Chapter 11: Introduction to Genetics

11-1 Key Words GeneticsGenetics FertilizationFertilization True-breedingTrue-breeding TraitTrait HybridHybrid GeneGene AlleleAllele SegregationSegregation GameteGamete

11-1 The Work of Gregor Mendel

Intro Every living thing- plant or animal, microbe or human- has a set of characteristics inherited from its parents. 11-1

Definition Genetics: the scientific study of heredity.Genetics: the scientific study of heredity. 11-1

Gregor Mendel, an Austrian monk (mid 1800’s) His basic principles of heredity are still accepted today. 11-1

Mendel’s experiments: 20,000 pea plants Used statistics Detailed notes 11-1

Mendel’s experiments: Why peas? Flower structure

–Mendel knew –the male part of each flower produces pollen –the female part of the flower produces egg cells. 11-1

Mendel’s experiments: Why peas? Flower structure Presence of distinctive traits Fast reproduction 11-1

Genes and Dominance A trait is a specific characteristic that varies from one individual to another. 11-1

Mendel’s work not recognized for 30 years (after his death). That’s just wrong! 11-1

Gregor Mendel’s Peas Mendel had true-breeding pea plants: that, produce offspring identical to themselves. He cut away the pollen-bearing male parts and dusted the plant’s flower with pollen from another plant. These were the “P” generation.These were the “P” generation. 11-1

Gregor Mendel’s Peas Cross Pollination two different parents 11-1

Pure lines Seed produced 11-1

Mendel’s experiments: What did he do?What did he do? Seed was produced. This seed was grown and called the first filial or “F1” generation.Seed was produced. This seed was grown and called the first filial or “F1” generation. 11-1

F1generation hybrids

Mendel’s F 1 Crosses on Pea Plants

Remember what a diploid organism is? 1 “allele” from each parent Hybrid Yy 11-1

Mendel's first conclusion: biological inheritance is determined by factors that are passed from one generation to the next. genes

Is that shortness trait lost forever? No baby, its only hidden.

The principle of dominance: that some alleles are dominant and others are recessive.The principle of dominance: that some alleles are dominant and others are recessive. An organism with a dominant allele: always exhibit that form of the trait.An organism with a dominant allele: always exhibit that form of the trait. An organism with the recessive allele: will exhibit that form only when the dominant allele for that trait is not present.An organism with the recessive allele: will exhibit that form only when the dominant allele for that trait is not present.

What happens during segregation? Segregation Mendel crossed the F1 generation with itself The traits controlled by recessive alleles reappeared in one fourth of the F2 plants. 11-1

Mendel's F 2 Generation P Generation F 1 Generation Tall Short F 2 Generation Segregation 11-1

The reappearance of the trait controlled by the recessive allele: the allele for shortness had been separated, or segregated, from the allele for tallness. segregated from each other during the formation of the sex cells, or gametes.

When each F 1 plant flowers and produces gametes, the two alleles segregate Each F 1 plant produces two types of gametes—allele for tallness, and the allele for shortness.

Alleles separate during gamete formation.

11-1 –Gametes are also known as genes. sex cells. alleles. hybrids.

11-1 –The offspring of crosses between parents with different traits are called alleles. hybrids. gametes. dominant.

11-1 In Mendel’s pea experiments, the male gametes are the eggs. seeds. pollen. sperm.

11-1 In a cross of a true-breeding tall pea plant with a true-breeding short pea plant, the F 1 generation consists of all short plants. all tall plants. half tall plants and half short plants. all plants of intermediate height.

11-1 If a particular form of a trait is always present when the allele controlling it is present, then the allele must be mixed. recessive. hybrid. dominant.

Law of dominance When an organism is hybrid for a pair of contrasting traits, only the dominant trait can be seen in the hybrid. 25-1

T+T=Tall T+t=Tall t+t=short

P F1 × × F2 Parental First filial Second filial Mendel’sCrosses (Review) 75% yellow, 25% green

P F1 × × F2 Parental First filial Second filial Mendel’sCrosses 3:1 Ratio

The Law of Segregation Factors that occur in pairs separate from each other during gamete formation and recombine at fertilization.Factors that occur in pairs separate from each other during gamete formation and recombine at fertilization. 25-1

If blending hypothesis were true, what would Mendel have seen in F1 generation? 25-1