Replication, Transcription, Translation Flashcards
DNA
- A polymer (macromolecule) build from series of joined nucleotides
- 2 backbone strands run parallel
- one stand goes 3-5, other goes 5-3
3 functions of DNA
- store info to build protein, control cell development & metabolic reactions
- replicate prior to cell division
- undergo mutations (rare, but give variability in a species)
Nucleotide parts
- deoxyribose sugar
- phosphate
- base (a, t, c, g) which attaches to the sugar
Replication
Making a copy of DNA before cell divides so copies of DNA can go to the new cells
Replication steps
- DNA unwinds & flattens out, then unzips down the middle (due to enzyme helicase). H-bonds btwn bases break.
- Free-floating nucleotides move into place through complementary base paring (due to DNA polymerase)
- Phosphate & sugars join together so the new DNA molecule is double stranded (due to DNA ligase)
Leading strand
The side of DNA strand that replicates continuously
Primer
Attaches to the exposed parts to give the new nucleotides a point to attach to
Okazaki Fragments
Small pieces of DNA that join together on the lagging strand during replication
Semi conservative replication
- Each new strand of DNA is half-old and half new
- semi: half
- conservative: one of the parental stands is present in each new double helix
Gene
Unit of heredity that
- directs development & behaviour of organism
- directs protein manufacturing
- contains introns (don’t make proteins)
Prompter
Shows where to start reading directions for protein/exons
Subprocesses of protein synthesis
- transcription
- translation
Messenger RNA (mRNA)
- copies instructions (transcription) for building protein from DNA
- carries blueprint to cytoplasm
- reads message & translates code into protein
Ribosomal RNA (rRNA)
- subunits made in nucleus
- subunit of RNA & proteins from ribosomes
Transfer RNA (tRNA)
- delivers correct amino acid to mRNA and pairs it up w/blueprint
- 20 different tRNA’s (one for each amino acid)
Transcription (RNA copies dna)
- Section of RNA unzips & becomes template to build mRNA (polymerase helps). When done, the mRNA breaks into codons
- mRNA leaves nucleus & moves to a ribosome in the cytoplasm
Triplet code
Set of 3 bases on DNA (called codons when mRNA is involved)
Translation (RNA makes protein)
- MRNA attaches to rRNA in cytoplasm
- Aug codon signals start/initiation
- tRNA anti codons attach to the matching codon on the mRNA
- Other end of tRNA has amino acid attached, which bond with mRNA peptide bonds
- Now-empty tRNA leaves & picks up new amino acid (can be reused)
- Process continues until the stop codon is reached (termination)
Elongation
Growth of polypeptide chain
Mutation
- permanent genetic change
- 2 types:
- gene mutation
- chromosome mutation
Gene mutations
- inheritable changes in DNA bases
- errors usually corrected (proofread)
- change DNA triplet code -> changes mRNA, amino acid, and shape & function of protein
Substitution (gene)
- point mutation
- one base changed for another
A) silent mutation - no affect on aa
B) nonsense mutation - very serious, like creating stop codon
C) missense mutation - affects shape of protein, creates sickle cell anemia
Addition (gene)
- One extra nucleotide is added
- frameshift
Deletion (gene)
- one nucleotide is deleted
- frameshift
