Download LAB 2 LECTURE The Molecular Basis for Species Diversity DNA

BIO 120
Field Natural History
Spring
LAB 2 LECTURE
The Molecular Basis for Species Diversity
DNA & RNA
I. Introduction.
A. Phenotype is produced by the genotype.
1. The phenotype is the outward expression of the genotype, or the genetic material of an
organism.
B. The central dogma1. DNA⇐ (replication) ⇐ DNA ⇒ (transcription) ⇒ RNA ⇒ (translation) ⇒ Proteins
2. In words, DNA is the material that contains the hereditary information.
a. It is capable of reproducing itself – DNA replication
b. It can supervise the manufacture of RNA – transcription.
c. The reading of the code in the RNA and making the protein is called – translation.
II. The molecules that make up DNA and RNA.
1. DNA and RNA are nucleic acids (organic molecules).
2. The nucleic acids are made up of subunits called nucleotides.
a. Sugar molecule.
b. A phosphate group
c. And a base molecule (which contains nitrogen atoms) Call it a nitrogenous base.
3. Two major differences between DNA and RNA
a. The type of sugar molecule they have.
b. The types of base molecules they have.
4. The sugar group
a. DNA is called deoxyribonucleic acid because it has a Deoxyribose sugar.
b. RNA is called ribonucleic acid because it has a Ribose sugar.
5. The nitrogen bases- the building blocks of the genetic code.
a. The large bases are adenine (A) and guanine (G).
b. The smaller bases are cytosine (C), thymine (T) and uracil (U).
c. Thymine is only found in DNA and uracil is only found in RNA.
6. DNA and RNA differ in one other major way.
a. DNA is actually two very long molecules.
b. RNA is only one long molecule.
7. The two strands of DNA are held together by weak chemical forces.
a. Adenine (A) always pairs with Thymine (T)
b. Guanine (G) always pairs with Cytosine (C)
• A gene is a segment of DNA, or a subset of bases within this long sequence of bases.
III. Making copies of DNA – Replication
1. The two strands unzip and separate from each other, and are then copied.
IV. Proteins
1. There are structural proteins and regulator proteins (enzymes).
a. Other proteins are called hormones; they regulate chemical processes in your body.
2. Proteins are made of amino acids.
a. An individual protein is made by linking amino acids together in a particular order.
BIO 120
Field Natural History
Spring
V. Making proteins from the genetic code (DNA).
A. Making a working copy of DNA is called transcription.
1. Each triple letter sequence of nucleotides is called a codon.
a. When DNA is copied, it starts at a particular spot called a “start codon”.
b. Copying by enzyme proceeds in only one direction until it reaches a “stop codon”.
c. One finished, there is a single strand of RNA.
d. There is no thymine (T) base in RNA molecules. Uracil (U) takes its place.
B. Making proteins from RNA is called translation.
1. Proteins are made in the ribosome.
2. Each sequence of 3 nucleotides (a codon) codes for a specific amino acid.
3. Length of codons read from the RNA determined by a ‘start code’ and a ‘stop code’.
a. For RNA, the start code (initiator) is AUG
b. There are 3 stop codes (terminators); UAA, UAG, UGA.
4. Each three letter codon between the start and stop codes for a different amino acids.
a. The amino acids are linked together in the order coded by the DNA, which is
translated from the RNA.