Answer:
A black-and-white TV has a single electron gun, a cathode Ray tube
Answer:
Natural selection is generally limited to modifying structures that were present in previous generations and in previous species
Explanation:
The basic idea of biological evolution is that populations and species of organisms change over time. Today, when we think of evolution, we are likely to link this idea with one specific person: the British naturalist Charles Darwin.
In the 1850s, Darwin wrote an influential and controversial book called On the Origin of Species. In it, he proposed that species evolve (or, as he put it, undergo "descent with modification"), and that all living things can trace their descent to a common ancestor.
Natural selection, genetic drift, and gene flow are the mechanisms that cause changes in allele frequencies over time. When one or more of these forces are acting in a population, the population violates the Hardy-Weinberg assumptions, and evolution occurs. The Hardy-Weinberg Theorem thus provides a null model for the study of evolution, and the focus of population genetics is to understand the consequences of violating these assumptions.
New gene variants (i.e., alleles) are produced by random mutation, and over the course of many generations, natural selection may favor advantageous variants, causing them to become more common in the population.
The correct answer is foot.
Mollusks have more diverse forms in comparison to any other animal phylum. They comprise, the slugs, snails, and other gastropods; squids and other cephalopods; clams and other bivalves; and other lesser known but identically different subgroups.
The cephalopods like octopuses and squids possess the head, which is prominent and the foot that has been amended into tentacles. The cephalopods have an absent or diminished shell and exhibit the most advanced nervous system of the invertebrates.
Answer:
Valine-Leucine-Proline-Lysine-Histidine
Explanation:
The central dogma of biology is the process by which DNA is used to synthesize RNA and subsequently amino acid sequence (PROTEIN). The processes of transcription and translation is used in gene expression. Transcription is the process whereby the information encoded in a DNA molecule is used to synthesize a mRNA molecule. Transcription is catalyzed by RNA polymerase enzyme, which uses complementary base pairing rule i.e Adenine(A)-Thymine(T), Guanine(G)-Cytosine(C) pairing.
N.B: Thymine is replaced by Uracil in the mRNA
For the above DNA sequence: CAC GAC GGA TTC GTA, the mRNA sequence will be: GUG CUG CCU AAG CAU
Translation is the second process of gene expression which involves the synthesis of an amino acid sequence from an mRNA molecule. The mRNA is read in a group of three nucleotides called CODON. Each codon specifies an amino acid (see attached image for genetic code)
Based on the attached genetic code, an mRNA sequence: GUG CUG CCU AAG CAU will encode an amino acid sequence: Valine(Val) - Leucine (Leu) -Proline (Pro) -Lysine (Lys) - Histidine (His).
GUG specifies Valine amino acid
CUG specifies Leucine amino acid
CCU specifies Proline amino acid
AAG specifies Lysine amino acid
CAU specifies Histidine amino acid
Answer:
The miRNAs act as post-transcriptional silencers, as they are similar to specific mRNAs and regulate their stability and translation. They are small endogenous non-coding ribonucleic acid (RNA) molecules, with about 22 nucleotides, which act as regulators of gene expression in plants and animals, at the post-transcriptional level through the cleavage of a target messenger RNA (mRNA) or repression of translation.
In general, most miRNA genes are transcribed by RNA polymerase II in the nucleus in primary miRNAs (pri-miRNAs). Individually, a pri-miRNA can produce a single miRNA or contain groups of two or more miRNAs that are processed from a common primary transcript. These long pri-miRNA are cleaved by a complex comprising the double-stranded RNAse III enzyme (DROSHA) and its essential cofactor, the binding protein DGCR8 (DiGeorge Syndrome Critical Region 8 protein) in mammals. DROSHA contains two domains of RNAse III, each of which cleaves a strand of the RNA resulting in the precursor microRNA (pre-miRNA) with about 70 base pairs, which contains a double-stranded stretch and a single-stranded loop, forming a structure in clamp. The pre-miRNA is exported to the cytoplasm by the protein exportin-5 (XPO-5), where it is cleaved by DICER1, an RNAse III that assesses the 3 'and 5' ends of the pre-miRNA, generating a mature miRNA with about 22 nucleotides. The processing of pre-miRNA by Dicer promotes the unfolding of the RNA duplex in the form of a clamp. The position in the formation of the clamp can also influence the choice of tape.
Explanation:
