Adv Bio 9 DNA/RNA

Frederick Griffith

developed transforming principle (a "transforming principle" could transfer from one strain to another; later identified as DNA)

Oswald Avery

supported Griffith's experiment by determining that DNA was the cause of transformation

Alfred Hershey and Martha Chase

studied viruses; found that DNA is a genetic material, not protein

Erwin Chargaff

determined there were not equal numbers of the four nucleotides in the strands of DNA; equal amounts of guanine and cytosine, adenine and thymine (basis for base pairing rules)

Rosalind Franklin

produced x-ray photographs of DNA that indicated its structure

Watson and Crick

credited with the discovery of the structure of DNA, awarded the nobel prize; essentially stolen from Franklin

double helix

structure of DNA, two strands of DNA are wound together like a twisted latter (strands are complementary, fit together, and opposites)

base pairing rules

A=T and C=G

nucleotides

base unit of DNA, composed of sugar, phosphate, and nitrogen base

pyrimidines

single rings, cytosine and thymine (& uracil in RNA)

purines

double rings, adenine and guanine

5' to 3'

the direction in which DNA is synthesized (replication) and read, 5' ends with a phosphate and 3' ends with a sugar

DNA replication

the process by which one strand of DNA splits to make two new identical strands, occurs in the S phase inside the NUCLEUS

helicase

an enzyme that unzips the DNA by breaking the hydrogen bonds that exist between complementary bases

DNA polymerase

an enzyme that adds the new, complementary nucleotides to the old strand of DNA

ligase

glues together okazaki fragments

unzipping

replication step 1: helicase unzips the DNA into single strands by breaking hydrogen bonds between base pairs

stabilizing

replication step 2: single-stranded binding proteins attach to the strands so they can't rejoin, enzyme topoisomerase relaxes the DNA structure

priming

replication step 3: primate attaches RNA primers to the DNA, providing a starting point for DNA polymerase

building and extending

replication step 4: DNA polymerase builds the new DNA strand by adding new nucleotides in the 5' to 3' direction, creating the leading and lagging strand

leading strand vs lagging strand

the leading strand is made smoothly in the 5' to 3' direction, while the lagging strand is made in pieces called okazaki fragments

okazaki fragments

small fragments of DNA formed on the lagging strand

replacing

replication step 5: the exonucleus removes RNA primers, DNA polymerase replaces them with DNA nucleotides

gluing

replication step 6: ligase joins/glues DNA fragments together (lagging strand)

proofreading

replication step 7: another type of DNA polymerase scans for errors and fixes any that are found

backbone

phosphate and sugar (covalent bonds)

rung

nitrogen bases connected by hydrogen bonds

RNA structure

ribose sugar, single-stranded, bases: adenine, uracil, cytosine, guanine; found in nucleus and cytoplasm

mRNA

messenger RNA carries the coding sequences for protein synthesis

rRNA

ribosomal RNA forms the core of ribosomes where protein synthesis occurs

tRNA

transfer RNA carries amino acids to the ribosome during protein synthesis

DNA & RNA similarities

made of nucleotides, nucleic acids, sugar and phosphate backbone

transcription

converts DNA into mRNA in the NUCLEUS, start of protein synthesis

process of transcription

1: RNA polymerase binds to the start site of a gene to unwind the DNA strand

2: RNA polymerase adds nucleotides to one strand of DNA according to base pairing rules

3: once transcribed, mRNA detaches from the DNA and is sent to the cytoplasm

RNA base pairing rules

A=U and C=G

RNA polymerase

enzyme that unwinds DNA and allows it to be transcribed into mRNA

translation

converts mRNA into a protein with the help of tRNA

process of translation

1: tRNA read the mRNA sequence in groups of three called a codon

2: codon matches a specific amino acid (there are 20)

3: amino acids build a protein

(occurs in the RIBOSOMES of cells)

codon

a group of 3 bases on mRNA, when read can code for a start, stop, or amino acid

start codon

AUG, starts the amino acid chain, always met(honing)

stop codon

ends the amino acid chain

ribosomes

the site of protein synthesis (specifically translation)

peptide bonds

what amino acids are held together by

polypeptide chain

chain of amino acids linked by peptide bonds, fold into proteins

anticodons

used by the tRNA to read the mRNA and is complementary to the codon

steps of protein sythesis

replication, transcription, translation

(DNA, RNA, proteins)

post-translational modifications

chemical changes to proteins after synthesis, can influence function, location in the cell, and ability to interact with other proteins

mutations

errors in the replication of the DNA, which alters the corresponding mRNA sequence and ultimately affects the amino acid sequence

effects of mutations

various genetic diseases, shorter polypeptide chains, and proteins with altered functions

point mutation

a genetic mutation that affects only one nucleotide

ex: substitution: changing one nucleotide to another

frameshift mutation

a genetic mutation that changes the way the codons are read, thus changing the protein made because multiple codons are affected

ex: insertion: adding one nucleotide

deletion: removing one nucleotide

nonsense mutation

a genetic (point) mutation that changes an amino acid to a stop codon

missense mutation

a genetic (point) mutation that changes the nucleotide, changing the amino acid, but the overall protein may still work as normal

silent mutation

a genetic (point) mutation that changes one nucleotide, but still produces the same amino acid; has no effect on the protein