Biology Chapter 8 review
Terms in this set (46)
What is the central dogma of genetics or of molecular biology means?
The central dogma of genetics just explains the flow of genetic information. It goes from DNA to RNA to protein. The DNA carries the genetic information and is transcripted to RNA and from their a mRNA molecule carries an amino acid sequence for which protein will be synthesised from there. Information flows in one directions: from DNA to RNA.
What are the three process of the central dogma
1. Replication copies DNA
2. Transcription converts a DNA message into an intermediate molecule, called RNA.
3. Translation interprets an RNA message into a string of amino acids, called a polypeptide. Either a single polypeptide or many polypeptides working together make up a protein.
Where do these three processes of the central dogma occur in prokaryotic cells?
In prokaryotic cells replication, transcription, and translation all occur in the cytoplasm at approximately the same time.
o Where do these three processes occur in eukaryotic cells?
In eukaryotic cells, replication and transcription occur in the nucleus and translation occurs in the cytoplasm.
What are the DNA and RNA similarities?
• Chain of nucleotides with sugar, phosphate group and nitrogen-containing bases
• Contain genetic information
What are the DNA and RNA difference?
• Sugars are different: deoxyribose vs. ribose
• RNA uracil vs. DNA thymine
• RNA is a single strand, DNA is a double strand
Define the process of transcription:
is the process of copying a sequence of DNA to produce a complimentary strand of RNA
Transcription is the process of providing an RNA message of what?
A gene—not the entire chromosome
What is RNA polymerase and what exactly does it do during transcription?
RNA polymerase is a very large enzyme that bonds nucleotides together to make the mRNA molecule.
What are the three steps the process of transcription
1. RNA polymerase recognizes the start site of gene and, along with other proteins, beings to assemble on the DNA strand and unzip the two strands.
2. RNA polymerase then strings together a complimentary strand of RNA nucleotides (using U for T)
3. Once the entire gene is copied, the RNA strand detaches and the DNA molecule reattaches.
What are transcription makes 3 types of RNA.
1. Messenger RNA (mRNA)
2. Ribosomal RNA
3. Transfer RNA
What is Messenger RNA (mRNA)?
mRNA is intermediate message that is translated to form a protein
What is Ribosomal RNA (rRNA)?
rRNA forms part of ribosome, cells protein factories
What is Transfer RNA (tRNA)?
tRNA brings amino acids from the cytoplasm to a ribosome to help make the growing protein.
True or False ~ Transcription is similar to replication
What are the similarities of transcription and replication?
• Both occur within nucleus of eukaryotic cells
• Both are catalyzed by large, complex enzymes
• Both involve unwinding of the DNA double helix
• Both involve complementary base pairing
• Both processes are highly regulated by the cell
What are the differences of transcription and replication?
• The end results are very different: Replication ensures that each cell has a complete copy of the DNA, where as Transcription only copies one gene
• Replication occurs only once during each cell cycle, where as transcription can occur many times
True or False ~ Translation converts an mRNA message into a polypeptide, or protein
What are Amino acids coded by?
mRNA base sequences
What is the process of translation?
The process that converts an mRNA message into a polypeptide
What is the language of DNA?
DNA: AT, CG;
o What is the language of RNA?
RNA: AU, CG
o What is the language of Proteins?
Protein: Amino Acids
What is a codon and how is one used in translation?
A codon is a sequence of 3 nucleotide bases which codes for a particular amino acid.
Why amino acids are coded for by more than one codon?
There are only 20 amino acids and there can be various combinations of nucleotide bases.
What is "punctuation" in the genetic code?
Punctuation refers to the "start" and "stop" codons...this determines where the copying and creating of polypeptide chains begins and ends—similar to punctuation in a sentence.
Please provide 2 specific examples of punctuation in genetic code?
Two examples are translation always begins with methionine—the start codon and stops with UGA.
Why is the genetic code said to be a common language?
The genetic code is shared by almost all organisms—the codon to amino acid sequencing.
True or False ~ Amino acids are not linked to become proteins
What are Ribosomes are the site of ?
What is the role of tRNA?
tRNA acts as an adaptor between mRNA and amino acids. They have anticodons which recognize the specific codon present in mRNA and bring the appropriate amino acid to the ribosome.
What are the three steps in the process of translation?
1. The exposed codon attracts the complimentary tRNA molecule bearing an amino acid and then the tRNA anticodon pairs with the mRNA codon.
2. The ribosome helps form a polypeptide bond between the two amino acids and then breaks the bond between the tRNA and the amino acid.
3. The ribosome then pulls the the mRNA strand the length of one codon to keep the strand moving and the used tRNA leaves and reenters the cytoplasm exposing the next mRNA codon. This process repeats until the stop codon is reached.
True or False ~ Mutations are not changes in DNA that may or may not affect phenotype.
True or False ~ Some mutations affect a single gene, while other affect an entire chromosome
What is a mutation?
A mutation is a change in the DNA
What are the two types of gene mutations?
point mutations and frameshift mutations
What are differences of point mutations and frameshift mutations?
• Point mutations substitutes a single nitrogen-base and thus often result in minimal effects due to the fact that many codons code for a single amino acid.
• Frameshift mutations insert or delete a nitrogen-base causing a change in each codon down the strand...this often results in more dramatic effects of phenotype
What are the two types of Chromosomal Mutations?
Gene Duplication and Gene Translocation
What are the differences between Gene Duplication and Gene Translocation?
• Gene duplication results when chromosomes end up having two copies of a gene or genes and the other chromosome may have no copy
• Gene Translocation results when a piece of one chromosome moves to a nonohomologous chromosome—this is often reciprocal which means the two segments exchange with each other
True or False ~ Mutations may phenotype
False ~ Mutations may or may not affect phenotype
Which type of mutation, chromosomal or gene, is likely to have a greater affect on phenotype and Why?
Chromosomal mutations are more likely to have an effect on phenotype because they alter the entire chromosome as opposed to one gene.
Explain if a mutation occurs in a non-coding region, will the phenotype be affected?
No, because if it is in a non-coding region then the mutation will not be a part of protein production, thus not altering the phenotype of the organism.
Why aren't mutations in body cells passed to offspring?
Mutations are only passed on to offspring in organisms cells if they are linked to sex cells.
True or False ~ Mutations can be cause by only one factors
False ~ Mutations can be cause by several factors
What are replication errors and how do they lead to mutations?
Replication errors occur when DNA polymerase, the proofreading enzyme, cannot keep up or does not catch the error. These build up over time and affect how the cell functions.
Why mutagens can damage DNA in spite of repair enzymes?
Mutagens are agents in the environment that can change DNA. If they infect our body cells, they can alter the DNA, mutate it, and then the functions of our cells change—this can lead to cancer or the uncontrolled growth of cells.
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