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Intro…GENETICS. MENDEL & MEIOSIS. MENDEL’S LAWS OF HEREDITY. I. WHY MENDEL SUCCEEDED Gregor Mendel – father of genetics 1 st studies of heredity – the passing of characteristics to offspring Genetics – study of heredity The characteristics passed on called traits. - PowerPoint PPT Presentation
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Intro…GENETICSIntro…GENETICS
MENDEL & MEIOSISMENDEL & MEIOSIS
MENDEL’S LAWS OF HEREDITYMENDEL’S LAWS OF HEREDITY
I. WHY MENDEL SUCCEEDEDI. WHY MENDEL SUCCEEDED Gregor Mendel – father of geneticsGregor Mendel – father of genetics 11stst studies of studies of heredityheredity – the passing of – the passing of
characteristics to offspringcharacteristics to offspring GeneticsGenetics – study of heredity – study of heredity The characteristics passed on called The characteristics passed on called
traitstraits
1. MENDEL CHOSE HIS 1. MENDEL CHOSE HIS SUBJECT CAREFULLYSUBJECT CAREFULLY
Used garden peas for a model organismUsed garden peas for a model organism Have male & female Have male & female gametesgametes (sex cells) (sex cells) Male & female same flowerMale & female same flower Know what Know what pollinationpollination & & fertilizationfertilization
meanmean He could control the fertilization processHe could control the fertilization process Not many traits to keep track ofNot many traits to keep track of
2. MENDEL WAS A CAREFUL 2. MENDEL WAS A CAREFUL RESEARCHERRESEARCHER
USED CAREFULLY CONTROLLED USED CAREFULLY CONTROLLED EXPERIMENTSEXPERIMENTS
STUDIED ONE TRAIT AT A TIMESTUDIED ONE TRAIT AT A TIME KEPT DETAILED DATAKEPT DETAILED DATA
II. MENDEL’S MONOHYBRID II. MENDEL’S MONOHYBRID CROSSESCROSSES
MENDEL STUDIED 7 TRAITS CAREFULLYMENDEL STUDIED 7 TRAITS CAREFULLY seed shape/color, flower color/position, pod seed shape/color, flower color/position, pod
color/shape, plant heightcolor/shape, plant height Mendel crossed plants w/ diff. traits to Mendel crossed plants w/ diff. traits to
see what traits the offspring would havesee what traits the offspring would have These offspring are called These offspring are called hybridshybrids – –
offspring of parents w/ different traitsoffspring of parents w/ different traits A A monohybridmonohybrid cross is one that looks at cross is one that looks at
only only oneone trait (let’s look at plant height trait (let’s look at plant height – tall or short)– tall or short)
A. THE 1A. THE 1STST GENERATION GENERATION
Mendel crossed two plants – 1 tall & Mendel crossed two plants – 1 tall & 1 short1 short
These plants are called the parental These plants are called the parental generation (generation (P generationP generation))
The offspring were all called the 1The offspring were all called the 1stst filial generation (filial generation (FF11 generation generation))
All the offspring were tallAll the offspring were tall
B. THE 2B. THE 2NDND GENERATION GENERATION
Next, Mendel crossed two plants Next, Mendel crossed two plants from the from the FF11 generation generation
The offspring from this cross are The offspring from this cross are called the 2called the 2ndnd filial generation ( filial generation (FF22 GENERATIONGENERATION))
Mendel found that ¾ of the offspring Mendel found that ¾ of the offspring were tall & ¼ were short (the short were tall & ¼ were short (the short plants reappeared!!!!!!)plants reappeared!!!!!!)
VOCABULARY:
AlleleGenotypePhenotypeDominantRecessiveTraitHeterozygousHomozygous
Laws:
Independent Assortment
Segregation
TO GO ANY FURTHER, WE TO GO ANY FURTHER, WE MUST UNDERSTAND ALLELES, MUST UNDERSTAND ALLELES, DOMINANCE, & SEGREGATIONDOMINANCE, & SEGREGATION
GenesGenes – a section of DNA that codes for – a section of DNA that codes for one proteinone protein These genes are what control & produce These genes are what control & produce
traitstraits The genes Mendel studied came in two The genes Mendel studied came in two
forms (tall/short - round/wrinkled - forms (tall/short - round/wrinkled - yellow/green…….etc.)yellow/green…….etc.)
