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Question
During the Silurian, the oxygen gas concentration in the atmosphere is postulated to have reached an amount equivalent to more than 10 percent of its present-day concentration. Thus, nearly all lethal ultraviolet radiation was unable to reach the Earth's surface, making dry land available for newly evolved forms. Which of the following major events in the evolution of animals and plants probably occurred at this time?
A) The amphibians developed watertight skins and eggs.
B) The crayfish become the first land organisms.
C) The first major groups of seed plants appeared.
D) Primitive bryophytes and fern-like plants appeared.
Answer
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Related questions
Q:
What is the relationship between DNA, chromosomes, genes, RNA, proteins, transcription, and translation?
Q:
How does the protein synthesis occur?
Q:
What are the basic differences between DNA and RNA molecules?
Q:
In translation, when an incoming tRNA with the next amino acid comes into the ribosome, it enters the ________ site, while the tRNA with the growing polypeptide chain is located in the ________ site.
Q:
During translation, the tRNA binds to the mRNA using its ________.
Q:
Match the following.A) DNAB) rRNAC) tRNAD) micro-RNAE) mRNAThis forms part of the structure of a ribosome.
Q:
During translation, one mRNA can be translated by many ribosomes at once.
Q:
The process by which genetic information in DNA is copied into RNA is called translation.
Q:
Hoxc8 genes are responsible for the development of:
A) abdominal structure in vertebrates.
B) thoracic structures in vertebrates.
C) cranial structures.
D) limbs in vertebrates.
E) the whole vertebrate body.
Q:
Which of the following is the best description of a gene?
A) a protein whose amino acid sequence is encoded in a segment of DNA
B) a collection of millions or billions of base pairs of DNA, encoding many proteins
C) a segment of DNA that is transcribed into an mRNA, a tRNA, or an rRNA
D) a segment of mRNA that is translated into a protein
E) A section of the nucleus where transcription takes place.
Q:
The process of translation is completed when:
A) a stop codon moves into the A site.
B) the cell runs out of amino acids.
C) the cell runs out of ribonucleotides.
D) the translation machinery reaches the end of the DNA molecule.
E) the stop codon is severed at the P site.
Q:
The set of nucleotides on a tRNA that base-pairs with nucleotides on an mRNA is the:
A) anticodon.
B) codon.
C) template.
D) primary transcript.
E) P site.
Q:
If a codon has the sequence CAG, tRNA with which anticodon will bind to it?
A) CTG
B) UGA
C) GTC
D) CAG
E) GUC
Q:
The genetic code:
A) tells us how RNA is assembled on a DNA template.
B) is a list of all the possible proteins that can be made.
C) describes the mechanics of translation.
D) shows the connection between nucleotide triplets and the amino acids they code for.
E) shows the connection between nucleotide triplets in DNA and their corresponding codons in RNA.
Q:
The enzyme responsible for transcribing DNA is:
A) DNA polymerase.
B) RNA polymerase.
C) helicase.
D) DNA transcription factor.
Q:
The form of RNA that carries the information from DNA to the site of protein assembly is called:
A) messenger RNA.
B) small nuclear RNA.
C) ribosomal RNA.
D) transfer RNA.
E) primary mRNA script.
Q:
When an mRNA moves into the cell's cytoplasm, it first becomes associated with a:
A) protein.
B) tRNA.
C) ribosome.
D) transcription factor.
Q:
These are linked together to form DNA.
Q:
Match the following.A) nucleotidesB) basesC) sugar-phosphate chainD) thymineE) cytosineThis forms the "handrails" of the double helix.
Q:
Match the following.A) nucleotidesB) basesC) sugar-phosphate chainD) thymineE) cytosineAdenine always base-pairs with this.
Q:
Which of the following would be considered an environmental mutagen?
A) free radicals
B) ultraviolet light
C) spontaneous events
D) the collision of water molecules with DNA
E) DNA replication errors
Q:
What is one mechanism by which a mutation can cause melanoma?
A) by causing the accumulation of Huntington protein in melanocytes, which keeps them moving through the cell cycle
B) by causing the accumulation of altered BRAF protein in germ-line cells
C) by the production of an altered BRAF protein that keeps melanocytes moving through the cell cycle
D) by preventing the BRAF protein from being able to repair damaged DNA
Q:
Which type of mutation will have the most impact from an evolutionary point of view?
A) a mutation in a somatic cell
B) a mutation in a liver cell
C) a mutation in a germ-line cell
D) a mutation in a brain cell
Q:
Melanoma is a cancer that is frequently associated with a mutation in what gene?
A) in the IT15 gene
B) in the DNA polymerase gene
C) in the BRAF gene
D) in the Huntington gene
Q:
On average, if you examine 1 million human cells looking at a single gene, you'll find one cell with a mutation in that gene. If you were looking at a gene that could lead to cancer when mutated, how many mutated copies of that gene would you find in a person? (Assume a person contains 100 trillion [100,000,000,000,000] cells.)
A) 100,000,000
B) 1,000
C) 1,000,000
D) 10,000,000,000
E) 100
Q:
There are two alleles for each gene in a cell. If each gene encodes for a particular protein, what would make two alleles different from each other?
A) The sequence of bases in the DNA for each allele would be slightly different and would lead to the production of slightly different proteins.
B) The sequence of bases in the DNA would be different for each allele, but they would result in the production of identical proteins.
C) The sequence of bases in the DNA would be identical for each allele, but they would produce very different proteins.
D) The sequence of bases in the DNA would be identical for each allele, but one would produce a protein and the other would not.
Q:
A DNA molecule can be described as a twisted ladder. The ________ form the sides, and the ________ form the rungs.
A) base pairs; sugar-phosphate chains
B) sugars; phosphates
C) sugars; base pairs
D) sugar-phosphate chains; base pairs
Q:
The three components of a DNA nucleotide are:
A) amino acids, phosphates, and deoxyribose.
B) bases, deoxyribose, and polymerases.
C) genes, sugars, and bases.
D) phosphates, sugars, and bases.
E) polymerases, ligases, and sugars.
Q:
The two strands of a double helix of DNA are linked by what kind of bond?
A) sugar-phosphate linkages
B) hydrogen bonds between bases
C) hydrogen bonds between sugars and phosphates
D) sugar-base linkages
E) base-phosphate linkages
Q:
What is the function of DNA polymerase?
A) synthesizing nucleotides from free sugars, phosphates, and bases
B) halting DNA replication if a cell becomes cancerous
C) breaking sugar-phosphate bonds to release free nucleotides for DNA synthesis
D) introducing mutations into DNA for evolutionary adaptation
E) joining together nucleotides as they are base-paired during DNA replication