Topic 3 Flashcards
central dogma of bio
DNA =>(transcription) RNA =>(Translation) Protein
Promoter
DNA sequence that tells cell where to start making mRNA
in what direction is RNA made
5’ to 3’
exons
e=expressed
are going to be made into protein
introns
i=interspersed
not made into protein
splicing
takes out introns and leaves the exons
pathway of posttranscriptional mRNA processing
DNA template (3' - 5') -transcription Pre-mRNA (5'-3') -cap and tail added Processed pre-mRNA -splicing Spliced mRNA
relationship between exons and proteins
exons correspond to protein domains
start codon is always
AUG (MET)
what is the start codon
where the cell starts translation (starts polypeptide)
promoters
sequence of DNA that proteins bind to, to initiate transcription of 1 RNA from the DNA
silencers
a DNA sequence capable of binding transcription regulation factors (repressors)
prevent genes from being expressed as proteins
enhancers
short pieces of DNA that increase transcription of target genes
origins of replication
sequence where replication is initiated
telomeres
the end of a chromosome (repetitive sequences of non-coding DNA that protect the chromosome from damage)
centromeres
what separates into short and long arm during cell division, holds together the sister chromatids
tRNA
transfer RNA - read codons on RNA & mRNA and deliver the appropriate amino acid to the ribosome for protein sythesis
rRNA
ribosomal RNA
carries out protein synthesis in ribosomes
snRNA
processes pre-mRNA in the nucleus
noncoding DNA
used to be called “junk DNA”, but now scientists are finding out that noncoding DNA does have function
codes for things like regulatory regions, origins of rep, chromosomal structures and transcriptions of RNA mols
can you change the amount of gene product and why?
yes for example, in a stressed environment, more gene products will be created more quickly
which regulatory region of DNA sequence do you hypothesize that genes that control the same processes have in common?
promoters, because they are all responding to the same promotion signal
what are single nucleotide polymorphisms (SNP)
the most common type of genetic variation among people
what does each SNP represent
a difference in a single nucleotide change in DNA
how often do SNPs occur
occur once in very 300 nucleotides, roughly 10 million SNPs in the human genome
alternative splicing
enables an mRNA to directly synthesize defferent protein variants (this is why worms and humans are different)
what things can mutations effect
- promoter/enhancer/inhibitor sequences
- termination signals
- splice donor and acceptor sites
- ribosome binding sites
- also effects noncoding regions
point mutations or base substituation
change from one base pair to another
missense mutation
results in new triplet code for different amino acid
nonsense mutation
results in triplet code for stop codon (translation terminated prematurely)
silent mutation
new triplet code still codes for same amino acid
base subs - transitions
pyrimidine replaces pyrimidine or purine replaces purine
base subs - transversions
purine and pyrimidine are interchanged
frameshift mutations
- result from insertions or deletions of base pairs
- loss or addition of nucleotide causes shift in reading frame
- frame of triplet reading during translation is altered
ex)
UAG AAA
GAA
loss of function mutation
reduces/eliminates function of gene product
null mutation
results in complete loss of function
dominant mutation
results in mutant phenotype in diploid organism
dominant gain of function mutation
results in gene with enhanced negative, or new function
haploinsufficiency
a situation where the total level of a gene product produced by the cell is about half of the normal level, which is not sufficient for the cell to function normally
dominant-negative
a mutation resulting in a gene product that can interfere with the function of the normal gene product in heterozygotes
spontaneous mutations
changes on nucleotide sequence that occur naturally
how do spontaneous mutations arise
from normal biological or chemical processes that alter nitrogenous bases
spontaneous mutation rates
vary, but are exceedingly low for all organisms
induced mutations result from…
- extraneous factors (natural or artificial)
- radiation
- UV light
- natural and synthetic chemicals
what do mutations arise from
replication
why do mutations arise from replication
- replication is imperfect
- DNA polymerase occasionally
- misincorporated nucleotides persist after proofreading
- errors due to mispairing predominantly lead to point mutations
mutagens
-natural or artificial agents that induce mutations
examples of mutagens
- fungal toxins
- cosmic rays
- ultraviolet light
- industrial pollutants
- medical x-rays
- chemicals in tobacco smoke
what do repair systems counteract
spontaneous and induced DNA damage
counteract genetic damage that would result in genetic diseases and cancer
DNA repair system
maintains the integrity of genetic material
mutations in what gene cause cystic fibrosis
CFTR
what mutation class does the CFTR mutation belong to
loss of function
what gene codes for the lactase enzyme
LCT
individuals who can digest lactose have…
a mutation in the LCT regulatory element that leads to sustained lactose production in the small intestine and the ability to digest lactose throughout life
mutations in what gene cause sickle cell disease
HBB gene
loss of function
the altered gene product lacks the molecular function of the normally functioning gene
reduction of function
reduces the normal function
dominant negative
a mutation whose product negatively effects the normal wild type gene product within the same cell
gain of function
more function to the wild type
dominant gain of function
mutation in which the altered gene product has a new molecular function or new pattern of gene ecpression
