Review Questions Chapter 12 Review Sheet
1. Below is a molecule of DNA. Label the following: sugar, phosphate, adenine, cytosine, guanine, thymine, nucleotide, hydrogen bond.
2. What is the name given to the shape of the DNA molecule?
Double Helix
3. Name the scientists who helped discover the shape of the DNA molecule using a technique known as X-ray diffraction.
Rosie Franklin
4. Name the scientists who figured out the correct arrangement of molecules to build the first correct model of DNA.
James Watson and Francis Crick
5. Through the process of _Replication__ ___, DNA makes a copy of itself.
6. The parent strand of a molecule of DNA looks like this: AATCGGTATCGC
What would the bases for the daughter strand look like?
TTAGCCATAGCG
7. Explain why the process of DNA replication is vital for living things.
Cells must copy DNA prior to cell division so each new cell has a complete copy of the genetic code.
8. What are some situations in which your body would make new cells?
For example: repair of cellular damage
(heal puncture wound or cut, blood loss, cellular growth, immune response – produce white blood cells, skin cells constantly replaced, etc.)
9. The process named in #7 takes place in the nucleus of the cell.
10. Identify how DNA is different from mRNA in each of the following:
a. Sugar – Deoxyribose (DNA), ribose (RNA)
b. Bases – RNA has a Uracil (U) instead of Thymine (T)
c. # of strands – 2 strands in DNA 1 strand in RNA
11. DNA can’t leave the nucleus. How does the DNA code get to the ribosome? (In other words, what molecule is produced from DNA to get that code to the ribosome?)
The genetic message (gene) is copied to a molecule called mRNA. RNA polymerase catalyzes this reaction.
12. If the DNA code is TTA GGG CTC CTA, what would the mRNA made from it look like? AAU CCC GAG GAU
13. Divide mRNA code written in #12 into codons. Then, use the chart at the end of your notes to translate it into amino acids.
ASN PRO GLU ASP
14. How is mRNA processed (edited) before it leaves the nucleus?
Introns are removed from the mRNA and exons are retained.
The mRNA is given a 5’ Cap and Poly A tail that protect it before it enters the cytoplasm
15. Identify the type of mutation in each sequence below. Circle the location of the error.
Original: AAUGGCGUUAAC
A. AAUCGCGUUAAC – Substitution
B. AAUGGCGCUUAAC - Insertion - Frameshift
C. AAUGGCUAAC – Deletion - Frameshift
16. List two ways (one beneficial/one harmful) that mutations could affect and organism.
Beneficial: polyploidy in plants (extra chromosomes actually make the plant stronger)
Harmful: Cystic fibrosis is a gene mutation that causes a protein in the cell membrane of lung cells to function improperly causing severe illness.
17. How can a point mutation become a frameshift mutation? What are the differences between silent, nonsense and missense mutations?
Point mutations such as insertions and deletions involve adding a base or removing a base from the dna code, this causes all the codons to change after the mutation, in turn cuasing all the amino acids to potentially change after the point of mutation resulting in a reading frame shift.
Silent – a base change in codon does not change the amino acid stipulated by the codon
Nonsense – a mutation causes a codon to change to a “stop” codon, terminating the production of the polypeptide prematurely.
Missense – a base change (mutation) causes the amino acid to change potentially affect the function of the protein.
18. Label the parts in the diagram below, then answer the questions that follow.
a. What is the molecule labeled “A” in the diagram above?
DNA
b. Label the nucleus in the diagram above.
c. Name the process occurring in the nucleus of the cell.
Transcription – DNA to mRNA
d. Where in the cell will the mRNA go once it has been constructed?
To the cytoplasm and join with the large and small subunit of the ribosome.
e. The mRNA is divided into groups of three bases called __codons____.
f. Label the parts that make up the ribosome in the diagram above.
g. Name the process occurring at the ribosome.
Translation - RNA to Protein
h. At the ribosome, the mRNA will meet with what (labeled “B” in the diagram above)?
tRNA – Transfer RNA
i. The group of 3 bases attached to “B” in the diagram is called a(n) ______anticodon ______
j. If the codon is “AAC”, the anticodon would be __ UUG ______.
k. The molecules labeled “C” in the diagram are called __ amino acids ______.
l. Joining amino acids together builds a ___ polypeptide (protein)__.
m. Amino acids are held together by ___ peptide ___ bonds.
n. How are proteins important to living organisms?
Protein and protein interactions are responsible for expressing our phenotype ( or the traits that we can see - eye color, hair color, skin color, shape of our noses, mouths, eyes, etc.) In addition, proteins are enzymes and therefore regulate many of the chemical reactions in our bodies
o. After the polypeptide is formed what path might it take in the cell before it is actually finished and functional?
The polypeptide may associate with other polypeptides at the rough ER, or simply be modified, then proceed via a vesicle to the Golgi apparatus where it could be further modified and packaged for transport within the cell or outside the cell.
19. Explain what a gene is:
A gene is a segment of DNA that holds the genetic code for making a specific protein that will express a trait.
20. Explain the primary function of DNA in the cell: DNA holds the genetic code for manufacturing proteins, thereby supporting (providing the instruction for) life.
21. What is gene expression?
The information encoded on a gene is used to direct the formation of a protein by the cell. Genes are typically expressed with the help of other RNA molecules (particularly mRNA, rRNA and tRNA).