Download Heredity

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Characteristics:
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Hair Color
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Earlobes
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Fingers
A feature that has different
forms in a population
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Traits:
Type of hair colorbrown, blonde, red
Attached/unattached
Longer index or ring
finger
Different forms of a
characteristic governed
by genes
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Traits are determined by genes. Genes are
the instruction manuals for our body. They
provide directions for building all the proteins
that make our bodies function.
DNA is found within a gene. Genes are
carried in chromosomes.
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Chromosomes are found in the nuclei of our
cells.
Everybody has 46 chromosomes (23 pairs)
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When a zygote (baby) is formed, it too has 46
chromosomes. It receives a copy of one of
each of Mom’s chromosomes and a copy of
each of Dad’s chromosomes for a total of 23
pairs of chromosomes.
Not all living things have 23 pairs of
chromosomes.
http://learn.genetics.utah.edu/content/begin/t
our/
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These parts are called alleles. An allele is one of the
alternative forms of a gene that governs a
characteristic.
◦ Alleles are represented by letters
 Capital letters represent dominant traits
 Lower case letter represent recessive traits
A = dominant
a = recessive
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Dominant trait- the
trait that always
appears when a
dominant allele is
present in gene
The trait observed in
F1 when parents that
have different traits are
bred
Ex) Brown hair is dominant over blonde
hair, so if one brown allele is passed on
from the parent the offspring will have
brown hair
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Recessive trait- the
trait that does not
appear unless there are
2 recessive alleles
present in gene
The trait that
reappears in the F2
after disappearing in
the F1 when parents
with different traits are
bred
Ex) In order for someone to have
blonde hair both parents must have
passed on a recessive gene, resulting
in 2 recessive alleles
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Phenotype: An
organism’s appearance
◦ Detectable physical
characteristics
◦ What an organism looks
like
Ex. Yellow or green seed
color
http://learn.genetics.utah.edu/cont
ent/begin/tour/
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Genotype: The entire
genetic makeup of an
organism
◦ the combination of genes
for one or more specific
traits
◦ Homozygous- 2 of the
same type of allele (2
dominant or 2 recessive)
◦ Heterozygous- 2 different
alleles, one dominant and
one recessive (purebred)
Ex. For a recessive trait to
show up the offspring must
receive 2 recessive alleles,
making it homozygous
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Used to organize all the possible combinations of offspring
from particular parents
◦ Born 1822 in Heinzendorf, Austria
◦ Worked in Monastery garden
 Patterns of inheritance not always clear, sometimes a trait
appeared in one generation (parents) and not in the next
generation (F1, offspring), but then it reappears again in
the generation after that (F2).
◦ Began investigating with pea plants
 Grow quickly
 self-pollination create true-breed
 parts of a flower
 cross-pollination
Characteristics
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Mendel's Experiments with peas
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Mendel realized that each parent must have 2
“sets of instructions” for each trait
◦ When parents reproduced they each gave their
offspring one set of each of their instructions (the
child will then end up with 2 “sets of instructions”
for each trait
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Mendel published his work in 1865 and not
until 30 years later was his work rediscovered
and understood
◦ A Gene is one set of instructions for an inherited
trait
◦ An Allele is one of the alternative forms of a gene
that governs a trait (ex. If earlobes are attached or
unattached)
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Used to organize all the possible combinations of offspring
from particular parents
◦ Cross of homozygous purple flower and homozygous white
flower
◦ P = Purple (dominant) , p = white (recessive)
Parent 1
Parent 2
Phenotype Purple
white
Genotype
pp
PP
F1 Generation:
Genotype:
Pp
p
P
P
Pp
Pp
Pp
Pp
Phenotype:
Purple
p
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Like Mendel’s 2nd experiment, we will self pollinate
the F1 generation
F2 Generation:
Genotype:
1PP, 2Pp, 1pp
Parent 1
Parent 2
Genotype
Pp
Pp
Phenotype
Purple
purple
P
p
Phenotype:
3purple, 1white
PP
Pp
P
Genotype Ratio:
1:2:1
Phenotype Ratio (dominant:recessive):
3:1
p
Pp
pp
T
t
t
Tt
Tt
2 Tt : 2 tt or 1:1
t
tt
tt
2 Tt : 2 tt or 1:1
Incomplete dominance