DNA-RNA: Structure, Function, and Replication Process

DNA-RNA: Chemical Composition

Formed by deoxyribonucleotides made up of phosphate, deoxyribose, and nitrogenous bases (adenine, guanine, cytosine, thymine), and by ribonucleotides made up of phosphate, ribose, and uracil.

Molecular Structure

Double-stranded structure and single.

Types

1. Nuclear DNA found in chromatin, mitochondrial DNA in mitochondria, plastid DNA in chloroplasts.
2. Messenger (mRNA), transfer, ribosomal.

Cell Location

1. Chloroplast, mitochondria, nucleus.
2. Cytoplasm, free or associated with ribosomes.

Function

1. Contains the organism's genetic info.
2. Synthesizes proteins according to genetic info in DNA.

Replication

Molecule of DNA replicates in the nucleus.

1. The double helix of DNA opens and the strands separate.
2. Free nucleotides attach to the separated DNA strands.
3. Attached nucleotides join together.
4. Two identical molecules of DNA are obtained.

Transcription

Molecule of mRNA is synthesized using a fragment of DNA as a template in the cytoplasm.

1. Double helix of DNA opens.
2. Complementary nucleotides are placed in front of the strands.
3. Only one DNA strand is copied.
4. An mRNA strand complementary to the DNA is created.
5. The mRNA molecule exits the cell nucleus.

Translation

Protein is synthesized using info in mRNA in ribosomes.

1. An mRNA molecule is created from the transcription of a DNA fragment.
2. Ribosomes can be free in the cytoplasm or joined to the endoplasmic reticulum.
3. tRNA carries amino acids to the ribosomes.
4. Free amino acids in the cytoplasm.

Process:

1. mRNA exits the nucleus with the copied DNA info.
2. mRNA places itself on top of the ribosomes.
3. tRNA carries amino acids to the ribosomes according to the genetic message in mRNA.
4. Ribosomes translate mRNA into a protein.
5. The finished protein separates from the ribosome.

Central Dogma of Molecular Biology

Modified due to the belief that cannot be questioned, discovery of certain viruses, prions, and ribozymes.