DNA + RNA Flashcards
Dna molecules contains
Genes
A gene is a segment of DNA that makes instructions for making
Protein/polypeptide
An allele are
Two versions of a gene
A cell needs many different types of proteins to function
Enzymes
Transport proteins
Enzymes carry out chemical reactions to sustain life
Transport proteins move ions and molecules across the cell membrane
Genes influence an organism’s characteristics by determining the
protein made
Early in the 1900s, people didn’t know if the basis for molecules was
Protein or dna
Frederick Griffith
killed pathogens and mixed harmless bacteria with their corpses, and some of the bacteria became pathogens
Hershey and Chase
found that viruses inject their DNA into cells to reproduce (nucleotides??)
Nucleotides are
Nitrogenous base
Five-carbon sugar (deoxyribose)
Phosphate group
Nucleotides are joined together by a
sugar-phosphate backbone
There are four nitrogen-containing bases
Adenine (A)
Cytosine (C)
Thymine (T)
Guanine (G)
DNA and RNA are
polymers of nucleotides
Purines have a double ring structure
Adenine, Guanine
Pyrimidines have a single ring structure
Cytosine, Uracil, Thymine
DNA abbrev
deoxyribonucleic acid
RNA abbrev
ribonucleic acid
RNA
Ribose
Uracil (U)
Single stranded
Copies genetic code for protein
DNA
Deoxyribose
Thymine (T)
Double stranded
Is genetic code for protein
Watson and Crick were the first to figure out the structure of DNA
two polynucleotide strands wrapped around each other in a double helix
Hydrogen bonds
holds the strands together
Each base has a complementary partner
Adenine and Thymine
Guanine and Cytosine
The genetic information in a chromosome is enclosed in
the nucleotide sequence in DNA
Enzymes use the stands to make new nucleotides
Nucleotides
DNA replication follows a semiconservative model
one old strand of DNA and one new strand
Meselson and Stahl researched
Dna replication
Steps of dna replication
Helicase splits DNA strands into two different pieces
Primase makes RNA strands called primers
DNA polymerase binds to the primer and make new DNA
DNA polymerase can only make DNA in one direction (5 prime to 3 prime), which is called the leading strand
The other strand, called the lagging strand, has to be filled in with fragments, called Okazaki fragments
DNA ligase binds the Okazaki fragments
Exonuclease removes the RNA primers and is filled in with DNA
DNA polymerase can only add to the 3 prime end because it has a
hydroxyl for dehydration reaction
Leading strand
Lagging strand
5’ to 3’
3’ to 5’
Transcription process
Hydrogen bonds between the bases of the DNA helix are broken by DNA helicase
RNA nucleotides line up and RNA polymerase joins them along one strand of DNA
The promoter signals the start and acts as a binding site for RNA polymerase
RNA polymerase adds RNA nucleotides until it reaches the terminator, which signals the end of the gene
RNA that encodes amino acid sequence is called
messenger RNA (mRNA) because it tells genetic messages from DNA to the translation machinery of the cell
Before leaving the nucleus as mRNA
eukaryotic transcripts undergo RNA splicing:
RNA splicing
Introns (non-coding segments of RNA) are spliced out
Exons (coding segments of RNA) are spliced together, and a 5’ cap and a poly A tail are added to the ends of the mRNA
The sequence of nucleotides in DNA provides a code for
Constructing a protein
Translation requires nucleotide sequence to turn to
amino acid sequence
DNA->Transcription->mRNA->Translation->Polypeptide
Got it?
The genetic instructions for the amino acid sequence is written in DNA and RNA called
Codon
Codons are a series of
nonoverlapping three-base “words”
The genetic code is a set of rules that translates mRNA to
amino acids/polypeptides
Ribosomes attach to mRNA and translates the message to polypeptides, aided by
transfer RNAs (tRNA)
tRNA is a folded molecule with a base triplet called.. on one end and an.. on the other
Anticodons ; amino acid attachment site
Ribosomes are made of
ribosomal RNA (rRNA) and proteins
Ribosomes have binding sites for
tRNA and mRNA
Translation has three phases
Initiation
Elongation
Termination
Initiation
An mRNA, a tRNA with methionine, and two subunits of a ribosome meet
The initiator tRNA binds them all to the P site, where the start codon AUG is located
Elongation+Termination
As the mRNA moves the codons, a tRNA with a complementary anticodon pairs with the codons, adding its amino acids to the polypeptide chain
The tRNA is then translocated from the P site to the E site
Elongation continues until a stop codon reaches the A site and calls for termination
Mutations are changes in the
.. for….
Genetic material ; cells or viruses
Point mutations are … in …
Chemical changes ; one nucleotide pair of genes
A change in a single nucleotide can cause
abnormal proteins
If a point mutation occurs in a gamete (reproductive cell), it may be transmitted to
To offspring
Point mutation
Single nucleotide-pair substitution
Nucleotide-pair insertion or deletion
Nucleotide-pair substitution
Replaces one pair of nucleotide and its partner with another pair
Silent mutation
The codons change, but they still code for the same amino acid, making it redundant
Missense mutation
The codons still code for an amino acid, just not the right one
Substitution mutations are usually missense mutations
