Proteins + Nucleic Acids Flashcards
How can an enzyme be phosphoralated? (2)
- Attachment of phosphate
- Hydrolysis of ATP
Explain how selection occurs in living organisms? (5)
- Variation due to mutations
- Due to different environmental conditions/selection pressures
- Selection for advantageous allele to survive + reproduce
- Which leads to change in alleles frequency
- Occurs over a long period of time
What is directional selection? (4)
- Selection for only one extreme
- Organisms with advantageous alleles will have increased reproductive success
- Alleles are passed onto future generations
- Overtime, frequency increases
What is stabilising selection? (3)
- Selection against both extremes
- Only mean phenotype will have reproductive success so alleles are passed onto future generations
- Over time, frequency of mean alleles increases
Definition of:
- Phenotype
- Genotype
- Characteristics
- Alleles in an organism
Describe 2 aseptic techniques used when transferring a sample of broth culture onto an agar plate? Explain?
1) Open petri dish as little as possible - to prevent unwanted bacteria contaminating the dish
2) Wear gloves/mask - to prevent contamination from bacteria on hands/mouth
3) Flame the loop/neck of culture - to maintain a pure culture of bacteria
Define ‘gene mutation’
Explain how a gene mutation can have:
- No effect on an individual
- A positive effect on an individual
Change in the bases resulting in the formation of new alleles
No effect:
- Genetic code is degenerate
- Change in amino acid but no effect on tertiary structure
Positive effect:
- Results in change in polypeptide that positively changes the properties
- May result in increased reproductive/survival success
Define the term exon
Base sequence coding for polypeptide
What are mutagenic agents? Includes? (3)
Increase the rate of spontaneous mutations
- High energy ionising radiation
- DNA reactive chemicals
- Biological agents
Consequences of a mutation? (2)
- May alter secondary structure - change in hydrogen bonds affecting alpha helices + beta-pleated sheets
- May alter tertiary structure - change position of H, ionic, disulphide bonds which changes active site of enzyme + make the protein non-functional
Types of mutations in DNA? What is it? (3)
- Substitution - silent mutation, sometimes degenerate
- Addition - frameshift
- Deletion - frameshift
Meaning of:
- Universal
- Degenerate
- Non-overlapping
- Same 3 bases on mRNA/DNA code for the same amino acid in all organisms
- More then 1 codon/triplet codes for the same amino acid
- Each base is only part of 1codon/triplet
Describe translation? (6)
- mRNA binds to ribosome
- TRNA’s anticodon binds to start codon of mRNA
- TRNA carries a specific amino acid
- TRNA is released as ribosome moves across mRNA strand
- Peptide bond forms between amino acids using energy from ATP
- Ribosome releases polypeptide when stop codon is reached
Describe transcription? (5)
- DNA helicase breaks hydrogen bonds
- Only 1 strand is used as a template
- RNA nucleotides are attracted to complimentary exposed bases (A+U, G+C)
- RNA polymerase joins adjacent nucleotides forming phosphodiester bonds through condensation reaction
- Pre-mRNA spliced to remove introns
Definition of:
- Allele
- Gene
- Histone
- Different version of a gene
- DNA base sequence that codes for a polypeptide
- A protein that linear DNA coils around