Genetics 2
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Men de l’ s T heo r y (Ch . 8-2 )
People used to think that we are a blend of characteristics. Ex. Tall + Short = Medium IT DOESN’T WORK THAT WAY!!!
During fertilization, the offspring receives one factor (one copy of a gene) for each trait. 1 copy from each parent
We call these factors genes.
Me ndel’s Hyp othese s 1 – For each inherited trait, an individual has two copies of the gene – one from each parent. 2 – There are alternate versions of genes. - these alternate versions are known as alleles. Ex. TT tt Tt
3 – When two different alleles occur together, one may be completely expressed while the other may not even appear. The alleles that are expressed are Dominant (T).
The allele not expressed when the dominant allele is present is called Recessive (t). 4 – Each gamete (sex cell) contributes one allele.
Me ndel’s F in din gs When two alleles of a gene are the same in an individual, they are called homozygous. Ex. A plant with PP is homozygous for flower color.
When two alleles of a gene are different, they are called heterozygous. Ex. A plant with Pp is heterozygous for flower color.
How could you describe this set of alleles? TT Answer Homozygous Dominant How could you describe this set? tt Answer Homozygous Recessive
The set of alleles of an individual is called a genotype. The physical appearance expressed by the alleles is called the phenotype.
Laws of He re dity 1. Law of Segregation Two alleles of a trait segregate (separate) when gametes are formed.
2 – Law of Independent Assortment Alleles of different genes separate independently of one another during gamete formation. Ex. Alleles for plant height don’t affect alleles for flower color.
People used to think that we are a blend of characteristics. Ex. Tall + Short = Medium IT DOESN’T WORK THAT WAY!!!
During fertilization, the offspring receives one factor (one copy of a gene) for each trait. 1 copy from each parent
We call these factors genes.
Me ndel’s Hyp othese s 1 – For each inherited trait, an individual has two copies of the gene – one from each parent. 2 – There are alternate versions of genes. - these alternate versions are known as alleles. Ex. TT tt Tt
3 – When two different alleles occur together, one may be completely expressed while the other may not even appear. The alleles that are expressed are Dominant (T).
The allele not expressed when the dominant allele is present is called Recessive (t). 4 – Each gamete (sex cell) contributes one allele.
Me ndel’s F in din gs When two alleles of a gene are the same in an individual, they are called homozygous. Ex. A plant with PP is homozygous for flower color.
When two alleles of a gene are different, they are called heterozygous. Ex. A plant with Pp is heterozygous for flower color.
How could you describe this set of alleles? TT Answer Homozygous Dominant How could you describe this set? tt Answer Homozygous Recessive
The set of alleles of an individual is called a genotype. The physical appearance expressed by the alleles is called the phenotype.
Laws of He re dity 1. Law of Segregation Two alleles of a trait segregate (separate) when gametes are formed.
2 – Law of Independent Assortment Alleles of different genes separate independently of one another during gamete formation. Ex. Alleles for plant height don’t affect alleles for flower color.
