Unit Eight - Molecular DNA Flashcards
Definition of DNA (2)
Classification & Function
- Type of Nucleic Acid
- Carries Genetic Material
Classification & Function
Definition of RNA (2)
- Type of Nucleic Acid
- Messenger in process of converting DNA to Protein
What is a nucleotide made up of? (3)
- Phosphate Group
- Pentose Sugar
- Nitrogen Base
What are the 3 main types of RNA? (3)
- mRNA (messenger RNA)
- rRNA (ribosomal RNA)
- tRNA (transfer RNA)
Definition of Deoxyribose (3)
Classification, Structure & Function
- Pentose Monosaccharide
- Forms the backbone of DNA
- Links w/ phosphate & nitrogenous bases in nucleotides
What is a saying that can help you memorize base pairings?
Apples in the Tree (Adenine & Thymine)
Cars in the Garage (Cytosine & Guanine)
What are the 4 nitrogenous bases of DNA?
Adenine, Thymine, Guanine and Cytosine
Definition of Purines (3)
Classification, Structure & Example
- Nitrogenous Base
- Two-ring structure
- Adenine & Guanine
Definition of Pyrimidines (3)
Classification, Structure & Example
- Nitrogenous Base
- Single ring structure
- Cytosine, Thymine & Uracil
What is the structure of DNA? (2)
- Backbone
- Rungs/Bases
Definition of the Backbone (2)
- Alternating Phosphates & Sugars
- Held together by strong covalent bonds
How are Nitrogenous Bases of DNA held together?
Hydrogen Bonds
What is Chargaff’s Base Pairing Rule?
Percent of Purines = Percent of Pyrimidines
(In each base pairing)
The amount of adenine (A) roughly equals the amount of thymine (T).
The amount of guanine (G) roughly equals the amount of cytosine (C).
What does it mean when DNA is antiparallel? (2)
- DNA has two strands that run in opposite directions
- One strand runs from 5’ to 3’, and the other runs from 3’ to 5’
What is 5’ and 3’ in context of DNA? (3)
- The ends of each strand is 5’ & 3’
- 5’ end has a phosphate group attached to 5th carbon atom of deoxyribose
- 3’ end has a hydroxyl group attached to 3rd carbon atom of deoxyribose
WHY is DNA antiparallel? (3) (READ THROUGH)
- H - bonds are formed between bases in a way that requires the strands to run in opposite directions
- Alignment maximizes H - Bonds & consistent distance between both strands, stabilizing the double helix structure
- Allows DNA polymerase to add new nucleotides bc it can only add nucleotides in one direction (5’ to 3’), so having the strands run in opp. directions ensures that both new strands can be synthesized simultaneously
What is the process of DNA Replication? (7)
- Helicase Unzips DNA
- Primase forms RNA primers to bind to template strand
- DNA Polymerase III adds nucleotides continuously (leading) & separately (lagging)
- RNA primers are replaced w/ DNA nucleotides by DNA Polymerase I
- Ligase seals Okazaki fragments
- DNA Polymerase I checks/corrects errors
- Semiconservative Replication is Complete
Definition of Replication Fork (3)
Structure, How, Function
- Y-shaped structure
- Formed during DNA replication (Helicase Unzips DNA)
- Forms two template strands for synthesis of new complementary strands
Definition of Okazaki Fragment (2)
- Short segment of DNA synthesized on the Lagging strand
- Fragments join together by Ligase to form a continuous strand
Definition of Lagging Strand (5)
Classification, Definition, & Importmant Characteristics
- Newly synthesized DNA strand in the process of DNA replication
- DNA Strand in the 3’ to 5’ Direction
- DNA Polymerase can only add nucleotides in the 5’ to 3’ direction
- Lagging Strand is synthesized in short fragments called Okazaki Fragments
- Ligase joins these fragments together to form a continuous strand
Definition of Leading Strand (3)
- Newly synthesized DNA strand in DNA replication
- DNA Strand in 5’ to 3’ Direction
- DNA Polymerase III adds nucleotides to the 3’ end, causing it to grow from in the direction of 5’ to 3’
Definition of DNA Polymerase III (2)
- Enzyme adds nucleotides to template strand
- Can only add nucleotides to the 3’ end
What do they mean by “Original DNA is a Template”?
Each strand of DNA guides the formation of a new complementary strand
What is the process of unzipping? (5)
- Enzyme Helicase
- Unwinds & Separates two strands of DNA
- Breaks H - Bonds between Bases
- Forms a Replication Fork
- Exposes Nitrogenous Bases
Where can free nucleotides be obtained from?
