Miller and Levine biology chapter 13 cornell
Terms in this set (53)
How does RNA differ from RNA?
There are three important differences between RNA and DNA:
1. The sugar in RNA is ribose instead of of deoxyribose
2. RNA is generally single stranded and not double stranded
3. RNA contains uracil in place of thymine
What did a cell have to do to replicate DNA?
Separate two strands of DNA and then use base pairing to make a new complementary strand for each
What did the structure of DNA by itself not explain?
How a gene actually works.
What discovery made answering the question of how a gene actually works possible?
The answer came from he discovery of another nucleic acid- ribonucleic acid, or RNA, that was involved in putting the genetic code into action
What does RNA consist of?
A long chain of nucleotides
What information do genes contain in the coded DA instructions?
Tells the cell how to build proteins.
What is the first step in decoding these genetic instructions?
To copy part of the base sequence of DNA into RNA.
What does RNA use the instructions to do?
To direct the production of proteins which help to determine an organisms characteristics.
What is RNA made up of?
A 5-carbon sugar, a phosphate group, and a nitrogenous base. (just like DNA)
The RNA molecule is a ___________ copy of a segment of DNA.
What are most RNA molecules involved in?
What does RNA control?
The assembly of amino acids into proteins
What are the three main types of RNA?
Messenger RNA, Ribosomal RNA, and Transfer RNA
What does the Messenger RNA do?
Carries copies of the instructions of the genes that tell the cell how to assemble amino acids into proteins. They carry the information from DNA to other parts of the cell.
What does the Ribosomal RNA do?
In the subunits of ribosomes, the place where proteins are assembled. These subunits are made up of several ribosomal RNA molecules and as many as 80 different proteins.
What does the Transfer RNA do?
When a protein is built, it transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA.
How does the cell make RNA?
In transcription, segments of DNA serve as templates to produce complementary RNA molecules.
What do the base sequences of the transcribed RNA complement?
They complement the base sequences of the template DNA.
In prokaryotes, where do protein and RNA synthesis take place?
In the cytoplasm.
In eukaryotes,where do protein and RNA synthesis take place?
RNA is produced in the cell's nucleus and then moves to the cytoplasm to play a role in the production of protein/
What enzyme does transcription require?
What is RNA polymerase?
It is similar to DNA polymerase. RNA polymerase binds to DNA during transcription and separates the DNA strands. It then uses one strand of DNA as a template from which to assemble nucleotides into a complementary strand of RNA.
What does the ability to copy a single DNA sequence into RNA make possible?
For a single gene to produce hundreds or even thousands of RNA molecules.
How does RNA polymerase know where to start and stop making a strand of RNA?
RNA polymerase doesn't bind to DNA just anywhere.
Where on a strand of DNA does RNA polymerase bind?
What are promoters?
Regions of DNA that have specific base sequences. They are signals in the DNA molecule that show RNA polymerase exactly where to begin making RNA. Similar signals in DNA cause transcription to stop when a new RNA molecule is completed.
What are introns?
Portions of pre-mRNA molecules that are cut out and discarded in the editing process of RNA
In eukaryotes, where are introns taken out of pre-mRNA molecules?
When they are still in the nucleus.
What are the remaining pieces of the mRNA molecules called?
What happens to the exons in the final mRNA?
They are spliced back together
Why do cells use energy to make a large RNA molecule and then throw parts of that molecule away?
Biologists still don't have a complete answer, but some pre-mRNA molecules may be cut and spliced in different ways in different tissues, making it possible for a single gene to produce several different firms if RNA.
What part do exons and introns play in evolution?
They make it possible for very small changes in DNA sequences have dramatic effects on how genes affect cellular function.
What is the genetic code, and how is it read?
The genetic code is read three "letters" at a time, so that each "word" is three bases long and responds to a single amino acid.
What is the first step in decoding genetic messages?
To transcribe a nucleotide base sequence from DNA to RNA.
What does this transcribed information contain?
A code for making proteins.
What are polypeptides?
Long chains of amino acids which make up proteins.
How many different amino acids are commonly found in polypeptides?
As many as 20 different amino acids
What determine the properties of different proteins?
The specific amino acids in a polypeptide and the order in which they are joined
What influences the shape of the protein?
The sequence of bases
How do you read codons?
What is the methionine codon?
What does the methionine codon do?
It serves as the initiation, or "start" codon for protein synthesis
What role does the ribosome play in assembling proteins?
Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.
transcribed in the nucleus and then enters the cytoplasm
Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to the bases of a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that bind methionine. The ribosome also binds the next codon and tis anticodon.
The Polypeptide "Assemble Line"
The ribosome joins the two amino acids- methionine and phenylalanine- and breaks the bond between methionine and its tRNA. The tRNA floats away from the ribosome, allowing the ribosome to bind another tRNA. The ribosome moves along the mRNA, from right to left, binding new tRNA molecules and amino acids.
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. Once the polypeptide is complete, it and the mRNA are released from the ribosome
What is the "central dogma" of molecular biology?
The central dogma of molecular biology is transferred from DNA to RNA to protein.
The way in which DNA, RNA, and proteins are involved in putting genetic information into action in loving cells
The Molecular Basis of Heredity
Molecular biology seeks to explain living organisms by studying them at the molecular level, using molecules like DNA and RNA.
role of tRNA in translation
converts the genetic message of mRNA into the language of proteins by picking up the appropriate amino acid and using a special triplet of bases, called an anticodon, to recognize the appropriate codons in the mRNA.
role of mRNA in translation
mRNA is transcribed from DNA and released into the cytoplasm before translation happens; attaches to a ribosome in the cytoplasm
role of rRNA in translation
rRNA molecules help hold ribosomal proteins in place and locate the beginning of the mRNA message; they carry out the chemical reaction that joins amino acids together
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