Exam 5 Short Answer Practice Questions

3 stages of translation

3 stages of translation

The process of protein synthesis that involves initiation, elongation, and termination, where ribosomes decode mRNA to assemble amino acids into polypeptide chains.

3 stages of transcription

The process of synthesizing RNA from a DNA template, involving initiation, elongation, and termination.

Difference between eukaryotic and prokaryotic cells

Eukaryotic cells have a defined nucleus and membrane-bound organelles, while prokaryotic cells lack a nucleus and are generally smaller and simpler in structure.

Prokaryotic cells are simpler structures, no nucleus, less time fo replication as compared to eukaryotic cells

What is the responsibility of enzymes

Enzymes are biological catalysts that speed up chemical reactions in the body by lowering the activation energy required for the reactions to occur, thereby increasing the rate of reaction.

What are the nucleotides placed down by primase?

RNA Nucleotides

How are new nucleotides brought in?

New nucleotides are brought in by DNA polymerase, which adds complementary nucleotides to the growing DNA strand during replication.

What type of cells have telomerase?

Telomerase is found in germ cells, stem cells, and lymphatic cells It adds repetitive nucleotide sequences to the ends of chromosomes, helping to maintain telomere length.

What are nucleotides composed of?

Nucleotides are composed of a sugar, a phosphate group, and a nitrogenous base. These components are essential for forming the building blocks of DNA and RNA.

What is a major groove in DNA? What is a minor groove in DNA?

The major groove and minor groove are the regions of the DNA double helix that form due to the twisting of the strands. The major groove is wider and provides more access for proteins to bind, while the minor groove is narrower.

What direction indicates the direction of synthesis and replication

5' to 3' end

What is meant by anti-parallel?

Anti-parallel refers to the arrangement of the two strands of DNA, where one strand runs in the 5' to 3' direction and the other runs in the 3' to 5' direction, allowing for complementary base pairing.

How many bases per turn?

There are approximately 10 bases per turn in a DNA double helix, contributing to its helical structure.

What are nucleosomes?

Nucleosomes are the fundamental units of DNA packaging in eukaryotic cells, consisting of a segment of DNA wrapped around a core of histone proteins, helping to organize and condense the DNA into a compact structure.

What does chromosome packing involve?

Chromosome packing involves the organization of DNA into a compact structure through interactions with histone proteins and higher-order folding, allowing for efficient storage and regulation of genetic material.

Explain linker DNA

Linker DNA refers to the stretch of DNA that connects nucleosomes together, playing a crucial role in the higher-order structure of chromatin and facilitating the compaction of DNA within the nucleus.

What are exons and introns?

Exons are the coding regions of a gene that are retained in the final mRNA after splicing, while introns are the non-coding regions that are removed during this process.

What are discrete units?

Discrete units are individual segments of genetic material, such as genes, that can be expressed independently and have specific functions in the organism.

Explain the difference between euchromatin and herterochromatin

Euchromatin is a loosely packed form of chromatin that is actively involved in transcription, allowing for gene expression, while heterochromatin is a tightly packed form that is generally transcriptionally inactive and plays a role in maintaining chromosome structure.

Identify and explain the two histone modification types

The two main types of histone modifications are acetylation and methylation. Acetylation typically enhances gene expression by loosening chromatin structure, while methylation can either activate or repress gene expression depending on the specific context and location of the modification.

Identify some key enzymes in chemical modifications of histones

Key enzymes include histone acetyltransferases (HATs) and histone deacetylases (HDACs) for acetylation, and histone methyltransferases (HMTs) and demethylases for methylation. These enzymes add or remove chemical groups to histones, influencing gene expression.

Explain modification in epigenetics

Modification in epigenetics refers to the chemical changes to DNA and histone proteins that affect gene expression without altering the underlying DNA sequence. These modifications can include methylation of DNA and various histone modifications, influencing chromatin structure and accessibility.

What does base pairing mechanism provide?

The base pairing mechanism provides the specificity of DNA replication and transcription, ensuring that adenine pairs with thymine and cytosine pairs with guanine. This complementary pairing is crucial for maintaining genetic information during cell division.

Explain the term wobble

Wobble refers to the flexibility in base pairing between the third base of a codon and the corresponding anticodon of tRNA, allowing for some variation in the genetic code. This phenomenon helps to accommodate different tRNA molecules and contributes to the efficiency of protein synthesis.

Explain single strand binding

proteins that stabilize unwound DNA during replication, preventing re-annealing and protecting it from degradation.

What does RNA primer establish? What does it enable?

The RNA primer establishes a starting point for DNA synthesis and enables DNA polymerase to initiate replication by providing a free 3' hydroxyl group for nucleotide addition.

Compare and contrast leading and lagging strands

Leading and lagging strands refer to the two different modes of DNA replication. The leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized discontinuously in short segments, known as Okazaki fragments, moving away from the replication fork.

Explain chaining process

A method used in DNA replication to link Okazaki fragments together, involving the enzyme DNA ligase, which covalently connects the sugar-phosphate backbones of adjacent fragments.

