DNA Test Study Guide PDF

Study Guide DNA (deoxyribonucleic acid) Is a nucleic acid They consist of long chains of polymers that are made up of nucleotides DNA Nucleotides have 4 different nitrogenous bases ○ Adenine (A) → Purines or Double-ringed structure ○ Guanine (G) → Purines or Double-ringed st...

Study Guide DNA (deoxyribonucleic acid) Is a nucleic acid They consist of long chains of polymers that are made up of nucleotides DNA Nucleotides have 4 different nitrogenous bases ○ Adenine (A) → Purines or Double-ringed structure ○ Guanine (G) → Purines or Double-ringed structure ○ Cytosine (C) → Pyrimidines or Single-ringed structure ○ Thymine (T) → Pyrimidines or Single-ringed structure Each DNA nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base ○ Deoxyribose → a sugar with one less oxygen atom ○ Nucleotides are linked by phosphodiester bonded to form polynucleotides Double-stranded helix which are two strands held together by hydrogen bonds RNA Also a nucleic acid RNA Nucleotides have 4 different nitrogenous bases ○ Adenine (A) → Purines or Double-ringed structure ○ Guanine (G) → Purines or Double-ringed structure ○ Cytosine (C) → Pyrimidines or Single-ringed structure ○ Uracil (U) → Pyrimidines or Single-Ringed Structure Has ribose sugar instead of deoxyribose sugar Are single-stranded helix DNA’s Nucleotide RNA’s Nucleotide DNA Replication DNA’s primary function is to store genetic information ○ Helpful during replication Each strand separates and serves as a template New strands are formed through complementary pairing ○ A - T (Double bonds) ○ A - U (Double bonds) ○ C - G (Triple bonds) Known as the semiconservative model b/c half stays the same and other half changes Essential enzymes involved Topoisomerase: Untangles and relaxes the DNA ahead of where it’s being unzipped to prevent twisting. Helicase: Unzips the DNA by breaking the bonds between the two strands. Primase: Adds a short piece of RNA (called a primer) to show where DNA copying should start. Single-Strand Binding Proteins (SSBs): Keep the DNA strands apart so they don’t stick back together. DNA Polymerase III: The main enzyme that builds the new DNA strand by adding matching bases. Also fixes mistakes as it goes. DNA Polymerase I: Removes the RNA primers and fills in those gaps with DNA. Ligase: Glues the pieces of DNA together to make one continuous strand. Leading strand Runs in a 5 prime to 3 prime direction ○ Continuously forming new strand Lagging Strand Runs in a 3 prime to 5 prime direction ○ Can’t continuously form new strands The lagging strand is synthesized discontinuously in short segments called Okazaki fragments Transcription Happens in the nucleus (in eukaryotes). DNA is used as a template to make mRNA (messenger RNA). The base pair rule changes: A pairs with U (RNA has uracil instead of thymine). mRNA carries the genetic code from the DNA to the ribosome. Translation Happens in the ribosome (cytoplasm). Codons: Groups of 3 mRNA bases code for 1 amino acid. ○ There are 64 codons and 20 amino acids Amino acids are linked together to form a protein chain (polypeptide). *Methione is the universal start-codon*  Key Points to Remember DNA → mRNA (transcription) → Protein (translation) mRNA acts like a “message” between the DNA and the ribosome. Proteins are made of amino acids. Translation tRNA (translation RNA) ○ Nucleic acid that decodes mRNA sequence into protein ○ It "reads" the mRNA sequence using its anticodon, which matches a codon on the mRNA. ○ Each tRNA carries a specific amino acid based on its anticodon. ○ It requires ATP and a special enzyme to attach the amino acid to the tRNA Ribosome ○ The ribosome’s small subunit attaches to the mRNA ○ The ribosome moves along the mRNA like a scanner, reading the sequence of bases in groups of three ○ The large subunit holds the tRNA in the A and P site The P site holds the initiator tRNA and the growing polypeptide  The A site holds the tRNA that carries the next amino acid in the polypeptide chain ○ Connects the amino acids with peptide bonds → forms a polypeptide chain ○ The ribosome stops when it reaches a stop codon on the mRNA. The completed protein is released to do its job in the cell Requires energy known as GTP