DNA and RNA Structure

Structure of DNA

• DNA (Deoxyribonucleic Acid) is a double-stranded molecule containing genetic information.
• It consists of a sugar-phosphate backbone made of deoxyribose and phosphate groups.
• Contains four nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).
• Two DNA strands run antiparallel, forming a double helix.
• Complementary bases are connected by hydrogen bonds: A-T (2 bonds), G-C (3 bonds).

Structure of RNA

• RNA (Ribonucleic Acid) is usually a single-stranded molecule, unlike DNA.
• RNA contains ribose instead of deoxyribose.
• RNA uses Uracil (U) instead of Thymine (T), pairing A-U and G-C.
• Three main types of RNA: mRNA, tRNA, rRNA.

Importance of Hydrogen Bonds

• Hydrogen bonds are weak, allowing strand separation during replication and transcription.
• G-C base pairs have 3 hydrogen bonds and are stronger than A-T pairs, which have 2.

Base Pairing in DNA Replication

• Ensures accuracy, with complementary bases pairing consistently.
• DNA replication is semi-conservative, producing new DNA molecules with one old and one new strand.

DNA Replication Process

• Initiation starts with the helicase enzyme unwinding the DNA helix.
• Elongation involves DNA polymerase adding nucleotides based on complementary base pairing.
• Termination results in two identical DNA molecules.

Nucleotide and Amino Acid Sequences

• DNA nucleotide sequence determines mRNA codon sequence.
• Each codon (3 bases) corresponds to a specific amino acid.
• Amino acid sequence forms a polypeptide, which folds into a functional protein.

Steps of Protein Synthesis

• Transcription occurs in the nucleus, where DNA is transcribed into mRNA by RNA polymerase.
• The resulting mRNA leaves the nucleus and moves to the ribosome.
• Translation occurs in the ribosome, where mRNA codons are read.
• tRNA brings amino acids based on the codon sequence.
• Peptide bonds form between amino acids, creating a protein.

Molecules in Protein Synthesis

• mRNA (messenger RNA) carries the genetic code from DNA to ribosomes.
• tRNA (transfer RNA) brings the correct amino acids to the ribosome.
• rRNA (ribosomal RNA) forms the ribosome structure, and catalyzes protein synthesis.

DNA Structure, Protein Structure, and Phenotype

• DNA contains genes which code for proteins.
• Proteins are responsible for cell functions and traits (phenotype).
• Mutations in DNA can alter protein function, which can affect an organism’s characteristics.

DNA and Phenotype

• A normal hemoglobin gene (HbA) produces normal hemoglobin protein.
• A mutated hemoglobin gene (HbS) can cause sickle cell anemia, which changes red blood cell shape.

DNA, Chromatin, and Chromosomes

• DNA is packed around histones, forming chromatin.
• During cell division, chromatin condenses into chromosomes.
• Humans have 46 chromosomes (23 pairs).

Chromosome Structure

• The centromere is the central region where sister chromatids join.
• Telomeres are protective ends that prevent degradation.

Types of RNA

• mRNA (Messenger RNA) carries genetic instructions from DNA to ribosome.
• tRNA (Transfer RNA) brings amino acids to ribosome during translation.
• rRNA (Ribosomal RNA) forms the ribosome and facilitates protein synthesis.

Explore the structure of DNA and RNA, including their components and base pairing rules. DNA is a double-stranded molecule and RNA is single-stranded with different bases. Understand the role of hydrogen bonds in maintaining the double helix structure and their impact on replication and transcription.