Molgen Final long/short answer
You are studying the body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown); br (red); bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The Bg allele is dominant to by but recessive to br. (a) You cross a pure breeding brown spider with a pure breeding red spider. Diagram the cross and predict the genotype and phenotype of the progeny. (b) You cross a pure breeding brown spider with a pure-breeding green spider. Diagram the cross and predict the genotype and phenotype of the progeny. (c) You cross the progeny from part (a) and (b). Diagram the cross and predict the genotype and phenotype of the progeny. (d) You cross the non-brown progeny from part c to a pure breeding yellow spider. Diagram the cross and predict the genotype and phenotype of the progeny.
(a) B/B x br à B/br (all brown) (b) B/B x bg à B/bg (all brown) (c) B/br x B/bg à B/B (brown), B bg (brown), Bbr (brown), brbg (red) (d) Brbg x byby à brby (red) bgby (green)
Present a description of the molecular mechanism of the mutagenic action of any two of the following mutagens: 5-bromouracil, proflavin, ultraviolet light
- Proflavin adds or removes single bases from DNA, thus causing frameshift mutations - Ultravioloet light causes thymine dimers
3 differences between stem and somatic cells
- Somatic cells are in G0, stem cells cycle - Somatic cells are differentiated, stem cells can give rise to cells unlike themselves - Stem cells are more adversely affected by chemotherapeutics than somatic cells
Describe the phenotypic ratios of progeny from the following crosses and explain why they occur: A. A wild type male with an IGF hetero female B. A wild type male with a dwarf IGF hetero female C. An IGF het male with a wild type het female D. A dwarf IGF het male with a wild type het female
- The IFG2 gene is maternally imprinted, so a mutation from the mother will not affect the offspring, hence all offspring from an IFG2 het mother will be normal. - Half of the offspring from a het IGF2 male will be dwarfed, as the male is the only parent that can supply IGF2 genetic information to the offspring
Methods to produce mutations in forward genetics
- UV: will give deletions/big changes - ENU or EMS: make point mutations, which will give nulls, gain of funtion
Describe some important differences between bacterial and eukaryotic cells that affect the way in which genes are regulated.
-Bacterial genes are frequently organized into operons, the genes within the operons can be translated -In eukaryotes, the chromatin must assume a more open state for access by transcription factors -Activators appear more common in eukaryotic cells than bacterial cells -Eukaryotes, the nuclear membrane separates transcription from translation which results in a greater diversity of regulatory mechanisms
Describe the 3 distinct genetic regions of the human Y chromosome
-PARs= pseudoautosomal regions -NRY= non-recombining region of the Y -SRY= sex-determining region
What are the three classes of "functional" RNAs (not including mRNA)? Briefly describe the role of each class of functional RNA.
-tRNA: brings the correct amino acid to the mRNA during translation. -rRNA: major component of ribosomes. -snRNA: helps process RNA transcripts (especially, helps remove introns).
Interpret the meaning of an H2 value (broad-sense heritability) that approaches 1. 1.0. 2. 0.0
1. Almost all the phenotypic variation is determined by heredity/genetics 2. Almost all the phenotypic variation is determined by the environment
Name the three basic steps of PCR and describe the molecular processes that occur in each. How is each step induced?
1. Denaturation: temp raised to 94C. strands of DNA separate 2. Annealing: temp lowered to 50-65C, primer strands anneal to the template strand 3. Extension: temp is raised to 72C, taq polymerase synthesizes a complementary DNA strand from dNTPs
2 different types of DNA repair
1. Direct repair: DNA damage is repaired by directly changing the damaged nucleotide back to its original structure 2. Base excision repair: the damaged base is excised, and the entire nucleotide is replaced
Name and describe two classical experiments to demonstrate DNA is genetic material. Can RNA be genetic material? Can RNA be genetic material, provide example.
1. Hersey and Chase experiment 2. Transformation in bacteria (Griffith through Avery et al.) 3. Yes, RNA can be genetic material, ex. retrovirus
Mario Capecchi, Sir Martin Evans, and Oliver Smithies recently won a Nobel prize for gene targeting (gene knockouts) in mice. Describe the steps involved in creating a knockout mouse.
