introductory genetics

Introductory Genetics

RIFAT ALI KHESHGI Student atNWFP AGRICULTURAL UNIVERSITY PESHAWARCell # 03139556067

GeneticsGenetics

Is the science of heredity.Is the science of heredity.

Heredity is the transmission of genetic or Heredity is the transmission of genetic or physical traits from parent to offspring.physical traits from parent to offspring.

Gregor MendelGregor Mendel

Austrian MonkAustrian Monk

Considered the “Father of Heredity”Considered the “Father of Heredity”

He conducted plant breeding experiments He conducted plant breeding experiments in their monastery garden.in their monastery garden.

In 1865 he made his work public, units of In 1865 he made his work public, units of inheritance.inheritance.

What makes us unique?What makes us unique?Each of the 100 Trillion cells in our body Each of the 100 Trillion cells in our body except the red blood cells contains the except the red blood cells contains the entire human genome, in the nucleus of entire human genome, in the nucleus of every cell is the genetic information every cell is the genetic information “blueprint” to construct the individual.“blueprint” to construct the individual.It is the Deoxyribonucleic acid (DNA)It is the Deoxyribonucleic acid (DNA)Function of DNA Function of DNA Genetic code for almost every organism.Genetic code for almost every organism. Provide template for protein synthesis.Provide template for protein synthesis.

Composition of DNAComposition of DNA

The structure of DNA was discovered by The structure of DNA was discovered by Watson and Crick in 1953.Watson and Crick in 1953.

It is a twisted double helix molecule, It is a twisted double helix molecule, containing sugar, phosphates, and containing sugar, phosphates, and nitrogenous bases.nitrogenous bases.

The sugar is deoxyribose and the phosphoric The sugar is deoxyribose and the phosphoric acid molecules are always the same and acid molecules are always the same and provides for the structure (side of the ladder).provides for the structure (side of the ladder).

The only difference between us is the order The only difference between us is the order and arrangement of the four bases (rungs of and arrangement of the four bases (rungs of the ladder).the ladder).

Bases of DNABases of DNA

Adenine= AAdenine= A

Thymine= TThymine= T

Guanine= GGuanine= G

Cytosine= CCytosine= C

A always pairs with TA always pairs with T

C always pairs with GC always pairs with G

Bases of RNABases of RNA

Adenine= AAdenine= A

Uracil= UUracil= U

Guanine= GGuanine= G

Cytosine= CCytosine= C

G always pairs with CG always pairs with C

T from the DNA = A in the RNAT from the DNA = A in the RNA

A from the DNA = U in the RNAA from the DNA = U in the RNA

DNA ModelDNA Model

ChromosomesChromosomes

The DNA in every cell is located in rod like The DNA in every cell is located in rod like segments called chromosomessegments called chromosomes

Chromosomes occurs in pairs in every cell Chromosomes occurs in pairs in every cell of our body except in the sperm and ovum.of our body except in the sperm and ovum.

Chromosomes numbers are the same for Chromosomes numbers are the same for each specie.each specie.

Chromosome NumbersChromosome Numbers

SpecieSpecie Diploid #Diploid # Haploid #Haploid #

CattleCattle 6060 3030

SwineSwine 3838 1919

SheepSheep 5454 2727

HorseHorse 6464 3232

HumanHuman 4646 2323

ChickenChicken 7878 3939

GoatGoat 6060 3030

DonkeyDonkey 6262 3131

ChromosomesChromosomes

There are 2 sex chromosomes included There are 2 sex chromosomes included in the diploid number of the in the diploid number of the chromosomes.chromosomes.

All of the other chromosomes are All of the other chromosomes are referred to as autosomes. referred to as autosomes.

In mammals if the sex chromosomes In mammals if the sex chromosomes are alike, XX it results in a female.are alike, XX it results in a female.

If the sex chromosomes are different, If the sex chromosomes are different, XY it results in a male.XY it results in a male.

Sex DeterminationSex Determination

Female can contribute only a X chromosome Female can contribute only a X chromosome towards the sex of their offspring.towards the sex of their offspring.Male can contribute an X or a Y chromosome Male can contribute an X or a Y chromosome toward the sex of their offspring.toward the sex of their offspring.Absence of an Y chromosome results in a the Absence of an Y chromosome results in a the embryo developing into a female.embryo developing into a female.Presence of an Y chromosome results in the Presence of an Y chromosome results in the embryo developing into a male.embryo developing into a male.

Sex DeterminationSex Determination

Gametogenesis = Gametogenesis = Formation of gametes Formation of gametes through meiosis.through meiosis.

