Gene expression Flashcards
What are introns and exons?
Introns- non-coding regions of DNA do not code for proteins)
Exons- coding regions of DNA (code for proteins)
How is gene expression controlled?
By the regulation of transcription and translation.
What does gene expression result in?
The phenotype of an individual human.
How are proteins formed?
From polypeptides.
What are polypeptides?
Chains of amino acids held together by peptide bonds and folded in various ways.
What are the three types of RNA needed during gene expression?
mRNA (messenger RNA), rRNA (ribosomal RNA), tRNA (transfer RNA)
Explain the structure of RNA.
RNA is single stranded, its nucleotides contain ribose instead of deoxyribose and the base Uracil (U) replaces Thymine found in DNA.
What happens during transcription?
- RNA polymerase moves along DNA, unwinding the double helix and aligning RNA nucleotides by complementary base pairing to form a primary transcript.
- introns are removed from the primary transcript and the exons spliced to form a mature mRNA transcript.
What is alternative RNA splicing?
Alternative splicing allows a primary transcript to form different mature mRNA molecules, depending on which sequences are treated as introns and which as exons.
What are codons?
Triplets of bases on mRNA.
What is produced during the translation of mRNA?
Polypeptides.
What are stop and start codons?
Most codons code for specific amino acids but there are also stop and start codons which stop and start translation.
What are ribosomes made of?
Ribosomal RNA (rRNA) and proteins.
Where do transcription and translation take place?
- Translation takes place in the ribosomes.
- mRNA carries a copy of the DNA code from the nucleus to the ribosomes where it is translated.
- Transcription takes place in the nucleus.
Give an account of Transfer RNA.
Transfer RNA folds because of base pairing and forms a triplet anticodon site and an attachment site for a specific amino acid.
