Genetics Final

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T to C mutation

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transition mutation

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G to T

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transversion mutation

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mutations that change nucleotide sequence but not the amino acid sequence

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silent mutation

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base substitution resulting in change of an amino acid

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missense mutation

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base substitutions resulting in a new stop codon

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nonsense mutations

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The activity of DNA Polymerase that removes incorrectly incorporated nucleotides is called

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proofreading repair

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Example of a chemical that is a base analog

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5-bromouracil

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Ultraviolet light primarily damages DNA by forming 1.----- dimers. A defect in the repair mechanism results in a human inherited autosomal 2.----- disease xeroderma pigmentosum.

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pyrimidine; recessive

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What is the minimum number of single-nucleotide substitutions that would be necessary for the replacement of amino acid methionine with tyrosine?

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3

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The molecular basis of the fragile-X chromosome has been traced to an 1.----- of the 5'-GGC-3' (repeat) present in the DNA at the site where the breakage takes place.

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expansion

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Developmental genes are often controlled by 1.----- of gene products, either within cells or across parts of the embryo

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gradient

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In higher plants differentiation takes place almost continuously throughout life in regions of actively dividing cells called 1.----- in both the vegetative organs and the floral organs.

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meristems

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Genes that function in the mother that are need for development of the embryo are called 1.----- genes. Mutations in these genes are easy to identify because 2.----- females produce eggs that are unable to support normal embryonic development, whereas homozygous males produce normal sperm.

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maternal-effect; homozygous

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Describe the two essential functions of cytoplasm in an animal egg.

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Storage of molecules to support cleavage divisions and rapid RNA and protein synthesis and Organization of molecules in the cytoplasm to provide positional information

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The 1.----- genes determine the principle coordinate axis of the embryo; the anterior-posterior, which defines the front and rear, and the dorsal-ventral axis, which define the top and bottom.

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coordinate

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The C. elegans lin-12 gene, which controls a number of yes-or-no developmental decisions, codes for a

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transmembrane receptor protein

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The homeotic genes encode

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transcriptional activator proteins

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Imprinting is

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DNA modification in gametogenesis that effects gene expression in the zygote.

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Induction of the morphogenic events in the Drosophilia imaginal disks is initiated by

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hormone ecdysone

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A cell that is capable of differentiating into a complete organism is called a(n)

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Totipotent cell

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The carrier DNA molecule used to propagate a desired DNA fragment is called a 1.-----.

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vector

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study of the genome (all the genes, dna sequences, function and organization)

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genomics

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studying all the proteins (functions, organization, interactions) in a cell or organism

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proteomics

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"sticky ends"

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asymmetric cleave

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"blunt ends"

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symmetric cleave

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Because many eukaryotic genes contain 1.----- that are present in the primary transcript, but are removed from the mature mRNA, the cDNA sequence is not identical with the genomic DNA.

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introns

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The backbone of each strand is cleaved by a restriction enzyme, creating a free 3' 1.----- group and a free 5' 2.----- group.

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hydroxyl; phosphate

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forms a covalent bond between the 3'OH and the 5' P groups

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DNA ligase

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synthesizes a complimentary DNA strand from a RNA template

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Reverse transcriptase

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synthesizes a strand of RNA from a DNA template

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RNA polymerase

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synthesizes a strand of DNA from a DNA template

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DNA polymerase

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Deliberate alteration of the genome for treatment of disease is called 1.-----.

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gene therapy

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All are true of what? 1.also called a polylinker 2. Useful vectors always contain MCS 3. contains unique cleavage sites for many different restriction enzymes

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true of a multiple cloning site

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Plasmids or BACs used for in vitro cloning of foreign DNA fragments are called

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vectors

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The bacterium used as the model for genetic recombination and engineering in plants is

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Agrobacterium tumefaciens

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The ability of an introduced DNA fragment to correct a genetic defect in a mutant organism is called a(an)

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transformation rescue

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At which level are genes regulated?

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All levels of transcription, translation etc..

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Default state of transcription is "on"

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negative regulation

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Default state of transcription is "off"

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positive regulation

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Repressor DNA binding protien keeps transcription OFF, unless inducer present

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Inducible transcription

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transcription is ON until an active repressor is formed and binds

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repressible transcription

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Which enzyme cleaves lactose to yield glucose and galactose?

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beta-galactosidase

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The negative regulator of the lac operon is encoded by the 1.----- gene and the positive regulator of the lac operon is the 2.----- complex.

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Lac I; cAMP-CRP

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1.----- refers to heritable changes in gene expression that are not due to changes the DNA sequence itself, but to something "in addition to" the DNA sequence, usually either chemical modification of the bases, or protein factors bound with the DNA.

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epigenetic

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Triggers degradation of RNA transcripts containing homologous sequences.

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RNA interference (RNAi)

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Heavy methylation is associated with

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low transcription rate.

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The helix-turn-helix and zinc finger are structural motifs found in

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DNA binding proteins.