1. In vitro mutation of the target gene in embryonic stem cells 2. ES cells containing a mutated gene being studies are introduced into mouse blastocysts - Chimeric mice contain tissues derived from either the transplanted ES cells (white) or the host cells (brown) - These cells can contribute to both the germ cell and somatic cell populations 3. Chimeric mice are mated to assess whether the mutation is incorporated into the germ lines 4. Heterozygous mice for the gene mutation are mated to produce mice that are homozygous for the mutated gene
Kornberg used the phage PhiX14 to demonstrate NDA pol I was able to produce biologically active DNA in vitro. Briefly describe the experimental methods that he used to draw the conclusions that DNA pol I could produce biologically active DNA.
1. Initial (+) strand of PhiX174 was labeled w/ 3H, added to DNA pol 1, ligase, bromouracil and 32 labeled dNTP to produce (-) strand 2. dsRF was nicked, made single stranded, and new (-) strand was isolated following centrifugation 3. (-) strand was used w/ DNA pol 1, ligase, unlabeled dNTPs to produce a new (+) strand in vitro 4. New (+) strand was isolated by gradient centrifugation 5. New (+) strand was successfully used to infect E coli and produce new PhiX174 phage particles 6. Demonstrated that DNA pol 1 was capable of producing biologically active DNA in vitro
List the following events in the pre-RNA processing of a one intron-two exon gene in correct sequence order:
1. Transcription of the DNA template into the pre-mRNA molecule 2. Addition of the 5' cap 3. Recognition and binding the 3' AAUAAA sequence by specific protein factors 4. Cleavage at the poly(A) site 5. Addition of the poly(A) tail 6. Attachment of snRNP U1 to the 5' splice site 7. Transesterification reaction at the branch point adenine 8. Release of lariat structuer 9. Splicing together of exons 10. Export to the cytoplasm Order: 3 8 4 5 6 1 2 9 10 7
3 key differences between a genomic and a cDNA library?
1. cDNA library represents only transcribed regions of the genomes 2. All genes are equally represented in genomic library while cDNA reflects the level of expression of a gene in a particular cell type or tissue 3. cDNA library contains only sequences found in mature mRNA- introns are removed
For a particular plant, red flowers (A) are dominant over yellow flowers (a). An initial cross was made between a plant that was true-breeding for red flowers, and another plant true-breeding for yellow flowers. F1progeny, all having red flowers, were allowed to form seeds (through self-fertilization), which were then planted to generate F2 progeny. Pollen from all the resulting F2 plants was pooled and used to fertilize true-breeding yellow plants. What proportion of the progeny resulting from this cross would be expected to have yellow flowers?
1/4
Apart from the enzyme, what 3 DNA molecules are required? What must be true about the sequences of these molecules? Note that dNTPs are individual nucleotides, not DNA molecules.
2 primers, 1 template, dNTPs. The primer sequences must be complementary to the ends of the sequence to be amplified.
You determine that you have only 3 copies left of an important DNA fragment, so you decide to amplify it. Using flanking primers, how many PCR cycles would you have to run to generate over one billion copies of the fragment?
28-30 cycles
Difference between test cross and backcross?
A backcross is when an F1 individual is tested back with one of the parents. A test cross is when an F2 individual is crossed with a known homozygous recessive individuals to see what trait it contains and if it is heterozygous.
In the genetic map of the human genome, one map unit is approximately 850,000 bp, For the genome of the eukaryotic yeast Saccharomyces cerevisiae, one map unit is approximately 3000 bp. What is a map unit, and why is it so different in these two different types of organisms?
A map unit is the amount of measured recombination between two linked points in a genome. Because one map unit in humans is many more base pairs than in yeast, the amount of homologous recombination per DNA length must be lower in humans than in Saccharomyces cerevisiae.
Give a brief definition of the term genetic equilibrium
A population in which the frequency of a given gene remains constant from generation to generation
What is meant by the term photoreactivation repair?
A process described in E. coli in which UV induced DNA damage can be partially reversed if cells are briefly exposed to light in the blue range of the visible spectrum
What is a map unit?
Amount of measured recombination between 2 points in a genome.
Why is it possible to "map" the centromere in Neurospora and not in most other organisms?
Ascospores are held in order as meiotic products. This order is dependent on centromere migration, and a comparison of ascospore patterns allows one to determine whether crossovers have occurred. Quantifying such crossovers allows one to estimate map distance between the gene in question and the centromere.
