Genes Flashcards
What is a gene?
A unit of DNA that expresses a function
- makes proteins
- makes RNA
Genes must be expressed or regulated.
What is the central dogma?
DNA stores information
RNA reads, decodes and uses that information to make proteins via ribosomes
Describe RNA?
- pentose sugar is ribose
- uracil instead of thymine
- single stranded
mRNA
tRNA
rRNA
snRNA
What is a codon?
How many are there?
How many amino acids do they code for?
A sequence of 3 amino acids
- 64 codons
- 20 amino acids
What are the stop codons?
TAA, TAG, TGA
What is the start codon?
AUG
What is the reading frame?
The frame in which transcription happens. Depending on the start base, different amino acids would be coded for.
Why is the genetic code redundant or degenerate?
Amino acids can be coded for by more than one codon.
What are the steps in transcription?
- DNA helicase ‘unzips’ the 2 stands of DNA
- promotor sequence tells RNA polymerase where to start.
- RNA ploymerase moves in a 3’-5’ direction
- terminator sequence tells it where to finish.
What happens in translation?
- mRNA moves from the nucleus to the ribosomes
2. tRNA decodes codons into amino acids
What do bacteria and archaea use to control transcription?
Each operon is regulated by one single promoter and operator mechanism.
Whether the operon is transcribed or not depends of whether the repressor is bound to the operator region or not.
What is Neoteny?
Where juvenile traits in the ancestor are retained in the adult of the evolved species.
e.g. human head shape is more similar to that of a juvenile chimp than an adult (probably to allow for a larger brain)
What is alternative splicing?
Single genes can code for more than one protein by rearranging the introns and exons. Occurs more in complex organisms.
