Genetics 2 Flashcards
protein synthesis is
the process where information encoded in the genome is translated into specific cellular function in the cytoplasm
genetic code=
sequence of adjacent bases ultimately determines the sequence of amino acids in the encoded poly peptide
rRNA
ribosomal RNA supports structural unit of the ribosomes
tRNA
transfer RNA is the link between code contained in base sequence of each mRNA and the AA sequence of the protein encoded
non transcribed strand=
coding or sense strand
transcribed strand=
non-coding or antisense strand
additions to primary DNA modification
addition of a chemical “cap” structure to the 5’ end
-addition of polyA tail to 3’ end
cleavage of ____ end in modification
cleavage of 3’ end at specific point downstream from the coding information
polyA
location specified by sequence AAUAAA found in 3’ untranslated portion of RNA transcript
provides stability to mRNA
prior to translation, how is RNA processed and spliced
-introns are removed
-exons are spliced together
(mRNA is then transported out of the nucleus and into the cytoplasm)
in translation, what does tRNA do
it brings the correct amino acid sequence into position
what are ribosomes
are macromolecular complexes made up of rRNA and are the sites of protein synthesis
initiator codon
AUG- methionine- establishes the reading frame for all subsequent codons
3 stop codons
UAA, UAG, UGA
post translational processing of polypeptide chain
-fold, bind, form 3D structure, combine (2 or more polypeptide chains) to form protein complex
what are transcription factors?
are specific proteins that regulate transcription
promoter sequence does
interacts with transcription factors
2 promoters found in tissue specific genes
TATA box
CAT
TATA box
conserved region rich in adenines and thymines
-appears to be important for determining the position of the start of transcription
CAT
conserved region
-involved in normal gene expression
what is the role of promoters
- play a role in gene regulation
- can be site of mutation that can interfere with its normal expression and function
house keeping genes (CG) are expressed where and contain what?
- expressed in most or all tissues that lack the CAT and TATA promoter boxes
- contain high proportion of cytosines and guanines
what do CG (house keeping genes) rich sequence elements serve as
serve as binding sites for specific transcription factors
what are house keeping genes associated with
repression of gene transcription
cancer, genomic imprinting, X chromosome inactivation
what do enhancers do?
stimulate transcription
- establishing tissue specificity
- level of expression on many genes
what is RNA splicing
splicing reactions guided by specific sequences in the primary RNA transcript at both 5’ and 3’
GT at 5’
AG at 3’
how common are alternative transcripts
2 to 3 alternative transcripts per gene in the human genome
what does alternative splicing lead to
the synthesis of multiple related but different mRNAs, each of which can be subsequently translated to generate different protein products
