Question

13. What are TWO of the insights Watson and Crick had with respect to the structure of DNA? a. DNA is a double-stranded helix held together by A:T or C:G base pairs b. DNA is a helix and has A:T or C:G base pairs c. DNA is a double-stranded helix and the amount of A=T and of G=C d. DNA has two strands in opposite orientation and the amount of A=T and of G=C 14. Griffith's experiment injecting a mixture of dead and live bacteria into mice demonstrated that: a. DNA is double-stranded b. Only heated bacteria can kill mice c. A factor could transform one bacterial cell type to another type d. Bacteria can recover from heat treatment with the aid of a live helper 15. Which of the following is a key aspect of the Hershey-Chase bacteriophage experiments? a. If DNA is destroyed cells are not transformed, only smooth bacteria kill mice b. Labeling of components 32P enters cells and is passed on to progeny phage c. If RNA is destroyed cells are transformed, rough bacteria do not kill mice d. All of the above are correct 16. The two major functions of nucleosomes are best represented as: a. Compacting the genome and access for replication and gene expression b. Compacting the genome an protecting the genome against damage c. Compacting the genome and proper genome segregation during cell division d. Protecting the genome against damage and access for replication and expression 17. Each nucleosome contains: a. Four histones b. Two each of four histones c. Histone Hi d. Only DNA, histones are only added to form DNA loops 18. If one wants to obtain precise quantitative relationships between variables(continuous traits) one should run this type of analysis: a. Regression b. Correlation c. Analysis of Variance d. No analysis is possible 19. When examining centromere sequences for a specific eukaryote one finds: a. They are all a simple repeat sequence b. All the chromosomes have a similar (consensus) sequence in their centromeres c. Centromere sequences are quite different from one chromosome to the next d. No specific sequence has been found to represent a centromere 20. Rosalind franklin used x-ray diffraction to show that DNA has: a. A helical structure b. A-T and C-G base pairs c. Equal amounts of A and T bases, and of C and G bases d. Two strands that are anti-parallel to each other 21. When looking at the organization and content of the human genome all of the following are true EX- CEPT: a. Twice as much of the genome is microsatellites (STR) compared to gene sequence b. Gene related sequences, such as introns, make up about a third of the genome c. Genome wide repeats make up nearly a third of the genome d. Genes represent about 10% of the genome 22. Beadle and Tatum's work was significant because it: a. Established neurospora as the primer genetic model organism b. Established that one gene encodes one polypeptide c. Established that amino acids can be synthesized by fungi d. Established that one gene encodes one enzyme 23. A mutation in an organism leading to a requirement for supplements of a nutrient is known as a(n): a. Auxotroph b. Prototrophic c. Nutriotrophic d. Lethal 24. You use PCR analysis on DNA from a couple and their developing fetus to screen for a genetic defect. You find that both parents have one large and two small DNA and, while the fetus has only the large DNA band. The most likely explanation for these results is: a. The infant is a heterozygote and the parents are both homozygotes b. All three are heterozygotes c. Both parents are heterozygotes, the fetus is a homozygote d. You cannot tell the allele combinations for the three individuals

Answer 1

Q.13. Answer- a. DNA is a double stranded helix held together by A:T or C:G base pairs

Explanation- The two insights Watson-Crick had with respect to the structure of DNA are - DNA is double helical and two strands are held together by A:T and G:C. Watson-Crick give the structural feature of DNA that DNA is double stranded helical structure and helicity of DNA is important to form stable structure of DNA. Two strands o DNA are held together by hydrogen bonds between base pairs , two hydrogen bonds between adenine and thymine and three hydrogen bonds between guanine and cytosine. The Watson-Crick base pairing between bases is responsible for internal stability of DNA.

Q.14. Answer- c. A factor could transform one bacterial cell type to another type

Explanation- Griffith's experiment injecting a mixture of dead and live bacteria into mice demonstrated that a factor could transform one bacterial cell type to another type. Griffith carried out experiment to determine transforming principle. When heat killed virulent strain of pneumococcus is injected in mice alongwith nonvirulent strain of live pneumococcus, mice dies because a transforming principle is transferred from heat killed virulent strain to live nonvirulent strain causing nonvirulent strain conversion to virulent and due to infection mice dies.

Q.15. Answer- b. Labeling of components 32​​​​​P enters cells and is passed onto progeny phage

Explanation- Harshey-Chase done experiments to confirm DNA as genetic material. For this they had labeled DNA of bacteriophage with 32​​​​​P and in another set they had labeled protein with 35​​​​​S. They confirmed that DNA is transforming principle because they find phosphorus radiolabeled DNA in progeny phage and do not find radiolabled sulphur in progeny phage.

Q.16. Answer- a. Compacting the genome and access for replication and gene expression

Explanation- In eukaryotes, nucleosome formation is first step for chromosome formation. The DNA is warpped around histone proteins to form 11nm beads on string structure and connecting the genome is major function of nucleosome. Another function of nucleosome is to regulate gene expression because when DNA is wrapped around histone then it is inaccessible for replication can gene expression but if DNA is unwrapped around hostone then DNA can be replicated and transcribed also.

Protection of genome against damage and genome segregation during cell division are not function of nucleosome.