Floats in the Nucleus from you Diet
What are RNA Primers? (4)
- Synthesized by Primase
- Binds to template strands
- Provides starting point for DNA polymerase to add nucleotides
- RNA primers later removed & replaced w/ nucleotide
Definition of Central Dogma
DNA Replication → Transcription → Translation
DNA → RNA → Protein
What is RNA made up of? (3)
- Phosphate
- Ribose
- Nitrogen Base
Definition of mRNA
Name, Function & Involement
- Messenger RNA
- Takes code instructions from DNA to Ribosomes
- Transcription & Translation
Definition of tRNA
Name, Function & Involement
- Transfer RNA
- Carries AA to Ribosome
- Translation
Definition of rRNA
Name, Function & Involement
- Ribosomal RNA
- Makes up Ribosomes
- Translation
Why does RNA leave the nucleus instead of DNA?
DNA is too large/complex to leave
(DNA code is converted to RNA code & interpreted by ribosome into AA sequence)
Definition of Transcription
Messenger RNA is synthesized from a template of DNA
What is the process of Transcription? (4)
- DNA Unzipped
- RNA Polymerase reads Antisense Strand
- Triplets of DNA is transcribed to complementary codon
- mRNA detaches & moves out of the nucleus
What is the Sense & Antisense Strand?
- Strand used as template for RNA synthesis is antisense strand
- Strand that has a sequence identical to the RNA is sense strand
Why is the RNA strand identical to the Sense strand rather than the Antisense Strand? (READ)
- RNA polymerase reads the template strand
- Builds the RNA transcript
- Creates an RNA sequence complementary to the template strand
- Sense strand is also complementary, making them both identical
Definition of Triplet & Codon
Triplet - 3 Base Letters of DNA
Codon - 3 Letters on RNA (Complementary to Triplet)
Triplet Sequence is Converted to a Codon Sequence
Definition of RNA Polymerase (3)
- Catalyzes the addition of RNA nucleotides
- Reads the DNA template strand from the 3’ to 5’ direction
- Synthesizes mRNA strand at 3’ end (in the 5’ to 3’ direction)
What does DNA Polymerase I do?
It removes RNA Primers in DNA Replication
What is the process of translation? (3)
- Step in Protein Synthesis
- Genetic Code Carried by mRNA decoded by Ribosomes
- Produces Specific Sequence of AA in a Protein
What are the three steps of translation?
- Initiation
- Translocation & Elongation
- Termination
What is initiation in translation? (4)
- Small ribosomal subunit binds to the mRNA
- Scans mRNA for Start Codon (initiates rxn)
- Initiator tRNA binds to Start Codon (later at P Site)
- Large Subunit Binds to create the A Site & P Site
Definition of Start Codon (3)
- AUG - Codes for Methionine
- Located on mRNA
- Signals beginning of translation
What is the Ribosome made of?
- Ribosomal RNA (rRNA)
- Ribosomal Proteins
- Small Subunit
- Large Subunit
What is the A Site? (3)
- 1st Binding Site on Ribosome
- Where new tRNA first bind to the ribosome
- New tRNA carrying the next AA will later be added to the growing polypeptide chain at the P Site during elongation
What is the P Site? (3)
- 2nd Binding Site on Ribosome
- Where Initiator tRNA first resides (initiation)
- Removes AA from tRNA to bind w/ other AA, creating a growing polypeptide
What is the E site? (2)
- 3rd Binding Site on Ribosome
- tRNA w/o AA exits Ribosome
What is the Anticodon?
- Triplet on tRNA
- Complementary to codon on mRNA
What is Translocation in Translation? (2)
- Ribosome moves down mRNA 5’ to 3’ from codon to codon
- Continues elongation & cycling of tRNA & AA between A Site, P Site & E Site
What is Termination in Translation?
When a Stopcodon is reached, a release factor binds to the A site and translation is terminated
Definition of Stopcodon
- Located at the end of mRNA
- Signals release factor to bind & terminate rxn
Definition of Initiator tRNA
- Carries AA Methionine
- Carries Anticodon (UAC) complementary to Start Codon
- Binds to Start Codon at P Site
Where did rRNA and tRNA come from?
Coded by DNA
Definition of Genetic Mutation
Alteration in Sequence of Nucleotides in DNA
(ALL MUTATIONS OCCUR IN DNA NOT RNA)
What are different types of Chromosomal Mutations?
- Addition/Deletion
- Inversion
- Translocation
What are 2 types of Genetic Mutations?
- Point Mutations
- Insertion/Deletion Mutations
Definition of Point Mutation (5)
- Changes a single nucleotide base pair
- Silent - No Affect/Still Codes for the Same AA (3rd Letter)
- Nonsense - STOPCode/Codes for no Protein
- Missense - Codes for Diff. AA (Changed Protein Shape = Changed Function)
- AKA Base - Pair Substitution
Definition of Insertion/Deletion Mutations (4)
- Insertion/Removal of Nucleotide
- AKA Frame Shift Mutation
- Changes the Reading Frame/Grouping of Codons
- Results in a completely different protein sequence (nonfunctional)
How do you know whether a DNA strand is sense or antisense strand?
In order to find the sense strand, if you convert the first triplet to a codon, the sequence should be AUG (STARTCODON)
