Module 4: Genetic Information, Variation & Relationships Flashcards
Describe prokaryotic DNA?
- Short, circular DNA molecules
- Not associated with histones
- Free floating in the cytoplasm
- Majority is coding DNA
Describe eukaryotic DNA?
- Long, linear DNA molecules
- Associated with histones
- Majority is non-coding DNA
- Located in the nucleus
What is a gene?
A gene is the base sequence of DNA that codes for a polypeptide or functional RNA.
What is a locus?
The fixed position of a gene on a particular DNA molecule.
What is a triplet?
A sequence of three DNA bases.
What are three features of the genetic code?
- Degenerate (some amino acids are coded for by more than one base triplet).
- Universal (each triplet codes for the same amino acids in all organisms).
- Non-overlapping (each base triplet is read once in the sequence & separate from the triplet before it and after it).
What is a codon?
Sequence of three bases on DNA.
What is an anticodon?
A group of three bases on a tRNA molecule.
What is an intron?
A non-coding sequence of bases within a gene.
What is an exon?
A sequence of bases within a gene that code for an amino acid.
What are multiple repeats?
Regions of non-coding DNA base sequences that are repeating.
What is the genome?
The complete set of genes in a cell.
What is the proteome?
The full range of proteins a cell is able to produce.
What is transcription?
The process where the DNA code is copied into mRNA.
What is translation?
The process where mRNA joins with a ribosome for protein synthesis to occur
Describe the structure of mRNA
- Linear shape
- Single polynucleotide strand
- A group of three adjacent bases form a codon
Describe the structure of tRNA
- Clover shape
- Single polynucleotide strand
- Hydrogen bonds present between specific base pairs
- Has an amino acid binding site at one end
- Specific sequence of three bases form an anticodon at the other end
Where does transcription occur in eukaryotes?
The nucleus
Where does transcription occur in prokaryotes?
The cytoplasm
What is the process of transcription?
- RNA polymerase attaches to DNA double helix.
- DNA helicase on RNA polymerase breaks hydrogen bonds between the two DNA strands, unwinding the DNA to expose the bases.
- One DNA strand acts as a template.
- The free RNA nucleotides are attracted to the exposed bases on the template strand & bind via complementary base pairing.
- RNA polymerase reforms the hydrogen bonds & the strands coil back into a double helix, forming pre-mRNA.
- RNA polymerase detaches from the DNA strand when it reaches a ‘stop’ triplet.
What is produced during transcription in a prokaryote?
mRNA
What is produced during transcription in a eukaryote?
pre-mRNA (containing introns & exons).
What is splicing?
The process of removing introns & joining exons in a pre-mRNA strand to form mRNA.
What is the process of translation?
- mRNA binds to the ribosome at the start codon.
- A tRNA molecule carries a specific amino acid (with a complimentary anti codon) binds to the codon on the mRNA molecule.
- A second tRNA molecule binds to the next codon on the mRNA.
- The two amino acids attached to the tRNA molecules are joined by a peptide bond (hydrolysis of ATP provides the energy).
- The first tRNA molecule moves away leaving behind its amino acid.
- The ribosome moves along the mRNA to produce the polypeptide chain