Lab Biology Lab Biology Chapter 9 - GeneticsChapter 9 - Genetics

Mrs. NemanicMrs. Nemanic

I. Mendel’s LegacyI. Mendel’s LegacyGenetics – Genetics – study of hereditystudy of heredity

A. Gregor MendelA. Gregor Mendel

1. Researched heredity – 1. Researched heredity – the passing of the passing of traits from parents to offspringtraits from parents to offspring..

2. Observed 7 characteristics of garden 2. Observed 7 characteristics of garden peas.peas.a. when he planted seeds from purple a. when he planted seeds from purple flowers, he noticed flowers, he noticed most offspring were most offspring were purple but some were whitepurple but some were white..b. seeds from tall plants produced b. seeds from tall plants produced mostly mostly tall but some short.tall but some short.

3. Mendel’s Methods3. Mendel’s Methods

a. pollination – occurs when pollen a. pollination – occurs when pollen grains produced in (anthers) grains produced in (anthers) male male reproductive partsreproductive parts of flower are of flower are transferred to (stigma) transferred to (stigma) female female reproductive parts.reproductive parts.

b. Self-pollination – b. Self-pollination – when flower is when flower is pollinated by same plantpollinated by same plant..

c. Cross-pollination – c. Cross-pollination – when flower when flower is pollinated by a different plantis pollinated by a different plant..

B. Mendel’s ExperimentsB. Mendel’s Experiments

1. Trait – 1. Trait – different forms for a different forms for a characteristic.characteristic.

2. Pure – 2. Pure – always produce offspring with always produce offspring with that traitthat trait..

3. Strain – 3. Strain – denotes plants that are puredenotes plants that are pure

4. P1 Generation – 4. P1 Generation – parental generationparental generation

5. F1 Generation – 5. F1 Generation – first filial generation first filial generation (offspring of P1)(offspring of P1)

6. F2 Generation – 6. F2 Generation – second filial second filial generation (offspring of F1)generation (offspring of F1)

C. C. Mendel’s Results & Mendel’s Results & ConclusionsConclusions

1. Recessive & Dominant Traits1. Recessive & Dominant Traits

a. Dominant – a. Dominant – it “masked” the it “masked” the other ‘factor’ ( gene).other ‘factor’ ( gene).

b. Recessive – b. Recessive – it is not expressed if it is not expressed if with dominant gene.with dominant gene.

Recessive traits did not appear inRecessive traits did not appear in F1F1 but reappeared in but reappeared in F2F2..

2. Law of Segregation – a pair of 2. Law of Segregation – a pair of ‘factors’ ( genes) ‘factors’ ( genes) is segregated, is segregated, or separated, during gamete or separated, during gamete formation.formation.

3. Law of Independent 3. Law of Independent Assortment – ‘factors’ ( genes) Assortment – ‘factors’ ( genes) for different characteristics are for different characteristics are distributed to gametes distributed to gametes independentlyindependently..

D. Chromosomes and GenesD. Chromosomes and Genes

1. Molecular Genetics – 1. Molecular Genetics – study of study of structure & function of structure & function of chromosomes & geneschromosomes & genes

2. Gene – 2. Gene – a segment of DNA that a segment of DNA that controls a traitcontrols a trait

3. Allele – 3. Allele – alternate forms of a gene alternate forms of a gene (Mendel’s factors)(Mendel’s factors)a. capital letters a. capital letters refer to refer to dominant genesdominant genesb. lowercase letters b. lowercase letters refer to refer to recessive genesrecessive genes

II. Genetic CrossesII. Genetic Crosses

A. VocabularyA. Vocabulary

1. Genotype – 1. Genotype – genetic makeup of genetic makeup of an organisman organism

-- consists of consists of alleles the alleles the organism inheritsorganism inherits

2. Phenotype – 2. Phenotype – appearance of an appearance of an organism as a result of its organism as a result of its genotypegenotype

3. Homozygous – 3. Homozygous – when both when both alleles of a pair are alikealleles of a pair are alike

a. a. dominant homozygousdominant homozygous Ex: TT Ex: TT

b. b. recessive homozygousrecessive homozygous Ex: tt Ex: tt

4. Heterozygous – 4. Heterozygous – when 2 alleles when 2 alleles in a pair are different or hybridin a pair are different or hybrid

Ex: Ex: TtTt

B. ProbabilityB. Probability

1. Probability – 1. Probability – the likelihood that a the likelihood that a specific event will occurspecific event will occur..

a. expressed as a a. expressed as a decimal or percentage decimal or percentage or fraction.or fraction.

b. probability =b. probability =# of times an event is expected to happen# of times an event is expected to happen# of opportunities for an event to happen# of opportunities for an event to happen

c. the results predicted by probability c. the results predicted by probability are more likely to occur when there are more likely to occur when there are many trials.are many trials.

C. Predicting Results of C. Predicting Results of Monohybrid CrossesMonohybrid Crosses

1. Monohybrid – a cross between 1. Monohybrid – a cross between individuals involving individuals involving one pair of one pair of contrasting traits.contrasting traits.

2. Punnett Square – a diagram 2. Punnett Square – a diagram used used to predict results of to predict results of crosses.crosses.

Homozygous x Homozygous Homozygous x Homozygous Ex: TT x ttEx: TT x tt

Homozygous x Heterozygous Homozygous x Heterozygous Ex: TT x TtEx: TT x Tt

Heterozygous x Heterozygous Heterozygous x Heterozygous Ex: Tt x TtEx: Tt x Tt

a. Ratios:a. Ratios:

– – Genotypic Ratio – Genotypic Ratio – ratio of ratio of genotypes in offspringgenotypes in offspring

– – Phenotypic Ratio – Phenotypic Ratio – ratio of ratio of phenotypes in offspringphenotypes in offspring

b. Testcross – individual of b. Testcross – individual of unknownunknown genotype is crossed with genotype is crossed with homozygous recessive.homozygous recessive.

C. Dominance:C. Dominance:

Complete Dominance – one allele Complete Dominance – one allele is is completely dominantcompletely dominant over over another. (Heterozygous and another. (Heterozygous and dominant homozygous plants dominant homozygous plants are indistinguishable in are indistinguishable in phenotype)phenotype)

Incomplete Dominance – two or Incomplete Dominance – two or more alleles more alleles influence the influence the phenotypephenotype, resulting in , resulting in intermediate phenotypeintermediate phenotype..

Codominance – both alleles for a Codominance – both alleles for a gene are gene are expressed in expressed in heterozygousheterozygous offspring. Neither offspring. Neither allele is allele is dominant or recessivedominant or recessive; nor ; nor do they blend in the phenotype.do they blend in the phenotype.

D. Predicting Results of D. Predicting Results of Dihybrid CrossesDihybrid Crosses

Dihybrid Cross – cross between Dihybrid Cross – cross between individuals that involves individuals that involves 2 pairs 2 pairs of contrasting traits.of contrasting traits.

a. Homozygous x Homozygousa. Homozygous x HomozygousEx: RRYY x rryy Ex: RRYY x rryy

b. Heterozygous x b. Heterozygous x HeterozygousHeterozygous

Ex: RrYy x RrYyEx: RrYy x RrYyLikely to result in 9 differentLikely to result in 9 different

genotypes & 4 different phenotypesgenotypes & 4 different phenotypes