Explain proofreading mechanism/ error checking in DNA

The proofreading mechanism in DNA replication involves the action of DNA polymerase, which can detect and correct mismatched nucleotides during synthesis. This error-checking process enhances the fidelity of DNA replication by ensuring that the correct base pairs are formed.

Explain the role of telomeres

Telomeres are repetitive nucleotide sequences at the ends of eukaryotic chromosomes that protect them from deterioration or fusion with neighboring chromosomes. They play a crucial role in maintaining chromosome stability and preventing the loss of genetic information during DNA replication.

What is telomere shortening

Telomere shortening refers to the progressive loss of telomere length that occurs during cell division, ultimately leading to cellular aging and senescence. This process limits the number of times a cell can divide, contributing to the aging of organisms.

Explain what the Hayflick Limit is

The Hayflick Limit is the maximum number of times a normal somatic human cell can divide before cell division stops, which is largely attributed to telomere shortening. This phenomenon is associated with aging and limits cellular proliferation.

Where does DNA transcription occur

DNA transcription occurs in the nucleus of eukaryotic cells, where the DNA is located. In prokaryotic cells, transcription occurs in the cytoplasm since they lack a defined nucleus.

Where does DNA translation occur

DNA translation occurs in the cytoplasm of both eukaryotic and prokaryotic cells, where ribosomes synthesize proteins from messenger RNA (mRNA).

What are the 2 main stages in gene expression

The two main stages in gene expression are transcription, where DNA is converted into messenger RNA (mRNA), and translation, where mRNA is used to synthesize proteins.

Explain what the central dogma is in biology

The central dogma of biology describes the flow of genetic information within a biological system, stating that DNA is transcribed into RNA, which is then translated into proteins.

What are codons and what is genetic code?

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids or stop signals during protein synthesis. The genetic code is the set of rules that defines how these codons are translated into proteins.

Explain mRNA processing

mRNA processing involves several modifications to the primary transcript, including the addition of a 5' cap, polyadenylation at the 3' end, and splicing to remove introns, resulting in a mature mRNA ready for translation.

Explain splicing

Splicing is the process by which introns are removed from the pre-mRNA transcript and exons are joined together, producing a continuous coding sequence that will be translated into a protein.

Explain spliceosomes

Spliceosomes are complex molecular machines composed of snRNPs and proteins that facilitate the splicing of pre-mRNA by recognizing splice sites and catalyzing the removal of introns.

Explain ribozymes

Ribozymes are RNA molecules that possess catalytic activity, enabling them to facilitate biochemical reactions, including the splicing of pre-mRNA and other RNA processing events.

Explain alternative splicing

Alternative splicing is a regulatory mechanism by which different combinations of exons are joined together from a single pre-mRNA transcript, allowing the generation of multiple protein isoforms from one gene.

What does the E site, P site, and A site do?

The E site (exit site) releases tRNA after it has donated its amino acid, the P site (peptidyl site) holds the tRNA carrying the growing polypeptide chain, and the A site (aminoacyl site) is where new tRNA molecules enter and add their amino acids to the chain during translation.

Explain what the replication fork is

The replication fork is a Y-shaped structure that forms during DNA replication, where the double helix is unwound, allowing the synthesis of new DNA strands by DNA polymerase.

Describe helicase

Helicase is an enzyme that unwinds the DNA double helix at the replication fork, separating the two strands to allow for replication to occur.

Describe single strand binding proteins

Single strand binding proteins are proteins that bind to and stabilize single-stranded DNA during replication, preventing the strands from re-annealing or forming secondary structures.

Describe topoisomerase

Topoisomerase is an enzyme that alleviates the torsional strain generated ahead of the replication fork by introducing temporary breaks in the DNA strands, allowing them to unwind and preventing supercoiling.

What does DNA replication machine mean

The DNA replication machine refers to the complex of enzymes and proteins involved in the process of DNA replication, including helicase, DNA polymerase, and single strand binding proteins, which work together to synthesize new DNA strands.

What is mismatch repair

Mismatch repair is a cellular process that corrects errors that occur during DNA replication, specifically mismatched base pairs, ensuring the accuracy of genetic information.

What is nucleotide excision repair

Nucleotide excision repair is a DNA repair mechanism that removes damaged DNA segments, particularly those caused by UV light or chemical mutagens, and replaces them with the correct nucleotides to restore DNA integrity.

What are the four types of histones

The four types of histones are H1, H2A, H2B, and H3. These proteins play a crucial role in the packaging of DNA into nucleosomes, helping to regulate gene expression and maintain chromatin structure.

Describe in great deal the EPA Cycle for DNA translation

The EPA Cycle refers to the stages of translation in protein synthesis: E stands for the Exit site where the tRNA leaves the ribosome, P represents the Peptidyl site where the tRNA holds the growing polypeptide chain, and A signifies the Aminoacyl site where new tRNA molecules bring amino acids to be added to the chain. This cycle is essential for the elongation of the polypeptide during translation.

Which is the process of how DNA is replicated

DNA replication is the process by which a cell duplicates its DNA before cell division, ensuring that each daughter cell receives an identical copy of the genetic material. This involves unwinding the double helix, synthesizing new complementary strands using DNA polymerase, and proofreading for errors.