Transcript Mendel`s genetics

Mendelian
Genetics
1
Gregor Johann Mendel
Austrian monk
Studied
inheritance in pea
plants
Called the
“Father of
Genetics"
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Site of
Gregor
Mendel’s
experimental
garden in the
Czech
Republic
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Mendel’s Pea Plant
Experiments
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Why peas, Pisum sativum?
Can be grown in a small
area
Produce lots of offspring
Produce pure plants when
allowed to self-pollinate
Can be artificially crosspollinated
•Contain easily
distinguishable traits
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Seven Pea Plant Traits
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Seven Pea Plant Traits
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How Mendel Began
Mendel
produced
pure
strains by
allowing the
plants to
selfpollinate
for several
generations
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Mendel’s Experimental
Methods
Mendel hand-pollinated
flowers using a
paintbrush
He could snip the
stamens to prevent
self-pollination
He traced traits
through the several
generations
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Genetics Terminology
 Trait - any characteristic that
can be passed from parent to
offspring. Ex: Eye Color
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Genetics Terminology
 Heredity - passing of traits
from parent to offspring
 Genetics - study of heredity
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More Genetics Vocab
 Alleles - two forms of a gene
(dominant & recessive)
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More Genetics Vocab
Dominant – allele that is
expressed when present;
represented by a capital letter (R)
Recessive – allele that is only
expressed when there are two
present; represented by a lowercase
letter (r)
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More Terminology
 Genotype - gene
combination for
a trait (ex: BB,
Bb, bb)
 Phenotype - the
physical feature
resulting from a
genotype (ex:
blue, brown)
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Genotypes
 Homozygous- 2 dominant or 2
recessive genes (ex: TT or tt);
also called purebred
 Heterozygous- one dominant &
one recessive allele (ex: Tt); also
called hybrid
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Monohybrid
Crosses
•Monohybrid cross - cross
involving a single trait. ex.
flower color
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Punnett Square
Tool used to
help solve
genetics
problems
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Generations
Parental P1 Generation = the parental
generation; cross of purebred
parents. Ex: round RR or wrinkled rr
Offspring of P generation
PRODUCES
F1 generation = the first-generation
offspring. (1st filial generation)
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F1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round
r – Wrinkled
Cross: Round seeds
x Wrinkled seeds
Pure bred
RR
x
rr
parents
r
r
R
Rr
Rr
R
Rr
Rr
F1 offspring produced:
Genotype: 0RR: 4Rr: 0rr
Phenotype: 4 Round:
0 wrinkled
F1
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Generations
F2 generation = the second
generation offspring. (2nd
filial generation)
From breeding individuals
from the F1 generation
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F2 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round
r – Wrinkled
Cross: Round seeds
x Round seeds
Rr
x
Rr
F1 offspring
R
r
R
RR
Rr
r
Rr
rr
F2 offspring produced:
Genotype: 1RR, 2Rr, 1rr
Phenotype: 3 Round &
1 wrinkled
F2
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Another look at P, F1, F2
Cross 2
Pure
Plants
TT x tt
Results
in all
Hybrids
Tt
Cross 2 Hybrids
get
3 Tall & 1 Short
TT, Tt, tt
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Practice Punnett
Squares
**Please note: To earn full
credit, you must include a key
and cross with each problem!**
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Construct a Punnett square to determine the
probability of white flowers if a heterozygous
purple (Pp) flower is crossed with a homozygous
white (pp) flower.
Key: __________________________
Cross: _________________________
Probability of
white flowers =
_____________
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Construct a Punnett square to determine the
probability of short pea plants if a
homozygous tall (TT) plant is crossed with a
heterozygous tall (Tt) plant.
Key: __________________________
Cross: _________________________
Probability of short
plants= ________
Probability of tall
plants= _________
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If round peas are dominant over wrinkled peas,
make a Punnett square to determine the genotype
and phenotype ratios of the offspring if a
heterozygous plant is crossed with a homozygous
recessive plant.
Key: __________________________
Cross: _________________________
Genotype ratio:
_________________
Phenotype ratio:
_________________
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