pea plants
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Mendels Peas
Easy to grow.
Easily identifiable traits
Can work with large numbers of
samples
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Mendels experiments
The first thing Mendel did was create apure generation or true-breeding
generation.He made sure that certain pea plantswere only able to self pollinate,eliminating unwanted traits.
He did this by cutting away the stamen,or male part of each flower
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Genes and dominance
Trait: a characteristic
Mendel studied seven of these traits
After Mendel ensured that his true-breeding generation was pure, he thencrossed plants showing contrasting
traits.He called the offspring the F1generation or first filial.
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What will happen when pure
yellow peas are crossed with
pure green peas?All of the
offspring were
yellow.Hybrids= the
offspring of
crosses betweenparents with
contrasting traits
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What did Mendel
conclude?Inheritance is determined by factors
passed on from one generation to
another.Mendel knew nothing about
chromosomes, genes, or DNA. Why?
These terms hadnt yet been defined.
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What were Mendels
factorsThe factors that Mendel mentioned
were the genes.
Each gene has different forms calledalleles
Mendels second principle stated that
some alleles are dominant and someare recessive.
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Mendels second cross
He allowed the F1 generation to self-
pollinate thus producing the F2
generation.Did the recessive allele completely
disappear?
What happened when he crossed twoyellow pea hybrid (F1) plants?
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Results:
of the peas were yellow, of
the peas were green.During the formation of the sex cells orgametes, the alleles separated or
segregated to different gametes. (pollen
and egg)
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Probability
The likelihood of a
particular event
occurring. ChanceCan be expressed
as a fraction or a
percent.
Example: coin flip.
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Punnett Square
Developed by
Reginald Punnett.
A diagram used toshow the probability
or chances of a
certain trait being
passed from onegeneration to
another.
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Reading Punnett
squaresGametes are placed above and to the
left of the square
Offspring are placed in the square.
Capital letters (Y) represent dominant
alleles.
Lower case letters (y) represent
recessive alleles.
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Punnett square example
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Homozygous= when an organism
possesses two identical alleles. ex.
YY or yy
Heterozygous= when an organism
possesses different alleles. ex.
Yy
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Phenotype vs genotype
Genotype
The genetic makeup
Symbolized withletters
Tt or TT
Phenotype
Physical
appearance of theorganism
Expression of the
trait
Short, tall, yellow,
smooth, etc.
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Probability and
statisticsNo one event has a greater chance of
occurring than another.
You cannot predict the precise outcomeof an individual event.
The more trials performed, the closer
the actual results to the expectedoutcomes.
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Punnett square review:
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Mendels death
Mendel published his paper on heredity
in 1866.
The scientific community saw little if anyimportance in his work.
Mendel died in 1884 with no recognition
for his contributions to genetics.
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Assignment:
worksheet
Pages 283-284
1-10, 13, 14, 17, 18, 24
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THE END
THANK YOU
ANDGOD BLESS US ALL ! ! !
GLENN CAGAS JAMODIONG
BSEBIOLOGY