Download Genetics - Tomball FFA

Genetics
Is the science of heredity.
 Heredity is the transmission of
genetic or physical traits from
parent to offspring.
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Gregor Mendel
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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What makes us unique?
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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.
Composition of DNA
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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).
Bases of DNA
Adenine= A
 Thymine= T
 Guanine= G
 Cytosine= C
 A always pairs with T
 C always pairs with G
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Bases of RNA
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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DNA Model
Chromosomes
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.
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Chromosome Numbers
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
Chromosomes
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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Sex Determination
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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.
Sex Determination
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Gametogenesis =
Formation of
gametes through
meiosis.
Male = 4 viable
spermatids
Female = 1 viable
ovum, 3 polar
bodies.
Tell me what I am ?????
Tell me what I am ?????
Cell Division
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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.
Genotype or Gamete
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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
Gamete or Genotype
State if its a gamete or genotype.
 Aa
D
 DdEeFFgg
 sRtxyq
 AaBBeeFF
 adgEFT
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List all the possible
gametes.
From the genotype
 AB
 Ab
 aB
 ab
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AaBb
Genes
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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Genes
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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Terms to know
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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.
What are dominant genes?
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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
What are Recessive
Genes?
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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Punnet Square
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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?
Punnet Square
B
b
b
Bb
bb
b
Bb
bb
Results
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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What are Sex Linked
Genes?
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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
If Dad is bald, will you be
bald?
Y
X B
X
X
X X
B
X X
B
X Y
X Y
Baldness is carried by the
mother
X
X B
X
X X B
X X
Y
X BY
X Y
What if Mom is bald?
X
X B
X B
X X B
X X B
Y
X BY
XB
Y
What is Incomplete
Dominance?
If both genes express themselves
 Shorthorn Cattle: Red male mated
to a White female = Roan calf
 RR crossed rr = Rr
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Punnet Square
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?
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Shorthorn: Red X White
R
R
r Rr
Rr
r Rr
Rr
Punnet Square
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If a red bull (RR) is mated to a roan
(Rr) cow, what color will the calves
be?
Shorthorn: Red X Roan
R
R
R
RR
RR
r
Rr
Rr
What if Both Parents are
Roan?
R
r
R
RR
Rr
r
Rr
rr
What is a Mutation?
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Dramatically different from what is
expected genetically
Horned calf from polled parents
Loss of some or extra body parts
Lethal Mutation: causes death at
birth
Sublethal Mutation: limits animals
ability to grow to maturity
Beneficial Mutation: loss of tail in lambs
What is Heritability?
Chance that traits will be inherited
 Low: multiple births, fat covering
 Medium: birth wt, wean wt, milk,
wool grade, carcass wt, rate of gain
 High: Loin eye area, fleece length &
quality
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Mating Systems
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Upgrading: mating purebreds with grade
animals
Inbreeding: mating closely related
animals
Linebreeding: mating distantly related
animals
Outcrossing: mating unrelated animals in
the same breed.
Crossbreeding: mating animals of same
species but different breeds.
What is Hybrid Vigor?
Heterosis
Offspring will outperform either of
the parents
 Corn Breed A yields 100 bu/acre
 Corn Breed B yields 100 bu/acre
 Crossbreed A & B yields corn that
yields 200 bu/acre
 Vigor only expressed in
crossbreeding
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