The structure of DNA is described as a double helix, resembling a twisted ladder.
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helix
The double helix structure, proposed by Watson and Crick, describes the two-stranded, twisted shape of DNA.
Question 2
Each strand of DNA is composed of repeating monomer units called nucleotides, which consist of a sugar, a phosphate, and a nitrogenous base.
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nucleotides
Nucleotides are the fundamental building blocks of DNA and RNA.
Question 3
In DNA, adenine always pairs with thymine, and guanine always pairs with cytosine, a principle known as complementary base pairing.
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complementary
Complementary base pairing describes the specific hydrogen bonding interactions between DNA bases.
Question 4
DNA replication is considered semi-conservative because each new DNA molecule consists of one original strand and one newly synthesized strand.
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semi-conservative
Semi-conservative replication ensures that each daughter DNA molecule retains half of the parental DNA.
Question 5
The enzyme DNA polymerase is primarily responsible for synthesizing new DNA strands by adding nucleotides to a growing chain.
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polymerase
DNA polymerase is the key enzyme that catalyzes the synthesis of DNA during replication.
Question 6
On the lagging strand during DNA replication, DNA is synthesized in short segments known as Okazaki fragments.
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Okazaki
Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication.
Question 7
Transcription is the process by which genetic information from a DNA template is used to synthesize a molecule of RNA.
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Transcription
Transcription is the initial step in gene expression, converting DNA into RNA.
Question 8
In gene expression, RNA polymerase binds to a specific DNA sequence called the promoter to initiate transcription.
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promoter
The promoter is a DNA sequence that signals the start site for gene transcription.
Question 9
The type of RNA that carries the genetic code from DNA to the ribosome for protein synthesis is messenger RNA, or mRNA.
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mRNA
mRNA molecules transport genetic information from the nucleus to the cytoplasm for translation.
Question 10
During translation, each three-nucleotide sequence on the mRNA, known as a codon, specifies a particular amino acid.
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codon
A codon is a sequence of three nucleotides that forms a unit of genetic code in a DNA or RNA molecule.
Question 11
Transfer RNA, or tRNA, molecules carry specific amino acids to the ribosome, matching them to the appropriate mRNA codons.
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tRNA
tRNA molecules are essential for translation, ensuring the correct amino acid is added to the polypeptide chain.
Question 12
The end product of translation is a polypeptide chain, which will fold into a functional protein.
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polypeptide
A polypeptide is a linear chain of amino acids linked by peptide bonds, which forms a protein upon folding.
Question 13
In prokaryotes, a group of genes with related functions that are regulated together is called an operon.
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operon
An operon is a functional unit of DNA containing a cluster of genes under the control of a single promoter.
Question 14
A repressor protein binds to the operator region of an operon, blocking RNA polymerase and preventing gene transcription.
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repressor
A repressor is a regulatory protein that inhibits gene expression by binding to DNA and blocking transcription.
Question 15
Enhancer sequences are DNA regions that can be located far from a gene but still increase the rate of its transcription by binding to activator proteins.
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Enhancer
Enhancers are regulatory DNA sequences that boost the transcription of specific genes.
Question 16
An insertion or deletion of nucleotides that is not a multiple of three can cause a frameshift mutation, altering all downstream codons.
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frameshift
A frameshift mutation changes the reading frame of the genetic code, leading to a completely different protein sequence.
Question 17
A silent mutation changes a single nucleotide but does not alter the amino acid sequence of the protein due to the redundancy of the genetic code.
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silent
A silent mutation is a point mutation that has no observable effect on the phenotype.
Question 18
In Mendelian genetics, a dominant allele expresses its phenotype completely when present in either a homozygous or heterozygous state.
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dominant
A dominant allele masks the expression of a recessive allele in a heterozygous individual.
Question 19
X-linked inheritance describes traits determined by genes located on the X chromosome, often showing different patterns in males and females.
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X-linked
X-linked inheritance refers to the pattern of inheritance for genes on the X chromosome.
Question 20
When two different alleles are both fully expressed in the phenotype of a heterozygote, such as in blood type AB, the inheritance pattern is called codominance.
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codominance
Codominance occurs when both alleles in a heterozygote are expressed equally and distinctly in the phenotype.