LEQ: What did Mendel discover about the passing on of traits? 9.1 to 9.3

LEQ: What did Mendel LEQ: What did Mendel discover about the passing discover about the passing on of traits?on of traits?9.1 to 9.39.1 to 9.3

Early MisconceptionsEarly Misconceptions

Lemark – proposed a Lemark – proposed a theory of evolution based theory of evolution based on the idea that acquired on the idea that acquired traits are inheritedtraits are inherited

Lamark thought that Lamark thought that organisms adapted to organisms adapted to changes in their changes in their environment through environment through altered behaviors. The altered behaviors. The behaviors lead to behaviors lead to selective use or disuse of selective use or disuse of given structures causing given structures causing them to increase or them to increase or decrease in size.decrease in size.

Lamark went on to claim Lamark went on to claim that this acquired change that this acquired change was then passed on to was then passed on to the offspring.the offspring.

Early MisconceptionsEarly Misconceptions

Blended Inheritance – Blended Inheritance – the traits of parents the traits of parents blend in the offspringblend in the offspring

Gregor MendelGregor Mendel

Father of Genetics – Father of Genetics – deduced the deduced the fundamental principles fundamental principles of inheritanceof inheritance

Published in 1866 – not Published in 1866 – not recognized as important recognized as important until long after his until long after his deathdeath

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Pea Plant ExperimentsPea Plant Experiments

Mendel used pea plants Mendel used pea plants for his heredity for his heredity experiments because…experiments because… Controlled breedingControlled breeding CheapCheap Easy to grow and Easy to grow and

maintainmaintain Grow many in a small Grow many in a small

spacespace Quick generation timeQuick generation time 7 contrasting traits7 contrasting traits

Fertilization in Pea Fertilization in Pea PlantsPlants

Self-fertilizationSelf-fertilization Pollen of one plant Pollen of one plant

fertilizes the egg of the fertilizes the egg of the same plantsame plant

Cross-fertilizationCross-fertilization Pollen of one plant Pollen of one plant

fertilizes the egg of a fertilizes the egg of a second plantsecond plant

True-breeding vs. True-breeding vs. HybridHybrid

True-breeding True-breeding Organisms that when Organisms that when

self-pollinated (or self-pollinated (or crossed with one of the crossed with one of the same) produce an same) produce an organism identical to organism identical to selfself

HybridHybrid Offspring produced Offspring produced

from crossing 2 from crossing 2 dissimilar organismsdissimilar organisms

GenerationsGenerations

P – Parent Generation; P – Parent Generation; the original crossthe original cross

F1 – First Filial F1 – First Filial Generation; Offspring of Generation; Offspring of the parent crossthe parent cross

F2 – Second Filial F2 – Second Filial Generation; Offspring of Generation; Offspring of the F1 generation the F1 generation

Seven Characteristics Seven Characteristics

Monohybrid CrossesMonohybrid Crosses

Genetic cross of Genetic cross of individuals differing in one individuals differing in one traittrait

Trait – a characteristic Trait – a characteristic that is inherited from that is inherited from parent to offspring; parent to offspring; controlled by a genecontrolled by a gene Examples: flower color, Examples: flower color,

plant height, etc…plant height, etc…

Punnett Square – diagram Punnett Square – diagram used to predict the used to predict the possible outcome of a possible outcome of a given crossgiven cross

Vocab…Vocab… Allele – Allele –

different forms of a genedifferent forms of a gene Example: flower color could be white or purple; Example: flower color could be white or purple;

plant height could be tall or shortplant height could be tall or short

Homozygous Homozygous HeterozygousHeterozygous alleles are the samealleles are the same alleles are differentalleles are different

DominantDominant Allele that is expressed when it is present; Allele that is expressed when it is present;

represented using capitol lettersrepresented using capitol letters

RecessiveRecessive Allele that is only expressed in the absence of the Allele that is only expressed in the absence of the

dominant allele; represented using lower case of dominant allele; represented using lower case of dominant letterdominant letter

PhenotypePhenotype GenotypeGenotype Physical appearance Physical appearance Genetic Make-up Genetic Make-up

(the letters)(the letters)

Mendel’s ExperimentMendel’s Experiment

Mendel’s Law of Mendel’s Law of SegregationSegregation

A sperm or egg carries only 1 allele for each A sperm or egg carries only 1 allele for each inherited trait because allele pairs separate inherited trait because allele pairs separate from each other during the production of from each other during the production of gametesgametes

When does segregation occur?When does segregation occur? Anaphase I of meiosis when homologous Anaphase I of meiosis when homologous

chromosomes are separated.chromosomes are separated.

LEQ: How are Punnett Squares LEQ: How are Punnett Squares used to predict the outcomes of used to predict the outcomes of

a cross?a cross? 4 boxes4 boxes

Define parentsDefine parents Aa X AaAa X Aa

Define allelesDefine alleles A = normal pigmentA = normal pigment a = albinoa = albino

Possible alleles from one parent across the Possible alleles from one parent across the toptop A or aA or a

Possible alleles from 2Possible alleles from 2ndnd parent along the parent along the sideside A or aA or a

Fill in boxes bring letters down and acrossFill in boxes bring letters down and across

Give genotype and phenotype ratiosGive genotype and phenotype ratios 1 AA: 2Aa: 1aa1 AA: 2Aa: 1aa 3 normal: 1 albino3 normal: 1 albino