8) DNA, genes and protein synthesis Flashcards
What is a gene?
A section of DNA that codes for a polypeptide or functional RNA.
What is a locus?
Specific location of a gene on a DNA
How many bases make up a codon in the genetic code?
Three bases.
Why must codons be made of 3 bases?
To provide 64 combinations, enough for 20 amino acids.
What does it mean that the genetic code is degenerate?
More than one triplet can code for the same amino acid
What is the start codon and what does it code for?
AUG, which codes for methionine.
What are stop codons?
Codons that signal the end of a polypeptide chain; they don’t code for amino acids.
Why is the genetic code called non-overlapping?
Each triplet is read separately and once
Why is the genetic code called universal?
Same codons are used across all organisms
What are exons?
Coding regions (used to build polypeptides)
What are introns?
Non-coding regions (removed before translation)
What else can DNA code for besides proteins?
rRNA or tRNA.
How is DNA packed into chromosomes?
DNA wraps around histones
Coils into loops
Coils form chromosomes.
What are homologous chromosomes?
Pairs of chromosomes with the same genes but possibly different alleles, one from each parent.
What is an allele?
A version of a gene that may result in different protein versions.
How can a mutation form a new allele?
By changing the base sequence, altering the protein’s shape/function.
What is RNA made of?
- A pentose sugar (ribose)
- A phosphate group
- A nitrogenous base (A,U,C,G)
Which base does RNA use instead of thymine?
Uracil (U).
What is the function of mRNA?
Carries the genetic code from nucleus to ribosomes.
How is mRNA formed?
By transcription, complementary to the DNA template strand.
What is the function of tRNA?
Carries specific amino acids
Anticodon that binds to the mRNA codon.
What is a codon?
3 bases on mRNA coding for an amino acid.
What is an anticodon?
3 bases on tRNA that pair with an mRNA codon.
What is transcription?
The process where DNA instructions are copied to make pre-mRNA.
What is the role of RNA polymerase?
Joins RNA nucleotides together to form pre-mRNA.
What happens in splicing?
Introns are removed, and exons are joined to form mature mRNA.
Where does mRNA go after transcription?
Through a nuclear pore to the ribosome in the cytoplasm.
What is translation?
The decoding of mRNA to assemble a polypeptide chain.
What initiates translation?
Ribosome binds to the start codon (AUG), and tRNA brings methionine.
How are amino acids joined?
Peptide bonds form using ATP and an enzyme.
What happens when a stop codon is reached?
Translation stops and the polypeptide is released.
How many proteins can be made from one mRNA strand?
Many—multiple ribosomes can translate it simultaneously.
What are the stages of protein folding?
Secondary (coils/folds), Tertiary (3D shape), Quaternary (multiple polypeptides combine).
