Patterns of Inheritance How are MOST traits inherited
- Slides: 7
Patterns of Inheritance
How are MOST traits inherited? • Mendel’s studies of traits can only yield two possible alleles. • Short/tall, purple flower/white flower, round pea/wrinkled pea. • This is a good way to begin studying genetics. • If you look around at your surroundings you may notice that traits do not follow such a simple pattern.
Incomplete Dominance • Incomplete Dominance: occurs when one allele is only partially dominant. • The flowers w/ the allele pair RR is red, the flowers w/ the allele pair WW are white. • Since both R and W are dominant, but neither is completely dominant, they are written RW. • Only enough color is produced to make the flower a little red, so it looks pink.
Codominance • Codominance: occurs when both alleles for a gene are expressed equally. • In chickens shown, neither white nor black feathers are dominant. • All of the offspring of a black hen and white rooster have both black and white feathers.
Multiple Alleles • Multiple Alleles: three or more possible alleles determine the inherited trait. • An organism can only inherit two alleles for a gene, one from each parent. Even if there are 4, 5, or more possible alleles. • More genotypes can occur w/multiple alleles than w/ just 2 alleles. • Ex: 4 alleles control fur color in some rabbits. • Ex: Eye color in humans
Polygenic Inheritance • Polygenic Inheritance: occurs when more than one gene affects a trait. • The alleles of the different genes work together to produce these traits. • Results in a broad range of phenotypes. • Ex: human height, flowers blooming
Inherited Vs. Acquired Traits • Inherited traits are ones in which you are born with. • Ex: Vocal cords and tongues for speech • Acquired traits are skills you learn or physical changes. • Ex: Learning a language, dying your hair. • Environmental factors an also influence the way genes are expressed. • Ex: Pollutants, tobacco smoke • Changes in body cells cannot be passed on to offspring, only changes in sex cells can be passed on.
