DNA Structure and Function

• Transcription occurs in the nucleus.
• Covalent bonds hold the sugar-phosphate backbone of DNA together.
• A frameshift mutation involves adding or deleting a nucleotide, shifting the reading frame.

DNA Location

• In eukaryotic cells, DNA is located in the nucleus.
• In prokaryotic cells, DNA is located in the cytoplasm, usually in a region called the nucleoid.

DNA Monomer

• The monomer of DNA is a nucleotide.

DNA Elements

• DNA nucleotides contain the elements carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and phosphorus (P).

Sugar in DNA

• The sugar found in DNA nucleotides is deoxyribose.

Four DNA Nucleotides

• The four DNA nucleotides are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

DNA Strands

• DNA is made of two strands of nucleotides.

Bonds in DNA

• Covalent bonds hold the sugar-phosphate backbone of DNA together, providing structural stability.
• Hydrogen bonds hold the two DNA strands together between complementary base pairs, allowing for easy separation during replication.
• Adenine (A) pairs with Thymine (T).
• Cytosine (C) pairs with Guanine (G).

DNA Shape

• DNA has a double helix shape.

DNA Replication

• DNA replication is semi-conservative, meaning one strand of the original DNA molecule is kept in each new DNA molecule.
• Helicase unwinds the DNA during replication.
• DNA polymerase adds complementary nucleotides during replication.
• Ligase seals up the new DNA strands during replication.
• Proofreading is important in DNA replication to ensure accuracy and prevent mutations.

What does a gene code for?

• A gene is a section of DNA that codes for a specific protein.

Protein Synthesis

• The two steps of protein synthesis are transcription (DNA → RNA) and translation (RNA → Protein).
• During transcription, A in DNA is paired with U in RNA (Uracil replaces Thymine in RNA).
• T in DNA is paired with A in RNA.
• C in DNA is paired with G in RNA.
• G in DNA is paired with C in RNA.

DNA vs RNA

• DNA is double-stranded, uses Thymine (T), and has deoxyribose sugar.
• RNA is single-stranded, uses Uracil (U) instead of Thymine (T), and has ribose sugar.

Transcription

• DNA is located in the nucleus, while proteins are made in the cytoplasm and RNA carries the information from the DNA to the cytoplasm.
• During transcription, the DNA template strand is read, and messenger RNA (mRNA) is made.
• Transcription takes place in the nucleus.

Translation

• During translation, mRNA is read, and a polypeptide chain is made.
• Translation takes place in the ribosome, in the cytoplasm.
• A codon is a sequence of three nucleotides on mRNA that codes for an amino acid.
• The start codon is AUG, which codes for the amino acid methionine.
• The stop codons are UAA, UAG, and UGA.
• tRNA carries amino acids and has an anticodon that matches the codon on mRNA.
• The polypeptide folds into its correct 3D shape to become a functional protein.
• Proteins serve as enzymes, structural components, transporters, antibodies, and more.

Mutations

• A mutation is a change in the DNA sequence.
• Point mutations affect one nucleotide.
• Frameshift mutations involve adding or deleting nucleotides, changing the entire sequence.