Compare the inheritance of traits that are governed by genes on autosomal chromosomes w/ the inheritance of traits governed by mitochondrial genes
Autosomal genes are inherited from the mother and father, while mitochondrial genes are usually inherited solely from the mother
Describe two ways in which bacterial DNA differs from eukaryotic DNA
Bacterial DNA is circular and not complexed to histone proteins.
What binds to a core promoter, consists of general transcription factors and RNA polymerase.
Basal transcription apparatus
Genetic Material must replicate faithfully, How does double-stranded nature of DNA give this property?
Bc of the complementary base-paring rule when given one strand of DNA you can find the sequence of the other strand. Each strand used as a template will generate 2 DNA molecules of identical sequence.
Why do insertions and deletions often have more drastic phenotypic effects than base substitutions do?
Because amino acid codons consist of three nucleotides, insertions and deletions that involve any multiple of three nucleotides will leave the reading frame intact. However the addition or removal of one or more amino acids may still affect the phenotype. Insertions or deletions that do not alter the translation reading frame are called "in frame" insertions and deletions.
Individuals with the same genetic background and a high degree of homozygosity are said to be isogenic. Of what value are isogenic strains in genetic studies?
Because the genetic background is the same (or at least very similar), phenotypic variation must be due to nongenetic factors
Compare and contrast positive and negative control of gene expression in bacteria.
Both forms of control result from an interaction of a molecule (usually considered to be a protein) with the genetic material (either RNA or DNA). Positive control results when the interaction stimulates transcription, whereas negative control occurs when the interaction inhibits transcription.
Define the term broad-sense heritability. What is implied by a relatively high value of H2? Express aspects of broad-sense heritability in equation form
Broad-sense heritability (H2) refers to the degree to which phenotypic variation is due to genetic factors. A very high value indicates that the environment had a relatively low impact on phenotypic variation. VP= VE + VG + VGE
Two "naked" double stranded fragments of DNA are exactly the same length. At 89 deg fragment A has completely denatured while fragment B is still double stranded. How do they differ?
Can be made of different structure, causing them to react differently in the same temperatuer
What is the Xist RNA and what does it do? What happens to an X chromosome that can't make it?
Coats the X chromosome are recruits the polycomb repressive complex 2 to cover the chromosome to heterochromatin. W/o it the X can't undergo inactivation
What is a cDNA molecule?
Complementary DNA, made form RNA in reverse transciption
A condition in which a gene or group of genes is expressed all the time.
Constitutive
2. Explain why the genetic map distance between two genes on the same chromosome may be inconsistent with the physical map distance, E.g for three loci A, B, and C, on the same chromosome, explain why the genetic distance might be A-(2o centrimorgans)-B-(20 cM)-S, while the physical distance might be A-(200 kilobases)-B-(100 kb)-C.
Different regions of the chromosome are more prone to recombinations than others.
How do incomplete penetrance and variable expressivity differ?
For incomplete penetrance, not everyone with the genotype will express the phenotype. For variable expressivity, everyone with the genotype expresses the phenotype to some degree. Of course, some traits may (and often do) exhibit both incomplete penetrance and variable expressivity.
What is the difference between a tumor suppressor and an oncogene?
Oncogenes tend to be factors that increase cell growth, while tumor suppressors are cell cycle brakes.
Define gene regulation. What are three ways gene regulation can be controlled in a cell?
Gene regulation is defined as the control of a gene's transcript and its protein product. It can be achieved by altering either the transcription of the gene (RNA level), the translation of the protein from that transcript, or by altering the structure of DNA such that transcription cannot occur.
Crossing over is often reduced around centromeric regions of chromosomes. If you were trying to construct a genetic map of two linked marker loci in this region, what results might you obtain and why? How would the genetic map correspond to the physical map?
Genes mapped based on recombination will appear to be very close together in centromeric regions due to low rates of recombination. Distances between the same genes on the physical map may be much greater when compared to other regions of the chromosome.
What the term for the equation used to examine the relative importance of genetic versus environmental factors?
H^2= Vg/Vp= variation of genetics/ variation of phenotype
In zoo animals, inbreeding often occurs because there is a lack of a sufficient pool of breeding individuals. Under such conditions, what characteristics often attend inbred organisms?
Higher frequency of aberrant phenotypes and higher mortality rates
Which of the following does NOT happen to inactivate X chromosomes?
Histone acetylation
Difference between homologous chromosomes and sister chromatids
Homologous chromosomes carry the same genes, but may have different alleles. Sister chromatids are duplicates and are identical in sequence.
