DNA & Protein Synthesis Flashcards
Define Gene Expression
The process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce protein as the end product.
Define Central Dogma
The process by which the instructions in DNA are converted into a functional product.
Define Degeneracy
The property of the genetic code that allows multiple codons to code for the same amino acid.
There are 64 possible codons and only 20 relevant amino acids. Codons for the same amino acid often differ in their third base.
Define Nucleic Acid
An organic molecule present in living cells, especially DNA or RNA, consisting of a chain of nucleotides.
Define Nucleotide
An organic molecule that is the building block of DNA and RNA. Made up of a phosphate group, a 5-carbon sugar, and a nitrogenous base.
Define Nitrogenous Base
Molecules that serve as main components of DNA and RNA. All contain nitrogen and display basic properties. The nitrogenous bases used in normal nucleus acids are adenine, guanine, cytosine, thymine, and uracil.
Define DNA Replication
The process by which DNA makes a copy of itself, necessary for cell reproduction prior to division.
Define Telomere
A repeating, non-coding sequence at the end of the chromosomes, thought to protect the DNA from degradation.
Telomeres shorten over time, a process that may be connected to aging and the medical problems that come with it.
Define Transcription
The process of copying a gene from DNA into mRNA.
Define mRNA
Messenger RNA. mRNA is a single stranded molecule of RNA that is the product of DNA transcription. It corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. It is short-lived in the cell, as its function is to be translated into protein. It cannot replicate itself and must be transcribed from DNA.
Define Splicing as it relates to transcription
Splicing is a form of RNA processing in which a newly made mRNA transcript is edited so that it can be translated into a protein. This process removes non-coding regions (introns) and joins together exons (coding regions). It is carried out by the spliceosome.
Define Exon
A segment of DNA or RNA that contains information coding for a protein or peptide sequence.
Define Intron
A non-coding segment of DNA or RNA that is eliminated by splicing before translation.
Define Translation
The process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins from the information contained in mRNA.
Define Ribosome
An organelle consisting of rRNA and associated proteins that translates mRNA into proteins.
Define tRNA
Transfer RNA. It is an adapter molecule that serves as the physical link between the mRNA and the amino acid sequence of proteins. On one end of a tRNA is an amino acid. On the other end is a specific sequence of nitrogenous bases.
Define rRNA
Ribosomal RNA. It is a type of non-coding RNA that carries out protein synthesis, and is the main component of ribosomes.
Define Codon
A block of three nucleotides that codes for an amino acid.
Define Mutation
An alteration in the DNA sequence. Mutations can arise spontaneously (often from errors in DNA replication) or be induced by mutagenic substances.
Mutations never arise in response to selective pressure.
Define Point Mutation
A mutation affecting a single nucleotide base.
Define Substitution Mutation
A mutation where one base is replaced with a different base.
Define Missense Mutation
A point mutation in which a single nucleotide change results in a codon that codes for a different amino acid.
Define Nonsense Mutation
A point mutation in which a single nucleotide change results in a premature stop codon.
This usually results in a shortened and likely non-functional protein.
Define Chromosomal Mutation
A mutation that affects whole molecules of DNA, rather than just a few bases.
Chromosomal mutations are typically the result of errors that occur during meiosis, or of mutagens.
Define Deletion (Chromosomal Mutation)
A chromosomal mutation in which a part of a chromosome is left out during DNA a replication and is lost.
Define Inversion (Mutation)
A chromosomal mutation in which a nucleotide sequence is completely reversed.
Define Translocation (Mutation)
A chromosomal mutation in which a nucleotide sequence moves to another position, either within the same or between different chromosomes.
Define Duplication (Mutation)
A chromosomal mutation in which part or all of a chromosome is repeated.
Define Frameshift Mutation
A mutation caused by indels of a number not divisible by three, shifting the three codon “frame” in which the sequence is read.
Define Insertion (Mutation)
The addition of one or more nucleotides; a point mutation.
Define Deletion (Mutation)
The removal of one or more nucleotides; a point mutation.
Define Silent Mutation
A mutation that does not have an observable effect on the organism’s phenotype.
Define Mutagen
A chemical or other substance that induces changes in DNA.
Mutagens are item also categorized as carcinogens, or cancer-causing substances.
Define Paralogous
Relating to genes that arose from a common ancestral gene by gene duplication in the course of evolution.
Define Pseudogene
A gene that loses its protein producing abilities or stops being expressed.
