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Robertsonian Translocation: Chromosome Diagram and Genetic Disorder - Prof. Pamela Hanratt, Exams of Education Planning And Management

Instructions for diagramming the result of a robertsonian translocation involving chromosomes 14 and 21, as well as a question about the genetic disorder that may result from such a translocation. Students are asked to label all chromosomes and parts of chromosomes in their diagrams, and to identify the name of the genetic disorder if the embryo is affected.

Typology: Exams

2011/2012

Uploaded on 04/28/2012

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Download Robertsonian Translocation: Chromosome Diagram and Genetic Disorder - Prof. Pamela Hanratt and more Exams Education Planning And Management in PDF only on Docsity!

E105 โ€ Exam 3 April 12th, 2011

Dr. Pam Hanratty Answer Key E105 Exam 3 Spring 2011

This exam contains 7 questions plus one bonus question. Please make sure your copy of the exam has them all. Please show all calculations/work for full credit. Question #1: (1 6 pts.) Question #2: (1 4 pts.) Question #3: (1 6 pts.) Question #4: (1 4 pts.) Question #5: ( 17 pts.) Question #6: (1 5 pts.) Question #7: ( 8 pts.) TOTAL: (100 pts.) Bonus: (5 pts.) GRAND TOTAL:___________________________ โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€โ€ NAME: __________________________________________________________________________________ SIGNATURE:____________________________________________________________________________

  1. The figures below show two different, unreplicated chromosomes before either underwent any chromosomal rearrangements. (2 pts. each; 16 pts. total) Figures aโ€h (below) show the same two, unreplicated chromosomes after one or the other or both underwent eight different, independent rearrangements. Name each of the chromosomal abnormalities in the blank next to each unreplicated chromosome you are describing. Please be as specific as possible in your answer. a. b. c. d. e. f. g. h.

2. (Continued) d) In the space below, draw a cell that contains the translocated chromosome that you drew in part (b) of this question and also contains (in the same cell) two copies of chromosome 14 and one copy of chromosome 21. Be sure to label all of the chromosomes and parts of chromosomes present in your diagram ( 2 pts.) (i) What is the phenotype of the embryo from which this somatic cell was taken? (Does the embryo have a genetic disorder or is this embryo phenotypically normal? If the embryo would have a genetic disorder, what is the name of that genetic disorder?) (1 pt.) This embryo would have trisomy 14. (ii) How many chromosomes (total) does this embryo possess? (0.5 pt.) 46 (iii) Would you expect this embryo to be viable? (0.5 pt.) No

