T C G A A C T G A G G A C T A T. 4) What type of bonds hold the two strands of DNA together? Are they strong or weak bonds?

Transcription

1 Fo Sci DNA Questions #1 Name Key Use PPT slides 1-11 to answer the following questions. 1) Who are these gentlemen and what did they discover? James Watson and Frances Crick discovered the structure of DNA. Won the Nobel Prize in What year did they make their discovery? ) DNA is composed of nucleotides. A nucleotide is a unit of a nucleic acid. Many nucleotides make a strand of DNA and two strands make the double helix of a DNA molecule. There are 4 different types of nucleotides. What are their names and what letter symbols are used to identify them? _Adenine nucleotide A Guanine nucleotide G Cytosine nucleotide C Thymine nucleotide T 3) DNA is considered a double helix. That means that it is made of two strands of nucleotides that sit opposite of each other joined by hydrogen bonds. If one side of a strand of DNA has the following code, what is the complimentary strand sequence of nucleotides? (Your strand will look a lot like the strand below but it will have complimentary nucleotides opposite the nucleotides listed A-T and C-G). A - G - C - T - T - G - A - C - T - C - C - T - G - A - T - A T C G A A C T G A G G A C T A T 4) What type of bonds hold the two strands of DNA together? Are they strong or weak bonds? Hydrogen bonds that are very weak bonds 5) What is a gene? What do coding genes carry the code for? What is the value of non-coding genes? Segment of the DNA. Coding genes carry the code for a protein. Non-coding genes can be used to make a DNA profile! 6) Why is it important for most coding genes in humans to be identical in nucleotide sequence? For example, why is it necessary for all humans to have the same nucleotide sequence for their hemoglobin molecules? Because they code for proteins that are necessary to survive. Any variations or mutations would form a nonfunctional protein and the person would die. 1

2 7) Fill in. There are two types of DNA found in your cells. The first type, ndna is found in the nucleus of your cells. It is in the form called chromosomes, which are linear structures that are made of DNA and proteins. Each of your cells has 46 (number) pieces of these linear structures in the nucleus. The linear structures are paired. One of the pairs is inherited from your mother (maternal) and the other is inherited from your father (paternal). The nucleotide sequences in your chromosomes (linear pieces) is an important type of forensic evidence even though it is class (individual/class) evidence. The strength of this evidence makes it as important as the individualized evidence you worked with in the last unit: _fingerprinting. Unfortunately, ndna is fairly fragile and breaks down easily. The second type of DNA is smaller, and is circular in shape. It does not break down as easily and can be obtained from very old or dried samples. This second type of DNA is mt DNA. This DNA is found in the organelle in your cells called the Mitochondria. You have hundreds of these organelles in one of your cells. Therefore, you have 1,000 s (a number) copies of this type of DNA in one cell. The function of the organelle is to be the site of cellular respiration to produce ATP. The DNA in this organelle is inherited from your mother. As such, the nucleotide sequence you inherit from your mother will be identical to the sequence any of your siblings inherits. Your aunts and cousins on your mom s side of the family will also have the same sequence of nucleotides in their mtdna because they all inherited the sequence from your grandmother! This type of evidence is helpful but it is only class (individual/ class) evidence and it is not as valuable as a ndna profile. Word Bank: ATP chromosomes class entomology father fingerprinting individualized mitochondria mother mtdna n DNA/ chromosomes nuclear DNA one ten thousands (1,000 s) 8) Are coding genes used in DNA fingerprinting? Why or why not? No. Coding genes code for important proteins. These proteins do not have much variation in the nucleotide sequence from person to person because any variations or mutations would cause the protein to be non-functional and the person would die. If the coding genes do not differ from person to person, you cannot use them to identify a specific person. All people would have the same sequence! 2

3 Match the following types of DNA to the statements below: a. ndna b.mtdna c. both types of DNA 9) Used to identify the source of evidence. c 10) The best type of class evidence. a 11) Fragile and easily broken down. a 12) Can be isolated from degraded skeletal remains. b 13) Is only inherited from the maternal side. b 14) Is identical in identical twins. c 15) Thousands of copies are found in each cell. b 16) Contains approximately 20,000 coding genes. a 17) Composed of a circular piece of DNA. b 18) Some genes code for proteins. c 19) Contains 3 billion base pairs. a 20) Contains alleles. c 21) Composed of A, T, G and C nucleotides. c 22) Represented by picture to upper right. a 3

