Exam 3 Flashcards
Monomer of DNA?
Nucleotides
What are Pyrimidines and give examples?
Nitrogenous base with one ring
C (cytosine)
T (Thymine)
What are purines and give examples?
Nitrogenous bases with 2 rings
A (adenine)
G (guanine)
Describe the structure of a DNA
Nitrogenous base (A,T,G,C)
Deoxyribose Sugar
Phosphate group
The backbone of dna is the _____
Sugar-phosphate backbone
What is found at the 5’ end and the 3’ end?
5’: Phosphate group
3’: OH-
What are the nitrogenous base pairings?
Adenine & Thymine
Guanine & Cytosine
Nitrogenous bases in DNA vs RNA
RNA swaps the Thymine in DNA for Uracil
DNA - A, T, G, C
RNA - A, U, G, C
The sugar in DNA is _______
deoxyribose
The sugar in RNA is _______
ribose
How are the nitrogenous bases connected within the double helix?
Hydrogen bonds
Describe mRNA
Messenger RNA
Translates DNA into form readable for cells. (T —> U)
Describe rRNA
Ribosomal RNA
Helps mRNA bind to a spot on ribosome
RNA that acts as enzyme is called _______
Ribozymes
Describe tRNA
Transfer RNA
Brings amino acids to ribosome and ensures it is the amino acid specified by mRNA
How do regulatory mRNA (miRNA & siRNA) maintain homeostasis?
Bind to mRNA molecules and reduce their stability or interfere with the translation
Topoisomers function
Prevents supercoiling
Prevents double helix from getting to tightly wound as it is being opened
Helicase function
Breaks the hydrogen bonds that bind the nitrogenous bases in DNA.
Splits the DNA.
Function of RNA Primer
What’s synthesizes primer?
Begins the synthesis of DNA strands
-Primase
What is DNA polymerase?
Enzyme that creates new DNA by adding nucleotides to growing DNA chain
In what direction do nucleotides get added?
5’ —-> 3’
What is the replication fork?
The Y-shape created by the splitting of the DNA helix
Describe the leading strand
5’ –> 3’ moves in the same direction as the DNA polymerase
Complimentary strand moves toward the replication fork
Describe the lagging strand
Moves away from the fork
Made in fragments because as the fork moves forward, the DNA polymerase has to detach and reattach on newly formed DNA
What is the Okazaki Fragments?
The small fragments made on the lagging strand. New primer is required for each fragment
Main function of DNA polymerase III?
Makes the bulk of new DNA
Main function of DNA polymerase I?
Removes RNA primers and replaces it with DNA
Basic DNA replication is called semi-conservative. What does this mean?
Each new strand of DNA contains one old and one new strand.
What is conservative DNA replication?
Replication results in one molecule consisting of both old strands and another molecule containing 2 new strands
Describe dispersive DNA replication
2 DNA molecules are formed as mixtures/patchwork of both the Parent & Daughter DNA
What enzyme is responsible for proofreading?
DNA polymerase
What is the function of Telomeres and how can you identify them?
Telomeres act as caps to protect internal chromosomes. (prevent loss of genes)
They are repetitive regions found at the end of some chromosomes
5’-TTAGGG-3’
What is the function of Telomerase?
How does it work?
Enzyme that prevents telomere shortening.
Synthesis of telomeres by creating DNA by using RNA as a template
Main idea of transcription
Copies DNA sequence from gene using RNA alphabet (A –> U)
Creates mRNA
What is gene expression?
Info from a gene is used to construct a protein
What is RNA polymerase?
Uses single strand of DNA as template to synthesize a complimentary strand of RNA
RNA polymerase vs DNA polymerase
DNA polymerase is the enzyme used in DNA replication whereas RNA polymerase is the enzyme used in transcription
Describe initiation and the promoter region
Initiation is the first step in gene expression in which RNA polymerase separates the DNA into single strands at the promoter.
Promoter - Tells RNA polymerase where to bind to
Describe elongation and what information the RNA transcript contains
Elongation is when a complimentary (coding) strand is created from a template strand. The RNA transcript copies the coding strand swapping the T –> A.
What are terminators?
Sequences on genes that signal the RNA polymerase to end the transcript
Which strand does RNA transcript bind to?
Template strand
What is the coding strand?
The complimentary strand
Where is mRNA found?
Nucleus
What is translation?
Converts information from mRNA into proteins at the ribosome
What is the start codon?
AUG
Define genetic code
Collection of the codon-amino acid relationships
What is the central dogma?
Process of information flow from genes to proteins
DNA -> RNA -> Proteins
(Substitution Mutation) Silent mutations
Has no effect on the amino acid
(Sub. Mutation) Nonsense mutations
Results in a stop codon where it shouldn’t be
(Sub. Mutation) Missense mutations
Changes the amino acid specified by the codon
Frameshift mutations
Insertion or deletion of one or more bases
What is an inducible operon?
A type of operon that is turned “off” until a small molecule called an inducer binds to it and turns it on.
Describe lac operon
An inducible operon responsible for enzymes that metabolize sugar lactose
What are repressible operons?
Type of operon that is turned “off” until small molecule called corepressor turns it on.
Describe trp operon
Repressible operon responsible for enzyme that synthesizes amino acid tryptophan
What is DNA Cloning and how does it work?
Identical copies of a piece of DNA
Gene is cut from DNA strands and attached to a plasmid that is given to a bacteria to reproduce it.
DNA Ligase
An enzyme that joins strands of DNA together
