Bio Exam 1
Molecular hybridization is important in many molecular methods used in the lab. What is meant by this?
"melted" single strands of DNA are cooled and anneal to other single strands w complementary base pair sequences
What does it mean if someone has Turner Syndrome? Kleinfelter syndrome?
(45, X) (47, XXY)
Which list of steps in the eukaryotic cell cycle is given in the correct order? (step order listed left to right)
. . . G1 - S - G2 - M - G1 . . .
What are Chargaff's rules?
1. A is proportional to T and G is proportional to C 2. sum of purines equal to sum of pyrimidines 3. ratio of (A+T):(G+C) varies b/t organisms
Describe the three steps of a single PCR cycle.
1. denaturing into single strands (via heat application) 2. primer binding to single stranded DNA (via cooling) 3. extension of DNA strands
Summarize Griffith's experiments:
1. inject mouse w living smooth bacteria, mouse dies 2. inject mouse w living rough bacteria, mouse lives 3. inject mouse w heat-killed smooth bacteria, mouse lives 4. inject mouse w heat-killed smooth + living rough bacteria, mouse dies, living smooth bacteria recovered
Summarize what two factors are in tension that drove human evolution of skin color variation:
1. need to protect against UV radiation 2. need to use some UV radiation for our own benefit
In contrast to the leading strand, the lagging strand is synthesized as a series of segments called Okazaki fragments. The diagram below illustrates a lagging strand with the replication fork off-screen to the right. Fragment A is the most recently synthesized Okazaki fragment. Fragment B will be synthesized next in the space between primers A and B. Drag the labels to their appropriate locations in the flowchart below, indicating the sequence of events in the production of fragment B. (Note that pol I stands for DNA polymerase I, and pol III stands for DNA polymerase III.)
1. pol III binds to 3' end of primer B 2. pol III moves 5' to 3', adding DNA nucleotides to primer B 3. pol I binds to 5' end of primer A 4. pol I replaces primer A with DNA 5. DNA ligase links fragments A and B
Name two key stages that produce variation in meiosis.
1. prophase I - crossing over 2. metaphase I - independent assortment of chromosomes at metaphase plate
Explain two ways that meiosis produces variation in gametes.
1. unique combinations of maternal and paternal chromosomes in haploid component 2. crossing over, genetic exchange w/in homologous chromosomes
Why was it important in the methodology of the Messelson-Stahl experiment that they used 15N?
15N important due to its stability, heavier weight than typical 14N, and ability to be distinguished from DNA containing 14N via sedimentation equilibrium centrifugation
At generation 0, all the molecules were:
15N only
At generation 1, when cells were only grown in 14N containing medium all the molecules were:
15N/14N
How many alleles does each person have for the leptin receptor gene?
2
In a diploid organism, there are ___ (number of copies) of most genes. In a population, there may be many different gene sequences, or versions of this gene called _____________. How do these new variations of gene sequences arise in a population?
2 alleles new variations arise via mutations
Adenine complementarily binds with thymine and forms __ (how many?) ____ (what type?) bonds.
2 hydrogen
What makes a SNP different from what geneticists might call a single nucleotide change or point mutation?
2+ versions of a SNP sequence must be present in at least 1% of general population, and no point mutation has that high a prevalence also, SNPs not necessarily located w/in genes, do not always affect protein function
Based on what scientists can accurately measure at this point, how many human conceptions lead to spontaneous abortion? And how many of these are due to chromososomal imbalance?
20% of all conceptions 30% of all spontaneous abortions
Which one (200 or 250 bp) would migrate farther (closer) to the positively charged pole? Why?
200 bp molecule would migrate further b/c shorter chains migrate at a faster rate through the gel than larger chains
If you could build a protein with 10 amino acids, and any amino acid could be at each position, how many variations are possible?
20^10
How do you calculate the total number of unique gametes formed with the haploid number n chromosomes?
2^n
How many chromosomes and chromatids are present prior to meiosis I?
2n chromosomes 2n chromatids
How many chromosomes and chromatids are present after the replication in prophase I?
2n replicated chromosomes 4n chromatids
diploid
2n, normal chromosome complement of organism's somatic cells
Up to how many phosphates will we find bound to a sugar and nitrogenous base?
3
Deoxyribonucleotides bind together to form polynucleotides. This bond occurs between the phosphate group of one nucleotide and the C-__' position of a ____ of another nucleotide. The type of bond formed in this interaction is called a ____ bond.
3 sugar phosphodiester
Guanine complementarily binds with cytosine and forms __ (how many?) ____ (what type?) bonds.
3 hydrogen
The nucleotide is always added to the _________________ of the growing polynucleotide chain.
3' end
If a typical somatic cell has 64 chromosomes, how many chromosomes are expected in each gamete of that organism?
32
In the Hershey and Chase experiment, ___ labeled the DNA and ___ labeled the proteins of phages.
32P 35S *used phages b/c made only of protein and DNA
Together LINES and SINES make up what percent of the DNA of the human genome?
34%
If 15% of the nitrogenous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine?
35%
How many telomeres are there on each chromosome?
4 per chromosome (2 arms w/ 2 ends each)
If you had an oligonucleotide that had 17 nucleotides, how many variations would be possible?
4^17 = 1.7E10 variations
If there are five molecules of DNA containing the target region at the beginning of a PCR reaction, how many copies of the target will be present after three rounds of amplification?
5 x 2^3 = 40
Phosphate groups are attached to the ____ carbon of the pentose sugar, and posses a ___ charge at physiological pH.
5' negative
antiparallel (DNA strands)
5' to 3' polarities run in opposing directions
What is the complementary DNA sequence to 5′ ATGCTTGACTG 3′?
5′ CAGTCAAGCAT 3′
The genetic code consists of a total of how many different codons?
64
A cell has 16 chromosomes. How many chromosomes would its daughter cells have after meiosis?
8
In an analysis of the nucleotide composition of double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true?
A + C = G + T
The ant Myrmecia pilosula is found in Australia and is named bulldog because of its aggressive behavior. It is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words, 2n = 2. (Males are haploid and have just one chromosome.) Which of the following figures would most likely represent a correct configuration of chromosomes in a metaphase I cell of a female?
A - one tetrad shown
What is a promoter?
A DNA sequence that specifies the start site for transcription
Which of the following correctly indicates the relationship between genes and chromosomes?
A chromosome is composed of DNA complexed with proteins, and many genes are found along the length of a single chromosome.
Which of the following are chromatid pairs that will be present during metaphase in mitosis?
Am Am Ap Ap Bm Bm Bp Bp Cm Cm Cp Cp
What chromosomes will be present at each pole at the completion of anaphase?
