GENETICS LESSON 2 MENDELS LAWS OF HEREDITY I

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GENETICS LESSON 2: MENDEL’S LAWS OF HEREDITY

GENETICS LESSON 2: MENDEL’S LAWS OF HEREDITY

“I Can” Statements • I can explain the difference between heterozygous and homozygous. •

“I Can” Statements • I can explain the difference between heterozygous and homozygous. • I can explain the difference between dominant and recessive. • I can explain the law of dominance. • I can explain the difference between purebred and hybrid. • I can explain the difference between genotype and phenotype.

A dominant allele is one whose trait always shows up in the organism when

A dominant allele is one whose trait always shows up in the organism when the allele is present. It blocks another genetic factor. Ex. Dimples A recessive allele is blocked, or covered up, whenever the dominant allele is present. Ex. No dimples

Dominant and recessive traits are represented by using letters. • Dominant traits are represented

Dominant and recessive traits are represented by using letters. • Dominant traits are represented by capital letters. • Recessive traits are represented by lower case letters. The law of dominance states that the dominant allele will ALWAYS be expressed WHEN PRESENT. Example: P = purple flower p = white flower PP = purple flower / purebred Pp = purple flower / hybrid pp = white flower / purebred

Purebred (True-bred)—An organism that always produces offspring with the same form of a trait

Purebred (True-bred)—An organism that always produces offspring with the same form of a trait as the parent. Also known as homozygous. “same” In Mendel’s experiments, P stood for the parent generation, F 1 stood for the first generation, and F 2 stood for the second generation.

Hybrid—An organism that has two different alleles for a trait. ALSO known as heterozygous.

Hybrid—An organism that has two different alleles for a trait. ALSO known as heterozygous.

Homozygous—an organism that has 2 identical alleles for a trait Example– PP – homozygous

Homozygous—an organism that has 2 identical alleles for a trait Example– PP – homozygous for purple flower pp– homozygous for white flower Heterozygous—an organism that has two different alleles for a trait Example – Pp – heterozygous for purple flower ***there cannot be a hetero white***

Phenotype—physical make-up of an organism ***you can actually see phenotype*** Ex. -- purple or

Phenotype—physical make-up of an organism ***you can actually see phenotype*** Ex. -- purple or white. Genotype—genetic make-up of an organism ***you cannot see genotype*** Ex. -- PP, Pp, pp