Download MOLECULAR BIOLOGY.rtf

MOLECULAR BIOLOGY
DNA(deoxyribonucleic acid)
• contains genetic info that encodes traits that you receive from
your parents
• in cell it’s packaged into chromatin (protein + DNA)
• groups of chromatin = chromosomes
• genes are groups of DNA that encode protein
• Structure of DNA -- strings of nucleotides (sugar +phosphate +
bases)
--1 sugar = deoxyribose
-- 4 bases = adenine, guanine, cytosine, and thymine
-- has 5’ and 3’ ends
-- double stranded in an antiparallel fashion (5’end of
1 strand bases pairs w/ 3’ end of the other strand)
-- stabilized by covalent bonds between sugar and
phosphate and between bases and sugar
-- also base-base interactions stabilized by hydrogen
bonds
-- adenine always pairs w/ thymine; guanine always w/
cytosine. So # A = # T and # C = # G
Process by which it is copied (during mitosis, for example) =
replication (occurs in nucleus) and is catalyzed by DNA
polymerase
It is semiconservative in that each parent strand separates
from its partner, and pairs up the complementary daughter strand
(remember A-T and G-C and antiparallel)
RNA (ribonucleic acid)
single stranded
has 5’ and 3’ends
contains sugar (ribose), 4 bases (adenine, guanine, cytosine,
uracil—replaces thymine)
made in nucleus by process know as transcription
RNA (ribonucleic acid) continued
Transcription—copies one of the DNA strands from the 3’end,
and makes RNA beginning at its 5’end.
The new RNA is complementary (A=U and G=C) and
antiparallel to the coding strand of DNA
Transcription is catalyzed in the nucleus by RNA polymerase
3 types of RNA
mRNA—Is the template read to make protein
tRNA—brings correct amino acid into position according to
mRNA’s code (3 bases in row from 5’ to 3’; the codon);
tRNA has the anticodon; read from 3’ to 5’ and is
complementary and antiparallel to the codon of mRNA) and
brings the correct amino acid to the correct codon.
For each amino acid, there is a codon (3 letter base code of
mRNA)
Ribosome—catalyzes the translation of RNA into protein by
linking the amino acids together brought by tRNA
Proteins are composed of amino acids; different “language” from
DNA and RNA
Instead of 5’ and 3’ ends, they have amino and carboxyl ends
Mutations
Are changes in the DNA sequence from the correct sequence
Caused by errors by DNA polymerase or by mutagens
nonsense—no protein made
sense—same mutation made
missense—different/altered protein made
DNA Fingerprinting
Used in forensics and paternity tests
Compares DNA fragment patterns (everyone is unique) or
restriction fragment length polymorphisms (RFLP’s)—
generated by cutting DNA w/ enzymes (restriction enzymes)
DNA fragments are analyzed by separating them on an agarose gel
and staining the DNA w/ methylene blue or ethidium
bromide