Genes become pseudo genes when they accumulate mutations over a long time. This only happens if the mutations do not compromise the organism’s survival; otherwise natural selection would eliminate the mutations.
What were Chargaff’s rules?
1) All species have different amounts of adenine, thymine, cytosine, and guanine in their DNA
2) In every species:
amount of adenine=amount of thymine
amount of cytosine=amount of guanine
What biological role is played by nucleic acids?
They store genetic material in the form of DNA, allowing it to be inherited. They also direct the formation of protein through translation from mRNA transcripts.
Describe the structure of double stranded DNA
Double stranded DNA forms a double helix. Two complimentary strands are held together in a twisting, or helical, shape. The strands are antiparellel, meaning they run in opposite directions. They are composed of nucleotides, or nitrogenous bases held together by a sugar phosphate backbone.
What is the relationship between histones, nucleosomes, and chromatin?
Histones are small proteins that form core complexes around which DNA warps tightly. A nucleosome includes a histone core and its associated DNA. These structures are present in chromatin, the tightly packed organizational structure that forms chromosomes.
What electric charge exists on DNA molecules?
A negative charge. This charge comes from the sugar-phosphate backbone, specifically the phosphate ion.
How are the ends of a DNA strand denoted?
5’ and 3’
The 5’ end contains an unbound phosphate group, while the 3’ end contains a free -OH.
Towards which electrode, the anode or cathode, will DNA migrate in gel electrophoresis?
The DNA will migrate toward the anode. The anode is positively charged, while the cathode is negatively charged. Since DNA is negatively charged, it will migrate toward the positively charged electrode.
What is the difference between a nucleotide and a nucleoside?
A nucleoside is a nucleotide without any phosphate groups. A nucleoside contains a nitrogenous base and a sugar molecule.
Give two examples of nucleotides with non-genetic functions
Adenosine Triphosphate (ATP)—a source of energy produced in cellular metabolism. Cyclic AMP (cAMP)—a signaling molecule involved in second messenger cascades. Other examples include GTP and modified nucleotides like NADH and FADH2.
Which base pair has stronger bonds?
The cytosine guanine pair has stronger bonds because it contains three hydrogen bonds, while the adenine thymine pair has two hydrogen bonds.
Researchers observe that DNA strand A denatures at a lower temperature than DNA strand B. Which property of the two strands might determine this result?
Strand A likely has a higher content of adenine and thymine bases, while strand B has more cytosine and guanine bases.
This property is referred to as GC content. Strands with more G and C bases will denature around a higher temperature because the three hydrogen bonds between guanine and cytosine form a stronger connection than the two between adenine and thymine.
What are the major differences between DNA and RNA?
RNA is a single stranded molecule, while DNA is double stranded. The sugar in RNA is ribose, which has one more oxygen atom than deoxyribose, found in DNA. RNA contains uracil instead of thymine.
Name the two main types of chromatin found in eukaryotic cells
Euchromatin and heterochromatin.
Euchromatin is loosely packed and appears light-colored when viewed under a microscope.
Heterochromatin is more dense, or tightly packed, and appears darker.
Bases on the same strand are ___________ bonded to each other by ________________ bonds.
covalently, phosphodiester
Which type of chromatin is likely to be more prevalent in genes that are actively being transcribed?
Euchromatin
Because it is more loosely wound, euchromatin allows enzymes like RNA polymerase access to the nucleotide structure. In contrast, the density of heterochromatin protects the DNA when it is not being transcribed.
Which nitrogenous bases does DNA contain?
Adenine, guanine, cytosine, and thymine. Adenine pairs with thymine and cytosine pairs with guanine.
Bases on opposite strands are _____________ bonded to each other.
hydrogen
Which nitrogenous bases does RNA contain?
Adenine, guanine, cytosine, and uracil. Adenine pairs with uracil and cytosine pairs with guanine.
Name the three main types of RNA
mRNA, tRNA, and rRNA
mRNA is a template that gets translated into a protein, tRNA carries the amino acids to the ribosome to be assembled, and rRNA is a main structural component of ribosomes.
Which two major groups are nitrogenous bases categorized into?
Purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil).
What are the similarities and differences between purines and pyrimidines?
Similarities: contain one or more nitrogenous heterocyclic rings, major component of DNA and RNA
Differences: pyrimidines consist of a single six membered ring that contains two nitrogens, while purines consist of two fused rings, one pyrimidine ring and one five membered imidazole ring.