Alternate forms of a gene are called Alternate forms of a gene are called allelesalleles
Alleles are represented by a one or two Alleles are represented by a one or two letter symbol (e.g. T for tall, t for short)letter symbol (e.g. T for tall, t for short)
ALLELES CONT’DALLELES CONT’D
THESE 2 ALLELS ARE NOW KNOWN THESE 2 ALLELS ARE NOW KNOWN TO BE FOUND ON COPIES OF TO BE FOUND ON COPIES OF CHROMOSOMES – ONE FROM EACH CHROMOSOMES – ONE FROM EACH PARENTPARENT
THE RULE OF DOMINANCETHE RULE OF DOMINANCE A A dominantdominant trait is the trait that will trait is the trait that will
always be expressed if at least one always be expressed if at least one dominant allele is presentdominant allele is present
The dominant allele is The dominant allele is alwaysalways represented by a capital letterrepresented by a capital letter
A recessive trait will A recessive trait will onlyonly be expressed if be expressed if bothboth alleles are recessive alleles are recessive
Recessive traits are represented by a Recessive traits are represented by a lower case letterlower case letter
DOMINANCE CONT’DDOMINANCE CONT’D
LET’S USE TALL & SHORT PEA LET’S USE TALL & SHORT PEA PLANTS FOR AN EXAMPLEPLANTS FOR AN EXAMPLE
WHICH OF THESE WILL SHOW THE WHICH OF THESE WILL SHOW THE DOMINANT & RECESSIVE TRAIT?DOMINANT & RECESSIVE TRAIT?
TT Tt TT Tt tttt
DOMINANT TRAIT RECESSIVE TRAITDOMINANT TRAIT RECESSIVE TRAIT
THE LAW OF SEGREGATIONTHE LAW OF SEGREGATION
MENDEL ASKED HIMSELF……..”HOW MENDEL ASKED HIMSELF……..”HOW DID THE RECESSIVE SHORT PLANTS DID THE RECESSIVE SHORT PLANTS REAPPEAR IN THE F2 GENERATION?”REAPPEAR IN THE F2 GENERATION?”
HE CONCLUDED THAT EACH TALL HE CONCLUDED THAT EACH TALL PLANT FROM THE F1 GENERATION PLANT FROM THE F1 GENERATION CARRIED TWO ALLELES, 1 DOMINANT CARRIED TWO ALLELES, 1 DOMINANT TALL ALLELE & ONE RECESSIVE TALL ALLELE & ONE RECESSIVE SHORT ALLELESHORT ALLELE
SO ALL WERE TtSO ALL WERE Tt
SEGREGATION CONT’DSEGREGATION CONT’D HE ALSO CONCLUDED THAT ONLY HE ALSO CONCLUDED THAT ONLY
ONE ALLELE FROM EACH PARENT ONE ALLELE FROM EACH PARENT WENT TO EACH OFFSPRINGWENT TO EACH OFFSPRING
HIS CORRECT HYPOTHESIS WAS HIS CORRECT HYPOTHESIS WAS THAT SOMEHOW DURING THAT SOMEHOW DURING FERTILIZATION, THE ALLELES FERTILIZATION, THE ALLELES SEPARATED (SEGREGATED) & SEPARATED (SEGREGATED) & COMBINED WITH ANOTHER ALLELE COMBINED WITH ANOTHER ALLELE FROM THE OTHER PARENTFROM THE OTHER PARENT
The law of segregation states that The law of segregation states that during gamete formation, the alleles during gamete formation, the alleles separate to different gametesseparate to different gametes
F1 GENERATIONF1 GENERATIONFATHERFATHER MOTHERMOTHER
