Genetics & Mendel 6.3, 6.4, 6.5 Name: ___________________________ KEY CONCEPT 6.3, 6.4, & 6.5 Mendel’s research showed that traits are inherited as discrete (individual) units. Mendel laid the groundwork for genetics. • _________________ are distinguishing characteristics that are inherited. (eye color, hair color) • __________________ is the study of biological inheritance patterns and variation. • ______________________________ showed that traits are inherited as discrete units. (like different colored marbles mixed together that can still be picked out separately) Mendel crossed (mated) many pea plants and observed these ____________________ . His results led to important conclusions about how traits/genes are inherited (more on that later). Ratios are all about 3:1…What does this mean?! • A _____________ is a piece of DNA that directs a cell to make a certain protein. • Each gene has a ________________, a specific position on a pair of homologous chromosomes. An allele is any ________________________ occurring at a _________________________ Gene = pea shape on a chromosome (gene=pea shape, Allele=smooth or wrinkled allele=smooth or wrinkled) Locus = location – Each parent donates one allele for every gene. -Genotype: The genetic makeup of a specific set of genes -Phenotype: The physical characteristics of an individual – what you actually SEE – _________________________ describes two alleles that are the same at a specific locus. Ex: _________________ – _________________________ describes two alleles that are different at a specific locus. Ex: _________________ -Also called a hybrid o __________________ can be represented using letters. NOTE: Capital letters are used for DOMINANT ALLELES, lowercase letters are used for recessive alleles. Dominant = R Recessive = r – A _____________________ allele is expressed as a phenotype when at least one allele is dominant. – A _____________________ allele is expressed as a phenotype only when two copies are present. – Dominant alleles are represented by ___________________ letters; recessive alleles by _____________________ letters. Mendel used pollen to fertilize selected pea plants. – He crossed the _____________________ generation to produce _______________________________________ generation. He interrupted the self-pollination process in the plants by removing male flower parts. Punnett squares illustrate genetic crosses. • The ________________________________ is a grid system for predicting all possible genotypes resulting from a cross. – – The ________________ represent the possible gametes of each ______________. – The ________________ show the possible genotypes of the _________________. The Punnett square yields the _________________ of possible genotypes and phenotypes • Mendel then allowed the resulting plants to ____________________________________. – Among the F1 generation, all plants had _______________________________ – this is the ______________________________ (describes physical traits, what we can see) – F1 plants are all _____________________________ this is the _____________________________ (describes the internal makeup of the genes, what we cannot see). A monohybrid cross involves one trait. • _________________________________ crosses examine the inheritance of only _______________ specific trait. (let’s do this one as an example). Phenotype (parents): Genotype (parents): • Among the ___________ generation, some plants had _________________________________________________________________________. • Let’s do this cross and see how he got these results. Phenotype: Genotype: • Practice • What words would you use to describe the P generation (parents)? • What would the phenotype and genotype be of the F1 generation? • Both homozygous dominant and heterozygous genotypes yield a _____________________________________________ Ex: _________________________________________ • The only combination that shows the ____________________________________________________ is the genotype Ex: _________________________________ Mendel drew three important conclusions. 1. Traits are inherited as ___________________________________. 2. Organisms ________________________________________________ of each gene, one from each parent. 3. The two copies _________________________________ during gamete formation. – The last two conclusions are called the _________________________________________________.