DNA structure and Function

Polymer (nucleic acids [DNA and RNA])

a long strand of monomers (nucleotide) formed with covalent bonds

Nucleotides

A,T,C,G,U 3 are needed to make a nucleic acid which make up DNA

Helicase

an enzyme that binds to chromosome that seperate hydrogen bonds

Translation

ribosomes in the cytoplasm decode mRNA which directs the sequence of Amino Acids in a polypeptide (protein synthesis)

Transcription

DNA template for RNA formation; mRNA then moves to cytoplasm

How Transcription Works

a specific segment of DNA is copied into RNA by enzyme RNA Polymerase (occurs in the nucleus)

How Translation Works

ribosomes read mRNA codons and match them with tRNA anticodons

mRNA (messenger RNA)

is a single-stranded molecule that carries genetic instructions from DNA in a cell's nucleus to the cytoplasm, directing the synthesis of specific proteins. It acts as a template for protein construction

rRNA (ribosomal)

non-coding RNA that acts as a structural component for ribosomes (catalyzes the formation of peptide bonds between amino acids)

tRNA (Transfer)

a small RNA molecule that acts as an adaptor during protein synthesis (decodes mRNA sequences by pairing specific amino acids with their mRNA codons)

RNAPolymerase

unzips DNA, reads one strand, and builds complimentary RNA strand through initiation, elongation, and termination

Initiation (Unzipping)

RNA polymerase binds to a specific region of DNA (promoter) to signal the DNA to unwind so the enzyme can read the bases

Elongation

RNA polymerase moves along the template strand of DNA, adding complementary RNA nucleotides to the 3' end of the growing RNA chain, synthesising it in a 5' to 3' direction

Termination

the enzyme keeps going until it reaches the stop codon which causes the enzyme to detach and release the new RNA molecule

anticodons

3-nucleotide sequences located on tRNA molecules (uracil) that are complimentary to codons on mRNA

Leading Strand

the new DNA strand continuously synthesized from the 5’ to 3’ direction during DNA replication building towards the replication fork using the old 3’ to 5’ strand. (faster)

Lagging Strand

also a new DNA strand created during replication but on the old 5’ to 3’ DNA it is synthesized on the opposite direction of the replication fork (3’ to 5’) (slower and shorter and segregated)

Okazaki Fragments

segregated parts of the lagging strand that are connected through ligase

DNA Polymerase

an enzyme responsible for synthesizing new DNA strands by assembling nucleotides (copys a cells genome before division, it then reads the existing strand and adds complimentary nucleotides in a 5’ to 3’ direction)

Promoter

segment of the DNA that defines the start of a gene and binding site for RNA polymerase (direction for transcription)

Terminator

segment of DNA that defines the end of a gene and stops RNA polymerase from moving forward

Introns

noncoding “dark DNA” (never expressed)

Exons

segments of Eukaryotic genes that are transcribed into RNA and retained in a final mRNA (genes that are actually expressed)

Differences of RNA and DNA Polymerase

DNA polymerase drives DNA replication by building double-stranded DNA and proofreading for accuracy RNA polymerase drives transcription by creating single-stranded RNA from a DNA template

Degenerate

most amino acids have more than one codon (1 start 3 stop)

Unambigous

universal (all living things obey the same code

Aneuoploids

mutations that result changes in chromosomal number

Monosomy

individual inherits a homologue instead of a pair (2n-1)

Trisomy

individual inherits 3 homologous chromosomes of one pair (2n+1)

Non-Dysjunction

a mistake in meiosis that results into an Aneuploid

What causes Changes in Chromo structure?

radiation, chemicals, or viruses or mistakes in crossing over that result in the chromosomes breaking (broken ends don’t rejoin in the same pattern)

Germ-Line Mutations

passed onto offspring (raw material for evolution)

Somatic-Line Mutation

only affect the organism but wont be passed down

Causes of Genetic Mutations

spontaneous, Enviornental mutagens: Radiation (UV), organic chemicals (tobacco & alcohol) (rare because DNA polymerase proof reads every new strand)

Point-Mutations

changes or substitutions in one or more nucleotide (base pair) in the sequence of DNA (usually affect a single amino acid in the protein)

Silent Mutations

generally neutral, usually single nucleotide substitutions that don’t change the amino acids coding sequence

Missense Mutations

a genetic mutation where a (usually) a single nucleotide substitutions that changes the genetic code resulting in a different amino acid being incorporated into the protein

EX: Sickle Cell

Nonsense Mutations

a genetic alteration in the DNA where the sequence prematurely tells the cell to stop building the protein (replaces amino acid w/ stop codon)

Frameshift Mutations

when a nucleotide is either inserted or deleted: may result in a change in EVERY amino acid that follows past the mutation

Genetic Engineering

the direct engineering of genes

Science behind DNA technology

made possible by bacterial enzymes that cut DNA molecules at limited number of specific locations

Restriction Enzymes

natural occuring bacterial enzymes that prevent them from being intruded by outside DNA of other organisms

How Restriction Enzymes Work

works by cutting up the foreign DNA or restricting their propogation (catalyzing their sugar-phosphate bonds between specific bases) - results in blunt or sticky

Blunt Ends

cuts directly through both strands (straight)

Sticky Ends

cuts through non-complimentary bases (sugar-phosphate bonds) but only through one strands

Analyzing DNA

The technique of taking DNA samples, cutting them with specific restriction enzymes to make DNA fragments of different sizes, and separating them based on their size in a gel

Gel Electrophoresis (DNA FIngerprinting)

technique that uses a gel as a molecular sieve to separate nucleic acids or proteins on the bases of size, electric charge, or other properties (uses friction to analyze)

RFLP’S (restriction fragment length polymorphisms)

DNA samples that are treated with specific restriction enzymes to be cut into fragments

How Gel Elctrophoresis Works

all RFLP’s from the sample are inserted into wells (many so that they can be analyzed side by side), an electrical charge is applied to the gel which causes them to migrate downwards according to length; this results in bands (longer strands have more friction so they travel slower)

Gene Splicing

the process where a gene from any source is taken and inserted into the genome of living cells

rDNA (recombinant)

DNA that is engineered to contain DNA from different sources

How they obtain rDNA

a vector gene and plasmid (vector DNA) are treated with the same restriction enzyme and then joined together using DNA ligase

Vector

organisms that insert their DNA into organisms naturally (Bacteria, Viruses, Ect.)

plasmid

Vector DNA

Recombinant Plasmid

can be inserted back into bacteria to reproduce asexually (makes multiple copies of the rDNA)

Gene Editing

CRISPR (allows for direct gene transformation without the use of existing sources)