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Do you look exactly like either one of your parents? What about your siblings? Why is this & how do you explain it???. Summing up Mendel’s Laws. The Key Terms!!. What is Genetics?. Study of heredity from generation to generation AND variation of organisms
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Do you look exactly like either one of your parents? What about your siblings? Why is this & how do you explain it???
Summing up Mendel’s Laws The Key Terms!!
What is Genetics? • Study of heredity from generation to generation AND variation of organisms • Heredity – passing of characteristics: parents → offspring • Traits – characteristics received by offspring (Ex: color, size)
A quick review of cells… Somatic Cells vs. Gametes
A quick review ofreproduction • Sexual reproduction – Sex cells (gametes) from male & female come together Sperm Egg • Fertilization – fusion of gametes;individual traits passed to fertilized cell (zygote)
DNA in sperm & egg cells carry geneson chromosomes • Genes – sections of DNA that code for traits (proteins); come in different forms called alleles • Allele – located on 2 different copies of a chromosome, 1inherited from mother, 1 from father Examples: Plant Height – Tall/Short Plant Color - Purple/White
Law of Dominance • Dominant allele – masks recessive trait • Recessive allele– trait that can be masked Example:Can you roll your tongue? Tongue rollers are dominant. Let’s symbolize the tongue rolling trait using a letter code – let’s use “T.” If dominant is T Then recessive must be t
Genotypes and Phenotypes • Letter codes can be joined together in various combinations…what are they? TT – tongue rollers Tt– tongue rollers tt – non-tongue rollers Genotype: gene combos Phenotype: observable character-isitics
How do we categorize these combinations??? • Homozygous – same 2 alleles → recessive alleles are ALWAYS homozygous TT, tt • Heterozygous – different alleles Tt
Mendel’s Laws • Law of Segregation – • Because each organism has 2 alleles →TWOdifferent types gametes can be produced • During fertilization, gametes randomly pair →produce combinations of alleles
Mendel’s Laws cont… • Law of Independent Assortment • Genes for different traits inherited independently of each other • Genes separate and recombine • This accounts for variation in genotypes/phenotypes!
