Bio Test 3 (Part 1)

Fred Griffith's experiment using two strains of Streptococcus pneumoniae demonstrated that harmless bacteria can become transformed into disease-causing bacteria by some association with pathogenic bacteria. This was a significant finding because it provided evidence for the concept of bacterial transformation, where genetic material can be transferred between bacteria and alter their characteristics. This experiment laid the foundation for understanding the role of DNA in genetic transformation and paved the way for further research in the field of molecular biology.

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In the mRNA language, each "word" consists of three letters. This means that the genetic code in mRNA is made up of sequences of three nucleotides called codons. Each codon codes for a specific amino acid, which is then used to build a protein during the process of protein synthesis. Therefore, the correct answer is 3.

In a mutation, any of the given statements may be true. A mutation can result in a new codon that specifies a different amino acid, which can change the function of the new protein produced. However, it is also possible for the new codon to specify the same amino acid as the old codon, maintaining the function of the protein. Additionally, the new codon and resulting amino acid may disrupt the function of the protein specified. Finally, a mutation can lead to a new codon that does not specify any amino acid, resulting in a non-functional protein. Therefore, all of these statements may be true in the context of a mutation.

The correct answer is all of these. Before leaving the nucleus, the RNA molecule undergoes several modifications. It acquires a poly-A tail, which consists of a long string of adenine nucleotides added to its 3' end. It is also released from the STOP signal on the template, allowing it to detach from the DNA strand. Additionally, the RNA molecule becomes capped, meaning a modified guanine nucleotide is added to its 5' end. Lastly, the process of splicing removes the introns, non-coding regions of the RNA molecule, leaving only the exons, which are the coding regions.

Sickle-cell anemia is a genetic disorder caused by a mutation in the gene that codes for hemoglobin, the protein responsible for carrying oxygen in red blood cells. This mutation involves a base-pair substitution, where one nucleotide is replaced by another in the DNA sequence. This change leads to the production of abnormal hemoglobin, causing the red blood cells to become sickle-shaped and leading to various health problems. Therefore, the correct answer is base-pair substitution.

DNA polymerase is responsible for synthesizing new DNA strands during DNA replication. It adds nucleotides to the growing DNA strand in a specific direction. The 5' to 3' direction refers to the orientation of the DNA molecule, where the 5' end has a phosphate group and the 3' end has a hydroxyl group. DNA polymerase can only add nucleotides to the 3' end of the growing DNA strand, resulting in synthesis occurring in the 5' to 3' direction. Therefore, the correct answer is that DNA polymerase assembles new strands in a 5' to 3' direction only.

The genetic code is nearly universal for all organisms, meaning that the same codons code for the same amino acids across different species. It is based on 64 codons, each made up of three nucleotides. Additionally, the genetic code includes "punctuation marks" such as start and stop codons that indicate the beginning and end of protein synthesis. The code is also redundant, as multiple codons can code for the same amino acid. Therefore, all of the given statements are correct.

Calico cats have a unique fur color distribution due to X chromosome inactivation. In female cats, one of the X chromosomes is randomly inactivated in each cell during early development. This results in patches of different colored fur, as the genes responsible for fur color are located on the X chromosome. This phenomenon is not caused by hybridization, nutritional deficiency, genetic defect, or selective breeding.

A linear stretch of DNA that specifies the sequence of amino acids in a polypeptide is called a gene. Genes contain the instructions for building proteins, and they are made up of codons, which are sequences of three nucleotides that code for specific amino acids. Introns are non-coding regions within genes, messengers are molecules involved in gene expression, and enzymes are proteins that catalyze biochemical reactions. Therefore, gene is the correct answer as it accurately describes the DNA segment responsible for protein synthesis.

In the Hershey and Chase experiments, 32P and 35S were used to label DNA and proteins respectively. The significance of these experiments is that they demonstrated that bacteriophages transfer their DNA, not their protein coats, into their hosts. This finding supported the idea that DNA may be the hereditary material, as opposed to proteins. By using radioactive isotopes to track the location of the labeled molecules, the researchers were able to show that the DNA from the bacteriophage was transferred to the host bacteria, while the protein coats remained outside. This provided strong evidence for the role of DNA in inheritance.