Unit 8 - Genes & Molecular Biology

DNA - structure

center of nucleus of a cell; organic molecule; contains very long strands

DNA - function

contains genetic info; has info to make proteins; has directions for all activities of the cell

DNA monomer

nucleotide

3 parts of nucleotides

1. sugar w/5 carbons

2. phosphate group

3. base (nitrogen and Adenine/Thymine/Cytosine/Guanine

2D shape vs 3D shape

like a ladder: base is the rungs and sugar/phosphate is the backbone; 3D shape is a double helix

How are bases held together?

hydrogen bonds

Chargaff’s Rule/Base Pairing Rule

amounts of adenine=amounts of thymine; amounts of guanine=amounts of cytosine

“Aunt Thelma Cooks Good!”

A-T and C-G

Melesons-Stahl’s experiment

• proves how DNA replicates

• processed DNA with two isotopes of nitrogen, N14 (light) and N15(heavy)

• DNA was centrifuged, and bands formed on the tube based on the weight or dominance of the isotope

Conservative

• possible method of DNA replication

• og strands are conserved through out the process

Semi-Conservative

• possible method of DNA replication

• DNA strand is halved after each replication

• new strands are half new half old

Dispersive

• possible method of DNA replication

• DNA strand is halved after each replication

• replicated strands are chunked together and not in full pieces

results of Meleson-Stahl’s experiment

Semi-Conservative

When does DNA replicate?

during the S phase of interphase

Helicase

enzyme that breaks H-bonds of the bases and allows the DNA to unwind

Topoisomerase

enzyme that reduces tension as the coiled double helix unwinds itself

primer

short section of RNA that helps DNA begin the replication

Primase

enzyme that builds RNA primer

Elongation

adding new nucleotides to the single DNA strand

DNA Polymerase III

adds in the new bases to pair up with the old ones (requires energy)

Antiparallel Elongation

the two DNA strands in a double helix run in opposite directions → DNA Polymerase III needs to build in different directions

top goes from 5’ to 3’ (forward, faster)

bottom goes from 3’ to 5’ (backward, slower)

Leading Strand

• the new strand that builds on the “top” strand

• continuous

• only needs one RNA primer

Lagging Strand

• the new strand that builds on the “bottom” strand

• built in sections, backward — not continuous

• needs multiple RNA primers

Okazaki fragments

sections the lagging strand is build out of

DNA Polymerase I

replaces RNA primer bases with the proper DNA

Ligase

enzyme that joins nucleotides together

Examples of how you can damage your DNA

smoking, x-rays, wearing no sunscreen/tanning, etc

DNA Polymerase II

fills in missing nucleotides that were removed because they were damaged or incorrect

Gene expression

process of transcribing genes to RNA then translating that to make proteins

Transcription

RNA molecule is made from a DNA sequence

aka, mRNA synthesis (only in nucleus)

Translation

RNA message assembles amino acids into protein at the ribosome (only in cytoplasm)

Why RNA

because DNA can’t leave the nucleus

Structure of RNA (5)

• single stranded

• polymer of nucleotides

• has a ribose, phosphate group, and base

• found in nucleus + cytoplasm

• Bases = G, C, A, and U (uracil)

mRNA (3)

• carries instructions

• long strand of bases

• found in nucleus and cytoplasm

tRNA (3)

• carries amino acids

• “t” shape w/ 3 bases on one end

• only in cytoplasm

rRNA (3)

• connects amino acids

• small (binds to mRNA) and large (forms peptide bonds) subunits

• only in cytoplasm

Promoter

enzyme that tells where the gene for a protein is

Steps of Transcription (6)

1. RNA Polymerase finds promoter

2. Initiation (DNA unwinds)

3. Elongation (new RNA nucleotides are added)

4. Termination (end of instructions)

5. mRNA leaves

6. DNA rezips

types of RNA in translation

mRNA carries instructions

tRNA delivers amino acids to ribosomes

rRNA connects the amino acids

codon

sets of three bases on mRNA that ribosomes read (1 codon = 1 amino acid)

Start Codon

AUG (could also be an amino acid)

Stop Codons

UAA UAG UGA

Steps of Translation (6)

1. mRNA attaches to ribosome

2. Ribosome reads codons and tRNA binds to mRNA

3. tRNA corrects the codons on mRNA w/ anticodon

4. specific amino acids hangout on the other end of tRNA

5. rRNA connects amino acids w/ peptide bonds

6. protein is made

Gene Mutations

changes in one or a few nucleotides (aka point mutations)

Substitution

base pair is replaced (may or may not cause problem)

insertion

additional base pair is inserted (dangerous)

deletion

base pair is deleted from the sequence (dangerous)

Fram shift exampeles

• silent (no change)

• nonsense (stop codon is made)

• missense (another amino acid/ protein is made)

Frame Shift Mutation

the more dramatic gene mutations are, the more a template frame is going to shift and mess up everything

Griffith

organisms can get new properties and noninhertiable gene exchange is possible

Avery, McCarty, and Macleod

nucleic acids are molecules of heredity

Hershey and Chase

DNA is the genetic material and carries genetic info

Chargaff

Frequency of bases in DNA vaires

Franklin

DNA has a helix structure

Watson and Crick

DNA has an anti-parallel structure

Kariko and Weissman

mRNA can be used therapeutically in meds like vaccines

Langer

RNA can be protected from enzymes by inserting them in a nanoparticle

how are mRNA vaccines different?

they use genetic info of the virus, specifically they code for proteins found on viruses to warn cells of the body what to watch out for

side effects of mRNA vaccines

Inflammation, destroyed the RNA before it could do anything

how did they fix the inflammation of RNA vaccines?

altered uridine to be a pseudouridine; also helped make more proteins

disadvantages of RNA

fragile and can be destroyed by enzymes of the body