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Example Questions
Example Question #1 : Understanding Gene Coding
The central dogma of molecular biology is the method by which cells transfer nucleic acids into functional molecules. Which of the following depicts the central dogma of molecular biology?
The central dogma of molecular biology states that DNA is transcribed into RNA, which is then translated into protein.
Example Question #2 : Understanding Gene Coding
A mutation occurs, changing the DNA sequence but leaving the final amino acid sequence unaltered. How is it possible that the underlying DNA sequence is different but the amino acid sequence remains the same?
Cells with mutated genomes will undergo apoptosis
The cell has a specific memory that corrects the DNA sequence before transcription
DNA checkpoints do not allow the cell to transcribe mutated genes
The genome encodes for "degenerate codons," indicating that more than one codon can encode for a particular amino acid
The genome encodes for "degenerate codons," indicating that more than one codon can encode for a particular amino acid
The human genome can code for 64 different codons, but only produces 20 different amino acids. This results in some amino acids having multiple codes in order to use the remaining 44 available codons.
This ability of a single amino acid to have more than one possible codon is called "degeneracy." Occasionally when DNA is mutated, it will results in a codon that encodes the same amino acid. For example, a mutation from CUU in the mRNA sequence to CUG will still code for leucine.
Example Question #71 : Genetics Principles
What term describes the section of DNA that codes for a single protein?
Allele
Locus
Gene
Genotype
Gene
DNA nucleotides are organized to form codes. When DNA is transcribed into RNA, these codes are read by the ribosomes to create proteins. Each gene refers to a sequence of DNA that codes for a specific protein. Mutation to a specific gene will affect that protein coded for by that sequence.
A locus is the location of a gene on a chromosome, and an allele is an alternative form of a given gene. A genotype is the description of the alleles for a specific set of genes.
Example Question #2 : Understanding Gene Coding
The first cross done between two individual parents is called the "Parental generation," or "P generation." What are the next two generations normally called?
G1 and G2
F1 and G1
P1 and P2
F1 and F2
F1 and F2
Following the P generation is the 1st offspring generation, called F1. When the F1 generation is crossed, the result is the 2nd offspring generation, called F2.
G1 and G2 actually refer to periods of growth during the cell cycle, and are not related to genetics and inheritance.
Example Question #3 : Understanding Gene Coding
What is the definition of an allele?
A different version of the same gene, or group of genes
A portion of unreplicated DNA
A location of a protein
A section of DNA that codes for a gene product
A different version of the same gene, or group of genes
A gene codes for a certain protein product, which is often associated with a certain trait. Each gene is found at a specific location, or locus, on a chromosome.
Alleles refer to different forms of DNA that can appear at the same locus. In other words, an allele is an alternative form of a given gene. Different alleles often result in different phenotypes, such as changes in color or size.
Example Question #6 : Understanding Gene Coding
In eukaryotic organisms, a DNA sequence of 10,000 nucleotides codes for a protein that is only 300 amino acids long. What is the best explanation of this phenomenon?
The entire seqeunce is translated, and the cell cleaves the amino acid chain so that the desired protein remains
Three nucleotides correspond with one amino acid
The gene is a mutation
Certain nucleotides are skipped when the mRNA sequence is transcribed
Eukaryotic DNA is comprised of coding and non-coding strands
Eukaryotic DNA is comprised of coding and non-coding strands
Eukaryotes possess coding (exon) and non-coding (intron) seqeunces that allow for incredibly long DNA sequences to correspond with relatively short peptides. Only the exons are translated after the mRNA sequence, which is transcribed fully from the DNA, undergoes mRNA splicing. Furthermore, while a codon (three nucleoties) does correspond with one amino acid, it does not account for the dramatic difference stated in the question. Also, the cell does not translate an entire unmodified mRNA sequence and cleave afterwards as that would be incredibly wasteful and potentially harmful to the cell.
Example Question #7 : Understanding Gene Coding
What defines the reading frame of a messenger RNA (mRNA)?
Presence of start codon
The ribosome binding site
A RNA polymerase binding site
A promoter
Presence of start codon
The reading frame of a mRNA is established by AUG (start codon) which codes for methionine.
Example Question #3 : Understanding Gene Coding
An individual having green eyes or being tall are examples of which of the following?
Phenotype
Heritable genetic identity
Genotype
None of these
Phenotype
A phenotype refers to the observable traits within an individual such as eye color, adult height, weight, and skin color. The genetic contribution to a phenotype is referred to as genotype. Some phonotypical traits are determined by the genotype, while others are shaped by environmental factors.
Example Question #1 : Understanding Prokaryotic Genes
What is the main difference between prokaryotic and eukaryotic genes?
Prokaryotic genes only have exons, but eukaryotic genes have exons and introns
Prokaryotic genes are not replicated, and only transcribed to RNA to then become protein
Prokaryotes have one large gene, but eukaryotes have many smaller genes
Prokaryotes do not have gene regulatory sequences, but eukaryotes do
Eukaryotes stores genes together in operons, but prokaryotes do not
Prokaryotic genes only have exons, but eukaryotic genes have exons and introns
The correct answer is that prokaryotes only have exons, whereas eukaryotes have exons and introns. As a result, in eukaryotes, when mRNA is transcribed from DNA, the introns have to be cut out of the newly synthesized mRNA strand. The exons, or coding sequences, are then joined together. Prokaryotes do not have to process their mRNA to this extent.
Example Question #2 : Genes And Dna
A segment of prokaryotic DNA that binds transcription factors, usually as repressors that prevent transcription, are best known as __________.
Operators
Exons
Untranslated regions
Enhancers
Promoters
Operators
The correct answer is operator. In most operons, repressors bind operators to prevent transcription of downstream genes.
Promoters are sequences of DNA upstream of genes that usually promote transcription by recruiting polymerases and other transcription factors. Enhancers are distant DNA sequences that promote transcription, whereas exons are the coding segments of a gene.
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