ap bio: unit 6 notes

ap biology unit 6: gene expression and regulation

hallo everyone! i’m a current student in ap bio and i’m updating my notes as we go along. so far my class has covered 6.1-6.3!

↪ if u don’t like times new roman… idk i’ll go cry.

⟡ 6.1 - DNA & RNA structure

• how heritable information provides for continuity of life

• DNA is inherited

• monomers of nucleotides in the DNA molecule carry “codes” of info about the organism

── .✦ DNA vs RNA

• DNA

  • replicates on its own

  • carries genetic info

• RNA

  • reads DNA to make proteins; mRNA, rRNA, tRNA

• Chargaff’s Rule of Base Pairings in DNA:

  • A = T

  • G = C

• for RNA:

  • A = U

  • G = C

• carbons of the deoxyribose sugar are numbered clockwise, DNA bases are “read” in the 5’ to 3’ direction

⟡ 6.2 - replication

• replication - DNA makes a copy of itself during cell division in the nucleus of the cell

  • replication of cells for growth or for reproductive cells to pass to offspring

• semi-conservative: two copies of the original DNA molecules are produced, conserving (replicating) the information from one half of the original DNA

• topoisomerase:

  • loosens tension of DNA strand

• helicase:

  • separates DNA strands by breaking hydrogen bonds between base pairs

• DNA primase:

  • adds nucleic acid that starts DNA synthesis

  • primer is the short RNA segment that helps to start the copying of DNA

✰ DNA polymerase:

• enzymes that replicate the existing DNA strand to make a complimentary strand

• adds DNA bases from 5’ to 3’ on the leading strand

  • leading strand adds nucleotides in the 5’ to 3’ direction of the NEW strand continuously

    • one primer needed

  • on the lagging strand, since DNA cannot be copied in the 3’ to 5’ direction, it is discontinuous and done in fragments called okazaki fragments

    • multiple primers are needed.  

• okazaki fragments

  • DNA cannot be copied in the 3’ to 5’ direction

  • DNA is copied in fragments

  • multiple primers are needed

⟡ 6.3 - transcription & RNA processing

• gene: DNA segment that codes for one polypeptide

• 2 steps of protein synthesis:

  1. transcription: genes transcribed from DNA to messenger RNA(mRNA)

  2. translation: mRNA ‘translated’ into proteins by ribosomes and transfer RNA (tRNA)

⟡ 6.4 - translation

⟡ 6.5 gene expression & regulation

vocab!

• regulatory gene: codes for a regulatory protein that activated or represses expression of a gene

• promoter: nucleotide sequence that enables a gene to be transcribed

• operator: region of DNA of operon that is the binding site for regulatory protein

• structural genes: genes that are co-regulated y the operon

• all cell types have the same DNA in their nucleus, but not all DNA is “expressed” in all cells

• operon: a genetic regularotry susem in bacteria which codes for proteins.

  • regulatory gene

  • promoter

  • made up of genes that produce an mRNA during transcription