Describe the difference between meiosis I and meiosis II
Homologs pair and segregate in meiosis I, sister chromatids are paired and segregate in meiosis II. Crossing over only occurs in meiosis I.
The Meselson and Stahl experiment provided conclusive evidence that DNA replication in E. coli is semiconservative. Imagine that DNA replication were conservative, rather than semiconservative. What pattern of bands would occur in a CsCl gradient after the first generation of replication? What pattern of bands would occur after the second generation of replication?
In a semiconservative DNA, the DNA splits and two new complement strands are made with either strand. If DNA replication were conservative, there would be two bands after the first generation of replication with 15N/15N and 14N/14N. This would happen bc the original 15N strand would stay "conserved" and not change, while a new 14N bands would be made. 15N/15N and 14N/14N bands would continue throughout future replications, as these structures would not form something new together.
Nucleic acid blotting is commonly used in molecular biology. Two types, Southern blots and northern blots, involve gel electrophoresis and a filter, which holds the nucleic acid. Briefly describe the procedure of "blotting" in this context and differentiate between southern and northern blots.
In a southern blot, the DNA to be "probed" is cut with a restriction enzyme, then the fragments are separated by gel electrophoresis. Alkali treatment of the gel denatures the DNA, which is then blotted onto the filter (nylon or nitrocellulose). A labeled probe (DNA or RNA) is then hybridized to complementary fragments on the filter. In a northern blot, RNA is separated in the gel and probed with the label DNA.
General categories of mutations?
Induced, morphological, regulatory
Describe the role of the various types of nucleic acids in the storage and expression of information in living organisms.
Information contained in the base sequences of DNA is transcribed into a variety of RNAs. Certain RNAs (tRNA) carry amino acids to the site of translation where proteins are assembled. Other RNAs (mRNA and rRNA) provide a mechanism for ordering the sequence of amino acids in proteins.
What might be a reasonable function of restriction endonucleases in a bacterium, distinct from their use by molecular biologists?
It may identify and cut out viral DNA
Fill in the blanks in the "level of transcription" column of this table with: + for high levels of transcription, and - for minimal levels of transcription of the lac operon. Consider regulation of both the lac repressor and CAP (catabolite activator protein). The strain is wild type, with no partial diploidy. Medium conditions: - High glucose, no lactose - no glucose, high lactose - High glucose, high lactose - No glucose, no lactose
Level of transciption (in order): -, +, -, -
Provide a simple definition of inbreeding:
Mating of closely related individuals which tends to increase the number of individuals homozygous for a trait
Explain the experimental method of "differential labeling"
Method used to differently label two molecules of interest in an experiment so that investigators are able to distinguish between the two molecules in the result.
Another word for a "DNA chip" (microscopic spots of oligonucleotides bound to glass that can be fluorescently labelled to identify levels of expression).
Microarray
Describe the general structure of a transcription factor. What two domains do transcription factors tend to have?
Modular shaped, dna binding domain (DBD) and trans activating domain (TAD)
Difference between neutral and silent mutations?
Neutral mutations are changes in the DNA sequence that alter the amino acid coding sequence of a polypeptide, but do not change its biological function. Silent mutations are changed in DNA sequences that produce synonymous codons specifying the same amino acid as the original, non-mutated sequence.
Are Okazaki fragments formed on the leading strand during DNA replication?
No, Okazaki fragments are formed on the lagging strand, which replicates discontinuously
A friend gave you the following molecule and told you that it was a fragment of his RNA. Do you believe him? Justify your answer. 5' TCC TGA CGA TGC TAC CGA 3'
No, it the molecule was RNA the T's would be replaced with U's.
What is the difference between positive and negative control? What is the difference between inducible and repressible operons?
Positive transcriptional control requires an activator protein o stimulate transcription at the operon. In negative control, a repressor protein inhibits or turns off transcription at the operon. An inducible operon normally is not transcribed. It requires an induced molecule to stimulate transcription either by inactivating a repressor protein in a negative inducible operon or by stimulation the activator protein in a positive inducible operon. Transcription normally occurs in a repressible operon. In a repressible operon, transcription is turned off either by the repressor becoming active in a negative repressible operon or by the activator becoming inactive in a positive repressible operon
A couple have a child with Prader Willi. The stress of the special needs child fractures thie relationship, and each remarries. What is the chance on another Prader Willi child for each parent?
