Introduction to DNA and Genetics

DNA and Chromosomes

• DNA is composed of four nucleotide building blocks: adenine (A), cytosine (C), guanine (G), and thymine (T).
• Nucleotides are linked together into polynucleotide chains forming a sugar-phosphate backbone
• DNA strands are held together by hydrogen bonds between complementary base pairs (A with T, C with G).
• DNA is organized in structures called chromosomes.
• DNA replication is the process by which DNA is copied. The original DNA molecule serves as a template for creating a new double helix.

The Central Dogma of Biology

• The central dogma is a fundamental concept in molecular biology. It describes the flow of genetic information.
• DNA -> RNA -> Protein. The genetic information encoded in DNA is transcribed to RNA, then translated into protein.

Genetics Introduction

• DNA encodes information in a unique sequence of nucleotides in a double helix.
• DNA replication involves the use of one strand as a template to generate complementary strand.
• DNA's information is transcribed into RNA.
• RNA translates the coded messages into proteins.

The Structure of DNA

• DNA consists of two polynucleotide chains that are anti-parallel.
• The repeating units of DNA include sugars, phosphates, and nitrogenous bases.
• The double-helix configuration is stabilized by hydrogen bonds between the bases.

DNA Replication

• DNA replication uses the existing DNA strand as a template to create a new complementary strand.
• DNA polymerase is the key enzyme responsible for DNA replication. It adds nucleotides to the growing strand.
• RNA primers are needed as starting points for DNA replication on the lagging strand.
• Okazaki fragments are formed on the lagging strand since replication is discontinuous.
• DNA ligase joins these fragments to a single continuous strand.

DNA Synthesis Begins at Replication Origins

• DNA replication begins at specific sites called replication origins.
• Helicase unwinds the DNA double helix.
• Replication forks are the sites where the DNA unwinds to create single strands.
• Single-stranded DNA binding proteins stabilize the DNA strands preventing them from re-annealing.
• Initiator proteins are responsible for opening the replication forks.
• DNA polymerase replicates the DNA strands.

DNA Synthesis Enzymes

• Helicase unwinds the DNA double helix separating the two strands.
• DNA polymerase III adds nucleotides to the growing strands.
• Ligase joins the DNA fragments together, especially the okazaki fragments.

A summary of DNA Replication

• Helicases unwind the DNA double helix.
• Single-strand binding proteins stabilize the DNA strands.
• Primase synthesizes RNA primers on the lagging strand to start DNA synthesis.
• DNA polymerase synthesizes new DNA strands based on the template strand.
• Okazaki fragments are formed on the lagging strand, and DNA ligase joins these fragments to form a continuous strand.

Transcription

• RNA polymerase is the enzyme responsible for copying DNA into RNA.
• Transcription produces a complementary RNA strand from a DNA template strand.
• The non-template strand, sometimes called the coding strand, has a sequence equivalent to the RNA produced.

Translation

• The genetic code is the set of rules for translating RNA sequence into an amino acid sequence for protein production.
• In this process codons ( mRNA sequences of three nucleotides) are translated into specific amino acids.

Eukaryotes handle their RNA transcripts differently

• Eukaryotic RNA transcripts undergo processing.
• mRNA transcripts undergo splicing to remove introns, cap addition and tail addition before translation in the cytoplasm.

Code, Codon, and anti codon

• A codon is a sequence of three nucleotides in mRNA that codes for a particular amino acid.
• An anticodon is a sequence of three nucleotides in tRNA that is complementary to a codon.
• tRNA carries the corresponding amino acid to the ribosome to build the polypeptide chain of the protein.

This quiz covers the basics of DNA structure, chromosomes, and the central dogma of molecular biology. Understand how genetic information flows from DNA to RNA to proteins, and learn about the importance of DNA replication. Test your knowledge on these fundamental concepts in genetics.