Biology DNA

• The double helix structure is held together by hydrogen bonds between complementary base pairs.
• DNA and RNA are nucleic acids made up of many nucleotides joined together, with a nucleotide consisting of a sugar, phosphate, and nitrogen base
• DNA is double-stranded with bases A, T, C, G, while RNA is single-stranded with bases A, U, C, G
• In DNA, A always pairs with T, C always pairs with G, while in RNA, A pairs with U
• During DNA replication, an enzyme called helicase separates the double strand of DNA into 2 strands by breaking the weak hydrogen bonds between the bases
• DNA replication is 'semi-conservative,' meaning each new copy of DNA contains one old/template DNA strand and one new strand
• Proteins are made of amino acids, and the order of amino acids in a protein is coded for by DNA
• Protein synthesis involves rewriting DNA as RNA (transcription) in the nucleus and then translating the RNA into a protein
• During translation, the mRNA strand attaches to the small subunit of the ribosome, and tRNA molecules match their anticodon to the codon on the mRNA to bring amino acids to be added to the protein chain
• Enzymes are proteins that catalyze chemical reactions, with an active site that fits specific molecules, and they lower the activation energy required for reactions to start
• Factors affecting enzyme activity include temperature, pH, inhibitors, and the concentration of enzymes and substrates
• All organisms start from a single cell (zygote) which divides to produce multiple cells with the same DNA
• Cells differentiate (or specialize) into different cell types due to genes being turned on or off, resulting in different proteins being made
• Different proteins are needed for different jobs; for example, muscle cells don't need the same proteins as eye cells
• Genotype is the genetic code, while phenotype is the observable outcome characteristic that the genotype codes for
• Environmental factors can affect phenotype expression by impacting the proteins that are made
• Factors affecting gene expression:

  • Methylation: methyl groups added to cytosine (C) bases in DNA block RNA Polymerase, leading to no transcription, no protein, and no phenotype/genotype expression; can be permanent or temporary
  • Acetylation: acetyl groups bind to Histone proteins to prevent them from coiling too tightly, affecting gene expression; presence of acetyl groups 'switches on' genes, absence 'switches off' genes
  • Non-coding RNA (ncRNA): transcribed from DNA but not translated into a protein, controls Methylation, Acetylation, and other factors in gene expression
  • Hormones: certain hormones switch genes on by binding to promoter regions on DNA, promoting protein synthesis and gene expression; others switch genes off by blocking RNA Polymerase and preventing transcription
  • Gene products: expression of one gene can affect the expression of other genes, influencing characteristics like secondary male sex characteristics
• Environmental factors can also impact gene expression; for example, lack of oxygen at high altitudes can result in increased expression of the gene coding for blood cell production
• Epigenetics are essential for cell differentiation; however, certain environmental epigenetic factors can have negative effects
• Epigenetic factors in parents' cells are passed to offspring through meiosis; genes that are silenced in an egg/sperm cell are also silenced in the zygote
• Replication begins at specific sites called origins of replication.
• DNA replication occurs through semiconservative replication, where the two strands separate and serve as templates to produce new complementary strands.
• DNA replication begins with the separation of the two DNA strands that are held together by hydrogen bonds between base pairs.
• Each daughter molecule contains one old (parent) strand and one newly synthesized strand.
• DNA replication occurs through semiconservative replication, where the two strands separate and serve as templates for new nucleotides to be added.
• DNA replication is semi-conservative, meaning that each new DNA molecule contains one original strand and one new complementary strand.
• The double helix structure is held together by hydrogen bonds between complementary base pairs.
• DNA replication is the process by which the information stored within an organism's DNA is copied and passed on to new cells during cell division.
• Each new strand is complementary to its parent strand due to base pairing rules.
• The enzyme helicase unwinds the double helix structure of DNA during replication.
• DNA replication occurs through semiconservative replication, where the two strands separate and serve as templates for new nucleotides to be added.
• The enzyme helicase breaks hydrogen bonds between nucleotides, allowing the strands to separate.
• The enzyme helicase breaks the hydrogen bonds between the bases on one side of the double helix, causing it to unwind into two single-stranded molecules.
• Single-stranded binding proteins stabilize single-stranded DNA during replication.
• Each newly formed strand is made up of alternating RNA nucleotides (ribonucleotides) and deoxyribonucleotides (deoxynucleotides).
• During DNA replication, the two strands separate and act as templates for the addition of new nucleotides.
• Single-stranded binding proteins bind to the separated strands, preventing them from reforming double helixes.
• The process of DNA replication involves unwinding the double helix structure of DNA, separating the two strands, and adding complementary bases to form new strands.
• The process involves the addition of free nucleotide triphosphates to the growing chain, catalyzed by DNA polymerase enzymes.
• Primers are short pieces of nucleotides that initiate DNA polymerization.