Molecular Biology: DNA & RNA Polymerases

<p>It showed that base ratios vary across different species. (C)</p> Signup and view all the answers

<p>To target specific genes for removal or replacement. (C)</p> Signup and view all the answers

<p>One strand runs 5’ to 3’, and the other runs 3’ to 5’ (D)</p> Signup and view all the answers

<p>Adenine-Thymine and Cytosine-Guanine (D)</p> Signup and view all the answers

<p>H1 histone (D)</p> Signup and view all the answers

<p>They require natural selection to maintain essential gene products (B)</p> Signup and view all the answers

<p>It contributes to growth, tissue repair, and cell replacement (D)</p> Signup and view all the answers

<p>S phase (C)</p> Signup and view all the answers

<p>By changing in concentration to trigger checkpoints (D)</p> Signup and view all the answers

<p>Preservation of closely related gene sequences (C)</p> Signup and view all the answers

<p>They phosphorylate target proteins in conjunction with CDKs. (C)</p> Signup and view all the answers

<p>They can turn into oncogenes, leading to excess cell proliferation. (D)</p> Signup and view all the answers

<p>Malignant tumors can invade neighboring tissues while benign tumors cannot. (D)</p> Signup and view all the answers

<p>Transcription regulation via RNA polymerase binding. (C)</p> Signup and view all the answers

<p>The degradation rate of mRNA molecules. (D)</p> Signup and view all the answers

<p>The genome contains both coding and non-coding DNA. (D)</p> Signup and view all the answers

<p>Messenger RNA (mRNA). (D)</p> Signup and view all the answers

<p>They arise from cells that have traveled from a primary tumor site. (D)</p> Signup and view all the answers

<p>It converts to allolactose, which changes the shape of the lac repressor. (B)</p> Signup and view all the answers

<p>It binds to a receptor in the cytoplasm, forming a hormone-receptor complex. (B)</p> Signup and view all the answers

<p>It represses transcription by methylating cytosine in promoter regions. (C)</p> Signup and view all the answers

<p>They can affect phenotype without changing genotype. (A)</p> Signup and view all the answers

<p>Maternal care type influenced epigenetic changes in subsequent generations. (A)</p> Signup and view all the answers

<p>They inherit only one working copy, with one allele silenced. (A)</p> Signup and view all the answers

<p>Widespread decrease in DNA methylation from air pollution. (B)</p> Signup and view all the answers

<p>Paternal imprinting favors larger offspring, while maternal imprinting favors smaller offspring. (B)</p> Signup and view all the answers

<p>RS (B)</p> Signup and view all the answers

<p>It serves as the starting point for RNA polymerase to bind and initiate transcription (B)</p> Signup and view all the answers

<p>It is part of the gene's regulatory region but not transcribed into RNA (C)</p> Signup and view all the answers

<p>The genome directly determines the specific proteins produced, while the proteome is the actual set of proteins present in a cell at a given time (A)</p> Signup and view all the answers

<p>The complete collection of proteins actively expressed in a cell or organism at a given time (C)</p> Signup and view all the answers

The two strands of DNA run in opposite directions, with one strand going from 5' to 3' and the other from 3' to 5'.

Adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). These base pairs have equal lengths, ensuring a consistent helix structure.

A core of eight histone proteins (an octamer) is wrapped by DNA, forming a nucleosome. Another histone protein (H1) holds the nucleosome together, and linker DNA connects adjacent nucleosomes.

DNA sequences that remain very similar over long periods of evolution. These sequences are important for essential functions and may be conserved due to natural selection or slower mutation rates.

The process of cell division that is essential for growth, repair, and replacement of damaged cells.

The first gap phase of interphase, where the cell grows, synthesizes proteins, and prepares for DNA replication.

The phase of interphase where the cell's DNA is replicated.

Regulatory proteins whose concentrations cycle throughout the cell cycle. Specific cyclin thresholds are required to pass cell cycle checkpoints.

Cyclins are proteins that bind to and activate cyclin-dependent kinases (CDK), which are enzymes that phosphorylate target proteins. This phosphorylation can either activate or deactivate the protein, acting like an on/off switch. These complexes are crucial for regulating the cell cycle.

