(A) Extrachromosomal DNA (B) RNA found in bacterial cells (C) Is part of the bacterial chromosome (D) Is part of the eukaryote chromosome

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1 Microbiology - Problem Drill 07: Microbial Genetics and Biotechnology No. 1 of A plasmid is? (A) Extrachromosomal DNA (B) RNA found in bacterial cells (C) Is part of the bacterial chromosome (D) Is part of the eukaryote chromosome A. Correct! Plasmids are small pieces of DNA that occur naturally in some bacteria. They are not part of the bacterial chromosome. Plasmids are found in bacteria naturally. However they are not composed of RNA. Plasmids are small pieces of DNA that occur naturally in some bacteria. They are not part of the bacterial chromosome. No typically plasmids are found in prokaryotes. Plasmids are small pieces of DNA. They are naturally found in prokaryotes. A plasmid is a small piece of extrachromosomal DNA typically found in bacteria. They typically carry only one (or a few) genes. When plasmids are transferred between organisms they confer a trait such as antibiotic resistance.

2 No. 2 of forms ionic bonds with eukaryotic DNA and stabilizes it? (A) Histones (B) Chromatin (C) Nucleosome (D) Bacteriocin A. Correct! An important characteristic of DNA is that it has a net negative charge. The positive charge on the histone protein facilitates strong ionic bond formation. Chromatin is a tread structure which consists of a complex of DNA and histones that become visible during mitosis. Nucleosome is a bead structure of DNA complexed with histones in the eukaryote. This is not a real word. An important characteristic of DNA is that it has a net negative charge. The positive charge on the histone protein facilitates strong ionic bond formation. Chromatin is a tread structure which consists of a complex of DNA and histones that become visible during mitosis. Nucleosome is a bead structure of DNA complexed with histones in the eukaryote

3 No. 3 of This structure is formed during replication of the lagging DNA strand in bacteria: (A) Operon (B) Okazaki fragment (C) mrna (D) Palindrome Operon is a model that explains gene regulation. B. Correct! Since DNA replication must proceed the 5' to 3 direction the lagging strand of DNA replication in the bacteria is done with a series of small DNA fragments that are eventually ligated together. These fragments are called Okazaki fragments. mrna is the molecule that is form during transcription not during DNA replication. A palindrome is a word that is spelled the same forward or backwards like the word DAD. The same is true for palindromic DNA sequences e.g. GAATTC CTTAAG (The opposite strand is the palindrome) Restriction enzymes cut at specific DNA sequences that typically are palindromes. DNA replication proceeds in the 5 to 3 direction. The lagging strand of DNA replication in the bacteria is done with a series of small DNA fragments that are eventually ligated together. These fragments are called Okazaki fragments. Operon is a model that explains gene regulation. mrna is the molecule that is form during transcription not during DNA replication. A palindrome is a word that is spelled the same forward or backwards like the word DAD. The same is true for palindromic DNA sequences e.g. GAATTC CTTAAG (The opposite strand is the palindrome) Restriction enzymes cut at specific DNA sequences that typically are palindromes.

4 No. 4 of Which of the listed is not part of the operon? (A) Operator (B) Promoter (C) Origin (D) Gene The Operon model consists of: a promoter, an adjacent regulatory element called an operator to which a repressor protein binds to stop transcription to a series of genes. The Operon model consists of: a promoter, an adjacent regulatory element called an operator to which a repressor protein binds to stop transcription to a series of genes. C. Correct! The Operon model consists of: a promoter, an adjacent regulatory element called an operator to which a repressor protein binds to stop transcription to a series of genes. The Operon model consists of: a promoter, an adjacent regulatory element called an operator to which a repressor protein binds to stop transcription to a series of genes. An operon is a model for DNA regulation. The Operon model consists of: a promoter, an adjacent regulatory element called an operator to which a repressor protein binds to stop transcription to a series of genes. Operons are either always turned on in which case they are referred to as Repressible Operons. Operons that are always turned off and need to be turned on to be expressed are Inducible Operons.

5 No. 5 of A triplet of mrna nucleotides that codes for an amino acid is call a. (A) Anti-codon (B) codon (C) cdna (D) rrna The anticodon is found on the trna molecule. B. Correct! The codon is a sequence of three nucleotides that code for an amino acid. cdna is short for complementary DNA. This is synthesized from mrna using reverse transcriptase. rrna is ribosomal RNA and generally refers to the RNA that is associated with the ribosome. There are 64 amino acids (3 of which signal stop to the ribosome). There are 64 possible arrangements of the four nucleotides when organized into triplets (4 3 ). These triplet sequences are called codons. The anti-codon is found on the trna. cdna is short for complementary DNA. This is synthesized from mrna using reverse transcriptase. rrna is ribosomal RNA and generally refers to the RNA that is associated with the ribosome.

