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OCR Biology A - 2.1.3 - Nucleotides and Nucleic Acids Part 2
This flashcard deck covers key concepts related to nucleotides and nucleic acids, including the nature of the genetic code, processes of transcription and translation, DNA structure, and the properties of ATP.
Nature of genetic code
Triplet code Non-overlapping Degenerate Universal
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Key Terms
Term
Definition
Nature of genetic code
Triplet code Non-overlapping Degenerate Universal
Synthesis of polypeptide
Transcription | Translation
Transcription
Conversion of the genetic code to a sequence of nucleotides in mRNA Reading the code and producing a messenger molecule to carry the code out to the c...
Translation
Converting the code in mRNA to a sequence of amino acids
Gene
A length of DNA that codes for one polypeptide
Start codon
Signals the start of a sequence that codes for a protein
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| Term | Definition |
|---|---|
Nature of genetic code | Triplet code Non-overlapping Degenerate Universal |
Synthesis of polypeptide | Transcription | Translation |
Transcription | Conversion of the genetic code to a sequence of nucleotides in mRNA Reading the code and producing a messenger molecule to carry the code out to the cytoplasm |
Translation | Converting the code in mRNA to a sequence of amino acids |
Gene | A length of DNA that codes for one polypeptide |
Start codon | Signals the start of a sequence that codes for a protein |
Stop codons | There are 3 codons that do not code for any amino acids and signal the end of a sequence |
Process of transcription | DNA strands separate (same process as replication) Sense strand contains code for protein (5’ to 3’) Free RNA nucleotides base pair to complementary bases exposed on antisense/ template strand (3’ to 5’) - used to build copy of coding strand RNA polymerase joins bases to form single-strand RNA (phosphodiester bonds) mRNA detaches from DNA template and strands reform helix. mRNA leaves through nuclear pores and enters cytoplasm |
Process of translation | mRNA enters ribosomal groove and binds to small subunit in ribosomes tRNA molecule carrying amino acid binds to mRNA start codon and another binds to next mRNA codon with complementary anti codons (max. 2) - these form H bonds Peptidyl transferase causes a peptide bond to form between amino acids Ribosome moves along mRNA, releasing first tRNA Process stops when ribosome reaches end of mRNA with stop codon and detaches |
Conservative model | Proposed that that the original DNA served as a complete template so that the resulting DNA was completely new |
Dispersive model | Proposed that the two new DNA molecules had part new and part old DNA interspersed throughout them |
Transcription unit | Comprises of at least one gene but often more |
mRNA vs complementary DNA sequence | They’re the same but T is replaced by U |
How many base pairs are there in one full turn of the DNA double helix | 10 |
Why is the double helix structure of DNA important | Keep DNA stable Enables it to fit much info in a small space Protects bases in the middle |
Role of DNA ligase | Joins sugar-phosphate backbone of DNA Catalyses formation of phosphodiester bonds Joins promoter to gene and promoter and gene to plasmids |
How is the replication fork formed | When the helicase starts to break H bonds between the bases on the two antiparallel strands |
Okazaki fragments | Short single stranded DNA molecule complementary to DNA on lagging strand |
Do start codons code for an amino acid | Yes only stop codons do not |
DNA polymerase | Reads in the 3' to 5' direction and builds in the 5' to 3' direction |
DNA extraction procedure | Grind sample in pestle and mortar - break cell wall Add detergent - breaks down csm Add salt - breaks H bonds between DNA and water Add protease - breaks down histones Add ethanol - causes DNA to ppt out of sol to be collected using a glass rod |
What types of activity does the cell require energy for | Synthesis e.g protein Transport Movement - sliding filament model |
What makes ATP a good immediate energy store | The interconversion of ATP and ADP is constantly happening so not much ATP is required |
Properties of ATP | Small - moves easily in and out of cells Water-soluble - energy requiring processes happen in aq Easily regenerated Releases energy is small quantities - energy not wasted as heat Contains bonds between phosphates w/ intermediate energy - large enough to meet needs of cellular reactions |