Presentation on theme: "Opener: Get out a clean piece of paper and Title it: #47 Mendel Notes"— Presentation transcript:
1 Opener: Get out a clean piece of paper and Title it: #47 Mendel Notes HAND COPY AND RETURN!!!Opener: Get out a clean piece of paper and Title it: #47 Mendel NotesFind your 3:00 BuddyUsing your textbook answer the following:What did Gregor Mendel do?
2 Prime Time Answers…Gregor Mendel experimented with pea plants to determine how parents pass traits to their offspring.
3 I. Mendel’s Experiments Crossing Pea PlantsMendel decided to cross purebred pea plant with contrasting traitsa. ex: crossing tall plants with short plantsb. Purebred – an organism which is homozygous for a trait
4 II. Dominant and Recessive Alleles A. Mendel determined that each trait exists in pairs (one coming from each parent).B. Genes and AllelesGene – factors that control a traitAlleles – the different forms of a geneex: The gene that controls stem height in pea plants has two different alleles; one for tall plants and one for short plants
5 An organism’s traits are controlled by the alleles it inherits from its parents. Some alleles are dominant and some are recessive.Dominant Allele – the allele whose trait always shows up in the organism when the allele is presentRecessive Allele – the allele that is hidden whenever the dominant allele is present
8 III. Mendel’s ResultsA. FertilizationFirst CrossThe two purebred “parents” were crossed and all of the offspring were tall.Second CrossThe offspring of the first cross were crossed with each other and Mendel noticed that about ¾ were tall and ¼ were short.
9 Alleles in Mendel’s Crosses Homozygous tall plants had two alleles for tall stems.Homozygous short plants had two alleles for short stems.A hybrid organism is one that is heterozygous for a trait.
10 Ex: ‘t’ – represents the allele for short plants Symbols for AllelesA dominant allele is represented by a capital letter.Ex: ‘T’ – represents the allele for tall plantsA recessive allele is represented by a lowercase letter.Ex: ‘t’ – represents the allele for short plantsPossible allele combinations are written as follows:TT = Homozygous Tall PlantTt = Heterozygous Tall Planttt = Homozygous Short Plant
11 Significance of Mendel’s Contribution Before Mendel, traits were thought to be a blend of the parents.Mendel’s experiments showed that traits don’t always blend.
12 Friday’s Quiz: Vocab: A Pea Plant Test Cross AlleleGeneGeneticsFertilizationTraitA Pea Plant Test CrossEssay question about why recessive traits cannot be hybrids.HybridPurebredHeredityRecessive AlleleDominant Allele