Protein synthesis Flashcards
How is DNA stored in eukaryotes?
DNA in eukaryotes is linear, stored as chromosomes, and found in the nucleus. It is wound around proteins called histones and coils tightly to form chromosomes.
How is DNA stored in prokaryotes?
DNA in prokaryotes is shorter, circular, not wound around histones, and condensed by supercoiling.
What is a gene?
A gene is a sequence of DNA bases that codes for a polypeptide or functional RNA.
What determines the primary structure of a protein?
The sequence of amino acids, which is determined by the sequence of bases in a gene, determines the primary structure of a protein.
What is meant by “triplet” and “degenerate” in the genetic code?
Each amino acid is coded for by a sequence of 3 bases (triplet). The code is degenerate because more than one codon can code for the same amino acid.
What is the function of mRNA?
mRNA is a transcript of a gene used to build a protein in translation.
What is the function of tRNA?
tRNA carries amino acids to ribosomes during translation. It has a complementary anticodon to the codons on mRNA.
What is rRNA and its role?
rRNA is the primary component of ribosomes and helps catalyse the synthesis of polypeptides.
What are introns and exons?
Introns are non-coding sections of DNA that do not code for polypeptides. Exons are the coding sections of DNA.
What are non-coding repeats?
Non-coding repeats are DNA sequences with multiple repeats that do not code for amino acids.
What is an allele?
An allele is a slightly different version of a gene that codes for a slightly different version of a polypeptide.
What happens in transcription?
- DNA polymerase attaches to the beginning of a gene. 2. DNA helicase breaks H-bonds to unwind DNA. 3. One strand acts as a template to form mRNA. 4. Free RNA nucleotides pair with exposed bases, joined by RNA polymerase. 5. RNA polymerase stops at a stop signal. 6. mRNA leaves the nucleus.
How does translation occur?
- mRNA attaches to a ribosome. 2. tRNA brings amino acids and pairs its anticodon with the first codon on mRNA. 3. A second tRNA binds, and amino acids join by peptide bonds. 4. This continues until a stop codon is reached. 5. The polypeptide chain detaches.
What is a mutation?
A mutation is a change in the sequence of DNA bases that affects coding for amino acids.
What does it mean that DNA is “non-overlapping”?
Base triplets do not share bases; each base is part of only one triplet.
Why is DNA described as “degenerate” and “universal”?
DNA is degenerate because multiple codons can code for the same amino acid. It is universal because the same triplets code for the same amino acids in all organisms.
What is an insertion mutation?
An insertion is when a new base is added, causing a frame shift.
What is a deletion mutation?
A deletion is when one or more bases are removed, causing a frame shift.
What is a substitution mutation?
A substitution occurs when one base is replaced by a different base.
What happens in inversion and duplication mutations?
Inversion: A group of bases is reversed. Duplication: One or more bases are repeated.
What is nondisjunction, and what condition can it cause?
Nondisjunction occurs when chromosomes fail to separate during meiosis, leading to gametes with extra chromosomes. It can cause conditions like Down’s syndrome.
What is the impact of frame shift mutations?
Frame shift mutations change the sequence of triplets, producing different amino acids and altering protein structure and function.
How do mutations contribute to natural selection?
Mutations create genetic variation, increasing chances of survival through natural selection.
What happens during Prophase I of meiosis?
The nuclear membrane breaks down, chromosomes condense, and crossing over may occur.