6 No. 6 of An effect of point mutation is. (A) Silent mutation (B) Missense mutation (C) Nonsense mutations (D) All of the above. A silent mutation is one in which a nucleotide is changed but because a specific amino acid can be coded for by more then one sequence, the amino acid sequence does not change. The mutation is therefore silent with respect to changes in the phenotype. This is not the best answer. Missense mutation is one that a point mutations results in a new amino acid. The sequence still makes coding sense but does not make sense for the functionality of the protein it codes for. This is not the best answer. Nonsense mutations are those that the change in nucleotide results in changing the codon to a stop codon. These usually result in significant impact. This is not the best answer. D. Correct! All of these types of mutations are a result of single mutations of a DNA base. Schematic of point mutation effects.

7 No. 7 of Cell X is unrelated to Cell Y. Cell X receives DNA from Cell Y and incorporates the new DNA into its chromosome. This is an example of? (A) Horizontal gene transfer (B) Vertical gene transfer (C) Transposition (D) Meiosis A. Correct! Horizontal gene transfer refers to an organism receiving DNA from another organism. The DNA may code for a gene. Is the passing of an organisms genes to its next generation. Transposition refers to large segments of DNA moving from one segment of a chromosome to another. Meiosis occurs in sexually reproducing organisms. It involves germ cells replicating their DNA (diploid) and reducing it to 1N or haploid. Horizontal gene transfer refers to an organism receiving DNA from another organism. The DNA may code for a gene. An example of horizontal gene transfer would be a plasmid from one bacteria being taken up or transferred (either actively or passively) to another unrelated bacteria or even eukaryote.

8 No. 8 of The gene synthesized from an mrna template is. (A) Primer DNA (B) Complementary DNA (C) Recombinant DNA (D) Reverse transcriptase Primer DNA is a short sequence of nucleotides that are complementary to a template sequence. This is used as a starting point for DNA replication for polymerase binding. B. Correct! cdna or complementary DNA is synthesized from RNA. Recombinant DNA is when DNA from one source is introduced to another. As an example would be the gene being inserted into a bacterial chromosome. The bacteria is now said to be a recombinant. Reverse transcriptase is an enzyme that is used to make cdna from mrna. The DNA of an organism consist of sequences that code for genes. Between these sequences are nucleotides that do not code for genes. When DNA is copied to mrna these non-coding sequences have been removed. mrna is made in millions of copies for genes that are being actively transcribed. Using an enzyme called reverse transcriptase the mrna serves as a template to make DNA. However this DNA is not identical to the original DNA because it has all the excess nucleotides removed. This DNA is distinguished from parental by calling it complementary DNA or cdna.

9 No. 9 of A restriction enzyme? (A) Restricts the movement of DNA (B) Cut or cleaves DNA at specific sites depending on the DNA sequence. (C) Is restricted or limited to repairing DNA. (D) Corrects mistakes in the DNA. Remember the function of an enzyme is to facilitate a chemical reaction. B. Correct! Restriction enzymes cleave DNA at specific sequences, typically palindromes. The origin of these enzymes is from bacteria. There are enzymes whose sole function is to repair DNA but these are broadly referred to as DNA repair enzymes. Enzymes that repair DNA are broadly referred to as DNA repair enzymes. Restriction enzymes cleave DNA at specific sequences, typically palindromes. The origin of these enzymes is from bacteria.

10 No. 10 of This is a method for introducing DNA into cells. (A) Electrolysis (B) Electrophoresis (C) Protoplast fusion (D) Heat shock Electrolysis is not involved in DNA transfer. Electrophoresis is a method used to separate DNA or proteins based on their charge in an electric field. C. Correct! Protoplasts are cells that have been treated such that their cell membranes are able to fuse when they come in contact with each other. Heat shocking a cell often induces certain DNA replication or repair pathways and is unrelated to gene transfer. Recall the definition of protoplast which is a cell whose cell wall has been enzymatic removed. This exposes their cell membranes which are able to fuse when two such cells come in contact with each other. Over time the cell walls will regenerate and the cell will return to normal.