Mutations in genes that control the cell cycle can lead to uncontrolled cell division, resulting in cancer. Proto-oncogenes, which promote cell growth and division, can mutate into oncogenes and cause excessive proliferation. Tumor suppressors, which normally inhibit cell growth, can lose their function when mutated, also contributing to cancer.

Benign tumors are non-cancerous and do not spread, while malignant tumors are cancerous and can invade surrounding tissues and organs. Metastatic tumors form when cancer cells travel through the bloodstream or lymphatic system to establish secondary tumors in distant locations.

Gene expression is primarily controlled at the level of transcription, which involves the binding of RNA polymerase to a specific region of DNA called the promoter. Transcription factors can bind to enhancer sequences on DNA, regulating the amount of mRNA produced. This process allows cells to control which genes are expressed.

Gene expression can also be controlled by regulating the translation of mRNA. mRNA transcripts have a lifespan, and their degradation by nucleases affects the amount of protein produced. The longevity of an mRNA transcript determines the expression levels of a gene.

The genome is the complete set of genetic information in an organism. Includes coding DNA (genes) and non-coding DNA. The transcriptome refers to all RNA transcripts, both coding (mRNA) and non-coding (rRNA, tRNA, etc.). The proteome is the complete set of proteins.

Monozygotic twins have identical DNA at birth. They may have different lifestyles, which influences their epigenomes over time.

During meiosis, the two alleles of a gene separate, and each gamete (sperm or egg) receives one allele. The orientation of homologous chromosomes is random, leading to a 50/50 chance of inheriting either allele.

The inheritance of one gene doesn't influence the inheritance of another gene, especially if they're on different chromosomes (unlinked).

Martha Chase and Alfred Hershey used radioactive isotopes (32P for DNA and 35S for protein) to prove that DNA is the genetic material. They infected bacteria with viruses labeled with these isotopes and found that only the radioactive DNA entered the bacteria, not the protein coat. This concluded that DNA, not protein, carries genetic information.

Chargaff's experiment proved that DNA base composition differs between species, contradicting the tetranucleotide hypothesis. He discovered a 1:1 ratio of adenine to thymine and cytosine to guanine, suggesting a specific pairing mechanism in DNA.

The Lac operon is a group of genes in prokaryotes responsible for lactose uptake and metabolism. When lactose is absent, the lac repressor binds to the operator, blocking RNA polymerase from transcribing the genes. However, when lactose is present, it converts to allolactose, which binds to the repressor, causing a shape change that prevents it from binding to the operator, allowing transcription to proceed.

Estradiol, a steroid hormone, is small and nonpolar, allowing it to easily pass through the cell membrane. It then binds to a receptor in the cytoplasm, forming a complex that binds to DNA and regulates the expression of specific genes. This, in turn, affects tissue development and function by influencing cell division and differentiation.

Epigenetic changes refer to alterations in gene expression without changes in the underlying DNA sequence. Methylation, a process that adds a methyl group to cytosine bases in DNA, can repress transcription. Additionally, methylation of amino acids in histone proteins can either activate or repress gene expression by influencing DNA packaging.

Epigenetic modifications can be passed down from one generation to the next, influencing phenotypic traits even without alterations in DNA sequence. This was demonstrated by Meaney's research on rats, showing that maternal care significantly affected the offspring's behavior and was passed down to subsequent generations.

Environmental factors can significantly impact epigenetic changes. For example, exposure to air pollution can lead to a widespread decrease in DNA methylation, suggesting a potential link between environmental stressors and changes in gene expression.

Imprinted genes are those where only one copy, either from the mother or father, is active. During the development of sperm and eggs, most epigenetic markers are erased, allowing for differentiation. The genetic conflict hypothesis suggests that imprinting arose from competition between males for maternal resources, leading to paternal imprinting favoring large offspring and maternal imprinting favoring smaller offspring.

Ligers, offspring of a lion father and a tiger mother, are larger due to the paternal growth gene being dominant. In contrast, tigons, offspring of a tiger father and a lion mother, are smaller because the maternal growth gene is dominant. This illustrates how imprinting can influence offspring size.

Gene expression is the process by which genetic information is used to create proteins. This process can be regulated by a variety of factors such as the presence of hormones, environmental signals, and the type of cell. Different cells express different genes because they need different proteins to perform their specialized functions. This can lead to differences in the phenotypes of individuals, even if they have the same genotype.