T tT t T tT t
TT TT TT tt tt ttF2 GENERATIONF2 GENERATION
- the law of dominance explained the - the law of dominance explained the heredity of the offspring of the f1 heredity of the offspring of the f1 generationgeneration
- the law of segregation explained the - the law of segregation explained the heredity of the f2 generationheredity of the f2 generation
PUNNETT SQUAREPUNNETT SQUARE
CROSS T T X TtCROSS T T X Tt
CONT’DCONT’D
T T X T tT T X T tTT TT
TT
tt
TT TT TT TT
TT tt TT tt
PHENOTYPES & GENOTYPESPHENOTYPES & GENOTYPES
PHENOTYPEPHENOTYPE – The Physical appearance – – The Physical appearance – how an organism looks – the Traithow an organism looks – the Trait
GENOTYPEGENOTYPE – the Allele combination…Aa – the Allele combination…Aa or AA or aa…….also Ttyy or ttyy or TTYYor AA or aa…….also Ttyy or ttyy or TTYY HOMOZYGOUSHOMOZYGOUS – 2 ALLELES SAME – 2 ALLELES SAME HETEROZYGOUSHETEROZYGOUS – 2 ALLELES DIFFERENT – 2 ALLELES DIFFERENT
Like Homo-Sexual…Like Homo-Sexual… Hetero-SexualHetero-Sexual Same gender couple Same gender couple Different gender Different gender
couplecouple
ANSWER ON YOUR SHEETANSWER ON YOUR SHEET
TRAITS = BLUE SKIN & YELLOW SKINTRAITS = BLUE SKIN & YELLOW SKIN
BBBB – IS THIS HOMOZYGOUS OR – IS THIS HOMOZYGOUS OR HETEROZYGOUS?HETEROZYGOUS?
IS BLUE SKIN OR YELLOW SKIN IS BLUE SKIN OR YELLOW SKIN DOMINANT? DOMINANT?
HOMOZYGOUSHOMOZYGOUS
BLUEBLUE
MENDEL’S DIHYBRID CROSSESMENDEL’S DIHYBRID CROSSES
MONOHYBRID – MENDEL LOOKED AT MONOHYBRID – MENDEL LOOKED AT ONE TRAITONE TRAIT
IN HIS DIHYBRID CROSSES – HE IN HIS DIHYBRID CROSSES – HE LOOKED AT 2 TRAITS LOOKED AT 2 TRAITS
WANTED TO SEE IF TRAITS ARE WANTED TO SEE IF TRAITS ARE INHERITED TOGETHER OR INHERITED TOGETHER OR INDEPENDENTLYINDEPENDENTLY
DIHYBRID CROSSDIHYBRID CROSS
TOOK TWO TRUE BREEDING PLANTS TOOK TWO TRUE BREEDING PLANTS FOR 2 DIFFERENT TRAITS FOR 2 DIFFERENT TRAITS (ROUND/WRINKLED SEEDS ------- (ROUND/WRINKLED SEEDS ------- YELLOW/GREEN SEEDS)YELLOW/GREEN SEEDS)
11STST GENERATION GENERATION WHAT WOULD HAPPEN IF HE CROSSED JUST WHAT WOULD HAPPEN IF HE CROSSED JUST
TRUE BREEDING ROUND W/ TRUE TRUE BREEDING ROUND W/ TRUE BREEDING WRINKLED (ROUND IS BREEDING WRINKLED (ROUND IS DOMINANT)DOMINANT)ALL THE OFFSPRING ARE ALL THE OFFSPRING ARE
ROUNDROUND
DIHYBRID CROSS – 1DIHYBRID CROSS – 1STST GENERATION CONT’DGENERATION CONT’D
SO WHAT DO YOU THINK HAPPENED SO WHAT DO YOU THINK HAPPENED WHEN HE CROSSED TRUE BREEDING WHEN HE CROSSED TRUE BREEDING ROUND/YELLOW SEEDS WITH TRUE ROUND/YELLOW SEEDS WITH TRUE BREEDING WRINKLED/GREEN SEEDSBREEDING WRINKLED/GREEN SEEDS
ALL THE F1 WERE ROUND ALL THE F1 WERE ROUND AND YELLOWAND YELLOW