Prader Willi is maternally imprinted, so mutant allele came from the father. He has half a chance of siring more Prader WIlli children, while the mother has only the lowest probability of doing so.
A major difference between eukaryotes and prokaryotes is that eukaryotes have a nucleus, whereas prokaryotes do not. Discuss the impact of having a nucleus on the creation of mature mRNA
Prokaryotes do not have a nucleus, so the translational machinery is able to attach to the mRNA as it is being synthesized, thus these is no time to process the mRNA. In eukaryotes, the translational machinery is not present in the nucleus, so there is time to process mRNA before it it transported from the nucleus to the cytoplasm and translated into protein.
What is meant by the term pseudogene?
Pseudogenes are nonfunctional versions of genes that resemble other gene sequences but that contain significant nucleotide substitutions, deletions, and duplications that prevent their expression.
What is the spliceosome?
RNA coded complex responsible fro intron-exon splicing in eukaryotes. Made of 5 ribonucleotide proteins (snRNPS)
What is the name of the process by which bacterial colonies (cells) are transferred from one agar plate to another, maintaining the same spatial pattern?
Replica plating
A "marker" in a genetic sense usually represents a site along a chromosome where a specific nucleotide sequence exists. What specific phrase is used when such markers are identified by restriction endonucleases and a particular set of DNA fragments is generated?
Restriction fragments length polymorphisms or RFLPs
Why is it that human males are so much more likely to express recessive sex-linked traits that females?
Sex-linked traits are carried on the X-chromosome. Since males only have one X, if a recessive trait is carried on it it will always be phenotypically expressed in males.
How can the expression of a gene be drastically altered by the presence of comparatively small numbers of RNA molecules? What is the term for this class of gene regulation?
Small RNA molecules are called siRNAs and miRNAs, and they affect RNA stability. They can cleave mRNA with a slicer enzyme and cause degradation, they inhibit translation, silence transcription, and cause degradation without a slicer present.(might want to mention the RISC or Rits complexes)
What enzyme is required for PCR? State the specific name of the enzyme, not just the type of enzyme.
Taq polymerase
A number of scientists have become interested in telomerase as a drug target. Why would they be interested in telomerase? How might cancer drug therapies that target telomerase work?
Telomerase is an enzyme that undergo continuous cell division is cells. Cells that lack telomerase exhibit progressive shortening of the telomeres, which leads to unstable chromosomes and ultimately apoptosis. Many tumor cells express telomerase, allowing them to infinitely replicate. If telomerase activity can be controlled, its possible to halt cancer cell growth. I strategy would be to target the DNA synthesis activity of the telomerase protein preventing the telomerase DNA from being synthesized.
What DNA sequence occurs at the end of the Tetrahymena chromosome? Give both the sequence and the name of the structure. How does this sequence affect the conclusion of chromosome replication?
Telomeres terminate in a 5'TTGGGG3' sequence, and telomerase is capable of adding repeats to the ends, thus allowing the completion of replication w/o leaving a gap and shortening the chromosome following each replication.
Intron frequency varies considerably among eukaryotes. Proved a general comparison of intron frequencies in yeast and humans. What about size?
The entire yeast genome has only about 240 introns, whereas some single genes in a human contain over 100 introns. In general, smaller genomes have smaller intron size in addition to lower intron number.
Briefly describe the structure and abundance of the lac repressor protein?
The lac repressor protein is encoded for on the lacI gene, and is able to diffuse throughout the cell and bind to any target sequence. It has a DNA binding domain (to bind the DNA strand), as well as a regulatory domain (which binds other small molecules)
Explain why mutations in the lacI gene are trans in their effects, but mutations in the lacO gene are cis in their effects.
The lacI gene encodes lac repressor protein that attaches to any operator, so it can affect the expression of genes on the same or different strands of DNA. LacO encodes the operator and affects the binding of DNA polymerase to the DNA, and affects the genes on the same strand. Feedback: The lac gene encodes the repressor protein, which can diffuse within the cell and attach to any operator. It can therefore affect the expression of genes on the same or different molecules of DNA. The lacO gene encodes the operator. It affects the binding of DNA polymerase (OR the lacI repressor) to the DNA, and therefore affects only the expression of genes on the same molecule of DNA.
