Download RNA chapter 13.1 - Red Hook Central Schools

Chapter 13.1 Notes
“RNA”
• A cell needs to be able to decode its DNA.
• What does the DNA code for?
• How is the DNA decoded?
RNA
Ribonucleic Acid
• A nucleic acid composed of long strands
of nucleotides
• Puts into action the genetic code of DNA
• Involved in the production of proteins by
controlling the assembly of amino acids
DNA vs. RNA
• DNA
– Double stranded helix
– Contains the sugar
deoxyribose
– Contains the nitrogen
bases Guanine,
Cytosine, Adenine,
and Thymine
– Stays “safely” in the
nucleus
• RNA
– Single stranded
– Contains the sugar
ribose
– Contains the nitrogen
bases Guanine,
Cytosine, Adenine,
and Uracil
– Goes to the ribosome
Three main types of RNA
• Messenger RNA: (mRNA) carry the DNA
code from the nucleus to the ribosomes
• Ribosomal RNA: (rRNA) compose the two
subunits that make up a ribosome
• Transfer RNA: (tRNA) carries amino acids
to the ribosome to be assembled into
proteins
RNA Synthesis- the role of DNA
• requires a lot of energy and raw materials by the
cell
– Transcription: DNA segments serve as templates in
creating complementary strands of RNA; occurs in
the nucleus
– RNA polymerase: the enzyme that binds to DNA and
separates the DNA strands so transcription of one
strand of DNA can take place
– Promoters: a region of DNA that shows the RNA
polymerase exactly where to begin making RNA
• Similar regions on the DNA signal the end of transcription
Cutting and Splicing RNA
• Introns: while still in the nucleus, regions of the
pre-RNA molecule are removed and discarded
• Exons: remaining pieces of the pre-RNA
molecule that haven’t been removed
• Exons are spliced back together to form the final
RNA molecule
• What is the purpose of cutting and splicing RNA
before sending it to the cytoplasm?
– Cutting and splicing in different ways for different
tissues enable a greater variety of RNA to be
produced – specific to different tissue