Chapter 12.3-12.6 Flashcards
What sugar is in RNA?
Ribose
What sugar is in DNA?
Deoxyribose
What bases make up RNA?
Adenine, Guanine, Uracil, Cytosine
What bases make up DNA?
Adenine, Guanine, Thymine, Cytosine
How does the structure of RNA compare to that of DNA?
RNA is single stranded and isn’t in a helix, while DNA is double stranded with base paring and is in the shape of a helix.
What are the three major classes of RNA?
Messenger RNA (mRNA), Transfer RNA (tRNA), Ribosomal RNA (rRNA)
What does mRNA do?
It takes the message from the DNA in the nucleus to the ribosomes in the cytoplasm
What does tRNA do?
Transfers amino acids to the ribosomes
What does rRNA do?
Makes up the ribosomes (along with ribosomal proteins),where poly peptides are synthesized
Name the two major steps involved in synthesizing a protein?
Transcription and Translation
What happens during transcription?
DNA serves as a template for RNA formation. DNA is transcribed into another type of polynucleotide (RNA)
What happens during translation?
The mRNA transcript directs the sequence of amino acids in polypeptide
What kind of code is the genetic code?
A triplet code
Through what experiment did Marshall Nirenberg and J. Heinrich Matthei lay the groundwork for cracking the genetic code?
1) Found that a cellular enzyme could be used to construct synthetic RNA
2) Used synthetic RNA and found that it could be translated in a test tube that contains cytoplasmic contents of the cell
3) First synthetic RNA was composed of only uracil, foudn that the protein that resulted was UUU (Phenylalanine)
What are three important properties of the genetic code?
1) The genetic code is degernate, amino acids have more than one codon
2) The genetic code is unambiguous. Each triplet codon has only one meaning
3) The code has 1 start signal and 3 stop signals.
The universal nature of the genetic code provides further evidence for what?
That all living things share a common ancestor. This is why it is possible to transfer genes from one organism to another. However, scientists have found that genetic code used by mammalian mitochondria and chloroplasts are a bit different
What occurs during transcription?
A segment of DNA serves as a template for the production of an RNA molecue
What are the steps in the formation of mRNA?
1) Segment of DNA helix unwinds
2) Complementary RNA nucleotides pair with the DNA nucleotides on the strand of the opposite gene (known as the template strand, other strand is called the nontemplate strand)
3) RNA Polymerase joins the nucleotides together in the 5’–>3’ direction.
When does transcription begin?
When RNA polymerase attaches to a region of DNA called the promoter
What is the promoter?
Defines the start of transcription, the direction of transcription, and the strand to be transcribed