WGSS 1105 Chapter Notes - Chapter 10: Messenger Rna, Transfer Rna, Protein Folding
23 Jan 2017
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10.1 Transcription Copies the Info in DNA
● Exome - the percent of the DNA of the human genome that encodes proteins
(1.5%)
○ Much of the rest of the genome controls how, where, and when protein are
made
● Transcription first synthesizes an RNA molecule that is complementary to one
strand of the DNA double helix for a particular gene
● THEN the RNA copy is taken out the nucleus and into the cytoplasm
● The process of translation uses the information in the RNA to manufacture a
protein by aligning and joining specified amino acids
● Watson and Crick → described the relationship between nucleic acids and
proteins as a directional flow of info called the central dogma
● Francis Crick → specificity of a piece of nucleic acid is expressed solely by the
sequence of its bases, and this sequence is a code for the amino acid sequence
of a particular protein
RNA Structure and Types
● RNA is a bridge between gene and protein
● Bases of an RNA sequence are complementary to those of one strand of
the double helix, which is called the template strand
● An enzyme, RNA poly, builds an RNA molecule
● Other, nontemplate strand of the DNA double helix is called the coding
strand
Replication → DNA → transcription → RNA → translation protein
DNA
● Stores RNA and protein encoding info and transfers info to daughter cells
● Double stranded
● Deoxyribose as the sugar
● Bases used: T C G A
RNA
● Carries protein encoding info and helps the make proteins
● Generally single stranded
● Ribose as the sugar
● Bases used: U C G A
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● As RNA is synthesized along DNA, it folds into a 3D shape, or conformation,
that arises from complementary base pairing within the same RNA molecule
● Messenger RNA (mRNA) carries the information that specifies a particular
protein
○ Each three mRNA bases in a row form a genetic code word, or codon,
that specifies a certain amino acid
● Ribosomal RNA (rRNA) - molecules range from 100 to nearly 3,000 nucleotides
long
○ Associated with certain proteins to form a ribosome
○ Certain rRNAs catalyze the formation of the peptide bonds between amino
acids → such an RNA with enzymatic function called a ribozyme
○ Other rRNAs help to align the ribosome and mRNA
● Ribosome has two subunits that are separate in the cytoplasm but join at the site
of initiation of protein synthesis
● Larger ribosomal subunit has three types of rRNA molecules, and the small
subunit has one
● Third major type of RNA molecule → transfer RNA (tRNA) binds an mRNA
codon at one end and a specific amino acid at the other
○ Only 75 to 80 nucleotides long
○ Some bases form weak chemical bonds with each other, folding the tRNA
into loops in a characteristics cloverleaf shape
● One loop of the tRNA has three bases in a row that form the anticodon - which
is complementary to an mRNA codon
● End of the tRNA opposite the anticodon strongly bonds to a specific amino acid
● tRNA with a particular anticodon sequence always carries the same amino acid
● Different cell types express different subsets of genes
● Proteins called transcription factors come together and interact, forming an
apparatus that binds DNA at certain sequences and initiates transcription at
specific sites on chromosomes
○ Respond to signals from outside the cell, such as hormones and growth
factors, and form a pocket for RNA polymerase to bind and begin building
an RNA chain
○ Include regions called binding domains that guide them to the genes they
control
Steps of Transcription
● Transcription factors and RNA polymerase (RNAP) “know” where to bind to DNA
to begin transcribing a specific gene
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Exome - the percent of the dna of the human genome that encodes proteins (1. 5%) Much of the rest of the genome controls how, where, and when protein are made. Transcription first synthesizes an rna molecule that is complementary to one strand of the dna double helix for a particular gene. Then the rna copy is taken out the nucleus and into the cytoplasm. The process of translation uses the information in the rna to manufacture a protein by aligning and joining specified amino acids. Watson and crick described the relationship between nucleic acids and proteins as a directional flow of info called the (cid:3247)central dogma(cid:3248) Francis crick specificity of a piece of nucleic acid is expressed solely by the sequence of its bases, and this sequence is a code for the amino acid sequence of a particular protein. Rna is a bridge between gene and protein.