Am, Ap, Bm, Bp, Cm, Cp
Many forms of DNA exist, but ___ DNA is the physiologically relevant form that Watson and Crick described.
B-DNA
How does transcription begin and end?
Begins at nucleotide sequence called promoter, where RNA polymerase attaches and begins RNA synthesis, and ends at nucleotide sequence called terminator, where polymerase detaches from RNA.
How does translation begin and end?
Begins when mRNA molecule binds to small ribosomal unit, then initiator tRNA (aa Met) binds to start codon. Next, large ribosomal subunit binds to small one to make functional ribosome. Ends at stop codon, where polypeptide chain is freed and ribosome splits back into subunits.
Which of the following outcomes would be most likely if the Hershey-Chase experiments were repeated without the step involving the blender?
Both preparations of infected bacteria would exhibit radioactivity.
What is the central dogma of genetics?
DNA --> RNA --> protein
The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid. Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II? (Note: Ignore any effects of crossing over.)
DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.
How does a cell know which strand needs to be fixed in a mispaired base?
DNA is methylated shortly after replication; therefore, repair enzyme recognized the mismatch on the new strand that has not yet been methylated and excises this newly synthesized nucleotide
Which of the following statements best represents the central conclusion of the Hershey-Chase experiments?
DNA is the identity of the hereditary material in phage T2.
Use these five words in one sentence to explain how proteins are made (this is also known as the "central dogma" of molecular genetics: DNA, mRNA, codon, translation, transcription
DNA is used to make mRNA via transcription, and then codons from mRNA are used to string amino acids into protein via translation.
UV light can penetrate living cells and cause what?
DNA mutations
Viral chromosomes exist in a variety of conformations and can be made up of ________.
DNA or RNA
Describe how gel electrophoresis works:
DNA placed in a well w agarose matrix, one negative and one positive end. DNA is negatively charged and is attracted to positive end of well. Shorter fragments move further than larger fragments.
The enzyme that can replicate DNA is called ____.
DNA polymerase
Which enzyme catalyzes the addition of nucleotides to a growing DNA chain?
DNA polymerase
____ removes the RNA primers and fills in the gaps with DNA nucleotides.
DNA polymerase I
What is the danger of depurination of not corrected before DNA replication begins?
DNA polymerase may insert a random nucleotide in the apurinic site
Mutations are any alteration in DNA sequence. They arise during the process of ____. They are the only source of new ____ that are acted upon by evolution.
DNA replication alleles
We'll look very briefly at transposons (we previously looked at how SINES and LINES were interspersed throughout the genome). What is a transposon and how could it cause a mutation?
DNA sequences that can move w/in and b/t chromosomes in genome, and insertion of these may lead to visible mutations mutations likely caused b/c elements transpose into or near genes, possibly terminating transcription or affecting level of gene expression or altering intron splicing
Which of the following statements about DNA replication is true? (in regards to leading/lagging strands)
DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand.
In 1944, Avery, MacLeod, and McCarty published a famous paper concluding what? What evidence did they provide?
DNA was genetic material evidence: soluble filtrate from heat-killed smooth bacteria treated w ribonuclease to destroy protein & RNA, but transformation still took place, so concluded DNA rather than proteins/RNA was genetic material
What is the DSCR?
Down syndrome critical region - hypothetical portion of chromosome 21 containing dosage-sensitive genes in this trisomy and responsible for many phenotypes associated w Down syndrome
If we want to use hybridization with a fluorescent probe to find say, the telomeres of each chromosome, we could use a technique called ________________________________.
FISH: fluorescent in situ hybridization
Which statement is true? (regarding hydrogen bonds between bases)
G-C base pairs have three hydrogen bonds while A-T base pairs have two hydrogen bonds.
How is genetic information encoded in a DNA molecule?
Genetic information is encoded in DNA by the sequence of bases.
Using the codon table, identify the Hb type(s) that can occur as a result of a single nucleotide change. Select all that apply.
Hb Oxford Hb Sydney Hb Bethesda Hb Saskatoon Hb Mexico Hb Toronto
Which of the following accurately describes a possible meiotic nondisjunction event?
Homologs fail to separate during meiosis I.
Describe the gametic result of nondisjunction in meiosis I vs meiosis II.
If nondisjunction occurs in meiosis I, homologs will end up together in 2 of the 4 gametes, while the other 2 will have no chromosomes. If the nondisjunction occurs in meiosis II, sister chromatids will end up together in 1 gamete, 1 gamete will have no chromosomes, and 2 gametes will be normal (diploid).
Contrast the end results of meiosis with those of mitosis.
In mitosis, there is no change in chromosome number or kind in the two daughter cells, whereas in meiosis, numerous potentially different haploid cells are produced.
cell cycle
Interphase: G1, G0, G1, S, G2 Mitosis: prophase, prometaphase, metaphase, anaphase, telophase
Introns are known to contain termination codons (UAA, UGA, or UAG), yet these codons do not interrupt the coding of a particular protein. Why?
Introns are removed from mRNA before translation.
How may it lead to a mutation?
It allows hydrogen bonding of normally noncomplementary bases.
All EXCEPT which of the following are characteristics of the genetic material?
It is composed of protein.
Which of the following statements about nondisjunction is false?
It separates maternal from paternal chromosomes.
The Hershey and Chase experiments involved the preparation of two different types of radioactively labeled phage. Which of the following best explains why two preparations were required?
It was necessary that each of the two phage components, DNA and protein, be identifiable upon recovery at the end of the experiment.
Why are liver extracts used in the Ames test?
Liver enzymes may activate some innocuous compounds, making them mutagenic.
List the components of a PCR reaction.
Mg2+ (cofactor), four deoxyribonucleoside triphosphates, single-stranded DNA (NOT RNA!) primers complementary to 5' end of one strand and 3' end of another, Taq. polymerase, and template DNA to be amplified
The incidence of Down syndrome, also known as trisomy 21, increases with increasing maternal age. Which of the following errors most likely produces this condition?
Nondisjunction during either meiosis I or II in the female gamete
____ are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.
Okazaki fragments
What are alleles? Is it possible for more than two alleles of a gene to exist?
One of the possible alternative forms of a gene is called an allele. yes
In your own words, describe PCR.
PCR amplifies target DNA to clone it rapidly and w/out a host cell
The immediate product of transcription is ________.
RNA
ribosomal RNA
RNA component of ribosome
The promoter is bound by which enzyme?
RNA polymerase
RNA primers are formed by ____ and serve as an initiation point for DNA synthesis on the template.
RNA primase
Which of the following statements about DNA replication is true? (in regards to protein function)
Single‑strand binding proteins stabilize the open conformation of the unwound DNA.
What does the DNA sequence look like at a telomere?
TTAGGG in vertebrates similar G-rich repeats in many organisms
What is the DNA sequence like at the telomeres?
