4 Genetic Information: 8 DNA, genes and protein synthesis Flashcards
(19 cards)
What is a gene?
A base sequence of DNA that codes for
- the amino acid sequence of a polypeptide
- a functional RNA (including ribosomal RNA and tRNAs)
What is a locus?
A fixed position on a particular DNA molecule that a gene occupies.
What is a triplet?
A sequence of three DNA bases that codes for a specific amino acid.
What features does the genetic code have? What do they mean?
Universal - the same triplet codes for the same amino acid in all organisms
Non-overlapping - each triplet only reads once
Degenerate - one amino acid can be coded for by more than one codon
What are exons?
Coding sequences for amino acids.
What are introns?
Non-coding sequences within a gene.
What are DNA molecules like in prokaryotic cells?
Short, circular, and not associated with proteins.
What are DNA molecules like in eukaryotic cells?
Long, linear, and associated with proteins (histones).
What are the DNA molecules like in mitochondrion and chloroplasts?
Like prokaryotic DNA, they are also short, circular, and not associated with proteins.
What is the genome?
The complete set of genes in a cell.
What is the proteome?
The full range of proteins that a cell is able to produce.
What is the structure of a molecule of mRNA?
- a single polynucleotide strand with more nucleotides
- has codons
- doesn’t have base pairing/ hydrogen bonding
- doesn’t have an amino acid binding site
What is the structure of a molecule of tRNA?
- single polynucleotide that is folded into a clover shape
- has hydrogen bonds between specific base pairs
- has an anticodon
- has an amino acid binding site
What is transcription?
The production of mRNA from DNA using RNA polymerase in joining mRNA nucleotides.
In prokaryotes, what does transcription result in?
mRNA
In eukaryotes, what does transcription result in?
The production of pre-mRNA which is then spliced to form mRNA.
What is translation?
The production of polypeptides from the sequence of codons carried by mRNA.
What is the process of transcription?
In eukaryotes:
1. DNA helicase breaks the hydrogen bonds between the two DNA strands, uncoiling the double helix to expose some bases.
2. One of the strands is used as a template to make an mRNA copy.
3. The RNA polymerase lines up free RNA nucleotides alongside the exposed bases on the template strand via complementary base pairing. (U instead of T)
4. RNA polymerase joins the RNA nucleotide, forming phosphodiester bonds to form pre-mRNA.
5. The hydrogen bonds reform between the DNA strands.
6. Once the RNA polymerase reaches the stop triplet, it detaches from the DNA.
7. Splicing occurs where introns are removed to leave only the exons, forming mRNA.
8. The mRNA then leaves the nucleus through a nuclear pore.
What is the process of translation?
- The mRNA attaches to a ribosome which moves along the strand.
- A tRNA molecule (carrying a specific amino acid) with a complementary anticodon attaches to the first codon on the mRNA.
- A complementary second tRNA molecule does the same.
- The two amino acids are joined by a peptide bond using ATP.
- The first tRNA molecule is released and free to collect another amino acid.
- The process continues until a stop codon is reached which causes the ribosome to detach, leaving a polypeptide chain.
