Modified by Patrick
Matous from the
Georgia
Agricultural
Education
Curriculum Office
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Is the science of heredity.
Heredity is the transmission of genetic or
physical traits from parent to offspring.
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Austrian Monk
Considered the “Father of Heredity”
He conducted plant breeding experiments in
their monastery garden.
In 1865 he made his work public, units of
inheritance.
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Each of the 100 Trillion cells in our body
except the red blood cells contains the entire
human genome, in the nucleus of every cell
is the genetic information “blueprint” to
construct the individual.
It is the Deoxyribonucleic acid (DNA)
Function of DNA
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Genetic code for almost every organism.
Provide template for protein synthesis.
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The structure of DNA was discovered by Watson
and Crick in 1953.
It is a twisted double helix molecule, containing
sugar, phosphates, and nitrogenous bases.
The sugar is deoxyribose and the phosphoric acid
molecules are always the same and provides for the
structure (side of the ladder).
The only difference between us is the order and
arrangement of the four bases (rungs of the ladder).
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Adenine= A
Thymine= T
Guanine= G
Cytosine= C
A always pairs with T
C always pairs with G
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Adenine= A
Uracil= U
Guanine= G
Cytosine= C
G always pairs with C
T from the DNA = A in the RNA
A from the DNA = U in the RNA
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The DNA in every cell is located in rod like
segments called chromosomes
Chromosomes occurs in pairs in every cell of
our body except in the sperm and ovum.
Chromosomes numbers are the same for each
specie.
Species
Cattle
Swine
Sheep
Horse
Human
Chicken
Goat
Donkey
Diploid #
60
38
54
64
46
78
60
62
Haploid #
30
19
27
32
23
39
30
31
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There are 2 sex chromosomes included in
the diploid number of the chromosomes.
All of the other chromosomes are referred to
as autosomes.
In mammals if the sex chromosomes are
alike, XX it results in a female.
If the sex chromosomes are different, XY it
results in a male.
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Females contribute an X chromosome towards
the sex of their offspring.
Males can contribute an X or a Y chromosome
toward the sex of their offspring.
Absence of an Y chromosome results in a the
embryo developing into a female.
Presence of an Y chromosome results in the
embryo developing into a male.
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Gametogenesis =
Formation of
gametes through
meiosis.
Male = 4 viable
spermatids
Female = 1 viable
ovum, 3 polar
bodies.
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Meiosis
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Is the form of cell division which results
reducing the chromosome number from the
diploid # to the haploid #.
Occurs only in the sex cells, sperm and ovum.
Mitosis
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Is the form of cell division which results in the
formation of identical daughter cells, keeps the
chromosome number constant.
Tissue growth and repair.
Occurs throughout the body except in the sex
cells.
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Genotype contains two copies of the gene.
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Gamete (sex cells) contains only one copy of
the gene.
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AaBB
AB
Determine the possible gametes of AaBB
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AB
aB
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State if its a gamete or genotype.
Aa
D
DdEeFFgg
sRtxyq
AaBBeeFF
adgEFT
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From the genotype AaBb
AB
Ab
aB
ab
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Chromosomes contains several units of
inheritance “genes”.
Genes usually occurs in pairs, one from each
parent.
Some traits are inherited directly from one set
of genes.
Some traits are inherited through several sets
of genes.
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It was presumed that we were composed of
about 100,000 genes to construct us.
Today, research has proven that number is a lot
less than 100,000.
Extra credit for the student that can find an
article about the current number of genes.
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Homozygous- contains 2 identical genes for the
same trait, AA, BB, cc
Heterozygous- contains 2 different genes for
the same trait, Aa, bB, Cc
Phenotype- Outward appearance of a trait,
coat color, polled, horned.
Genotype- Genetic classification of a gene,
AA, Aa, aa.
Allele- Location of a gene on the chromosome.
F-one = First cross mating.
F-two = Second cross mating.
http://www.biology.arizona.edu/vocabulary/mendelian_genetics/
mendelian_genetics.html
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The gene that express itself, the powerful
and dominant gene.
It has the power to overshadow the
recessive gene when there is complete
dominance.
Some examples are:
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White faced in cattle
Droopy ears in swine
Polled in cattle
Black coat color in Angus cattle
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The gene that is overshadowed by a
dominant gene
Recessive genes can only express
themselves in the absence of the dominant
gene
Polled vs Horned (Pp) (pp)
Black wool vs white (Ww) (ww)
Dwarfism vs normal size (dd)
Albino
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Angus- Black coat color is dominant.
BB = Homozygous Dominant and Black
Bb = Heterozygous and is black
bb = Homozygous recessive and red
A heterozygous bull is mated to 50
homozygous recessive cows.
How many calves are black?
How many calves are red?
What is the genotypic and phenotypic
ratios?
B
b
b
Bb
bb
b
Bb
bb
2 heterozygous = Bb
 2 Homozygous
Recessive bb
 25 Black, 25 Red
 Genotypic ratio =
0:2:2
 Phenotypic ratio =
2 Black: 2 Red
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Some recessive genes are attached to the X
and Y chromosomes
Humans: Colorblindness and Baldness are
on the X chromosomes
In Men, traits expressed anytime present
In Women, must have two recessives to
show trait
Children get baldness from mothers
Y
X B
X
X
XX
B
XX
B
X Y
XY
X
X B
X
XX B
XX
Y
X BY
XY
X
X B
X B
X X B
X X B
Y
X BY
XB
Y
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If both genes express themselves
Shorthorn Cattle: Red male mated to a White
female = Roan calf
RR crossed rr = Rr
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Shorthorn Cattle
RR = Red
rr = white
Rr = roan
If a red bull (RR) is mated to a white cow (rr),
what color will the calves be?
R
R
r Rr
Rr
r Rr
Rr
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If a red bull (RR) is mated to a roan (Rr) cow,
what color will the calves be?
R
R
R
RR
RR
r
Rr
Rr
R
r
R
RR
Rr
r
Rr
rr
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Noticed when a gene has more than 2 alleles
that code for multiple phenotypes.
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This is the property of a gene that causes it to
have multiple phenotypic effects. Pg. 262
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A gene at one locus alters the effects of a gene
at another locus. In many cases it is masked!
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A single characteristic that is controlled by
two or more genes!
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http://www.indiana.edu/~oso/lessons/Genetics/figs/HairColor/browns.jpg
http://facweb.bhc.edu/academics/science/robertsk/biol100/Patterns_files/image033.jpg
http://www.google.com/imgres?imgurl=http://www.biology.arizona.edu/men
delian_genetics/problem_sets/dihybrid_cross/graphics/13punnet.gif&imgrefurl=
http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cr
oss/13t.html&usg=__0lXOAHlJKQyfZdIKnbTteDlksaU=&h=195&w=301&sz=6&h
l=en&start=9&zoom=1&um=1&itbs=1&tbnid=8rHyQaubxSBvSM:&tbnh=75&tbn
w=116&prev=/images%3Fq%3Depistasis%26um%3D1%26hl%3Den%26sa%3DN%
26rlz%3D1T4GGIH_en__266US273%26tbs%3Disch:1&ei=6l9ATeG7OMqr8AaA7qj
vAw
http://www.nature.com/scitable/nated/content/45524/human_height_illustrati
on_MID_1.gif
http://bioweb.wku.edu/courses/BIOL115/Wyatt/Ge
netics/Meiosis.asp