TTGGGG in protozoan, TTAGGG in vertebrates
Why is it important that a Taq polymerase specifically is used in a PCR reaction?
Taq polymerase can function at higher temperatures, making it suitable for PCR
What is tautomeric shift?
Tautomeric shift is an intramolecular proton shift that changes the bonding structure of the molecule.
What was the result? What conclusions were drawn?
The DNA was proven to be the "transforming principle". Treatment with deoxyribonuclease resulted in the loss of transforming ability.
What is the relationship and sequence correspondence of the mRNA transcript to the DNA coding strand?
The coding DNA strand and the RNA transcript are identical, except that thymidine nucleotides in the DNA are uridine nucleotides in corresponding sites of the mRNA transcript and The coding DNA strand and the RNA transcript are parallel to each other.
It has been recently determined that the gene for Duchenne muscular dystrophy (DMD) is more than 2000 kb (kilobases) in length; however, the mRNA produced by this gene is only about 14 kb long. What is a likely cause of this discrepancy?
The introns have been spliced out during mRNA processing.
Which statement is true? (regarding temp needed to separate DNA strands)
The more hydrogen bonds between bases, the higher the temperature needed to separate the pair.
What observation did Griffith make in his experiments with Streptococcus pneumoniae?
The mouse did not survive when injected with a mixture of live, avirulent (rough) Streptococcus pneumoniae and heat-killed, virulent Streptococcus pneumoniae.
Which of the following statements about DNA structure is true?
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.
Which of the following statements about meiosis is true?
The second meiotic division is similar to mitosis in that the sister chromatids separate.
What is the relationship and sequence correspondence of the RNA transcript and the DNA template strand with respect to transcription?
The template DNA strand and the RNA transcript are antiparallel to each other and The template DNA strand and the RNA transcript are complementary.
Which of the following statements about the basic structural features of DNA are true?
The twisting of the DNA double helix is attributed to the tight packing of DNA bases and base-stacking. In a DNA macromolecule, the two strands are complementary and antiparallel.
Assume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of a single meiotic event. Which of the following statements would be true if crossing over did not occur?
There would be less genetic variation among gametes.
What is the purpose of raising the temperature to 90-95°C at the beginning of each cycle of PCR?
To separate the double‑stranded DNA
Which of the following statements about the products produced when nondisjunction occurs during meiosis I is true?
Two products of the second meiotic division have both the maternal and paternal chromosomes of a set and the other two products have none for that set.
Why did human skin evolve to be darker?
UV radiation and less eumelanin decreases folate and leads to severe birth defects
Scientists wanted to know if BPA was mutagenic. If so, they wanted to know if it caused base substitutions or frameshift mutations. Design an experiment to test this.
Using Ames test, high number of reversions (his- to his+) suggests mutagen causes mutations if original mutated strain that requires histidine has a point mutation, only mutagen that causes point mutation will revert it if original mutation strain has frameshift mutation, only mutagen that causes frameshift mutation will revert it
The diagram below shows a replication bubble with synthesis of the leading and lagging strands on both sides of the bubble. The parental DNA is shown in dark blue, the newly synthesized DNA is light blue, and the RNA primers associated with each strand are red. The origin of replication is indicated by the black dots on the parental strands. Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.
a and h (earliest) b and g c and f d and e (lastest)
Which is bigger, a gene or a chromosome?
a chromosome
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
a frameshift deletion at the beginning of the gene
Why did deCODE select Iceland for its ambitious research project?
a relatively low degree of genetic diversity
Assume we have a diploid organism in which 2n = 26. What might the number be if the organism was: a) aneuploid? b) diploid? c) trisomic? d) triploidy? e) monosomic?
a) 28 b) 26 c) 27 d) 39 e) 25
Can you identify the banding patterns predicted by each model after the first round of replication? Drag the test tubes to the appropriate locations in the table to show the banding patterns that each model predicts. Test tubes may be used once, more than once, or not at all.
a. dispersive - 14N/15N single band of density b. semiconservative - 14N/15N single band of density c. conservative - 14N/14N band and 15N/15N band
Can you identify the banding patterns predicted by each model after the second round of replication? (Note: The dispersive model's prediction is already shown; see Hint 1 if you need help understanding it.) Drag the test tubes to the appropriate locations in the table to show the banding patterns that each model predicts. Test tubes may be used once or not at all.
a. semiconservative - 14N/14N band and 14N/14N band b. conservative - 14N/14N band and 15N/15N band
regulatory mutations
affect regulation of gene product
How did their experiments rule out conservative replication?
after one generation, isolated DNA was present in only a single band of intermediate density (14N/15N) - not consistent w conservative replication, in which two distinct bands would occur
All EXCEPT which of the following mutagenic events occur spontaneously?
alkylation
cell theory
all organisms composed of basic units (cells) derived from similar preexisting structures
What is telomerase and what cells express this protein?
an enzyme that adds base to end of telomeres, remains active in gametes
The condition that exists when an organism gains or loses one or more chromosomes but not a complete haploid set is known as ________.
aneuploidy
What can you summarize about plants and monsomy or trisomy that is different from animals?
anueploidy is generally better tolerated in plants than in animals
If a person had a single nucleotide substitution in the DNA leading to a single amino acid change, where would it be most detrimental to the function of LEP-R? Why?
at AUG start codon b/c no protein would form at all
Why is monosomy so lethal?
b/c organism becomes completely dependent on one allele rather than 2
Compare the number of origins of replication in bacteria, yeast (single-celled eukaryotes) and mammals:
bacteria = 1 yeast = 250-400 mammals = up to 25,000
What can you conclude from Table 2.1, "the relationship between gene size and mRNA size"?
bacteria do not have introns gene length increases w organism complexity, but mRNA length does not therefore intron length increases w organism complexity
____ are those structures formed by the synapsis of homologous chromosomes.
bivalents
Chromosomes from what kind of cells were used to measure telomere length?
blood cells
Meiosis guarantees that in a sexual life cycle, offspring will inherit one complete set of chromosomes (and their associated genes and traits) from each parent. The transmission of traits from parents to offspring is called heredity. Another important aspect of meiosis and the sexual life cycle is the role these processes play in contributing to genetic variation. Although offspring always resemble their parents, they are genetically different from both of their parents and from one another. The degree of variation may be tremendous. Sort each process into the appropriate bin according to whether it contributes to heredity only, genetic variation only, or both. (Note that a bin may be left empty.)
both: DNA replication before meiosis, crossing over, chromosome alignment in metaphase I and separation in anaphase I, chromosome alignment in metaphase II and separation in anaphase II, fertilization
Avery, MacLeod, McCarty experiment summary
broke down specific parts of cell (either none (control), lipids and polysaccharides, proteins, RNA, or DNA) and repeated Griffith's 4th trial (virulent heat killed + nonvirulent living) to determine identity of transforming factor
How long does it take for an entire eukaryotic genome to be replicated?
