Presentation on theme: "Opener: Get out a clean piece of paper and Title it: #47 Mendel Notes"— Presentation transcript:
1Opener: 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?
2Prime Time Answers…Gregor Mendel experimented with pea plants to determine how parents pass traits to their offspring.
3I. 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
4II. 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
5An 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
8III. 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.
9Alleles 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.
10Ex: ‘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
11Significance 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.
12Friday’s Quiz: Vocab: A Pea Plant Test Cross AlleleGeneGeneticsFertilizationTraitA Pea Plant Test CrossEssay question about why recessive traits cannot be hybrids.HybridPurebredHeredityRecessive AlleleDominant Allele