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low free tryptophan resulting in termination of transcripti

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Attenuation

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mRNA leader sequence able to change its conformation when triggered by direct binding of a small molecule (SAM)

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Riboswitches

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expressed constitutively at low levels

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Housekeeping genes

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function irrespective of orientation, bind with transcriptional activators to control/activate transcription

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Enhancers

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short nucleotide sequences are targets for DNA binding proteins trigger complex protein assemble to block transcription

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Silencers

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means by which enhancers activate transcription, physical interactions between regions of DNA

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DNA looping

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In prokaryotes, mRNA molecules commonly contain coding sequences for several different polypeptide chains; such a molecule is called a 1.-----.

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polycistronic mRNA

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The excision of the introns and joining of the exons constitutes 1.-----.

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RNA splicing

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What is true of the promoter sequence of E. coli as discussed in class:

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(1.) consensus sequences are located 35 and 10 nucleotides upstream from the transcription start site (2). the -10 consensus sequence is termed the TATA box.( 3.) promotors affects the RNA polymerase binding strength which in turn affects gene expression

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Which amino acid has a free amino group?

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Met

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Which amino acid has a free carboxyl group?

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Gin

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The carboxyl group of what amino acid formed a peptide bond with the amino end of His?

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Trp

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Which amino acid was added last?

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Gin

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All true of RNA

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(1) . RNA has a hydroxyl group at the 2' carbon (2) In RNA uracil is used in the place of thymine (3) RNA polymerase is able to initiate chain growth without a primer.

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True of RNA processing

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It may be autocatalytic

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All are true

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(1) DNA polymerase has proof-reading activity (2) The 3' end of mRNA corresponds to the carboxyl terminus of the protein. (3) Inverted repeats are characteristic of many termination sites of RNA synthesis.

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provides coding sequence of bases that determines the amino acid sequence

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Messenger RNA

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where protein synthesis occurs, move along mRNA and align amino acids forming peptide bonds

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Ribosome

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adaptor molecule attached to a specific amino acid and having a specific anticodon

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Transfer RNA

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enzymes that attaches each tRNA to its specific amino acid

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Aminoacyl-tRNA synthetases

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The anticodon of one tRNA can bind with several codons.

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True

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In eukaryotes, the enzyme responsible for transcribing all protein-coding genes is

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RNA polymerase 2

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DNA transferred by bacteriophage from cell to cell

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transduction

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cell acquires genes from DNA in surrounding media

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transformation

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DNA transferred from bacterial donor cell to recipient cell by contact

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conjugation

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Cotransformtion of two genes at a frequency substantially 1.----- than the product of the single-gene transformations implies that the two genes are close together in the bacterial chromosome.

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greater

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Because the F factor can exist either separate from the chromosome or incorporated into it, it qualifies as an 1.----- ; a genetic element that can exist free in the cell or as a segment of DNA integrated in to the chomosome.

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episome

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The integrated phage DNA is called the 1.-----, and the bacterial cell carrying the integrated phage DNA is called the 2.-----.

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prophage; lysogen

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In E.coli, the 1.----- plasmid can mobilize the chromosome for transfer to another cell in the process of conjugation.

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fertility

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A leu+ strain carring a cloned copy of leu on a plasmid is an example of

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partial diploidy

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In time-of-entry mapping, the use of compounds to inhibit the growth of donor cells is called

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counterselection

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What are the 2 principle mechanisms restricting the developmental potential of cells within a lineage?

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Autonomous development and intercellular signaling

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4. In C. elegans, describe how the lin-3 gene controls the fate of other cells in the development of the vulva

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The important role of the lin-3 gene product is suggested by the opposite phenotypes of loss-of-function and gain-of-function alleles. Loss of LIN-3 results in the complete absense of vulval development, where overexpression of LIN-3 results in excess vulval induction. LIN-3 is a typical example of an interacting molecule, or ligand, that binds with an EGF- type transmembrane receptor.

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5. What type of genes have homeoboxes? How do they work?

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Homeotic genes. They are transcriptional activators of other genes. Most HOX genes contain more than one copy of characteristic of a sequence of about about 180 nucleotides (homeoboxes) that are found in key genes concerned with development of embryonic segmentation in organisms. Homeobox sequences are found in exons and code for a protein-folding domain that includes a helix-turn-helix DNA binding motif.

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Why are missense mutations less likely to result in proteins lacking normal function than frame shift mutations?

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Missense changes only one amino acid into another, while frameshift will change an amino acid and every amino acid downstream from the site of the mutation.

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8. What is a base analog and why are some mutagenic?

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A molecule similar enough to a purine or pyrimidine base to substitute for the normal bases, resulting in abnormal base pairing. A key feature of mutagenic base analogs is that they form base pairs with more than one other base. This can cause mutations during the next round of replication, when the replication machinery tries to pair a new base with the incorporated mutagen. For instance, 5-bromo-deoxyuridine (5BU) exists in two different forms. One mimics thymine and therefore pairs with adenine during replication, while the other mimics cytosine and therefore pairs with guanine. In its thymine-mimicking form, 5BU can be incorporated across from an adenine. If it then converts to its cytosine-like form, during the next round of replication, it will cause a gua-nine to enter the opposite strand, rather than the correct adenine.