Describe how the sigma subunit of E. coli RNA polymerase participates in transcription
The sigma subunit may give specificity to the RNA polymerase and play a regulatory function. It may be involved in the recognition or initation sites or promoters
Assume that one conducted a typical cloning experiment using pUC18 transformed an appropriate host bacterial strain (one carrying the lacZ completing region), and plated the bacteria on an appropriate X-gal medium. Blue and white colonies appeared. Which of the two types of colonies would most likely contain the recombinant pUC18? Explain.
The white colonies because of insertional inactivation of the lacZ component
Why are telomeres and centromeres particularly difficult to sequence?
They consist of highly repetitive DNA so strand slippage issues can confuse the determination of a consensus sequence.
What is the purpose of an antibiotic resistance gene in a plasmid cloning vector?
Used as a marker to indicate that the plasmid has been taken up
Describe an experiment in which transgenic mice were used to identify the male-determining region of the Y chromosome
When DNA containing only the mouse SRY is injected into normal XX mouse eggs, most of the offspring develop into males.
Regarding the tryptophan operon, trpR- maps a considerable distance from the structural genes. The mutation either inhibits the interaction with tryptophan or inhibits the repressor formation entirely. In the presence of tryptophan in the medium, would you expect the tryptophan operon to be transcriptionally active in this mutant? Explain.
With either of the two scenarios mentioned in the problem, absence of repressor function in a repressible system means that there would be no repression of the operon. The operon would be transcriptionally active.
Is it possible that the characteristic in the pedigree below could be x-linked recessive? If so, what are the genotypes of each individual (use alleles A and a)? If not, explain why not, giving specific genotypes.
X-linked recessive is possible, if I-1 is XaY, I-2 is XAXa, II-1 is XAY, and II-2 is XaXa
How is it that you inherited imprints from your parents but give off your own in your gametes?
Your parents imprints were erased early in gametogenesis in primordial germ cells, subsequently gametes were given imprints compatible with your gender.
In animals, the inability to make the pigment melanin results in albinism, a recessive somatic condition. Two normal parents, who have decided to have three children, have a first child that is albino (genotype aa). Determine the following probabilities. a. That the second and third children are also albino. b. That the second and third children are normal
a) 1/16 b) 9/16
What is the probability of drawing one card at random from a deck and obtaining the following? (A deck has 52 cards. Each card has a suit—spade, heart, diamond, or club—and a number [1(Ace)-10] or a face—jack, queen, king. Thus, there are 13 cards of each suit and four cards of each number or face.) a. The queen of diamonds b. Any heart c. A 10 (any suit) d. Any even-numbered card e. An even-numbered spade
a) 1/52 b) 13/52 c) 4/52 d) 20/52 e) 5/52
Huntington's disease is a late-onset disease caused by a single, dominant mutation. The following pedigree is for a family with a history of Huntington's disease. Those individuals who are already suffering from the disease are shaded black. However, some additional individuals in generations II and III also have the Huntington's allele and will develop Huntington's disease but have not yet shown symptoms. Assume that individuals marrying into the family have no history of Huntington's disease (that is, they are homozygous recessive for the gene). Also assume that the diseased male in generation I is heterozygous for the disease gene.
a) 1/8 b) 1/4 c) 1/2
The following cross produced 125 progeny: aaBbCcDd x AaBbccDD. Assume all the genes are unlinked and that the uppercase letters represent dominant alleles. a. How many offspring are expected to express the dominant phenotype for each gene? b. How many offspring are expected to have the genotype aaBBccDD? c. How many offspring are expected to have the genotype AaBbCcDd?
a) A= 1/2, B=3/4, C=1/2, D=1 b) 1/32, 4 individuals c) 1/16, 8 individuals
A test cross is performed on an individual to examine three linked genes. The most frequent phenotypes were abc and ABC a. What was the genotype of the individual tested? b. What is the order of the gene loci? c. Indicate the genotypes of each progeny class.
a) AaBbCc b) b a c c) Aabbcc, aabbcc, AABBCC
A plant with round seeds was crossed with a plant with wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled. a) What is the most probable genotype of each parent? b) What genotypic and phenotypic ratios are expected? c) What are the expected #s of progeny (400) total of each phenotypic class?
