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Genetics: Study of Heredity

Science, Grade 6

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P Generation F1 Generation F2 Generation 1 2 B B B B b b b b B B BB Bb b Bb bb b tall tall tall tall tall seed shape seed color pod shape pod color stem height short (recessive) green smooth yellow green round re ce ss iv e al le le do m in an t al le le wrinkled pinched yellow tall (dominant) chromosome bb BB Bb white rabbit black rabbit black rabbit cell nucleus DNA strand gene nucleolus How many chromosomes? Human 46 Gorilla 48 Crayfish 200 Cat 38 Dog 78 Pea plant 14 Black fur BB Black fur Bb White fur bb Phenotype Genotype Mendel’s Experiments In a typical experiment, Mendel crossed purebred tall-stemmed plants with purebred short-stemmed plants (parental or P generation). The first-generation or F1 generation resulted in all tall-stemmed plants. The subsequent, F2 generation had about 75% tall and 25% short- stemmed plants. Chromosomes and Inheritance The cell nucleus of most organisms contains chromosomes. The number of chromosomes is unique for each species. Each chromosome is made up of thousands of different genes which contain the instructions for an organism’s traits. Phenotypes and Genotypes A phenotype is the physical appearance of a particular organism. The genotype is the genetic make-up of a particular organism. Punnett Square A Punnett Square is a chart that shows all the possible combinations of alleles that result from a genetic cross. A capital letter (B) is used to represent a dominant trait and a lowercase letter (b) the recessive trait. Dominant and Recessive Alleles Mendel began to notice that some of the pea plants had similar traits as their parents. He hypothesized that each parent passes to the offspring a factor or a set of genetic “information” which controls a trait. The factors now called genes exist in pairs known as alleles, one inherited from each parent. An allele is a different form of a gene. A dominant allele is one whose trait will always show up in its presence. A recessive allele is one whose trait will be masked whenever the dominant allele is present. Gregor Mendel Gregor Mendel (1822-1884) an Austrian monk is known for his pea plant experiments that demonstrated the process of heredity. His discoveries form the foundation of genetics – the study of heredity. www.newpathlearning.com © Copyright NewPath Learning. All Rights Reserved. 94-4603 Genetics: The Study of Heredity tall short short

1 2 B B b b B B b b tall tall tall tall tall bb BB Bb Key Vocabulary Terms • allele • inheritance • chromosome • nucleolus • DNA strand • nucleus • dominant • parent • experiment • phenotype • gene • Punnett Square • generation • purebred • genotype • recessive • heredity • trait Mendel’s Experiments Describe Mendel’s typical experiment below: ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ Chromosomes and Inheritance The cell nucleus of most organisms contains ___________________. The number of chromosomes is unique for each species. Each chromosome is made up of thousands of different ___________________ which contain the instructions for an organism’s traits. Phenotypes and Genotypes What is the difference between a phenotype and genotype? ____________________________________________________ ___________________________________ ___________________________________ Punnett Square What is a Punnett Square? ______________________________ ______________________________________________________ Complete the Punnet Square below: Dominant and Recessive Alleles Describe: trait _____________________________________________________ gene _____________________________________________________ allele _____________________________________________________ dominant _____________________________________________________ recessive _____________________________________________________ Gregor Mendel Who is Gregor Mendel? __________________ __________________ __________________ __________________ www.newpathlearning.com © Copyright NewPath Learning. All Rights Reserved. 94-4603 Genetics: The Study of Heredity tall short short seed shape seed color pod shape pod color stem height short (recessive) green smooth yellow green round re ce ss iv e al le le do m in an t al le le wrinkled pinched yellow tall (dominant) \|xiBAHBDy01750pzY

Genetics: Study of Heredity

Science, Grade 6

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