bio ch 10 Flashcards
who discovered that there is the same amount of A and T and C and G
Chargraff
who discovered that genetic material is DNA not protein
Hershey and Chase
who discovered that DNA has a double helix structure by using x-ray diffraction patterns
Rosalind Franklin
who published the structure and took credit for what rosalind discovered
watson and crick
what are DNA and RNA made of
nucleic acids
what are nucleic acids made of
long chains of nucleotides
how are the phosphate and sugar molecules joined together in the sugar-phosphate backbone
covalent bonds
what are nucleotides made of
a nitrogenous base, a sugar, and a phosphate group
how are nucleotides joined together
covalent bonds between the sugar of one nucleotide and the phosphate of the next
what are the structural differences of dna vs rna
RNA’s sugar has an OH group attached to one of its C atoms and it has uracil instead of thymine
why is the model for DNA replication known as semi-conservative replication
bc half the parent model is maintained (conserved) in each daughter molecule
which are the enzymes that link DNA nucleotides to a growing daughter strand
DNA polymerase
which enzyme links the Okazaki fragments together into a single DNA strand
DNA ligase
which end of the strand does DNA polymerase add nucleotides to
3 prime
what is the daughter strand that is synthesized continuously called
the leading strand
what is the daughter strand that is synthesized in fragments called
the lagging strand
what are the fragments on the lagging strand called
okazaki fragments
what does DNA polymerase do besides adding nucleotides to the DNA chain
Proofreads –> removes nucleotides that have base-paired incorrectly during replication
does DNA have to replicate before it divides
yes
what is an organism’s genotype
its genetic makeup
what is an organism’s phenotype
its physical traits
what is transcription
the synthesis of RNA under the direction of DNA
what is translation
the synthesis of a protein under the direction of RNA
what is the one gene polypeptide hypothesis
the function of a gene is to dictate the production of a polypeptide
in what way does information within the cell flow
DNA –> RNA –> Protein
what is the triplet code
the genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as a series of non overlapping three-base “words” called codons
what is the genetic code
the set of rules that relate codons in RNA to amino acids in proteins
what enzyme joins RNA nucleotides together
RNA Polymerase
where does transcription take place
the nucleus
what is a promoter
a specific biding site for RNA polymerase and determines which of the 2 strands of the dna double helix is used as the template in transcription
what kind of RNA encodes amino acid sequences
mRNA
what happens to eukaryotic transcripts before they leave the nucleus as mRNA
they are processed in several ways
what are some of the ways mRNA is processed before leaving the nucleus
caps and tails are added to the ends to facilitate the export, protect the mRNA, and help ribosomes bind to the mRNA
RNA splicing
what is RNA splicing
the process that removes introns from RNA and joins the exons to produce an mRNA molecule with a continuous coding sequence
what are the steps of transcription
INITIATION: RNA polymerase attaches to promoter-a binding site (chooses which DNA strand to read and signals the beginning of a gene)
ELONGATION: RNA strand is made and peels away from DNA strand
TERMINATION: RNA polymerase reaches the terminator (signals the end of the gene)
what is transfer RNA
converts codons to amino acids
what two parts of tRNA give it its ability to match a particular codon in mRNA to its corresponding amino acid
the anticodon and the amino acid attachment site
what is the function of rRNA
ribosomes hold the mRNA and tRNA close together, and connects amino acids from the tRNA to the growing polypeptide chain
what are the 3 phases of translation
initiation, elongation, termination
what are the steps of translation initiation
an mRNA molecule binds to a small ribosomal subunit. A special initiator tRNA binds to the specific codon, called a start codon, where translation begins on the mRNA molecule. the initiator tRNA carries the amino acid Met; its anticodon binds to the start codon. next, a large ribosomal subunit binds to the small one, creating a functional ribosome. the initiator tRNA fits into one of the 2 tRNA binding binding sites on the ribosome called the p site. this site will hold the growing polypeptide. the other tRNA binding site - the A site - is vacant and is ready for the next amino acid bearing tRNA
what are the steps of translation elongation
- codon recognition - the anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome
- peptide bond formation - the polypeptide separates form the tRNA in the P site and attaches by a new peptide bond to the amino acid carried by the tRNA in the A site
- Translocation - the P site tRNA now leaves the ribosome and the ribosome moves the remaining tRNA in the A site to the P site
what is the termination step of translation
when elongation stops when a stop codon reaches the A site
describe amino acid attachment
each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP
what is a mutation
any change in the nucleotide sequence of DNA
what is point mutation
when a base is substituted for another
what are the types of point mutations
silent, missense, and nonsense
what is a silent mutation
a substitution that does not change the protein produced because the new codon still ends up coding for the same amino acid
what is a missense mutation
a substitution that changes the amino acid coding
some have little or no effect on the on the shape/function of the resulting protein, but others prevent the protein from performing its normal function
what is a nonsense mutation
a substitution that changes an amino acid codon into a stop codon, which will prematurely terminate the protein
what is a frameshift mutation
when nucleotides are added or deleted and the whole sequence is altered
what is a mutagen
chemicals or agents that cause mutations
ex: x rays or uv light, the anti-aids drug AZT which works bc its structure is similar enough to thymine that it gets put into DNA but then that DNA cant be replicated
