DNA and RNA Structure and Function

DNA Structure and Function

• DNA (deoxyribonucleic acid) is a double-stranded helix, resembling a twisted ladder.
• The "rungs" of the ladder are composed of complementary base pairs: adenine (A) with thymine (T), and guanine (G) with cytosine (C).
• The sugar-phosphate backbone forms the "sides" of the ladder.
• DNA stores genetic information in the sequence of these base pairs.
• DNA replication is a crucial process where the double helix is unwound and each strand serves as a template for a new complementary strand.
• This ensures accurate transmission of genetic information during cell division.
• DNA's structure allows for storage and transmission of complex genetic information.

RNA Structure and Function

• RNA (ribonucleic acid) is a single-stranded molecule.
• It contains ribose sugar instead of deoxyribose, and uracil (U) replaces thymine.
• Different types of RNA exist, with distinct roles:
  • Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes.
  • Transfer RNA (tRNA): Delivers amino acids to the ribosomes during protein synthesis.
  • Ribosomal RNA (rRNA): Forms part of the ribosome, the site of protein synthesis.

Chromosomes

• Chromosomes are organized structures composed of DNA and proteins.
• They condense during cell division for efficient distribution.
• Each species has a characteristic number of chromosomes.
• Humans have 23 pairs of chromosomes, with one set inherited from each parent.
• Autosomes are the non-sex chromosomes.
• Sex chromosomes determine the sex of an individual (XX for female, XY for male).
• Chromosomes contain many genes, which are segments of DNA that code for specific proteins.
• Genes hold instructions for building and maintaining an organism.
• DNA is packaged into chromatin, then into chromosomes, allowing it to fit within the cell's nucleus.
• Tightly packaged DNA is harder to access by transcriptional machinery.
• The process of packaging and un-packaging of DNA influences gene expression.

DNA, RNA, and Chromosomes Relationship

• DNA contains the genetic code.
• DNA is transcribed into messenger RNA (mRNA).
• The mRNA is translated into proteins in the ribosome, a structure made up of rRNA and protein.
• Chromosomes organize and package DNA in the nucleus.
• Proteins associate with DNA to regulate gene expression (transcription factors).
• RNA plays a crucial intermediary role between DNA and proteins.
• The relationships between DNA, RNA, and chromosomes are critical to cellular function.
• Errors in DNA replication or expression can lead to genetic diseases.