DNA and the Genetic CodeFlashcards - AQA Biology

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Define the term 'allele' in the context of genetics.

An allele is one of a number of alternative forms of a gene. Most genes occur in two, occasionally more, different forms.

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"Define the term 'allele' in the context of genetics."	"An allele is one of a number of alternative forms of a gene. Most genes occur in two, occasionally more, different forms."
"Describe the structure of DNA in eukaryotic cells."	"In a eukaryotic cell nucleus, DNA is stored as chromosomes. The DNA is tightly wound around proteins called histones to form a complex called a nucleosome. Chromosomes in eukaryotic cells are linear in shape."
"How does the structure of DNA in prokaryotic cells differ from that in eukaryotic cells?"	"In prokaryotic cells, the DNA is still coiled and stored in chromosomes, but the chromosomes are free-floating in the nucleus and are not protein-bound. Chromosomes in prokaryotic cells are short and linear in shape."
"Define the term 'locus' in the context of genetics."	"The locus is the location of a particular gene on a chromosome."
"Describe the three special features of the genetic code."	"The genetic code is degenerate, universal, and non-overlapping."
"Explain the role of polypeptides in the formation of proteins."	"A section of DNA contains a code for making a polypeptide. Polypeptides make proteins, and genes determine the proteins of an organism."
"What is a homologous pair of chromosomes?"	"A homologous pair of chromosomes is exactly the same size, has exactly the same genes, but might have different alleles."
"Define the term 'start codon' in the context of genetics."	"A 'start codon' is the first codon of a messenger RNA (mRNA) transcript that is translated by a ribosome. In eukaryotes and Archaea, the start codon always codes for methionine in the mRNA. The most common start codon is AUG."
"What is the role of a 'stop codon' in gene translation?"	"A 'stop codon' is a nucleotide triplet within mRNA that signals the end of translation. It marks the end of a polypeptide chain and stops further translation."
"Explain the concept of the genetic code being 'degenerate'."	"The genetic code is said to be 'degenerate' because there are more possible combinations of codons than there are amino acids. This means that each amino acid is actually coded for by more than one triplet of bases. For example, the amino acid tyrosine is coded for by both ATA and ATG."
"How many bases are needed to code for at least 20 amino acids and why?"	"Three bases are needed to code for at least 20 amino acids. This is because there are four DNA bases, and three bases make enough combinations (64) to code for all 20 amino acids."
"What is the function of the genetic code wheel?"	"The genetic code wheel is a tool that enables you to work out all combinations of bases that code for each of the 20 amino acids. The amino acids are on the outside of the wheel, abbreviated to the first three letters of each one."
"What happens to the methionine coded by the start codon if it is not needed for the protein structure?"	"If the methionine coded by the start codon is not needed for the protein structure, it is later removed from the protein."
"Describe the universal nature of the genetic code."	"The genetic code is described as universal because the same triplet of bases codes for the same amino acid in all organisms."
"Define the term 'non-overlapping' in the context of the genetic code."	"In the genetic code, 'non-overlapping' means that each base in a gene is only part of one triplet of bases that codes for one amino acid. Each codon, or triplet of bases, is read as a discrete unit."
"Explain the difference between introns and exons."	"Introns are sections of DNA that do not code for amino acids and therefore polypeptide chains. These get removed, spliced, out of mRNA molecules. Exons are the sections of DNA that do code for amino acids."
"How do the genome and proteome of an organism differ?"	"The genome is an organism's complete set of DNA in one cell, whereas the proteome is the complete set of proteins in one cell. The genome should never change, whereas the proteome of the cell is constantly changing depending on which proteins are currently needed."
"What is the function of a histone protein?"	"The function of a histone protein is to provide a structure around which DNA is wrapped."
"If all the DNA were distributed equally between the chromosomes, what is the mean length of DNA in each one (in miles)?"	"0.05 miles."
"Calculate in mm the length of DNA in a human brain cell (in miles)."	"2300 miles."