can be replicated in a matter of minutes to hours
neutral mutation
can occur in protein-coding or noncoding region of genome, effect on genetic fitness is negligible
All polymerases have an exonuclease activity meaning they can do what?
can pause, reverse direction, and excise nucleotides
Deamination causes what kinds of mutations?
causes transition point mutations
G1 checkpoint
cells decide to either enter cell cycle or enter G0 at a checkpoint at the end of G1
missense mutation
change in one nucleotide, new triplet codes for different amino acid (point mutation)
spontaneous mutations
changes in nucleotide sequence of genes that appear to have no known cause
____ refers to the structure, when viewed microscopically, of crossed chromatids.
chiasmata
What is the problem with DNA that is bound to histones and compacted?
chromatin fiber, when complexed w histones & folded into various levels of compaction, make DNA inaccessible to interaction w important nonhistone proteins
mitosis
chromosomes in cell nucleus separated into two identical sets of chromosomes, each set ends up in own nucleus, results in 2 diploid daughter cells
Which of these characteristics describe viral chromosomes? (Circle any that apply.) Circular, linear, made of DNA (single or double-stranded), made of RNA (single or double-stranded)
circular or linear, DNA or RNA, single- or double-stranded
Which of these same characteristics describe bacterial chromosomes? (Circle any that apply.) Circular, linear, made of DNA (single or double-stranded), made of RNA (single or double-stranded)
circular, made of DNA, double-stranded in nucleoid region
What does the MC1R gene do?
codes for protein involved in switch from production of pheomelanin to eumelanin
open reading frame
coding region, beings w start codon (AUG on mRNA, TAC on DNA) and ends at termination region of protein
What is the first order of chromatin packing?
coiling around nucleosomes
The biological anthropologist, Nina Jablonski, asks the scientific question, "is there a relationship between the global distribution of UV intensity and the variation of human skin color"? Who are the groups or individuals that she collaborates with on this question to collect and interpret data? What kind of data does she collect on UV light? on Skin color? What pattern does she find in global UV distribution (light intensity)? What pattern does she find globally in human skin color? What conclusion does she make about the question above?
collaborates w NASA and her husband, a geographer collects NASAs data on worldwide UV intensity and skin pigment measurements from anthropologists studying indigenous peoples UV more intense near equator and at high altitudes darker skin near equator and at high altitudes there is a relationship b/t global distribution of UV intensity and variation of human skin color
DNA polymerase III is a holoenzyme. in a few words, what does this mean?
complex enzyme w multiple subunits
What are spindle fibers made of and what is their function in the cell during mitosis and meiosis?
composed of microtubules consisting of polymers of polypeptide subunits of the protein tubular, and they play a role in the movement of chromosomes as they separate during cell division
dyad
composed of two sister chromatids joined at a common centromere
In the Meselson-Stahl experiment, which mode of replication was eliminated based on data derived after one generation of replication?
conservative
How are telomeres an example of repetitive DNA? Are there genes that code for proteins in the telomeres?
consist of multiple tandem repeats of sequence 5' - TTAGGGG - 3' no
LINES and SINES are longer sequences and they do not repeat in tandem. Why are they called repetitive?
consist of sequences interspersed individually throughout genome (just not in tandem)
coding region
contains information for the structure of the expressed protein
messenger RNA
conveys genetic info from DNA to ribosome
____ is the exchange of genetic material between chromatids.
crossing over
After replication is complete, the new DNAs, called ____, are identical to each other.
daughter DNA
transfer RNA
decodes mRNA codon sequence into proteins
Messelson and Stahl provided evidence that replication in prokaryotes was semi-conservative; what did Taylor-Woods-and Hughes demonstrate?
demonstrated replication in eukaryotes was also semiconservative
Which three steps constitute a PCR cycle?
denaturation, annealing, and extension
What are the differences between ribose and deoxyribose?
deoxyribose has a hydrogen at C-2' where ribose has a hydroxyl group
bioinformatics
develops hardware & software to store, retrieve, analyze nucleotide/protein data
4 lifestyle changes that lengthen chromosomes (telomeres)
diet, exercise, sense of community, stress management
Compare diploid and haploid number.
diploid (2n): each chromosome exists in pairs haploid (n): gametic chromosome number, cell has one member of each pair of homologous chromosomes
meiosis
diploid parent cell divides (meiosis I and II) to make 4 haploid daughter cells, gametes
primase
directs synthesis of RNA primer primer needed b/c pol III cannot bind to DNA directly, needs 3' hydroxyl group to begin synthesis
What does the control help discern from the experimental group in this experiment?
discerns the normal number of his+ reversions from the number of reversions caused by the mutagen
Okazaki fragments are short DNA fragments synthesized in a ____ manner.
discontinuous
linked SNPs
do not reside w/in genes, do not affect protein function, but correspond to particular drug response or disease risk
X-ray diffraction was an important tool in the discovery of the structure of DNA. What information was learned about DNA from this methodology?
double helical structure
How is the Watson & Crick model different from previous models of DNA?
double helix antiparallel strands bases inside helix and phosphates outside it hydrogen bonding bt purine position 1 and pyrimidine position 1 or purine position 6 and pyrimidine position 6
What happens when DNA is subjected to heat?
double helix is denatured & unwinds
How is DNA packaged into a chromosome?
double helix; DNA wrapped around histone proteins, which pack tightly together to form chromosome
purines
double ring A and G
When do sister chromatids separate?
during anaphase
____ are the "post-S phase" structure of replicated chromosomes. Because they are composed of two chromatids joined by a centromere, they are also called ____
dyads sister chromatids
semiconservative replication
each replicated DNA molecule consists of one old and one new strand
transition mutation
either a pyrimidine replaces a pyrimidine or a purine replaces a purine
As is the case with a syndrome, not everyone with Down Syndrome exhibits the same phenotypic characteristics. What are some of these?
epicanthic fold in eye, flat face, round head, short stature, protruding/furrowed tongue, short/broad hands, physical/psychomotor/mental retardation, poor muscle tone, shorter life expectancy (50ish years)
Where would you find linear chromosomes?
eukaryotes (in nucleus), viruses
What does figure 10-13 show?
eukaryotic DNA replication has multiple points of origin
What are some differences about chromosome structure in eukaryotes that might make replication different compared to prokaryotes?
eukaryotic chromosomes are linear rather than circular, so replication may differ
chromosome theory of inheritance
explains how inherited traits are controlled by genes residing on chromosomes transmitted through gametes, maintaining genetic continuity b/t generations
____ is the processing of genetic information that results in synthesis of proteins which contribute to the phenotype of the organism.
