Tuesday, February 28, 2006

Hey Class!!

Here are the notes in case you missed class today.

What is DNA?
- DNA is the code of life. DNA contains the blueprints for the cell’s proteins. The proteins are then used to carry out critical functions within the cell.

What is the shape of DNA?
- DNA is in the shape of a double helix.

What is DNA made up of?
- DNA is a polymer made up of repeating units called nucleotides. Nucleotides then join together to form long chains of nucleic acids.

The four types of Nitrogen bases found in DNA are: Thymine, Guanine, Cytosine, Adenine. They connect together as: Adenine connects to Thymine. Guanine connects to Cytosine. It would be represented as A-T and G-C.

Traits are the characteristics that are inherited. The passing of traits from parents to offspring is called heredity.

How can traits be passed on?
- Asexually- Results in offspring that are identical to the parent. Individuals are a product of mitosis.
- Sexually- The donation of a gamete (sex cell) by each parent. The resulting zygote will have characteristics of each parent.

Why do we resemble our parents?
- Gregor Mendel was the first person to succeed in predicting how traits would be transmitted from one generation to the next.

How was Mendel able to solve this problem of heredity?
-He used the following rules called “Mendel’s Rule of Unit Factors” :
- Mendel concluded that each organism has 2 factors that control each of its traits. These factors are called GENES.
- Genes exist in an alternate form called alleles.
- Alleles that express the trait are called Dominant. They are expressed with at least one Dominant allele ( TT or Tt ).
- Alleles that do not express the trait are called Recessive. They are expressed with two Recessive allele ( tt ).

Mendel used Pea Plants….. why?
- They reproduce sexually.
- They have 2 distinct sex cells ( gametes ) .
- The gene combination an organism contains is its genotype – Tt
- The way an organisms looks is its phenotype.

-An organism is homozygous for a trait if its two alleles for a trait are the same ( TT or tt).
-An organism is heterozygous for a trait if its two alleles for the trait are different. ( Tt )

Mendel’s laws of separation:
-The alleles separate when gametes are formed. This means that if you have TT and tt, when they combine they will form Tt.

-Sheena will be the new Scribe.