a) Assuming round (W) is dominant to wrinkled (w): Ww X ww b) 1:1 for both c) 200 of each (1:1 ratio of 400)
Assume that you have a garden and some pea plants have solid leaves and others have striped leaves. You conduct a series of crosses (a through e) and obtain the results given in the table. CROSS PROGENY solid striped (a) solid X striped 55 60 (b) solid X solid 36 0 (c) striped X striped 0 65 (d) solid X solid 92 30 (e) solid X striped 44 0 Define gene symbols and give the possible genotypes of the parents of each cross. Some crosses may have more than one potential genotype
a) Dd, dd b) DD, DD c) dd, dd d) Dd, Dd e) DD, dd
In the fruit fly, Drosophila melanogaster, a spineless (no wing bristles) female fly is mated to a male that is claret (dark eyes) and hairless (no thoracic bristles). Phenotypically wild-type F1 female progeny were mated to fully homozygous (mutant) males, and the following progeny (1000 total) were observed: Phenotypes Number Observed spineless 321 wild 38 claret, spineless 130 claret 18 claret, hairless 309 hairless, claret, spineless 32 hairless 140 hairless, spineless 12 (a) Which gene is in the middle? (b) With respect to the three genes mentioned in the problem, what are the genotypes of the homozygous parents used in making the phenotypically wild F1 heterozygote? (c) What are the map distances between the three genes?
a) Hairless b) wing bristles, light eyes, thoracic bristles c) 30 mu between spineless and hairless, 10 mu between hairless and claret, 40 mu between spineless and claret
Suppose that the red flower color (RR or Rr) is dominant to the white flower color (rr) in Petunia. A friend has a petunia plant with red flowers and wants to determine whether the plant is RR or Rr. In order to determine the genotype, you cross it with a white-flowered petunia. (a) What is the name of the type of cross performed? (b) How will this cross help you determine the genotype of the red flowered petunia? This is, how will the results from this cross differ if the red flowered petunia is RR vs Rr
a) Test cross b)You will observe different segregation in the testcross progeny, depending on the genotype of the red petunia. If the red petunia is RR, then all the testcross progeny will be red; if the red petunia is Rr, then the testcross progeny will be red (Rr) and will be white (rr)
The red kernel color in wheat is caused by the presence of at least one dominant allele from each of two independently segregating gene pairs (e.g., R-B-). Wheat plants with rrbb genotypes have white kernels, and plants with genotypes R-bb and rrB- have yellow kernels. If you cross a plant true breeding for red kernels with a plant true breeding for white kernels, a. what is the expected phenotype(s) and ratios of the F1 plants? b. what are the relative proportions of the phenotypic classes expected in the F2 progeny after selfing the F1 progeny?
a) all would have red kernals b) 9:3:3:1
The following table lists several genotypes associated with the lac operon in E. coli. For each, indicate with a "+" or a "_" whether Beta-galactosidae would be expected to be produced at induced levels. (Assume that glucose is not present in the medium.) No lactose // With lactose a. I+ O+ Z+ / F' I- O+ Z+ b. I- Oc Z+ / F' I- O+ Z- c. Is Oc Z+ / F' I+ O+ Z+ d. I- O+ Z+ / F' I- O+ Z+
a. -, + b. +, + c. +, + d. +, +
Briefly state and describe the four primary ingredients [other than DNA polymerase I] that are needed for the in vitro synthesis of DNA. Note that for the purposes of this question, buffering, temperature, and nonspecific concentrations are considered conditions, not ingredients.
dNTP, DNA template, primer DNA or RNA, Mg++
An enzyme that methylates cytosine on the 5 position de novo
dmnt3
This hypothesis suggests that many factors or genes contribute to the phenotype in a cumulative or quantitative manner
multiple factor
4 applications of PCR technology
paleobiology, cell free cloning, forensics, screening for genetic disorders
Describe the positive control exerted by the catabolite activating protein (CAP). Include a description of catabolite repression
regarding regulation of the lac operon, in the absence of glucose, CAP (dependent on cAMP and adenyl cyclase) binds to the CAP site and facilitates transcription (positive control). Transcription of the operon is inhibited in the presence of glucose (catabolite repression).
Briefly describe two major differences between RNA and DNA at the level of the nucleotide
ribose in RNA, deoxyribose is DNA Uracil is RNA, thymine in DNA
In the case of complete dominance in a population in equilibrium, we cannot tell which individuals are homozygous dominants and which are heterozygous. However, we can estimate the frequency of homozygous dominant and heterozygous genotypes if we know what?
the frequency of the homozygous recessives
