Protein Synthesis and Selection Flashcards
Define the term exon
Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;
Describe Transcription in Eukaryotes
- Hydrogen bonds (between DNA bases) break;
- (Only) one DNA strand acts as a template;
- (Free) RNA nucleotides align by complementary base pairing;
- (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
- RNA polymerase joins (adjacent RNA) nucleotides;
- (By) phosphodiester bonds (between adjacent nucleotides);
- Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
Describe Translation
- (mRNA attaches) to ribosomes
- (tRNA) anticodons (bind to) complementary (mRNA) codons;
- tRNA brings a specific amino acid;
- Amino acids join by peptide bonds;
- (Amino acids join together) with the use of ATP;
- tRNA released (after amino acid joined to polypeptide);
- The ribosome moves along the mRNA to form the polypeptide;
Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA)
- mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
- mRNA does not have an amino acid binding site, tRNA does;
- mRNA has more nucleotides;
- (Different) mRNAs have different lengths, all tRNAs are similar / same length;
- mRNA has codons, tRNA has an anticodon;
What is an allele?
(Different) form/type/version of a gene / different base sequence of a gene
A mutation of a tumour suppressor gene can result in the formation of a tumour.
Explain how
rate of cell division is too fast becomes out of control, as tumour suppressor becomes inactive, isnt able to control
Not all mutations result in a change to the amino acid sequence of the
encoded polypeptide.
Explain why.
code degenerate, another triplet codes for the same amino acid.
mutation in non-coding DNA
Aspartic acid and proline are both amino acids. Describe how two amino acids differ from one another.
have a different R group
Name 2 mutagenic agents
Ionising radiation - damage DNA molecules that alter DNA structure
Biological agents - viruses and bacteria
DNA reactive chemicals
Define what a gene mutation is
A gene mutation is a change to a single base in DNA sequence.
Explain how selection occurs in living organisms
- Variation due to mutation;
- Different environmental/abiotic/biotic conditions / selection pressures;
- Selection for different/advantageous, features/characteristics/mutation/ /allele;
- Differential reproductive success / (selected) organisms survive and reproduce;
- Leads to change in allele frequency;
- Occurs over a long period of time;
Define degenerate code
More than one codon for one amino acid
Explain what the term non-overlapping DNA means.
A base from one triplet cannot be used in an adjacent triplet
A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how
- Change in base sequence (of DNA/gene);
- Change in amino acid sequence / primary structure (of enzyme);
- Change in hydrogen/ionic/ disulphide bonds;
- Change in the tertiary structure/active site (of enzyme);
- Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.
- Triplets code for same amino acid (degenerate)
2. Occurs in introns /non-coding sequence;
