Chapter 8: Nucleic Acids
and Protein Synthesis
Developed by Nancy Manikas (6-18-97)
DNA - the cell's "code" or "program"
I. The Genetic Code
History:
A. Frederick Griffith (1928)
transformation -
B. Oswald Avery (1944)
DNA -
C. Alfred Hershey & Martha Chase (1952)
bacteriophages
radioactive tracers
II. The Structure of DNA
DNA is a polymer of ___________________.
A nucleotide
is a molecule made up of:
-a)
--b)
--c)
-
- cytosine
Discovering the structure of DNA:
1.
Rosalind Franklin and Maurice Wilkins (1950's)
2. Erwin Chargaff
3. James Watson (age 25) and Francis Crick
published 1953
Nobel prize 1962
III. The Replication
of DNA
Click here for
informaiton on DNA replication - history of research
leading to today's theory
- before a cell divides, it must ________________ its DNA. This is called replication.
- enzymes _____________ the two strands of the double helix, ______________ appropriate bases, and produce the sugar phosphate linked "backbone."
- enzymes ________________ the strands to be sure
they are inserted properly.
Comparison of Largest Known DNA Sequence with
Approximate Chromosome and Genome Sizes of Model Organisms and Humans. A major
focus of the Human Genome Project is the development of sequencing schemes
that are faster and more economical.
|
Comparative Sequence |
Sizes (Number of Bases) |
| Yeast chromosome (3) | 350 Thousand |
| Escherichia coli (bacterium) genome | 4.6 Million |
| Largest yeast chromosome now mapped | 5.8 Million |
| Entire yeast genome | 15 Million |
| Smallest human chromosome (Y) | 50 Million |
| Largest human chromosome (1) | 250 Million |
| Entire human genome | 3 Billion |
IV. RNA
DNA codes genetic info by the sequence or pattern of its nucleotides. To decode the message, part of the sequence is copied into RNA (ribonucleic acid).
RNA acts as a _______________ between DNA and ____________ and carries out the process of protein synthesis.A. The Structure of RNA
RNA is a long chain of nucleotides just like DNA, except:
a)
b)
c)
B. Transcription (RNA Synthesis)
- the process by which a molecule of DNA is copied into a complementary strand of RNA.
- there are three types of RNA:
1. messenger RNA (mRNA)
2. transfer RNA (tRNA) - see protein synthesis below.
3. ribosomal RNA (rRNA) - see protein synthesis below.
- RNA polymerase
C. Protein Synthesis
1. Coding
- proteins are made of long chains of ____________________ called polypeptides.
- there are __________ different amino acids
- to code for one amino acid, it takes ________ nucleotides
- each set of 3 nucleotides on the mRNA is called a ____________. Each codon specifies one amino acid to be put in the polypeptide chain.
- some amino acids have more than one different _________ which codes for them.
- AUG can code for the amino acid methionine or serve as an __________ codon (tells where to start making the protein).
- there are _______ different stop codons which tell the _____________ where the end of the protein is (termination code).
2. Translation - decoding of mRNA into a protein.Transfer RNA (tRNA) - carries amino acids to the _________________
- ______________ strand, loops back on itself.
- different ____________ for each amino acid
- tRNA is held in shape by _______________. Folds around until only 3 nucleotides are exposed. These 3 match with 3 on the mRNA and are called the _________________.
- process:
Ribosome - organelle made of 2 subunits consisting of _______________ and proteins.
- process:
Click here for an overview of transcription and translation.
Link to Chapter Index
