Download Gregor Mendel Mendel`s 7 Pea Plant Traits

Lecture 6 OUTLINE
Why do you look like your Mother
(or Father)?… Essential Genetics
•DNA is a Blueprint for Life
–Traits, Genes & Alleles
–From Genes to Proteins
•Sex and Genetic Variability
Gregor Mendel
• “Father” of modern
genetics
• First developed rules
now used to predict
inheritance
• Chose to study the pea
– Easily manipulated in
breeding experiments
Mendel’s 7 Pea Plant Traits
• Plant height
• Flower color
• Flower
position
• Pod color
• Pod shape
• Seed color
• Seed shape
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Flower Characteristics are Passed on to Offspring
in Specific Ways
•Different forms for the same
characteristic are called
TRAITS.
•Some forms are DOMINANT
•Some forms are RECESSIVE
FLOWER COLOR is the
PHENOTYPE
Mendel’s Interpretation
• Assumed that each form of trait
was controlled by a”Hereditary
Factor”
• Dominant traits (“P” for purple)
mask presence of recessive (“p”
for white) alleles
– Individuals with the same
phenotype may have different
hereditary factors.
• GENES are Mendel’s
“Hereditary Factor”
• The TOTAL complement
of genes present in an
organism constitute its
Genotype
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DNA
Contains Genes
GENE - region of DNA that
produces a functional protein
Eg. The Purple Pigment Protein which
give a flower its purple color are
“encoded” by a specific set of genes.
DNA
Contains Genes
GENE - region of DNA that
produces a functional protein
Eg. The proteins which give a
flower its purple color are “encoded”
by a specific set of genes.
Transcription
• Messenger RNA (mRNA ) carries
genetic info from DNA in the Nucleus
– All mRNAs are made from a DNA Template
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DNA
Contains Genes
Translation – is the process of
“decoding” the genetic message into
cellular proteins.
Translation
• mRNA relays Genetic Info to the Protein
Synthesis Machinery
• Proteins are synthesized on Ribosomes
• Transfer RNAs bring in the Amino Acids
P and p Alleles
•Different forms for the same characteristic are called
ALLELES
•Some forms are DOMINANT
•Some forms are RECESSIVE
P = dominant gene that makes
pigment protein è P U R P L E f l o w e r
p = recessive gene that makes NO
pigment è WHITE flower
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P and p Alleles
• Plants have TWO alleles for
Flower Color
• H o m o z y g o t e = alleles are the
SAME
(PP or pp)
• Heterozygote – alleles are
different (Pp – not shown)
P and p Alleles
• When plants reproduce only
ONE allele is found in each
EGG or SPERM cell
(GAMETES)
• INDEPENDENT
ASSORTMENT
P
P
P
P
What happened when Mendel crossed
these two types of pea plants?
Punnett Squares
• Gene combinations determine Color
Plant with PURPLE FLOWER
Plant
With
WHITE
FLOWER
p
p
P
P
Pp
Pp
Pp
Pp
What color are the progeny (offspring)?
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P and p Alleles
• Progeny or Offspring all have
a PURPLE FLOWER
PHENOTYPE
• Progeny have a Pp, or
Heterozygote GENOTYPE
• Phenotype – appearance of
the plant
• G e n o t y p e - alleles that are
present in the plant genome
What happens when THESE plants reproduce?
P and p Alleles
• Progeny have different
Genotypes and Phenotypes
Human Sex Determination
• Gene combinations determine SEX
Mother
X
X
X
XX
XX
Y
XY
XY
Father
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Some Traits are determined by more
than one set of Alleles
Human Genome
Contains 23 Pairs of
Chromosomes
Male
Why do you look like your
Mother (or your Father)?
• Chance
–Alleles are randomly donated
from parents to offspring
–Specific Genetic combinations
are therefore a product of
chance.
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