ap bio unit 3.2 - replication, transcription, translation, and mutations

semiconservative

the area of DNA that replication begins at (has specific sequence of nucleotides that allows starting proteins to attach to)

the Y-shape formed by separating the two strands of DNA

unwinding the helix at the replication fork

bind to unpaired DNA to keep the strands from pairing again

relieves strain caused by unwinding on/around replication fork (keeps DNA strands straight and avoids supercoiling)

is a sequence of 5 - 10 nucleotides made by primase; synthesis can’t start on its own and builds from the 3’ end of the primer

synthesizes new DNA by attaching complementary base pairs to the template strands

joins phosphate backbones of fragments into a continuous strand

single, circular DNA molecule

linear DNA and many proteins

1. DNA (double helix)

2. proteins called histones (+ charge) bind to phosphate backbones of DNA (- charge)

3. chromatin folds so histones form bead-like nucleosomes

4. fold into chromatin fiber as histone tails interact with other nucleosomes

5. fiber folds into “looped domains”

6. looped domains coil into condensed chromosomes

heterochromatin, which is inaccessible to transcription because of its folding

“true chromatin”, less compact and not condensed; able to be transcribed

polypeptides (that make up proteins)

• ribose sugar instead of a deoxyribose sugar

• contains uracil instead of thymine, which is less stable (and therefore unsustainable for DNA)

the synthesis of RNA using DNA as a template

the synthesis of a polypeptide using info from mRNA, occurs at the ribosomes

they do not have nuclei

Crick’s theory stating genetic information flows in one direction: DNA —> RNA —> proteion

three (triplet code)

complementary and antiparallel

a set of three nucleotides of DNA that codes for one amino acid

several codons may code for the same amino acid, but will only code for that amino acid

the genetic code is nearly universal, which suggests a shared common ancestor

• synthesizes RNA by attaching RNA nucleotides to template strand

• assemble in 5’ to 3’ direction

• able to start a chain from scratch (doesn’t need a primer like DNA polymerase)

section of DNA transcribed

1. initiation - RNA polymerase binds to the promoter (eukaryotes: transcription factors form a transcription initiation complex and help RNA polymerase bind and initiate)

2. elongation - RNA polymerase reads DNA from 3’ to 5’ and synthesizes 5’ to 3’, adding bases to the 3’)

3. termination

   1. bacteria - reaches a terminator sequence + releases the transcript w/out modification

   2. eukaryotes - proteins cut off RNA from polymerase at a transcribed signal + pre mRNA goes through modification

• 5’ methyl cap attached to 5’ end

• poly-A tail added to 3’ end

• facilitate export of mRNA from nucleus + help protect RNA from hydrolytic enzymes

• help mRNA attach to ribosomes

removal of RNA that was initially synthesized that occurs in the nucleus; non-coding sections are cut and not translated

introns are intervening sequences and are removed; exons are coding regions that are expressed

exons from the same gene are arranged in different combos which = more possible proteins formed from the same transcription

protein complex that removes introns, degrades them, and joins exons on either side of the intron together

RNA molecules that function as enzymes

in the cell’s cytoplasm or are taken in from surrounding solution

codon on mRNA; corresponds to one type of amino acid

is reused and picks up another amino acid in the cytosol

enzymes that help the tRNA and its amino acid bind

• P site - holds tRNA adding to the polypeptide

• A site - holds the next tRNA in line

• E site - discharges tRNA after amino acid has been deposited

• polypeptide will exit through an exit tunnel

attachment of mRNA

rRNA (ribosomal RNA, which act as ribozymes)

1. initiation - mRNA binds to small subunit and an initiator tRNA; mRNA is scanned until start codon so the initiator tRNA can bind to it

2. elongation - mRNA is read from 5’ to 3’ and amino acids are added one by one; rRNA forms peptide bonds between amino acids of A and P site & removes bond to tRNA; tRNA is moved A —> P, P—> E

3. termination - stop codon reaches A site and release factors hydrolyze bond between polypeptide and tRNA; polypeptide is released through exit tunnel

chemical changes to amino acids, removal of amino acids, change to polypeptides length; must be modified to become functional proteins and do specific jobs

changes in a single nucleotide pair of a gene

when mutations have adverse effects on the phenotype

• single nucleotide-pair substitution - replacement of one base and its complement

• insertion/deletion - addition or loss of nucleotide pairs in a gene

are not harmful b/c of redundancy of genetic code/translate to the same amino acid

mutations that change an amino acid to another

codon for amino acid is changed into a stop codon, ending translation prematurely

physical or chemical agents that interact with DNA and can cause mutations (ex. X-rays, UV radiation, nucleotide analogs)