Download DNA: deoxyribonucleic acid

DNA: deoxyribonucleic acid
DNA is a nucleic acid made of nucleotides.
DNA nucleotides contain deoxyribose (sugar), a phosphate group,
and one of four nitrogen bases.
The four nitrogen bases are adenine (A), thymine (T), cytosine (C),
and guanine (G).
The shape of DNA was determined by Franklin, Watson and Crick
to be a double helix.
The backbone (sides) of DNA is made of alternating sugarphosphate groups. The “rungs” of DNA are made by pairs of
nitrogen bases joined by weak hydrogen bonds.
Adenine always bonds with Thymine. (A=T)
Cytosine always bonds with Guanine. (C=G)
DNA makes an exact copy of itself in a process called DNA
replication.
In DNA replication, one DNA molecule becomes two identical
DNA molecules each with one new strand and one original strand
(this is called semi-conservative replication)
The arrangement of the nitrogen bases is different for all organisms
BUT it carries the same type of information for making proteins.
The information is DNA is used to make proteins.
DNA is found in the nucleus BUT proteins are made by the
ribosomes (which are found in the cytoplasm of the cell.
The information in DNA has to be sent to the ribosomes where
amino acids can be joined to make proteins.
Ribosomes can’t read DNA, so the information in DNA is copied
into messenger RNA (mRNA).
RNA is ribonucleic acid, the other nucleic acid made of
nucleotides.
An RNA nucleotide consists of ribose (sugar), a phosphate group,
and one of four nitrogenous bases.
The four nitrogen bases in RNA are:
Adenine (A)
Guanine (G)
Cytosine (C)
Uracil (U)
In RNA:
Adenine bonds with Uracil (A=U)
Cytosine bonds with Guanine (C=G)
All of the Ts in DNA are copied as “A”s in RNA…There are NO
Ts in RNA.
When the information in DNA is copied into messenger RNA
(mRNA) this is called transcription.
There are three types of RNA:
1. messenger RNA (mRNA): an exact copy of the information
in DNA that travels to ribosomes in the cytoplasm.
2. ribosomal RNA (rRNA): this type of RNA is what ribosomes
are made of
3. transfer RNA (tRNA): RNA that moves amino acids from the
cytoplasm to the ribosome to be joined by peptide bonds and
become proteins.
mRNA carries the message of DNA to the ribosomes
(transcription) and the information in RNA is used to make
proteins (translation)
At the ribosomes, mRNA is divided into codons: a set of 3
nitrogen bases that code for an amino acid
tRNA brings amino acids to the ribosome that match the codon
As a way of checking, each tRNA molecule has an anticodon
attached to it (an anticodon is a set of corresponding nitrogen bases
that are complementary to the codon).