Chapter 6: Nucleic Acids & Protein Synthesis Flashcards
What are the 4 topics under this unit?
- Structure and function of nucleic acids
- DNA replication
- Protein Synthesis
- Mutation
What is a nucleotide composed of?
- Phosphate group
- Pentose sugar
- Nitrogenous base
What are the bonds between neighbouring nucleotides and what is the bond between base pairs?
- Between nucleotides: Phosphodiester bond
- Between base pairs: Hydrogen bond
Name the 5 kinds of nitrogenous bases and identify which base pairs together
- Adenine & Thymine
- Guanine & Cytosine
- Uracil & Adenine
How many rings does a purine have? Which nitrogenous bases are purines?
- 2 rings
- Guanine & Adenine
How many rings does a pyrimidine have? Which nitrogenous bases are pyrimidine?
- 1 ring
- Cytosine, Uracil & Thymine
Differenciate between RNA and DNA
- RNA is usually single-stranded while DNA is usually double-stranded // double-helix structure
- RNA has a ribose sugar while DNA has a deoxyribose sugar
- RNA has URACIL while DNA has THYMINE
What are 3 examples of polynucleotides?
RNA
DNA
ATP
Identify 3 kinds of RNA and state their function
mRNA: transfers replicated genetic information to ribosomes for protein synthesis
rRNA: forms ribosomes, needed for protein synthesis
tRNA: brings amino acids from the cytoplasm to the ribosomes to create proteins
What is ATP composed of?
- 3 phosphate groups
- Adenine molecule
- a Ribose sugar
What is the function of ATP?
Used as the energy “currency” of the cell; provides energy needed for work
State the name for the model on how DNA is replicated and explain what it means.
- Semi-conservative
- Half of each DNA molecule contains 1 strand of the original parent DNA
Identify the 4 enzymes and their purposes in DNA replication
- Helicase - unwinds DNA
- DNA polymerase - adds base pairs to template strands and proofreads its own work
- Primase - adds “RNA primers” on the lagging strand that indicate to the DNA polymerase on where it should work
- Ligase - “glues” or joins together Okazaki fragments to the lagging strand
DNA is replicated in the ____ to _____ direction
So the leading strand is in the ___ to ___ direction
5’ –> 3’ direction
3’ –> 5’ direction
Why is DNA antiparallel?
This arrangement allows for complementary nucleotide bases to pair with one another
Define gene
A sequence of nucleotides that composes part of a DNA molecule that codes for a polypeptide // protein
What is a codon?
Series of 3 nucleotides in a DNA molecule that codes for 1 amino acid
State 3 characteristics of codons and what it means.
- UNIVERSAL: same for all organisms; can be read by all organisms
- REDUNDANT // DEGENERATE: some codons code for the same amino acid, which protects the body from mutations
- NON-OVERLAPPING: each triplet is separate from other triplets; each triplet is strictly 3 nucleotide bases
State 2 stages of Protein Synthesis
- Transcription (DNA –> RNA)
2. Translation (mRNA –> Proteins)
State the 4 stages of Transcription and outline what happens at each stage
- INITIATION: RNA polymerase attaches to a region of DNA called the “Promoter”
- ELONGATION: Strands separate and RNA polymerase begins to form a strand of complementary nitrogenous bases to the template strand
- TERMINATION: newly-synthesized RNA strand is detached from original DNA molecule and DNA returns to its double-helical structure
- POST-TRANSCRIPTIONAL MODIFICATION: Addition of Guanine to the start, Addition of 100 Adenine nucleotides to the tail, removal of introns
What are introns?
The non-coding components of a DNA or RNA strand
Why are 100 adenine molecules added to the mRNA during transcription?
It serves as protection from breakdown by nucleases
Outline 5 stages of translation
- AMINO ACID ACTIVATION: amino acids bind with tRNA through the usage of ATP. ATP will also be used later on to form peptide bonds with other amino acids.
- ATTACHMENT TO RIBOSOME: mRNA strand binds to the ribosome.
- tRNA: tRNA (each with their own amino acid) will bind with sites found on the ribosome (P -> A -> E) based on the anticodon of tRNA being complementary to the codon found on the mRNA.
- MOVEMENT OF RIBOSOME: After neighbouring amino acids are bonded together via, peptide bonds, to form a strand, the ribosome moves further along the mRNA strand, releasing amino acids found on the E-site, and allowing space for more amino acids to be bound to the ribosome.
- STOP CODON: When the ribosome reaches a stop codon, the polypeptide chain is released from the ribosome.
Define Mutation
a random unpredictable change in DNA
State 3 ways how mutations can arise
- change in the sequences of bases of one part of a DNA molecule
- addition of DNA or loss of DNA from a chromosome
- change in the total number of chromosomes in a cell
What is a point mutation?
Genetic mutation where a single nucleotide base is changed, deleted or inserted
Identify and explain 3 possible effects of point mutations:
- SILENT MUTATION - mutation in DNA that does not cause a subsequent change in amino acid output
- MISSENSE MUTATION - mutation in DNA that results in a codon for a different amino acid
- NONSENSE MUTATION - mutation in DNA that causes a protein to stop//terminate earlier than expected; codes for a STOP codon
What kind of point mutation is Sickle Cell Anaemia?
Substitution mutation
What is the importance of hydrogen bonding in DNA?
- Holds 2 polynucleotide strands together // prevents unwinding
- Allows for the double-helix structure of DNA
- Increases stability of DNA molecule
Gene codes for _____
Codon codes for ____
- Protein // polypeptide chain
- Singular amino acid
