BIL 150 Chapter Notes - Chapter 17: Gene Expression, Coding Strand, Primary Transcript
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Ch. 17 Gene Expression: From Gene to Protein
1. Gene expression- DNA directs the synthesis of proteins or RNA
a. Two stages: transcription and translation
2. The genetic code- triplet code- set of three base pairs codes for one amino acid
a. Template strand- one strand of DNA that provides template for sequence of
nucleotides in an RNA transcript
b. Codon- DNA nucleotide triplets along the non-template strand
i. Complementary to template strand and identical to mRNA
ii. Coding strand- non-template DNA strand
c. Reading frame- groups of 3 that allow the right sequence to be coded
d. Genetic code is universal among living organisms
3. Transcription- synthesis of RNA using information from DNA
a. mRNA is made by template of DNA
i. carries genetic info from DNA in nucleus into ribosomes
b. Primary transcript- initial RNA transcript that may or may not translate into a
protein
c. RNA polymerase- separates two DNA strands and joins RNA nucleotides
opleetary to DNA strad, assele i 5’-3’, do’t eed a prier
i. Promoter- sequence where RNA polymerase attaches and starts
transcription, includes transcription start point
ii. Transcription unit- DNA downstream that is transcribed into RNA
d. Transcriptions factors- help bind RNA polymerase to transcription
i. Transcription initiation complex- complex of transcription factors and
RNA polymerase II bound to the promoter
ii. TATA box- promoter DNA sequence
e. RNA processing- RNA spliig after trasriptios ad additio of 5’ ap ad poly-
A tail to 3’ ed
i. RNA splicing- introns are removed and exons are joined
1. Spliceosomes- aids in splicing
ii. Introns- noncoding
iii. Exons- coding, are included in mRNA
4. Translation- synthesis of a polypeptide using the information in mRNA
a. Ribosomes- site of translation
i. Link amino acids into polypeptide chains
b. tRNA- translates mRNA message into protein
c. aminoacyl-tRNA synthetase- lines up tRNA with anticodon
d. ribosome- facilitates binding from mRNA and tRNA
5. Mutations- point mutations- change in one DNA nucleotide pair
a. Nucleotide-pair substitutions- can cause missense or nonsense mutations
b. Insertions/deletions- can cause frameshift mutations
c. Mutagens- chemical or physical agents that can damage DNA and alter genes
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