  1. Fill in the blank with the most appropriate word or phrase related to the following methods of prenatal testing. (1 pt. per blank, 1 6 pts. total) a. Chorionic Villus Sampling (CVS) : Method of sampling fetal chorionic villus cells by insertion of a catheter through the vagina (or cervix) (or occasionally through the abdominal wall ) into the uterus. b. CVS is usually performed during the 10 th^12 th^ week of pregnancy. c. Two ADVANTAGES associated with CVS: (Must mention TWO; may be additional correct answers.) Earlier Results and, Can follow up with amniocentesis The cells are actively dividing, and do not need to be grown in culture prior to karyotyping d. Two DISADVANTAGES (or risks) associated with CVS: (Must mention TWO; there may also be additional correct answers.) 1% risk of miscarriage Risk of maternal or fetal infection Rh sensitization Risk of injury to fetus or mother Cannot perform AFP (alpha fetoprotein) test to detect neural tube defects (because there is no amniotic fluid to test) d. Amniocentesis : Method of sampling the fluid around the developing fetus/amniotic fluid by insertion of a hollow needle into the uterus (through the wall of the abdomen). e. Amniocentesis is usually performed during the 16th week of pregnancy. f. Two REASONS or INDICATIONS for performing amniocentesis: (Must list TWO; may also be other correct answers.) Woman over the age of 3 5 Previous child with genetic disorder Parents are carriers of a genetic condition Parents work in high risk occupations (nuclear power plant) Parents belong to high risk group (have received/been exposed to radiation, etc., belong to a group at genetic risk) g. Two DISADVANTAGES (or risks) associated with amniocentesis: (Must list TWO. May also be other correct answers.) 0.5% risk of miscarriage Risk of maternal or fetal infection Rh sensitization Risk of maternal or fetal injury Cells may fail to grow in culture
  1. This question concerns the process of transcription. ( 1 pt. per blank, Parts (a) and (b); 2 pts Part (c), 1 7 pts. total.) a. Transcription is the transfer of genetic information from the base sequence of a(n) DNA molecule into the base sequence of a(n) RNA molecule, brought about by RNA synthesis. The enzyme responsible for catalyzing this synthesis is RNA polymerase. This enzyme binds to a region on the template called the promoter. The three subsequent stages of transcription, in order, are initiation , elongation , and termination. b. In eukaryotes, the product of transcription is modified or processed before it leaves the nucleus of the cell. A nucleotide cap is added to the 5โ€™ end, and a poly A tail is added to the 3โ€™ end. Next, introns , which are sequences that do not code for an actual protein, are removed. Finally, exons , which are the sequences that code for a protein, are spliced to form the mature molecule. c. Why are introns important in eukaryotes? (2 pts.) They allow different forms of a gene to be expressed under different conditions; for example, at different stages of development, or in males and females.
  1. Answer the following questions regarding the production of proteins. (15 pts.) a. What is the name of the molecular process that assembles proteins? (1 pt.) Translation b. Proteins, like DNA and RNA, are comprised of individual monomer subunits. What are these protein subunits called? (1 pt.) Amino Acids c. This structure, found in the cytoplasm of cells, is the site where proteins are synthesized, using a specific type of RNA as a template. (1 pt.) Ribosome d. What type of RNA is a structural component of the cellular structure described in (c)? (1 pt.) rRNA (ribosomal RNA) e. Name and describe the function of the other two types of RNA that are involved in the production of proteins. (2 pts. each; 4 pts. total) mRNA: (Messenger RNA) Single stranded, complementary copy, of the nucleotide sequence of a gene. Contains information specifying the amino acid sequence of a protein. tRNA: (Transfer RNA): Carries a specific amino acid to the site of protein synthesis on the ribosome, and also contains an anticodon that base pairs with the codon corresponding to the amino acid it carries. (Acts as an adaptor between the codons in the mRNA and the growing polypeptide chain.) f. The genetic code describes the way in which a DNA sequence will be transformed into a protein. Answer the following question regarding the transformation from DNA to RNA and RNA to protein. (i) Given the following template (antisense) strand of DNA, provide the corresponding coding (sense) strand of DNA and the mRNA sequence. Please pay attention to the polarity of the DNA (3โ€™ and 5โ€™ indicate direction) and indicate the polarity of the DNA coding strand and mRNA sequence. (2 pts. each; 4 pts. total) (a) DNA Template Strand: 5โ€™ TTA CCA CAA ATG CGG CAT 3โ€™ (b) DNA Coding Strand: 3โ€™ AAT GGT GTT TAC GCC GTA 5โ€™ (c) mRNA Sequence: 3โ€™ AAU GGU GUU UAC GCC GUA 5โ€™ (ii) Use the mRNA sequence from above and the genetic code table on the next page to determine the order of the monomer units in the protein. Be sure that you โ€œreadโ€ the message in the correct direction! (2 pts.) Met Pro His Leu Trp Stop (iii) Does every codon code for the actual sequence of the protein molecule, or do some codons serve a different purpose? Please explain. (1 pt.) Some codons are stop codons, and AUG also functions as a โ€œstartโ€ codon.
  1. Consider the following situation. Darla and Mark met at the age of 35, married two years later, and decided to begin a family as both of them were approaching the age of 40. One year later, Darla gave birth to a beautiful baby boy, whom they named Nathan. The new parents were alarmed then their doctor informed them that their newborn son had an aneuploid condition. (8 pts. total) a. What does the term โ€œaneuploidโ€ mean? Please define or explain. (2 pts.) This refers to a situation in which an individualโ€™s set of chromosomes has lost or gained one or a few chromosome, but has not lost or gained an entire set of chromosomes. b. The doctor reassured them that the condition, known as XYY syndrome, was not serious. What are the symptoms or phenotypic characteristics known to be associated with XYY syndrome? (1 pt.) These individuals are males of above average height. c. Darla was greatly upset, because she was certain baby Nathanโ€™s condition must have been a result of her age. She was surprised to learn that, in this case, nonโ€disjunction occurring in her husband, Mark, was the source of the babyโ€™s aneuploid condition. a. What is meant by the term โ€œnonโ€disjunctionโ€? Please explain or define. (2 pts.) Non-disjunction is the failure of chromosomes to separate normally during Meiosis I or Meiosis II (or occasionally during mitosis). b. Please draw a series of diagrams that illustrate how nonโ€disjunction in Mark (the babyโ€™s father) could lead to the conception of a child who has XYY syndrome. Also, in a separate diagram, show which sex chromosomes were present in the gamete contributed by the mother. You may assume that nonโ€disjunction occurred during only one meiotic division, and only in the father. Please be sure to include all of the following in your diagrams. (i) The correct number of sex chromosomes and chromatids in each diagram, (ii) chromosomes are clearly labeled, (iii) clearly indicate the meiotic division in which nonโ€ disjunction occurred, (iv) clearly indicate which gamete produced by the father was involved in baby Nathanโ€™s conception, (v) clearly labeled diagram showing the sex chromosome(s) present in the gamete contributed by the mother. (3 pts.)

Bonus Question: (5 pts.) Name the specific chromosomal abnormality present and two major phenotypic characteristics for each of the two following syndromes: (a) Prader-Willi syndrome: Type of chromosomal abnormality present : __ Deletion (on chromosome 15) __(0.5 pt.) Two major phenotypic characteristics: (2 pts.) Severe compulsive eating disorder Morbid (life-threatening) obesity May develop heart disease at an early age May develop diabetes Endocrine abnormalities Hypogonadism (reduced size of male testes and genitalia) Intellectual impairment (mild) (b) Cri-du-Chat syndrome: Type of chromosomal abnormality present : _ Deletion (on chromosome 5, p arm) (0.5 pt.) Two major phenotypic characteristics: (2 pts.) Cry of newborn baby resembles the cry of a cat. Microencephaly (small head size) Low IQ Deformity of larynx Widely set eyes Low set ears