BIMM 100 1-3

What are the building blocks and components of DNA?

→ Nucleotides = phosphate + deoxyribose sugar + base; Bases: A, T, G, C

What are DNA base pairing rules and bonds?

→ A–T (2 hydrogen bonds), G–C (3 hydrogen bonds); Hydrogen bonds hold bases together; Phosphodiester bonds hold backbone together

What is DNA strand direction and why is it important?

→ Antiparallel: 5’→3’ and 3’→5’; Important for replication + enzyme function

What is DNA replication and its key rule?

→ Copying DNA before division; Semiconservative: 1 old + 1 new strand

What does DNA polymerase do and what are its limits?

→ Synthesizes DNA 5’→3’; Adds to 3’ OH; Cannot start → needs primer

What enzymes are involved in replication?

→ Helicase (unwinds); Topoisomerase (relieves tension); SSB proteins (stabilize); Primase (makes RNA primer); DNA polymerase (extends + fills gaps); DNA polymerase I (removes primer, prokaryotes); DNA ligase (joins fragments)

What are leading vs lagging strands?

→ Leading = continuous (toward fork); Lagging = discontinuous (away from fork)

What are Okazaki fragments and why do they form?

→ Short DNA fragments on lagging strand; Because DNA polymerase only works 5’→3’

What were the results of Griffith’s experiment?

→ S (virulent) → mouse dies; R (non-virulent) → mouse lives; Heat-killed S → lives; Heat-killed S + R → dies

What did Griffith conclude and why did the mouse die?

→ Transformation occurred; R cells took up DNA from S → became virulent

How did Avery prove DNA is genetic material?

→ Destroy DNA → no transformation

How did Hershey-Chase prove DNA is genetic material?

→ Phage experiment; DNA labeled with 32P, protein with 35S; Only DNA entered cells

Why were phosphorus and sulfur used in Hershey-Chase?

→ DNA has phosphate; Proteins have sulfur

What is a genome and DNA location?

→ Genome = all genetic material; Eukaryotes: nucleus; Prokaryotes: circular DNA

How is DNA packaged?

→ Chromatin = DNA + proteins; Histones = proteins DNA wraps around; Nucleosome = DNA + histones

Why is DNA packaged and chromatin states?

→ Fit DNA + regulate genes; Euchromatin = active; Heterochromatin = inactive

What is the central dogma?

→ DNA → RNA → Protein

How is RNA different from DNA?

→ Ribose sugar; Uracil instead of thymine; Single-stranded

What are types and functions of RNA?

→ mRNA = carries code; tRNA = brings amino acids; rRNA = ribosome

What happens in transcription and where?

→ DNA → RNA; Occurs in nucleus

What does RNA polymerase do and key differences from DNA pol?

→ Synthesizes RNA 5’→3’; Does NOT need primer

Template vs coding strand?

→ Template = used to build RNA; Coding = same as RNA (T→U)

What is a promoter and its function?

→ DNA sequence where transcription starts; Controls gene expression

What are mutations and main types?

→ Change in DNA sequence; Substitution, insertion, deletion

What are frameshift and point mutations?

→ Frameshift = insertion/deletion; Silent = no change; Missense = different AA; Nonsense = stop codon

What actually drives DNA elongation chemically?

→ Addition of nucleotides to the 3’ OH group

What is the role of the 3’ OH group in DNA replication?

→ It is the site where new nucleotides are added

Why are RNA primers required in replication?

→ DNA polymerase cannot initiate synthesis; it can only extend existing strands

Why does DNA replication only occur 5’→3’?

→ Because nucleotides can only be added to the 3’ OH group

What determines where and whether transcription occurs?

→ Promoter sequence

What is a key difference between RNA polymerase and DNA polymerase?

→ RNA polymerase does NOT require a primer

Why is G–C base pairing stronger than A–T?

→ G–C has 3 hydrogen bonds; A–T has 2

What is transformation?

→ Uptake of external DNA by a cell