chapter 10 test 3 - Handout for CHAPTER 10 Patterns of...

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Handout for CHAPTER 10 - Patterns of Inheritance Definition and basic information about inheritance Characteristics of individuals are passed on to their offspring Key is genes- parental genes are passed on to offspring during reproduction Our focus : diploid organisms that use sexual reproduction (fusion of gametes) -yeast reproduces by budding Genes in a diploid organism Diploid organisms have 2 copies of every chrom., so also 2 copies of every gene -the 2 matching chrom.-homologous chrom. Are the 2 gens copies on each chrom. Identical (same DNA sequence)? Maybe Mutations can cause the sequences to be diff. What is an allele? Basic allele terminology and information Different DNA base sequences for the same gene= alleles -diff. forms of the same gene A gene can have from 1 t o dozens of alleles -normal and sickle cell alleles at hemoglobin gene -“blood type” gene has 3 alleles: A, B, O In a cell, 2 homologous chrom. Have the SAME allele - homozygous ( cell- homozygote) If the 2 homologous chrom have different alleles -heterozygous (cell = heterozygote) 1
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One cell cant ever have more than 2 alleles -cant have A and B and O (blood type) So what is the pattern of inheritance then? Since once cell/organism can have two different alleles at the same gene… Which one is expressed? -only one are expressed , both , neither???not a black and white-a ariety of patterns of expression exist Mendelian genetics Well start with simplest p[pattern Discovered and described by Gregor Mendel Trait characteristics of interest: -is controlled by one gene -That gene has two alleles -One allele is dominant, the other is recessive Definition of dominant and recessive alleles If found together, one allele completely masks (hides the other -dominant allele (expressed) -recessive allele (present but not expressed) Genes are often designated by a letter Dominant allele signified by a capital letter Recessive allele by a small letter (same letter) Mendel’s pea plants (example using flower color) Flower color: gene signified by letter P P (PURPLE) is dominant P (white) is recessive 2
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Genotype versus phenotype (genetics lingo) Genotype= the actual combination of alleles and organism has for a given gene (PP, Pp, pp) Phenotype= how the trait appears in the organism (curly hair, blood type 0, white flowers, etc) Genotype =PP phenotype=purple flowers Genotype=pp phenotype=white flowers Check yourself to make sure you understand the difference between genotype/phenotype If P= purple flowers, p = white flowers What is the genotype of a plant that is heterozygous for this trait?
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