expression
T/F: A dyad is composed of two homologous chromosomes joined at a common centromere.
false
T/F: A missense mutation causes premature chain (protein) termination.
false
T/F: All compounds that have been found to be mutagenic in the Ames test are also carcinogenic.
false
T/F: Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 25 chromosomes would be triploid.
false
T/F: During a PCR, heat is provided to inactivate the polymerase enzyme.
false
T/F: Each human contains an identical set of VNTRs.
false
T/F: Females with only one X chromosome do not develop; this condition is lethal.
false
T/F: Haploid cells do not undergo mitosis.
false
T/F: In a typical PCR, primers are used to cleave specific regions of the DNA template.
false
T/F: In order to create the possibility of generating a trisomy, nondisjunction must occur during meiosis II.
false
T/F: Skin color is a single gene trait.
false
T/F: The data obtained from the Meselson-Stahl experiment after one generation of replication eliminated the dispersive model of DNA replication.
false
T/F: The second order of chromatin packing occurs when nucleosomes coil together to form a fiber that is 300 nm in diameter.
false
T/F: The thermostability of Taq polymerase is required during the annealing phase of PCR.
false
True or False? The length of a species telomeres predicts the lifespan of that species.
false
True or false: Mutations are bad
false
The Ames test is used to determine whether or not a compound causes __________.
gene mutations
Why were there two types of molecules in generation 2?
generation 1 15N strands produced 15N/14N DNA while generation 1 14N strands produces 14N/14N DNA
The _____ of an organism is defined as its specific allelic or genetic constitution.
genotype
What was the conclusion of the study?
group w lifestyle changes experienced 10% increase in telomere length
In 1928, Frederick Griffith established that _______.
heat-killed bacteria harbor the constituent(s) necessary to convey genetic properties to living bacteria
As DNA replication continues and the replication bubble expands, the parental double helix is unwound and separated into its two component strands. This unwinding and separating of the DNA requires three different types of proteins: helicase, topoisomerase, and single-strand binding proteins. Sort the phrases into the appropriate bins depending on which protein they describe.
helicase: binds at the replication fork, breaks H-bonds between bases topoisomerase: binds ahead of the replication fork, breaks covalent bonds in DNA backbone single-stranded binding protein: binds after the replication fork, prevents H-bonds between bases
Genetics is the study of ________.
heredity and variation
Which bacteria grow on the agar plate if the Ames test is positive?
his+ prototrophs
Bacteria with a specific mutation won't grow on agar without histidine (his- strains). What are the control and experimental groups?
his- auxotrophs are the control, while the potential mutagen is the experimental group
A substantial amount of proteins are associated with DNA in eukaryotes. What are these proteins and what are their function?
histones, positively charged proteins specific to DNA H2A, H2B, H3, H4 occur as two types of tetramers that compose nucleosomes H1 links nucleosomes together
What happens in prophase I of meiosis? How is this different from prophase of mitosis?
homologous chromosomes paired up in synapsis; synapsed homologs give rise to tetrads (two pairs of sister chromatids); non sister chromatids undergo crossing over at chiasma; nucleolus and nuclear envelope break down, tetrad centromeres attach to spindle fibers
How are bases paired together in DNA? Is this a stable interaction that holds the two polynucleotides together?
hydrogen bonding yes
What is the leading hypothesis as to why there is a correlation with maternal age and Down Syndrome?
hypothesis: all primary oocytes have developed and gone through meiosis I by (female) birth, but do not enter meiosis II until ovulation, so each ovum in later years has been arrested in meiosis I for much longer
proteomics
identifies set of proteins present in cell under given conditions, studies functions and interactions
Native people living near the arctic circle would be predicted to have light skin, but they have dark skin. Why might this be so based on the second hypothesis?
if peoples' diets include sufficient vitamin D, dark skin may not be selected against
Telomeres are believed to protect the linear chromosomes of eukaryotes from what two outcomes?
improper fusion and degradation
If protein was the genetic material, then Hershey and Chase would find radioactive protein _______________ at the end of their experiment.
in host cell
If being dark-skinned offers an advantage, why aren't all humans dark-skinned?
in northern latitudes, dark skin makes it bard to produce vitamin D necessary, so selective pressure towards lighter skin
Why would chromatin need to be remodeled?
in replication and gene expression, chromatin must relax structure but be able to re-compact during inactive periods
To be certain that the extract prepared from virulent cells still contained the transforming principle that was present prior to lysis, Avery _______.
incubated nonvirulent cells with the complete extract
What was the independent variable that was different between the experimental group and the control group in this study?
independent variable was set of lifestyle changes: plant-based diet, moderate exercise, stress reduction
What can an Ames test tell us?
info about the mutagenicity of specific substances
regulatory region
information on where and when a gene will be transcribed during development; usually upstream, of the coding region
frameshift mutation
insertion/deletion of one or more nucleotides alters frame of triplet reading during translation
Where did the radioactively labeled DNA end up after centrifugation?
inside the cell
gap phases 1 and 2
intensive metabolic activity, cell growth, cell differentiation volume of cell doubled by end of G2
lethal mutation
interrupts a process essential to survival or organism
interphase
interval b/t divisions (ie. not mitosis)
The nitrogenous bases of each nucleotide project ____ the double helix. They form complementary base pairs through the formation of ____ bonds with bases on the opposite DNA strand.
into hydrogen
termination region
is the "stop" signal for where transcription should end; downstream of coding region
Okazaki fragments appear on the ____ strand during DNA replication.
lagging
During replication, because the RNA primers are removed, a gap is found on the ____ strand. With each round of replication, this means what happens to chromosome length?
lagging chromosomes shorten throughout replication
What is significant about the bond between the 2nd and 3rd phosphate in ATP or GTP?
large amount of energy stored here and, when released, is used for cellular function
The new DNA strand that grows continuously in the 5' to 3' direction is called the ____.
leading strand
Why are there "leading strands" and "lagging strands" during replication?
leading strand synthesized continuously and lagging strand synthesized discontinuously b/c DNA can only be synthesized 3' --> 5' and the two strands run antiparallel
As the two parental (template) DNA strands separate at a replication fork, each of the strands is separately copied by a DNA polymerase III (orange), producing two new daughter strands (light blue), each complementary to its respective parental strand. Because the two parental strands are antiparallel, the two new strands (the leading and lagging strands) cannot be synthesized in the same way. Drag each phrase to the appropriate bin depending on whether it describes the synthesis of the leading strand, the synthesis of the lagging strand, or the synthesis of both strands.
