Chapter 16: Central Dogma Flashcards
What is gene expression?
the set of processes that convert information in DNA into a product (typically a protein)
What does the one-gene, one-enzyme hypothesis say?
each gene contains the information encoded to make one (and only one) enzyme
What is the central dogma?
DNA (nucleus) —–> RNA ——> protein (cytoplasm)
Describe transcription in the central dogma.
uses DNA template to make an RNA molecules with a complementary sequence
Describe translation in the central dogma.
uses information in mRNA to synthesize protein
What are the two modifications of the central dogma?
- RNA molecules do not code for protein
- reverse transcriptase
Which RNA molecules do not code for proteins?
- ribozymes
- introns with pre-mRNA
- sequences that regulate gene expression
What is reverse transcriptase?
- enzyme that makes DNA from RNA
- used by many viruses
- important tool for researchers
What is a codon?
a group of three DNA bases that specifies a particular amino acid
What is the start codon?
AUG (codes for Met)
What are the 3 stop codons?
UAA, UAG, UGA (don not code for amino acids)
How do you predict amino acid sequences from codons?
- draw the non template DNA strand 5’ to 3’
- draw the template strand by flipping non template 3’ to 5’
- Transcription (A goes to U, T goes to A, etc.)
- Translate with amino acids
What are the 5 features of the genetic code?
- redundant
- unambiguous
- non-overlapping
- universal
- conservative
- redundant (genetic code)
most amino acids coded for by multiple genes (degeneracy)
- unambiguous (genetic code)
each codon codes for only one amino acid
- non-overlapping (genetic code)
codons are read one after another (reading frame)
- universal (genetic code)
codons code for the same amino acids in (almost) all organisms
- conservative (genetic code)
when multiple codons code for the same amino acid, usually only the third base differs (wobble base)
What are point mutations?
alters the sequence of one or a small number of base pairs
What are the 4 types of point mutations?
- silent
- missense
- nonsense
- frameshift
What is a silent mutation?
- change in nucleotide sequence that doe snot change the amino acid specified by a codon
- no change in phenotype; neutral with respect to fitness
What is a silent mutation?
- change in nucleotide sequence that doe snot change the amino acid specified by a codon
- no change in phenotype; neutral with respect to fitness
What is a missense mutation?
- change in nucleotide sequence that changes the amino acid coded by a codon
- change in primary structure of protein (can be beneficial, neutral, or deleterious)
What is a nonsense mutation?
- change in nucleotide sequence that causes early stop codon
- leads to mRNA breakdown or a shortened polypeptide; usually deleterious