Male = 4 viable Male = 4 viable spermatidsspermatids

Female = 1 viable Female = 1 viable ovum, 3 polar bodies.ovum, 3 polar bodies.

Tell me what I am ?????Tell me what I am ?????

Cell DivisionCell Division

MeiosisMeiosis Is the form of cell division which results reducing Is the form of cell division which results reducing

the chromosome number from the diploid # to the the chromosome number from the diploid # to the haploid #.haploid #.

Occurs only in the sex cells, sperm and ovum.Occurs only in the sex cells, sperm and ovum.

MitosisMitosis Is the form of cell division which results in the Is the form of cell division which results in the

formation of identical daughter cells, keeps the formation of identical daughter cells, keeps the chromosome number constant.chromosome number constant.

Tissue growth and repair.Tissue growth and repair. Occurs throughout the body except in the sex Occurs throughout the body except in the sex

cells. cells.

Genotype or GameteGenotype or Gamete

Genotype contains Genotype contains twotwo copies of the copies of the gene.gene. AaBBAaBB

Gamete (sex cells) contains only one Gamete (sex cells) contains only one copy of the gene.copy of the gene. ABAB

Determine the possible gametes of Determine the possible gametes of AaBBAaBB ABAB aBaB

Gamete or GenotypeGamete or Genotype

State if its a gamete or genotype.State if its a gamete or genotype.

AaAa

DD

DdEeFFggDdEeFFgg

sRtxyqsRtxyq

AaBBeeFFAaBBeeFF

adgEFTadgEFT

List all the possible gametes.List all the possible gametes.

From the genotype From the genotype AaBbAaBb

ABAB

AbAb

aBaB

abab

GenesGenes

Chromosomes contains several units of Chromosomes contains several units of inheritance “genes”.inheritance “genes”.

Genes usually occurs in pairs, one from Genes usually occurs in pairs, one from each parent.each parent.

Some traits are inherited directly from one Some traits are inherited directly from one set of genes. set of genes.

Some traits are inherited through several Some traits are inherited through several sets of genes.sets of genes.

GenesGenes

It was presumed that we were composed It was presumed that we were composed of about 100,000 genes to construct us.of about 100,000 genes to construct us.Today, research has proven that number Today, research has proven that number is a lot less than 100,000.is a lot less than 100,000.Extra credit for the student that can find an Extra credit for the student that can find an article about the current number of genes.article about the current number of genes.

Terms to knowTerms to know

HomoHomozygous- contains 2 identical genes for the zygous- contains 2 identical genes for the same trait, AA, BB, ccsame trait, AA, BB, ccHeterHeterozygous- contains 2 different genes for ozygous- contains 2 different genes for the same trait, Aa, bB, Ccthe same trait, Aa, bB, CcPhenotype- Outward appearance of a trait, Phenotype- Outward appearance of a trait, coat color, polled, horned.coat color, polled, horned.Genotype- Genetic classification of a gene, Genotype- Genetic classification of a gene, AA, Aa, aa.AA, Aa, aa.Allele- Location of a gene on the chromosome.Allele- Location of a gene on the chromosome.F-one = First cross mating.F-one = First cross mating.F-two = Second cross mating.F-two = Second cross mating.

What are dominant genes?What are dominant genes?

The gene that express itself, the powerful The gene that express itself, the powerful and dominant gene.and dominant gene.

It has the power to overshadow the recessive It has the power to overshadow the recessive gene when there is complete dominance.gene when there is complete dominance.

Some examples are:Some examples are: White faced in cattleWhite faced in cattle Droopy ears in swineDroopy ears in swine Polled in cattlePolled in cattle Black coat color in Angus cattleBlack coat color in Angus cattle

What are What are Recessive GenesRecessive Genes??

The gene that is overshadowed by a The gene that is overshadowed by a dominant genedominant geneRecessive genes can only express Recessive genes can only express themselves in the absence of the themselves in the absence of the dominant genedominant genePolled vs Horned (Pp) (pp)Polled vs Horned (Pp) (pp)Black wool vs white (Ww) (ww)Black wool vs white (Ww) (ww)Dwarfism vs normal size (dd)Dwarfism vs normal size (dd)AlbinoAlbino

Punnet SquarePunnet Square

Angus- Black coat color is dominant.Angus- Black coat color is dominant.

BB = Homozygous Dominant and BlackBB = Homozygous Dominant and Black

Bb = Heterozygous and is blackBb = Heterozygous and is black

bb = Homozygous recessive and redbb = Homozygous recessive and red

A heterozygous bull is mated to 50 A heterozygous bull is mated to 50 homozygous recessive cows.homozygous recessive cows.