4 Fo Sci DNA Questions #2 Name Key Use slides to answer the following questions: (some questions may be answered using previous slides) 23) Which of the following is true about your nuclear-ndna? ( 2 answers) a. It is identical to your mother s DNA. b. It is similar to your both of your parents DNA. c. It is part of your paired chromosomes. One of each pair is inherited from your mother (maternal) the other is from your father (paternal). d. It contains genes that code for carbohydrates and fats. e. Some chromosomes are linear while the smaller ones are circular in shape. 24) A gene is located at a specific spot (or loci) on a chromosome. The allele at that loci is the nucleotide sequence for the gene found at that location. If a gene found on the paternal #20 chromosome has the following allele sequence: A_T_G_C_C_A_T_A, and the alleles between the maternal and paternal homologs are heterozygous, which of the following alleles could be on the maternal #20 chromosome at the same gene loci? (circle two possible answers) a. A_T_C_C_C_A_T_A b. A_T_G_C_C_A_T_T c. A_T_G_C_C_A_T_A 25) What percent of your DNA codes for proteins (coding DNA)? a. 97% b. 50% c. 25% d. only 2-3% 26) You can find non-coding DNA a. In between genes c. Within genes b. In ndna d. All of these 27) How is non-coding DNA different from coding DNA? Which type of DNA is best for DNA profiling? Why? (This question is redundant it WILL be on the test!) Non-coding DNA does not code for important proteins. Your coding genes code for important proteins that are necessary for survival. Coding genes do not have much variability in the nucleotide sequences from person to person because mutations would create non-functioning proteins and the person would die. Everyone needs to make the same protein in order to survive. Non-coding DNA does not code for proteins so mutations that take place in those genes will not affect the person. The different, unique nucleotide sequences that result from these variations can be used in DNA profiling to distinguish between different people. 28) A tool used to determine the identity of, or verify the identification of and individual based on DNA is called a DNA fingerprint or DNA profile. Do not confuse it with a regular fingerprint! 4

5 29) DNA profiling uses non-coding (coding, non-coding) regions of the DNA to compare body fluids at a crime scene to an individual. 30) What does S-T-R stand for? short tandem repeat Is it a length polymorphism? YES! Some alleles have only 3 repeats while others may have 5. The two repeats will be different in size. 31) How do tandem repeats like STR s differ from person to person? The differences are in the number of repeats. Some repeats are the same in number between people, but others can be different. 32) A person has 5 tandem repeats for an STR with the sequence: TATC. Write the sequence for the allele below: TATC TATC TATC TATC TATC The 5 repeats are on the paternal homolog for chromosome 15. If the person is heterozygous for the polymorphism, what number of repeats might you find on the maternal homolog? (answers can be various but will not be 5 repeats) Write out a possible (there are many different answers here) sequence for the maternal homolog: TATC TATC TATC TATC TATC TATC TATC 33) How many nucleotides are in a single repeat of a typical Short Tandem Repeat (STR)? ) What does purification do to DNA? separates DNA from other parts of the cell 35) What is amplification? What is the process called that can amplify segments of the DNA? Amplification means to copy segments of the DNA. PCR can amplify target sequences of DNA up to billions of copies. 36) Which of the following might be a source of DNA? all but RBC s a. saliva c. urine e. red blood cells g. feces b. buccal cells d. skin cells f. white blood cells h. semen Note: Red blood (erythrocytes) cells are formed from stem cells in your bone marrow. Shortly after they are formed, they dump their nucleus and organelles. They contain thousands of hemoglobin molecules which function to carry oxygen throughout your body. They only live about 100 days after which they are broken down in the spleen by white blood cells. Approximately ¼ of your cells are red blood cells! 5

6 Fo Sci DNA Questions #3 Name Key Use slides to answer the following questions: (some questions may be answered using previous slides) 37) What does PCR stand for? What is the function of the PCR process? polymerase chain reaction PCR amplifies or copies the DNA to form billions of copies of the target sequences of interest. 38) What process that normally takes place in a cell is most similar to PCR amplification? DNA replication 39) Which of the following is a significant difference between amplification of DNA in a cell (DNA Replication) and amplification of DNA by PCR for a DNA profile? a. replication takes place in the cytoplasm while amplification takes place in the nucleus of the cell b. replication copies all of the DNA in the nucleus but amplification only copies shorter, target sequences c. replication makes thousands of copies of the nuclear DNA while PCR amplification makes only one copy of each target sequence. d. replication occurs in a thermocycler while PCR can take place inside of a living cell. 40) Place the following in order of how the process of PCR takes place: a. weak hydrogen bonds between complimentary nucleotides break b. Begin again c. DNA polymerase helps to add nucleotides to the single strands of DNA d. Primers attach to ends of the target sequences e. Cool down stabilizes new strands f. Heat up DNA answer: F-A-D-C-E-B 41) What is the correct order of the following processes in DNA profiling? a. Gel electrophoresis to visualize the DNA b. Purification of sample to eliminate all cellular material from the D c. PCR to amplify the DNA to produce billions of copies d. Extraction of DNA from the cells answer: D-B-C-A 42) Visualize means to see something. Do you think you could visualize a few strands of DNA? NO! How many strands of DNA are produced during PCR? billions (10 s, 100 s, 1000 s, billions) Why do you have to run a PCR on the DNA before you can visualize the results in gel electrophoresis? If you don t amplify the target sequences to a billion copies, you will not be able to see them on the gel. 43) Which of the following are true? (Correct any false statements.) a. When PCR is used, all of the DNA is amplified. no, only the target sequences b. The product of the PCR process is several copies of the target sequence. _no, billions 6