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[{"id":1330108,"front":"Define the term 'allele' in the context of genetics.","back":"An allele is one of a number of alternative forms of a gene. Most genes occur in two, occasionally more, different forms.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Alleles are variations of a gene that can lead to different traits. They are located at the same position on homologous chromosomes and can be dominant or recessive. Alleles are crucial in determining an organism's genetic makeup and the traits it expresses.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330126,"front":"Describe the structure of DNA in eukaryotic cells.","back":"In a eukaryotic cell nucleus, DNA is stored as chromosomes. The DNA is tightly wound around proteins called histones to form a complex called a nucleosome. Chromosomes in eukaryotic cells are linear in shape.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The structure of DNA in eukaryotic cells is organized into chromosomes within the nucleus. The DNA is tightly wound around histone proteins to form nucleosomes. Eukaryotic chromosomes are linear, allowing for the orderly arrangement of genetic material.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330134,"front":"How does the structure of DNA in prokaryotic cells differ from that in eukaryotic cells?","back":"In prokaryotic cells, the DNA is still coiled and stored in chromosomes, but the chromosomes are free-floating in the nucleus and are not protein-bound. Chromosomes in prokaryotic cells are short and linear in shape.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Prokaryotic cells have a simpler structure with DNA forming circular chromosomes that are not enclosed within a nucleus. Eukaryotic cells, on the other hand, have linear chromosomes enclosed within a nucleus. This difference in DNA structure reflects the contrasting complexity of cellular organization between prokaryotic and eukaryotic cells.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330138,"front":"Define the term 'locus' in the context of genetics.","back":"The locus is the location of a particular gene on a chromosome.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"In genetics, the term \"locus\" refers to the specific position or location of a gene on a chromosome. It is important because it helps scientists identify and study the inheritance patterns of genes. By understanding the locus of a gene, researchers can determine how it is passed down from one generation to the next and how it may be associated with certain traits or diseases. The locus is crucial for mapping and studying the genetic variations within a population.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330142,"front":"Describe the three special features of the genetic code.","back":"The genetic code is degenerate, universal, and non-overlapping.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The genetic code's degeneracy allows multiple codons to code for the same amino acid, providing redundancy. Its universality means it's shared across species. Non-overlapping nature ensures each nucleotide is part of only one codon, preventing ambiguity in translation.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330145,"front":"Explain the role of polypeptides in the formation of proteins.","back":"A section of DNA contains a code for making a polypeptide. Polypeptides make proteins, and genes determine the proteins of an organism.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Polypeptides play a crucial role in protein formation as they are the building blocks of proteins. The sequence of amino acids in a polypeptide chain is determined by the genetic code, and this sequence ultimately determines the structure and function of the protein. Genes encode the information for specific polypeptides, which in turn form the diverse array of proteins essential for various biological processes in an organism.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330146,"front":"What is a homologous pair of chromosomes?","back":"A homologous pair of chromosomes is exactly the same size, has exactly the same genes, but might have different alleles.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Homologous pairs of chromosomes are crucial for genetic diversity. They allow for genetic recombination during meiosis, leading to variation in offspring. This variation is essential for adaptation and evolution in populations.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330152,"front":"Define the term 'start codon' in the context of genetics.","back":"A 'start codon' is the first codon of a messenger RNA (mRNA) transcript that is translated by a ribosome. In eukaryotes and Archaea, the start codon always codes for methionine in the mRNA. The most common start codon is AUG.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The start codon initiates the translation process in protein synthesis. It signals the ribosome to start assembling the amino acids into a polypeptide chain. In eukaryotes and Archaea, the start codon is almost always AUG, which also codes for methionine. This codon serves as the starting point for protein synthesis.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330153,"front":"What is the role of a 'stop codon' in gene translation?","back":"A 'stop codon' is a nucleotide triplet within mRNA that signals the end of translation. It marks the end of a polypeptide chain and stops further translation.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The stop codon serves as a signal for the ribosome to terminate protein synthesis. When it is encountered during translation, it prompts the release of the completed polypeptide chain. This crucial function ensures that the protein is not elongated beyond its intended sequence.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330154,"front":"Explain the concept of the genetic code being 'degenerate'.","back":"The genetic code is said to be 'degenerate' because there are more possible combinations of codons than there are amino acids. This means that each amino acid is actually coded for by more than one triplet of bases. For example, the amino acid tyrosine is coded for by both ATA and ATG.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The genetic code is considered 'degenerate' due to the redundancy in codon-amino acid correspondence. With 64 possible codons and only 20 amino acids, multiple codons can encode the same amino acid. This redundancy provides a buffer against errors during protein synthesis.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330155,"front":"How many bases are needed to code for at least 20 amino acids and why?","back":"Three bases are needed to code for at least 20 amino acids. This is because there are four DNA bases, and three bases make enough combinations (64) to code for all 20 amino acids.