leading strand: made continuously, only one primer needed, daughter strand elongates toward replication fork lagging strand: multiple primers needed, made in segments, daughter strand elongates away from replication fork both strands: synthesized 5' to 3'
Let's conclude with an interesting fun fact... the human genome has about 20,000 functional genes. This DNA sequence only accounts for what percent of the entire human genome
less than 2%
Which of the following molecules is not required for a PCR reaction?
ligase
What does a phosphodiester bond link in DNA structure?
links 3' carbon of one deoxyribose to 5' carbon of the next
Where are telomeres located on a chromosome?
located at ends of chromosomes
All EXCEPT which of the following are desirable qualities in a model organism?
long life span
eumelanin
looks brownish black in color
pheomelanin
looks reddish yellow in color
During translation, what molecule bears the codon?
mRNA
What happens to mRNA before leaving the nucleus?
mRNA is modified: cap and tail (extra nucleotides) added to prevent attack from cellular enzymes and help ribosomes recognize mRNA mRNA is spliced: introns are removed and exons are joined together
The relationship between a gene and a messenger RNA is that ________.
mRNAs are made from genes
gyrase
makes single- or double-stranded cuts (breaks covalent bonds) that prevent supercoiling, catalyzes movements that undo twists and knots
How many alleles are in the population?
many - various mutations along length of gene, each coding for an allele
What are the consequences on the protein if there is a nucleotide substitution in the DNA?
may have no effect (silent mutations) or result in codon change that codes for a different amino acid (missense mutations) or a stop codon (nonsense mutations)
Melanin is found inside melanosomes inside what cell type?
melanocytes
Mendel's first law: law of equal segregation
members of a gene pair (alleles) separate equally into each gamete
If the sequence was much shorter, such as GA and repeated 50 times in tandem, this would be known as a _________________.
microsatellite, or short tandem repeat (STR)
A sequence such as TATAGCGTAGCTAGCT repeated in tandem (next to each other) 75 times is an example of a ______________________________.
minisatellite
The chapter begins by reviewing some important differences between mitosis and meiosis. List these:
mitosis: replicate somatic cells, produce 2 identical diploid cells, no variation produced, 1 equal division meiosis: produce gametes, 4 diploid cells, variation produced, 2 divisions (unequal in oogenesis)
A sister chromatid is also called a ____.
monad
Eukaryotic cells contain DNA in the mitochondria and chloroplasts (in addition to the nucleus). Is the organization of DNA in these organelles more similar to bacteria or eukaryotic chromosomes. Why?
more similar to bacterial chromosomes b/c they mostly exist as double-stranded, enclosed structures
Why are liver enzymes added in the Ames test?
most substances entering the human body must be metabolically activated to a more chemically reactive product
If you performed electrophoresis of two DNA molecules (one of 200 base-pairs and one of 250 base-pairs) on an agarose gel, would they move towards or away from the positively charged pole? Why?
move towards positive pole since DNA phosphate groups are negatively charged
____ is the random variation of genetic material that provides the basis for evolution.
mutation
How many chromosomes and chromatids are present after meiosis I (but before meiosis II)?
n chromosomes, still replicated 2n chromatids
haploid
n, normal chromosome complement of germ cells
What was the negative control in the Avery, MacLeod, and McCarty experiment?
negative control = no components of cell destroyed, expect mouse to die
The three essential components of the building blocks are:
nitrogenous base, pentose sugar, phosphate group
three components of a DNA monomer
nitrogenous base, pentose sugar, phosphate group
Adenine, guanine, cytosine and thymine are ____.
nitrogenous bases
Are the number of genes proportional to genome size?
no
Do homologous chromosomes ever pair in mitosis?
no
Can we predict relative genome size based on complexity of the organism?
no - for example, many plant genomes are much larger than the human genome
Are homologous chromosomes identical to one another?
no - one maternal, one paternal
Is ligase needed in PCR?
no - there is no lagging strand
Did Griffith determine DNA was the genetic material?
no, but did prove existence of chemical "transforming agent"
Is bacterial DNA compacted tightly around histones, like in eukaryotic cells?
no, but it does contain DNA-binding proteins
Down Syndrome most frequently happens as a result of non-disjunction in meiosis I or II? In the mother or the father during gamete formation?
nondisjunction in meiosis I in mother
Describe NIPGD:
noninvasive prenatal genetic diagnosis - fetal cells cultured and karyotyped via cytogenic analysis
What were the two different bacterial strains that Griffith used in his experiments?
nonvirulent strain, rough or non-encapsulated, and virulent strain, smooth or encapsulated
In eukaryotes, DNA and its associated proteins are called ____
nucleosomes
The building blocks of DNA are called:
nucleotides
The genetic material DNA consists of basic subunits called ________.
nucleotides
DNA is comprised of four different types of ____. Each one is made up of a pentose ____, a ____ group, and one of four ____.
nucleotides sugar phosphate nitrogenous bases
somatic mutations
occur in body cells
germ-line mutations
occur in gametes
If non-disjunction happens in meiosis I, what is the outcome?
one of the two cells produced in meiosis I will contain two homologs and the other will contain none, so two of the four cells produced in meiosis II will be diploid and two will have no chromosomes, resulting in two potentially trisomic and two potentially monosomic gametes
Chromatin assembly factors are specific to eukaryotic cells, why?
only found in eukaryotes b/c they make new histones for DNA and histone proteins are only found in eukaryotes
Do all eukaryotic cells express/produce telomerase? Why would an anti-telomerase drug be useful in treating cancer?
only malignant cells maintain telomerase activity and are this way immortalized, so an anti-telomerase drug may be effective in cancer treatment
In a prokaryote, such as E.coli, where does replication begin? Is it uni-directional or bi-directional?
oriC bidirectional
If DNA was the genetic material, then Hershey and Chase would find radioactive protein _______________ at the end of their experiment.
outside host cell
dispersive replication
parental strands cleaved during replication and dispersed into two new double helices
euchromatin
parts of chromosomes that are uncoiled
heterochromatin
parts of chromosomes that remain condensed in interphase and are mostly genetically inert, found primarily in cells that are less active/inactive
What kind of bond is formed between successive amino acids during translation?
peptide bond
The ____ of an organism is defined as its observable sum of features.
phenotype
If we are referring to a trait for coat color in dogs and the dog looks black, this is the dog's ________________________. If you are told the dog has two different alleles, B/b, then this is the dog's ________________________.
phenotype genotype
What is bound to the 5' carbon in pentose sugars?
phosphate group
DNA ligase then forms ____ bonds between DNA Okazaki fragments.
phosphodiester
The classic Hershey and Chase (1952) experiment that offered evidence in support of DNA being the genetic material in bacteriophages made use of which of the following labeled component(s)?
