genetics genetics. genetics is the science of heredity. heredity is the transmission of genetic or...
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GeneticsGenetics
GeneticsGenetics
• Is the science of heredity.• Heredity is the transmission of
genetic or physical traits from parent to offspring.
Gregor MendelGregor 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.
What makes us unique?What makes us unique?• 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
– Genetic code for almost every organism.– Provide template for protein synthesis.
ChromosomesChromosomes
• 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.
Chromosome NumbersChromosome Numbers
Specie Diploid # Haploid #Cattle 60 30Swine 38 19Sheep 54 27Horse 64 32Human 46 23Chicken 78 39Goat 60 30Donkey 62 31
ChromosomesChromosomes• 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.
Sex DeterminationSex Determination
• Female can contribute only a X chromosome towards the sex of their offspring.
• Male 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.
Tell me what I am ?????Tell me what I am ?????
Tell me what I am ?????Tell me what I am ?????
GenesGenes
• 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.
Terms to knowTerms to know• 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?What are dominant genes?
• 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:– White faced in cattle– Droopy ears in swine– Polled in cattle– Black coat color in Angus cattle
What are What are Recessive Recessive GenesGenes??
• 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
Punnet SquarePunnet Square
• 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 SquarePunnet Square
B b
b
b
Bb bb
Bb bb
ResultsResults
• 2 heterozygous = Bb
• 2 Homozygous Recessive bb
• 25 Black, 25 Red• Genotypic ratio
= 0:2:2• Phenotypic ratio
= 2 Black: 2 Red
What are What are Sex Linked Sex Linked GenesGenes??
• 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
What is What is Incomplete Incomplete DominanceDominance??
• If both genes express themselves
• Shorthorn Cattle: Red male mated to a White female = Roan calf
• RR crossed rr = Rr
What is a What is a MutationMutation??• 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
Monohybrid CrossesMonohybrid Crosses• Cross 1 character – Flower Color• Purple Flowers are dominant – P• White Flowers are recessive – p• Cross a Heterozygous with a
homozygous recessive
Genotype Ratio:2 Pp; 2 pp
Phenotype Ratio:2 Purple 2 WhiteProbabilities:
Being Purple: 2 out of 4
Being White: 2 out of 4
Cross:
Pp X ppP p
p
p
P p p p
P p p p
PedigreesPedigrees• A family history that shows how a
trait is inherited over several generations
• Helps to track down the carriers (heterozygotes) of recessive disorders.
Reading PedigreesA shaded box – affected male …………
A shaded circle- affected female……….
A clear box - normal male…………..
A clear circle - normal female………...
Pedigree PracticePedigree Practice
?
I
II
III
IV ?Legend:
Hemophilic Male: ………
Hemophilic Female: …...
Normal Female: ………
Normal Male: ………
CodominanceCodominanceCase in which both forms of the character are
displayed. Ex. The ABO blood groups
Neither IA nor IB are dominant is dominant over the other.
Both are dominant over i (Type O). When both IA and IB are present they are codominant
and the individual is type AB
Blood TypingBlood Typing
iiIBiIAi
IBiIBIBIAIB
IAiIAIBIAIA
IA IB iIA
IB
i
OBABABlood Types