How many calves are black?How many calves are black?

How many calves are red?How many calves are red?

What is the genotypic and phenotypic ratios?What is the genotypic and phenotypic ratios?


B b

b

b

Bb bb

Bb bb

ResultsResults

2 heterozygous = Bb2 heterozygous = Bb2 Homozygous 2 Homozygous Recessive bbRecessive bb25 Black, 25 Red25 Black, 25 RedGenotypic ratio = Genotypic ratio = 0:2:20:2:2Phenotypic ratio = Phenotypic ratio =

2 Black: 2 Red2 Black: 2 Red

What are What are Sex Linked GenesSex Linked Genes??

Some recessive genes are attached to Some recessive genes are attached to the X and Y chromosomesthe X and Y chromosomes

Humans: Colorblindness and Baldness Humans: Colorblindness and Baldness are on the X chromosomesare on the X chromosomes

In Men, traits expressed anytime presentIn Men, traits expressed anytime present

In Women, must have two recessives to In Women, must have two recessives to show traitshow trait

Children get baldness from mothersChildren get baldness from mothers

If Dad is bald, will you be If Dad is bald, will you be bald?bald?

X Y

X XX X Y

XX XYX

B

B

B

Baldness is carried by the Baldness is carried by the mothermother

X Y

X XX X Y

XX XYX

BB B

What if Mom is bald?What if Mom is bald?

X Y

X XX X Y

XX XYX

BB B

B B B

What is What is Incomplete Incomplete DominanceDominance??

If both genes express themselvesIf both genes express themselves

Shorthorn Cattle: Red male mated to a Shorthorn Cattle: Red male mated to a White female = Roan calfWhite female = Roan calf

RR crossed rr = RrRR crossed rr = Rr


Shorthorn CattleShorthorn Cattle

RR = RedRR = Red

rr = whiterr = white

Rr = roanRr = roan

If a red bull (RR) is mated to a white cow If a red bull (RR) is mated to a white cow (rr), what color will the calves be?(rr), what color will the calves be?

Shorthorn: Red X WhiteShorthorn: Red X White

R R

r

r

Rr Rr

Rr Rr


If a red bull (RR) is mated to a roan (Rr) If a red bull (RR) is mated to a roan (Rr) cow, what color will the calves be?cow, what color will the calves be?

Shorthorn: Red X RoanShorthorn: Red X Roan

R R

R

r

RR RR

Rr Rr

What if Both Parents are Roan?What if Both Parents are Roan?

R r

R

r

RR Rr

Rr rr

What is a What is a MutationMutation??

Dramatically different from what is Dramatically different from what is expected geneticallyexpected genetically

Horned calf from polled parentsHorned calf from polled parents

Loss of some or extra body partsLoss of some or extra body parts

Lethal MutationLethal Mutation: causes death at birth: causes death at birth

Sublethal MutationSublethal Mutation: limits animals : limits animals ability to grow to maturityability to grow to maturity

Beneficial Mutation: loss of tail in lambsBeneficial Mutation: loss of tail in lambs

What is Heritability?What is Heritability?

Chance that traits will be inheritedChance that traits will be inherited

Low: multiple births, fat coveringLow: multiple births, fat covering

Medium: birth wt, wean wt, milk, wool Medium: birth wt, wean wt, milk, wool grade, carcass wt, rate of gaingrade, carcass wt, rate of gain

High: Loin eye area, fleece length & High: Loin eye area, fleece length & qualityquality

Mating SystemsMating SystemsUpgrading: mating purebreds with grade animalsUpgrading: mating purebreds with grade animalsInbreeding: mating closely related animalsInbreeding: mating closely related animalsLinebreeding: mating distantly related animalsLinebreeding: mating distantly related animalsOutcrossing: mating unrelated animals in the Outcrossing: mating unrelated animals in the same breed.same breed.Crossbreeding: mating animals of same species Crossbreeding: mating animals of same species but different breeds.but different breeds.

What is What is Hybrid VigorHybrid Vigor? ? HeterosisHeterosis

Offspring will outperform either of the Offspring will outperform either of the parentsparents

Corn Breed A yields 100 bu/acreCorn Breed A yields 100 bu/acre

Corn Breed B yields 100 bu/acreCorn Breed B yields 100 bu/acre

Crossbreed A & B yields corn that yields Crossbreed A & B yields corn that yields 200 bu/acre200 bu/acre

Vigor only expressed in crossbreedingVigor only expressed in crossbreeding

The EndThe End

You can use your notes to do the next two You can use your notes to do the next two worksheets.worksheets.

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introductory genetics

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