1. Define heredity.
2. Describe the role of chromosomes in heredity.
3. Identify dominant and recessive alleles in a gene pair.
HEREDITY is the passing of traits from parent to offspring, by either sexual or asexual reproduction. In asexual reproduction, all of the genetic information is passed directly from parent to offspring, so that all of the offspring are the exact same, or clones, of the parent. In sexual reproduction, only half of each parents genetic information is passed on, so that the offspring end up with a combination of traits from their parents.
A TRAIT is a characteristic. Some traits can be inherited from parents (such as the natural color of your skin, or the shade of your hair). Some traits are a result of your environment, or lifestyle (such as dark skin from too much sun, or dying your hair). Traits that are inherited, which we will focus on in this unit, are passed down to you from your parents. Inherited traits are carried on chromosomes, which is how they travel from parent to child.
A CHROMOSOME is a package of genes that carry your genetic information (or DNA). This genetic information is a complex chemical code that determines the traits you have. You have thousands of traits that make you unique, and all of these traits are packaged into bundles of DNA called chromosomes. Almost every cell in your body contains 46 chromosomes, which is like a data bank that contains all the information your cells need to make YOU! Where did these chromosomes come from? Exactly half of them came from the father and the other half from the mother.
ALLELES are all the different forms of the gene for the same trait. Most traits are determined by a pair of alleles (called a gene)- one from the father and one from the mother. Alleles are written as a pair of letters, either a capitol or lower-case letter.
The strongest form of a trait is called the DOMINANT allele. It is written as a capitol letter. If at least one allele in the pair is dominant, then the stronger form of the trait will be expressed.
The weaker form of a trait is called the RECESSIVE allele. It is written as a lower-case letter. Both of the alleles in the pair must be recessive for the weaker form of the trait to be expressed.
This is the first part of our heredity vocabulary. Fill in the notes as you go along, and bring them with you to science the next day to use in the "Make Your Own Chromosome" activity in class.
Source: Sam Youts