phosphorus and sulfur
silent mutation
point mutation alters codon but does not change amino acid
nonsense mutation
point mutation leads to triplet coding for stop codon, terminated translation
Each of the following events occurs during mitosis except _______.
polar microtubules contract, pulling attached chromosomes toward the poles
DNA is a ____ of repeating monomers. In this case the ___ is the monomeric unit.
polymer nucleotide
DNA polymerase I was the first polymerase discovered (by Kornberg), but cells without it could still replicate their DNA in vivo. We now know that _____________________________ is the enzyme responsible for DNA replication in vivo.
polymerase III
If Avery had observed transformation using only the extracts containing degraded DNA, degraded RNA, and degraded protein, but NOT the extract containing degraded polysaccharides, he would have concluded that _______.
polysaccharides are the genetic material
Consequence of mutation in germ cell?
present in all/many tissue types
Consequence of mutation in somatic cell?
present in one specific tissue type
What is the centromere and what does the DNA sequence look like at the centromere?
primary constrictions along eukaryotic chromosomes, region at which sister chromatids remain attached after replication DNA sequences at centromeres of multicellular eukaryotes vary
DNA polymerases can extended a DNA polymer ONLY if a ____________ already exists to build upon.
primer
Now imagine a pool of polynucleotides, all of different sequences, but we are interested in knowing if the sequence above is in that pool. We could use your pentanucleotide as a tool, and we would call this a ______________. How could we detect or "visualize" this? (What would be attached to the pentanucleotide?)
probe may be radioactive/fluorescent to label for detection
What has the universality of the genetic code allowed scientists to do?
program one species to produce a protein from another species by transplanting DNA
Where would you find circular chromosomes?
prokaryotes (in nucleoid region), mitochondria and chloroplasts, viruses
Describe the differences in how the many genes are organized in the genomes of eukaryotes vs. prokaryotes.
prokaryotes: no/few introns, smaller spaces b/t genes eukaryotes: larger spaces b/t genes (may consist of repetitive DNA)
For a long time, there was not scientific agreement that DNA could be the genetic material. The other leading hypothesis was that ________________ was the genetic material.
protein
What did 35S label in the Hershey and Chase experiments? 32P?
protein DNA
Adenine and guanine, which have a nine-member double-ring, are called ____.
purines
tautomeric shifts
purines and pyrimidines exist in alternate chemical forms that differ by a proton shift and allow non complementary base pairing
transversion mutation
pyrimidine replaces purine or vice versa
Cytosine and thymine, which have a six-member single-ring, are called ____.
pyrimidines
Radiation is often used to kill cancer cells. Why might this work?
radiation creates free radicals that can alter bases, break phosphodiester bonds, and produce chromosomal deletions, translocations, and fragmentation thus, radiation can ruin cancerous DNA
loss-of-function mutation
reduces/eliminates function of gene product (protein may be altered or less abundant) typically recessive b/c one normal functioning alley can still produce normal phenotype
DNA ligase
removes RNA primers and joins Okazaki fragments in lagging strand
____ is the process that leads to the production of identical copies of the existing genetic information.
replication
During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a ____.
replication fork
S phase
replication of DNA of each chromosome
When scientists were first looking for the genetic material, they knew it had to possess four major characteristics, they were:
replication, storage of info, expression of info, variation by mutation
induced mutations
result from influence of extraneous factors
null mutation
results in complete loss of function (no mRNA or no protein produced)
gain-of-function mutation
results in gene product w enhanced or new functions (protein might be altered or more abundant)
What makes RNA different from DNA?
ribose replaces deoxyribose, uracil replaces thymine, and RNA is generally single-stranded
What is recombinant DNA technology and how is it direct evidence that DNA is the genetic material?
segments of eukaryotic DNA spliced into bacterial DNA and genetic expression in bacteria monitored presence of corresponding eukaryotic protein is evidence that DNA is directly functional in bacteria
Two months later, Watson & Crick proposed a model for what?
semiconservative mode of replication
gene
sequence of DNA encoding trait/allele
homologous chromosomes
set of one maternal and one paternal chromosomes that pair up inside cell during meiosis
When does a telomere shorten? What is the consequence of a shortening telomere?
shorten when cells divide, and shortening limits the number of times a cell can divide before becoming senescent or dying
pyrimidines
singe ring C, T, and U
What is haploinsufficiency?
single copy of recessive gene due to monosomy is insufficient to provide life-sustaining functions for the organism
What is a SNP?
single-nucleotide polymorphism: a nucleotide base substitution prevalent in large portion of population
What is the physical state of DNA after being denatured by heat?
single-stranded
As human populations evolved to be more hairless, what happened to skin color?
skin color darkened because melanin production increased
In the Ames Test, the appearance of his+ revertants in the presence of a non-mutagenic control compound indicates that _______.
some of the reversion mutations are not caused by the mutagen being tested
haplotype
specific combination of multiple SNPs not all holotypes actually exist in a population, and each individual has 2 haplotypes, one maternal and one paternal
What is a trinucleotide repeat sequence and what consequence might it have if in the coding region of a gene, as is seen with Huntington's disease?
specific short DNA sequence repeated many times when repeated in a coding region, can be translated into long tracks of glutamine, causing proteins to aggregate abnormally and cause diseases like Huntington's
Mutations that arise in nature, from no particular artificial agent, are called ________.
spontaneous mutations
single-stranded binding proteins (SSBPs)
stabilize DNA opened by helicase
The genetic material must be stable enough to maintain information in ____ from one cell to the next and one organism to the next.
storage
If one double-stranded DNA has a higher melting temperature than another, what does this tell us about the structure of this DNA?
strand w higher melting point has a higher percentage of G-C base pairs (as these have 3 hydrogen bonds, where A-T pairs have 2)
genomics
study of structure, function, evolution of genes/genomes
Garrod didn't work directly with genes, but what did he propose was the reason for different phenotypes in the individuals he was studying?
suggested genes dictate phenotypes through enzymes, and that inherited diseases reflect an inability to produce an enzyme
____ is the point-by-point pairing of homologous chromosomes during prophase of meiosis I.
synapsis
Reverse transcriptase is an enzyme found in association with retroviral activity. It has the property of ________.
synthesis of DNA from an RNA template
During translation, what molecule bears the anticodon?
tRNA
All EXCEPT which of the following are examples of repetitive DNA?
telomerase gene DNA
The purpose of the Ames Test is to _______.
test the mutagenic effects of chemicals
When a solution of cesium chloride (CsCl) is subjected to high-speed centrifugation, a stable density gradient is formed. Meselson and Stahl found that when cell contents were subjected to centrifugation with a CsCl solution, a band of DNA formed at the CsCl density that matched the density of the DNA. This technique is called density-gradient centrifugation. The test tubes below show the results of density-gradient centrifugation of five different DNA samples. Drag the description of each DNA sample to the appropriate location to identify the expected appearance of the DNA band(s) after density-gradient centrifugation.