DIHYBRID CROSS – 2DIHYBRID CROSS – 2NDND GENERATIONGENERATION
TOOK THE F1 PLANTS AND BRED TOOK THE F1 PLANTS AND BRED THEM TOGETHER (PHENOTYPE WAS THEM TOGETHER (PHENOTYPE WAS ROUND/YELLOW X ROUND/YELLOW)ROUND/YELLOW X ROUND/YELLOW)
22NDND GENERATION GENERATION FOUND ROUND/YELLOW - 9FOUND ROUND/YELLOW - 9 FOUND ROUND/GREEN - 3FOUND ROUND/GREEN - 3 FOUND WRINKLED/YELLOW - 3FOUND WRINKLED/YELLOW - 3 FOUND WRINKLED/GREEN - 1FOUND WRINKLED/GREEN - 1 ( 9 : 3 : 3 : 1 RATIO) ( 9 : 3 : 3 : 1 RATIO)
EXPLANATION OF 2EXPLANATION OF 2NDND GENERATIONGENERATION
MENDEL CAME UP W/ 2MENDEL CAME UP W/ 2NDND LAW – THE LAW – THE LAW OF INDEPENDENT ASSORTMENTLAW OF INDEPENDENT ASSORTMENT Genes for different traits (Pea color, and Genes for different traits (Pea color, and
flower color) are inherited independently flower color) are inherited independently of each otherof each other
Just because you have brown hair, Just because you have brown hair, doesn’t mean you will be short!doesn’t mean you will be short!
DIHYBRID CROSSESDIHYBRID CROSSES
A LITTLE DIFFERENTA LITTLE DIFFERENT H h G g X H h G gH h G g X H h G g What are the possible Allele What are the possible Allele
combinations?combinations? USE THE USE THE FOILFOIL METHOD METHOD
First, Outer, Inner, LastFirst, Outer, Inner, Last
H h G g X H h G gH h G g X H h G g
1. HG1. HG
2. Hg2. Hg
3. hG3. hG
4. hg4. hg
FOIL – FIRST, OUTSIDE, INSIDE, LASTFOIL – FIRST, OUTSIDE, INSIDE, LAST
BOTH PARENTS BOTH PARENTS ARE THE SAME ARE THE SAME
NOW LET’S DO A DIHYBRID NOW LET’S DO A DIHYBRID CROSSCROSS
H h G g X H h G gH h G g X H h G gHGHG HgHg hGhG hghg
HGHG
HgHg
hGhG
hghg
HHGGHHGG HHGgHHGg HhGGHhGG HhGgHhGg
HHGgHHGg HHggHHgg HhGgHhGg HhggHhgg
HhGGHhGG HhGgHhGg hhGGhhGG hhGghhGg
HhGgHhGg HhggHhgg hhGghhGg hhgghhgg
WHAT ARE THE PHENOTYPIC WHAT ARE THE PHENOTYPIC RATIO’S?RATIO’S?
H h G g X H h G gH h G g X H h G gHGHG HgHg hGhG hghg
HGHG
HgHg
hGhG
hghg
HHGGHHGG HHGgHHGg HhGGHhGG HhGgHhGg
HHGgHHGg HHggHHgg HhGgHhGg HhggHhgg
HhGGHhGG HhGgHhGg hhGGhhGG hhGghhGg
HhGgHhGg HhggHhgg hhGghhGg hhgghhgg
DD:DD:
Dr:Dr:
rD:rD:
rr:rr:
99
33
33
11
PROBABILITYPROBABILITY Does real life follow Punnett Squares??Does real life follow Punnett Squares?? NO!!!!!! – only shows what will NO!!!!!! – only shows what will
PROBABLY occurPROBABLY occur Like flipping a coin 10 times:Like flipping a coin 10 times:
PROBABILITY says you’ll get heads 50% of PROBABILITY says you’ll get heads 50% of the time.the time.
But you may not … try it.But you may not … try it. Certainly over time, with hundreds and Certainly over time, with hundreds and
hundreds of flips, YES, you’ll end up with hundreds of flips, YES, you’ll end up with 50% heads 50% heads