DNA and RNA Structure
DNA Replication
Transcription and Translation
Gene Regulation, Expression, and Specialization
Mutations
100
What type of bonds hold the two strands of DNA together?
Hydrogen bonds
100
What is the name of the model for DNA replication where both parental strands are copied, and the resulting daughter molecules each have one parental and one new strand.
The semi-conservative model
100
Which RNA molecule is this and what does it carry?
tRNA and it carries an amino acid and an anticodon.
100
What is the name for a group of genes that can be turned on or off?
Operons
100
Mutations are changes in genetic material of a cell which can alter phenotypes; as a result, they are the primary source of ___________ ___________.
Genetic Variation
200
(1) What is the monomer of DNA?
(2) Identify all the specific components of this monomer.
1. Nucleotide
2. Deoxyribose (sugar), phosphate, nitrogen bases (A,T,C,G)
200
If the two strands of DNA fail to separate during DNA replication, this issue is most likely due to a defect in which enzyme?
Helicase
200
What will the mRNA transcript be if the template strand of DNA reads:
3'-TTACGGTCAGAC-5'?
5'-AAUGCCAGUCUG-3'?
200
During eukaryotic development, what physical process gives an organism its shape?
Morphogenesis
200
(1) Which mutation codes for a premature STOP codon?
(2) Identify the mRNA codon for a STOP.
(1) Nonsense mutation
(2) UAA, UAG, UGA
300
What percentage of cytosine can be found in a DNA sample, if the thymine percentage is 23.5.
26.5%
300
Telomeres, which protect the ends of eukaryotic chromosomes, gradually shorten with each cell division. When telomeres become too short, cells stop dividing permanently.
What enzyme adds repetitive nucleotide sequences to the ends of telomeres to counteract this shortening?
Telomerase
Also: Telomerase is usually inactive in most somatic cells, limiting their number of divisions. However, in cancer cells, telomerase is often reactivated.
300
For each of the following statements, determine whether the process occurs in prokaryotes or eukaryotes.
A. Transcription factors must bind first for RNA polymerase to attach.
B. RNA polymerase binds directly to the DNA.
Eukaryotes - Transcription factors must bind first for RNA polymerase to attach.
Prokaryotes - RNA polymerase binds directly to the DNA.
300
What does DNA methylation do to the chromatin structure to regulate gene expression?
It adds methyl groups to DNA which causes the chromatin to condense and reduces gene expression.
300
What mutation causes Down syndrome when chromosomes fail to separate properly during meiosis?
Nondisjunction
400
(1) How do the nucleotides pair up in DNA?
(2) How many hydrogen bonds hold each pair together?
1. A = T, C = G
1. A = T have two hydrogen bonds
C = G have three hydrogen bonds
400
You and a group of scientists are trying to inhibit DNA replication by maintaining DNA in its supercoiled state instead of allowing it to relax. Which enzyme would you most likely target to achieve this inhibition?
Topoisomerase
400
Both the 5' cap and poly-A tail are modifications that occur before mRNA goes from transcription to translation. What would happen to the mRNA strand if these modifications were absent?
The mRNA strand would rapidly degrade, preventing it from binding to a ribosome and efficiently producing proteins during translation.
400
What type of operon is the E. coli lac operon if it is a regulatory system in which transcription is initially off because a repressor is bound to the operator?
Inducible operon - transcription is off, but can be induced (started/on)
Repressible operon - transcription is on, but can be repressed (stopped/off)
400
What type of chromosomal mutation is occurring in the image below?
Translocation - because segments from one chromosome are moved to an entirely different chromosome.
500
1. What are the pyrimidine bases found in nucleic acids?
2. How would you describe the molecular structure of pyrimidines?
1. Cytosine, Thymine, and Uracil
2. Single ring structure
500
(1) Examine the image below and determine which strand is Strand A and which is Strand B.
(2) If DNA polymerase III (DNA Pol III) moves in the 5' to 3' direction on each strand, how would you describe its movement?
(1) Strand A = leading strand, Strand B = lagging strand
(2) On the leading strand it moves continuously and on the lagging strand it moves discontinuously.
500
Antibiotics are medicines that stop infections caused by bacteria by either preventing bacterial reproduction or killing the bacteria. Many antibiotics specifically affect translation. Edeine is one antibiotic in particular that works to stop the small ribosomal subunit from binding to the mRNA. Based on this information, which stage of translation would be most directly affected in cells exposed to edeine?
Initiation
500
Because DNA is tightly wound and less accessible for transcription, certain modifications to the chromatin are required. What process helps modify the chromatin and regulates gene expression by loosening the DNA?
Histone acetylation
500
Since mutations can sometimes be beneficial, how does natural selection determine whether a mutation becomes more common in a population over time?
Natural selection increases the frequency of beneficial mutations by favoring organisms that survive and reproduce. Over generations, the more advantageous traits will increase or become more common, while harmful or neutral mutations are less likely to persist.