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9. Scientists at a company have just developed a new cleaning agent. Before the company goes further in developing the product they want to determine if it could be carcinogenic. Describe in some detail the initial test you would recommend they perform.

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The Ames test uses strains of Salmonella that have been altered to make them more susceptible to mutation than normal Salmonella. To perform the test, the altered Salmonella strains are combined in a test tube with the chemical of interest. Because Salmonella bacteria lack the enzymes that animals use to metabolize chemicals, animal liver enzymes are often added to the test tube. That way, the test is able to detect what might happen if the chemical entered a human body. The Salmonella are then transferred to a petri dish to grow for one or two days. The altered Salmonella used for the test require the amino acid histidine to grow, and a positive result in the test is indicated when, in response to mutation, the Salmonella no longer require histidine to grow.

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12. Most mutagens are also carcinogens, and most carcinogens are also mutagens. Explain why this is the case

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A mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are typically also carcinogens.

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17. Identify 4 factors that can contribute to phenotype variation.

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Genotypic variation, Environmental variation, variation due to genotype-by-environment interaction, variation due to genotype-by-environment association.

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18. What is the cause of inbreeding depression?

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Harmful effects on traits such as yield of grain and egg production. Comes from rare harmful recessive alleles becoming homozygous because of inbreeding

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Circular DNA molecules, which replicate independently of the chromosome are called

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plasmids

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The process by which a bacterial DNA fragment is transferred from one bacterial cell to another by a phage particle is known as

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transduction

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DNA element that encodes a site-specific recombinase as well as a recognition region that allows other sequences with similar recognition regions to be incorporated by recombination is called

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Integron

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A mutant microorganism unable to synthesize an essential compound but able to grow if that compound is supplied exogenously is called a

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Auxotroph

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In a mating between Hfr and F- cells, the Hfr donor

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remains Hfr

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Phage DNA integrated into the chromosome is called a(n)

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prophage

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In E. coli, the plasmid that can mobilize the chromosome for transfer to another cell in the process of conjugation is called

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F factor

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The transferred marker that is selected by the growth conditions is called a

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Selected

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How long does it take under usual conditions for an entire bacterial chromosome to be transferred during conjugation?

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100 min

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E. coli cell that contains F factor integrated into bacterial chromosome is called a(n)

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Hfr

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In polypeptide Arg-Pro-Ser, what amino acid has a free carboxyl group?

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Pro

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A nucleotide substitution that creates a stop codon and results in premature chain termination during translation, is called a

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Nonsense

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The enzymatic synthesis of an RNA molecule complementary to one strand of the DNA is called

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transcription

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RNA splicing takes place in nuclear particles, composed of protein and several specialized small RNA molecules, known as

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spliceosomes

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In prokaryotes, mRNA molecules commonly contain coding sequences for several different polypeptide chains; such a molecule is called a

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polycistronic

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The excision of the introns and the joining of the exons constitutes

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RNA splicing

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The genetic code is degenerate because

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Some amino acids are coded by more than one codon

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A consensus sequence is a sequence of bases determined by

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majority rule

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Genetic evidence for a triplet code came from

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three-base deletions and insertions

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The model of protein evolution through the combination of different exons is called the

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Exon shuffle model

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How many proteins are bound to the trp operon when tryptophan and glucose are present?

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1

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The lactose operator is an essential site for

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repression

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Transcriptional cosuppression in Drosophila, is associated with the

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Polycomb group of transcriptional silencer proteins

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In S.cerevisiae, the genetic basis of mating-type interconversion is

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DNA rearrangement

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Heavy methylation is associated with

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Low transcription rate

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The production of the lac repressor is

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constitutive

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A regulatory base sequence in eukaryotic cells that increases the rate of transcription of nearby genes regardless of orientation is called a(n)

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enhancer

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The development of the mammalian immune system involves

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Programmed DNA rearangements

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How does the lac repressor prevent transcription of lac operon?

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By binding to the operator, which makes the promoter inaccessible to RNA polymerase

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The type of gene expression, which is constant and independent of on/off regulatory control is called

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Constitutive

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The cloning site containg unique cleavage sites for many different restriction enzymes is called a(an)

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Polylinker

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The procedure used to determine experimentally the physical limits of a gene is called

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Transformation resque

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A DNA molecule has 28 occurrences of the sequence 5'-GGCC-3' along one strand. How many times does the same sequence occur along the other strand?

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28

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A number of restriction enzymes cleave both DNA strands at the center of symmetry, forming

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Blunt ends

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You digested a linear DNA molecule with the restriction enzyme and got 3 fragments. How many restriction sites does this DNA have for this particular endonuclease?

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2

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Deliberate alteration of the genome for treatment of disease is called

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gene therapy

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Term for the double-stranded DNA produced by reverse transcriptase is

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cDNA

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DNA produced by reverse transcriptase11. ________________________Use of a transgenic organism

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12

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n gene-targeting experiments, the replacement of the wildtype gene in the genome with the completely unfunctional gene results in a (n)

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knockout mutation

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Loss of b-galactosidase activity is often used to detect

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recombinant vectors