AP Bio Unit 6 Molecular Genetics

- DNA vs RNA Structure - DNA Replication (Enzymes and how DNA gets copied) - DNA --> RNA --> Protein (transcription + translation) - Operons (How bacteria control their genes: epigenetics, Transcription initiation complex, RNA processing, MicroRNA) - Restriction enzymes (Restrictive enzymes, PCR, gele electrophoresis)

Timeline of Genes to Proteins

DNA → RNA → Protein

DNA amino pairs

AT

CG

RNA amino pairs

AU
CG

DNA Structure

Double Helix - 2 strands

RNA Structure

1 strand

DNA duplication (Replication)

5’ - TTTTTACGTTAATGGC - 3’

….?

5’ - TTTTTACGTTAATGGC - 3’

3’ - AAAAATGCAATTACCG - 5’

DNA Replication Summary

Why? Create 2nd set of DNA prior to cellular reproduction.

When? S phase of interphase.

Where? Eukaryotes Nucleus.

How? ENZYMES

Result? Semi-conservative strand

DNA Replication Enzymes

• helicase - unzipper / strand separator

• topoisomerase - snips and prevents super coiling

• primase - directions for DNA made out of RNA primers

• DNA polymerase - builder of new DNA chain that attaches at 3’ end(s)

• DNA ligase - glue connects enzymes

Helicase Enzyme

unzipper / strand separator

Tipoisomerase Enzyme

snips and prevents super coiling

Primase Enzyme

directions for DNA

made out of RNA primers

DNA Polymerase Enzyme

builder of new DNA chain that attaches at 3’ end(s)

Ligase Enzyme

glue connects enzymes

Transcription in Prokaryotes

transcription happens for one strand of mRNA and the translation happens before transcription is over.

• more than one protein can be produced during translation

Transcription in Eukaryotes

transcription happens for one strand of mRNA and the translation happens after transcription is over.

• usually only on protein is produced

DNA to RNA (Transcription)

5’ - TTTTTACGTTAATGGC - 3’

….?

5’ - TTTTTACGTTAATGGC - 3’

3’ - AAAAAUGCAAUUACCG - 5’

That is an mRNA molecule

RNA to Proteins (Translation)

3’ - AAAAAUGCAAUUACCG - 5’

…?

3’ - AAAA-AUG¹-CAA²-UUA³-CCG⁴ - 5’

met¹-Gin²-Leu³-Pro⁴

That is an amino acid sequence

Operons

• structure for turning genes on & off

• regulate genes

• how prokaryotes control protein production

Operon Pieces

• RNA polymerase - makes mRNA

• promoter - region that RNA polymerase attaches to

• Operator - on

• Repressor - off (attaches to operator and blocks RNA poly)

• Termination sequence - region where RNA polymerase stops and detaches

Inducible

Can be induced

Off →On

Removal of repressor

Repressible

Can be repressed

On → Off

Insertion of repressor

Transcription Initiation Complex

• facilitate the binding of RNA polymerase to the DNA strand

• start synthesizing mRNA based on the DNA template

• transcription factors that help recognize the promoter sequence and stabilize the RNA polymerase before the actual transcription process begins

Transcription Factors + Mediator Proteins

When bound to the promoter, they help the RNA Polymerase move onto the operon / genes etc…

micro RNA

short, non-coding RNA molecules that block RNA polymerase

Differential Gene Expression

same genomes, but difference in expression of gene

• expressed = on

• not expressed = off

Euchromatin

loosely bound DNA genes that can be loosened by aceytl groups where RNA poly can pass through

• “on”

Heterochromatin

when the genes and dna are too tightly wound, preventing RNA poly from going through

• “off”

Histone Acetylation

loosen the chromatin to let the RNA poly through

(temporary)

DNA Methylation

DNA gets marked and blocks the transcription because it’s tightening, preventing RNA poly from readin it

Alternative RNA Splicing

The process of variants from different exons being kept

2^{(# of exons)} - 1

Technologies for Genetic Modifications

• Restriction Enzymes - cuts DNA at specific sequences and creates multiple segments

• PCR (Polymerase Chain Reaction) - Generates Millions of Copies

• Gel Electrophoresis - separating the segments / molecules and making gaps to analyze

Restriction Enzymes

cuts DNA at specific sequences and creates multiple segments

PCR (Polymerase Chain Reaction)

Generates millions of copies of the DNA segments

• To visualize DNA bands

Gel Electrophoresis

• separating the segments / molecules and making gaps to analyze

• DNA is Negative, so it will go toward the positive
  

Direction Impactors

• Charge → goes to opposite

• Size

  • Small = Far / Fast

  • Large = Less Far / Slow