test tube 1 - DNA from E. coli cells grown in N14 test tube 2 - DNA containing one strand of 15N-DNA and one strand of 14N-DNA test tube 3 - DNA from E. coli cells grown in 15N test tube 4 - a 1:1 mixture of DNA from cells grown in N14 and cells grown in N15 test tube 5 - a 1:1 mixture of DNA from cells grown in 14N and 15N, heated (to disrupt hydrogen bonds) and cooled (to allow reannealing)
____ are synapsed homologous chromosomes, which are composed of four chromatids.
tetrads
What is the difference between metaphase of mitosis and metaphase I of meiosis? How is this linked to genetic variation?
tetrads align on metaphase plate, as opposed to individual chromosomes lining up in mitosis law of independent assortment: random arrangement of maternal/paternal chromosomes w/in tetrads creates variation in gametes
The discontinuous aspect of replication of DNA in vivo is caused by ________.
the 5' to 3' polarity restriction
RNA differs from DNA in all EXCEPT which of the following ways?
the 5'-3' orientation of the polynucleotide strand
Mendel's second law: law of independent assortment
the equal segregation of one allele pair is independent of the equal segregation of the other allele pair during gamete formation
The Beadle and Tatum hypothesis has since been refined by scientists later in history to:
the function of a gene is to dictate the production of a polypeptide
What was the conclusion of the Avery, MacLeod, and McCarty experiment?
the mouse injected w bacteria w removed DNA lived, demonstrating DNA was transforming factor
The phenotype of an organism is __________.
the observed features of an organism
Describe figure 10-16 and what telomerase accomplishes during this process.
the telomerase enzyme binds to the 3' G-rich DNA tail and constructs repeating telomere sequences; primase and DNA polymerase then fill the gap, and DNA ligase seals it when the primer is removed
Immediately after the primers have annealed to the target sequence, _______.
the temperature is raised so that taq polymerase can extend the primers
What does a linked SNP tell us?
there is an association b/t linked SNP that is easily genotyped w a nearby gene variant
The role of the primers in PCR is _______.
to define the target region and provide a 3' end that can be extended by taq polymerase
What was the purpose of these experiments? [Avery, MacLeod, and McCarty]
to determine the exact molecular species of the "transforming principle"
Electrophoresis of DNA is used for what purpose?
to separate different sized fragments of DNA/RNA
genome
totality of all genetic material in a given organism
untranslated region
transcribed to initial mRNA, found in "mature" mRNA that leaves nucleus, but is not translated into protein
RNA synthesis from a DNA template is called __________.
transcription
transcription
transfer of genetic info from DNA to RNA, occurs in nucleus
translation
transfer of genetic info from RNA to protein, occurs in cytoplasm
When a gene from a bacterium is inserted into a corn plant, we would call this corn plant a __________________ organism. Why is this done with crops?
transgenic advantageous b/c of traits such as resistance to herbicides, insects, and nutritional enhancements
Are tautomeric shifts transitions or transversions?
transitions
What is the process of synthesizing proteins from mRNA sequences?
translation
How does the percent of human genome containing transposons compare to the amount coding for genes?
transposons are about 50% of genome and gene coding sequence DNA is about 2%
When three nucleotides are bound together we call this a __________________. When we have about 20, we call this an ___________________________________. (When we talk about PCR, we'll also call these "primers") When we have long chains, we call this a ____________________________________.
trinucleotide oligonucleotide polynucleotide
The flow of information from gene to protein is based on a _________ code.
triplet
G and C are present in both DNA and RNA.
true
T/F: A chromosome may contain one or two chromatids in different phases of the mitotic or meiotic cell cycle.
true
T/F: An intron is a section of an RNA that gets spliced out.
true
T/F: DNA has no sulfur, and proteins have no phosphorus.
true
T/F: DNA strand replication begins with an RNA primer.
true
T/F: Guanine and adenine are purines found in DNA.
true
T/F: If a typical G1 nucleus is 2n and contains 2C (two complements) of DNA, a prophase I cell is 2n and contains 4C of DNA.
true
T/F: In general, DNA replicates semiconservatively and bidirectionally.
true
T/F: Many chemicals are more mutagenic after being processed in the liver.
true
T/F: Most human transposons appear to be inactive.
true
T/F: Nondisjunction is viewed as a major cause of aneuploidy.
true
T/F: S phase is the part of interphase when DNA duplication takes place.
true
T/F: The E. coli chromosome is circular and double-stranded DNA.
true
T/F: The triplet AUG is commonly used as a start codon during translation.
true
T/F: When considering the structure of DNA, we would say that complementary strands are antiparallel.
true
T/F: When treating an organism with a mutagen, although it is possible that homozygous mutations will occur, it is more likely that most new mutations will be heterozygous or hemizygous.
true
True or false. These two repetitive types of sequences do not code for genes. (referring to minisatellites and STRs)
true
All of the following events occur during normal meiosis except _______.
two haploid gametes fuse to form a diploid cell
What is a thymine (pyrimidine) dimer and what is its effect on your DNA?
two identical pyrimidines on the same strand of DNA bound together, often produced by UV radiation dimers distort DNA conformation, inhibit normal replication, introduce errors, partially responsible for killing effects of UV radiation on cells
conservative replication
two new strands come together and parent strands reassociate
If non-disjunction happens in meiosis II, what is the outcome?
two of the four cells produced in meiosis II will be haploid, one will be diploid, and one will have no chromosomes, resulting in two potentially normal, one potentially trisomic, and one potentially monosomic gametes
What makes up the protein component of a nucleosome?
two tetramers of histone proteins
helicase
unwinds DNA helix into single strands
Why was sedimentation equilibrium centrifugation used in their experiments?
used to measure ratio of 15N:14N in successive generations via density bands
What are the consequences on the protein if there is a nucleotide insertion or deletion in the DNA?
usually have larger or more disastrous consequences b/c adding/subtracting nucleotides will alter triplet reading frame
How did their experiments rule out dispersive replication?
when heated, denatured, and separated, densities of single-stranded DNA were either 15N or 14N, but not a hybrid of the two - not consistent w dispersive mode
Besides Down Syndrome, do any other human aneuplodies survive to birth?
yes - Patau syndrome (47, 13+) and Edwards syndrome (47, 18+) no monosomies survive
DNA polymerase makes mistakes during replication. When it does happen, can mistakes be repaired? If so, how?
yes - exonuclease activity allows excision of incorrect nucleotides, known as proofreading
Do both the leading and lagging strands of the DNA get replicated at the same time? How?
yes b/c lagging strand gets spooled out to form a loop
