Biology Unit Test T2 P2 Flashcards
(29 cards)
What are nucleotides composed of?
Nucleotides compose of a nitrogenous base (adenine, guanine, cytosine and thymine or uracil), a phosphate group and a sugar (deoxyribose in DNA, ribosome in RNA)
What type pf bond links nucleotides together in a single strand of DNA
Phosphodiester bonds are strong covalent bonds that connect nucleotides in DNA and RNA strands. They form between the phosphate group of one nucleotide and the sugar of the next nucleotide. This creates a sugar-phosphate backbone that gives the strand stability and structure. These bonds are essential for linking nucleotides into long chains of genetic material.
What is found in RNA but not DNA
Uracil (U) is a pyrimidine base that is found only in RNA. In DNA, uracil is replaced by thymine (T), which serves a similar role. This difference in nitrogenous bases is one of the main distinctions between RNA and DNA. It helps scientists identify and understand the structure and function of each molecule.
What pairs of bases are purines?
Purines are nitrogenous bases that have a double-ring structure, making them larger than other bases. The two purines found in both DNA and RNA are adenine (A) and guanine (G). These bases pair with specific pyrimidines to form the rungs of the nucleic acid ladder. Their structure plays an important role in the stability and pairing of genetic material.
What is the function of mRNA in the cell?
Messenger RNA (mRNA) serves the key role of transporting genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm. At the ribosomes, these instructions are used to build proteins. This transfer of information is a vital step in gene expression. It is a central part of the molecular biology process known as the central dogma.
What enzyme is responsible for unzipping the DNA double helix during replication?
Helicase is an enzyme that plays a crucial role in DNA replication by unwinding the double helix. It breaks the hydrogen bonds between the complementary base pairs, which allows the two strands to separate. This separation creates a structure known as the replication fork, enabling the replication process to continue.
What type of RNA carries amino acids to the ribosome?
Transfer RNA (tRNA) plays a key role in protein synthesis by transporting amino acids to the ribosome. Each tRNA molecule contains an anticodon that is complementary to the mRNA codon, ensuring the accurate addition of the correct amino acid to the polypeptide chain. This process ensures the proper sequence of amino acids, which is essential for forming functional proteins.
What is the structure of a DNA structure?
The DNA molecule has a double-stranded helical structure, a discovery made by James Watson and Francis Crick. This unique shape enables complementary base pairing, which is crucial for the accurate replication of genetic material. The double helix also provides a stable way to store genetic information within cells. This structure is fundamental to the transmission of hereditary traits.
What is the directionality of DNA synthesis during replication?
DNA synthesis occurs in the 5’ to 3’ direction because of the specific structure of DNA polymerase. This enzyme can only add nucleotides to the 3’ end of the growing strand. As a result, the new DNA strand is synthesized in the 5’ to 3’ direction, following the template strand in the opposite direction. This ensures accurate replication of the genetic material.
What is a key feature of RNA compared to DNA?
One of the main differences between RNA and DNA is that RNA contains uracil (U) instead of thymine (T). In RNA, uracil pairs with adenine, similar to how thymine pairs with adenine in DNA. This distinction in base pairing is a key feature that sets RNA apart from DNA. As a result, uracil plays the role of thymine in RNA’s structure.
In DNA replication, the enzyme responsible for synthesising the new strand by adding nucleotides is what?
DNA polymerase is the enzyme that builds new DNA strands by adding nucleotides complementary to the template strand. It functions in the 5’ to 3’ direction, meaning it can only attach new nucleotides to the 3’ end of the growing strand. This directional activity ensures accurate and efficient DNA replication. The enzyme plays a critical role in maintaining genetic continuity during cell division.
The central dogma of molecular biology refers to the flow of genetic information from what?
The central dogma of molecular biology, introduced by Francis Crick, explains how genetic information is transferred within a cell. It describes the process where DNA is first transcribed into RNA. Then, the RNA is translated into proteins, which carry out various functions in the body. This flow of information from DNA to RNA to protein is fundamental to gene expression.
Where does the process of transcription occur?
In eukaryotic cells, transcription takes place inside the nucleus, where the DNA is stored. During this process, a messenger RNA (mRNA) molecule is produced based on the DNA template. Once formed, the mRNA exits the nucleus and enters the cytoplasm. There, it serves as a guide for protein synthesis during translation.
During transcription, RNA polymerase binds to which region of the DNA to initiate the process?
The promoter is a particular DNA sequence found just before the start of a gene. It acts as the binding site for RNA polymerase, the enzyme responsible for starting transcription. By attaching to the promoter, RNA polymerase can begin synthesizing RNA from the DNA template. This sequence plays a crucial role in controlling when and where a gene is expressed.
What is the difference between exons and introns?
RNA processing involves modifying the pre-mRNA before it becomes a functional messenger RNA. During this process, introns, which are non-coding regions, are removed through splicing. The remaining exons, which contain the coding information, are then joined together. This results in a mature mRNA strand that can be used for protein synthesis.
The process by which a mature mRNA is translated into a protein occurs in what?
Translation is the process of building proteins using the sequence of codons in mRNA as a guide. This process takes place at ribosomes, which are the cell’s protein factories. Ribosomes may float freely in the cytoplasm or be attached to the surface of the rough endoplasmic reticulum. Their location often depends on where the protein being made is needed.
What is the role of rRNA in translation?
Ribosomal RNA (rRNA) plays an essential role in protein synthesis. It forms the structural core of ribosomes, helping to hold the ribosomal proteins in place. In addition to providing stability, rRNA also has catalytic functions, specifically in forming peptide bonds between amino acids. This makes it vital for assembling proteins accurately and efficiently.
What process results in the formation of a polypeptide?
Translation is the process where the genetic information in mRNA is interpreted to build a specific polypeptide chain, or protein. It takes place at the ribosome, the site of protein synthesis in the cell. During translation, amino acids are assembled in the correct order according to the sequence of codons on the mRNA. This step is essential for producing functional proteins based on genetic instructions.
What is the key difference between leading and lagging strands during DNA replication?
Because DNA strands are antiparallel and DNA synthesis only occurs in the 5’ to 3’ direction, the leading strand is synthesised continuously in the same direction as the replication fork progresses. In contrast, the lagging strand is synthesized in short segments called Okazaki fragments. These fragments are produced in the opposite direction of the fork’s movement. Later, they are joined together to form a complete strand.
What term has the enzyme that unwinds DNA double helix?
Helicase
What term has the process of synthesising RNA from DNA?
Transcription
What term has the type of DNA that carries the genetic code from DNA to the ribosome?
mRNA
What term has the sequence of three bases on MRNA that correspond to an amino acid?
Codon
What term has the enzyme responsible for synthesising new DNA strands?
DNA polymerase
