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