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Three bases are needed to code for at least 20 amino acids because there are four DNA bases available. With three bases, there are 64 possible combinations, which is more than enough to code for all 20 amino acids. This is due to the fact that each combination of three bases can represent a different amino acid, allowing for a wide range of possibilities.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330156,"front":"What is the function of the genetic code wheel?","back":"The genetic code wheel is a tool that enables you to work out all combinations of bases that code for each of the 20 amino acids. The amino acids are on the outside of the wheel, abbreviated to the first three letters of each one.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The genetic code wheel is designed to facilitate the determination of the combinations of bases that correspond to each of the 20 amino acids. By using this tool, researchers can easily identify the specific sequence of bases that code for a particular amino acid, aiding in genetic analysis and protein synthesis.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330157,"front":"What happens to the methionine coded by the start codon if it is not needed for the protein structure?","back":"If the methionine coded by the start codon is not needed for the protein structure, it is later removed from the protein.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The methionine coded by the start codon is typically removed from the protein during or after the translation process. This is because the start codon serves as an initiation signal for protein synthesis, and the methionine is often cleaved off to form the mature functional protein. This process ensures the proper functionality of the protein.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330158,"front":"Describe the universal nature of the genetic code.","back":"The genetic code is described as universal because the same triplet of bases codes for the same amino acid in all organisms.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The universality of the genetic code is attributed to its conservation across diverse species. This consistency in the relationship between DNA sequences and the corresponding amino acids enables the same fundamental processes of protein synthesis to occur in all living organisms, underscoring the shared ancestry of life on Earth.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330166,"front":"Define the term 'non-overlapping' in the context of the genetic code.","back":"In the genetic code, 'non-overlapping' means that each base in a gene is only part of one triplet of bases that codes for one amino acid. Each codon, or triplet of bases, is read as a discrete unit.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"In the context of the genetic code, the term \"non-overlapping\" refers to the principle that each nucleotide is part of only one codon, or triplet of bases, which encodes for a specific amino acid. This ensures that there is no ambiguity in the reading of the genetic information during protein synthesis.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330173,"front":"Explain the difference between introns and exons.","back":"Introns are sections of DNA that do not code for amino acids and therefore polypeptide chains. These get removed, spliced, out of mRNA molecules. Exons are the sections of DNA that do code for amino acids.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Introns are non-coding sections of DNA that are transcribed into mRNA but are later removed during RNA processing. Exons, on the other hand, are coding sections of DNA that contain the instructions for building proteins. The removal of introns allows for the production of mature mRNA molecules that can be translated into proteins. This process is known as splicing and is essential for generating functional proteins.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330181,"front":"How do the genome and proteome of an organism differ?","back":"The genome is an organism's complete set of DNA in one cell, whereas the proteome is the complete set of proteins in one cell. The genome should never change, whereas the proteome of the cell is constantly changing depending on which proteins are currently needed.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The genome refers to an organism's entire DNA sequence, while the proteome represents all the proteins produced by the organism. Unlike the genome, which remains constant, the proteome is dynamic and can change based on the cell's needs. The genome serves as a blueprint for protein synthesis, but the proteome is influenced by various factors such as gene expression, post-translational modifications, and environmental conditions. Therefore, while the genome provides the genetic information, the proteome reflects the functional and regulatory aspects of the organism.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330182,"front":"What is the function of a histone protein?","back":"The function of a histone protein is to provide a structure around which DNA is wrapped.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"Histone proteins play a crucial role in DNA packaging and organization. They form a complex structure called chromatin, around which DNA is wrapped. This compact packaging allows for efficient storage of genetic material and regulates gene expression. Additionally, histones help in maintaining the stability and integrity of DNA by preventing tangling and damage.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330183,"front":"If all the DNA were distributed equally between the chromosomes, what is the mean length of DNA in each one (in miles)?","back":"0.05 miles.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The mean length of DNA in each chromosome can be calculated by dividing the total length of DNA by the number of chromosomes. Since the question assumes that all the DNA is distributed equally, the total length of DNA is divided equally among the chromosomes. Therefore, the mean length of DNA in each chromosome is 0.05 miles.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}},{"id":1330184,"front":"Calculate in mm the length of DNA in a human brain cell (in miles).","back":"2300 miles.","front_language":"English","back_language":"English","front_image":"","back_image":"","order":0,"explanation":"The length of DNA in a human brain cell is typically measured in millimeters, not miles. DNA is a microscopic molecule that is tightly coiled and packed within the nucleus of a cell. It would be impractical to measure its length in miles, as it would be an extremely large value.","deleted_at":null,"flashcard_deck_id":"GjMUE","original_id":null,"examMode":{"text":"","correct":"","incorrect":"","info":""}}]

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