BISC 336 Final Exam
An advanced life form found in the water among the moons of juipiter was found to have a greater variety of amino acids (61 amino acids ) compared to life on earth (20 amino acids). How many basepairs are required for this greater complexity? Although this organism was able to create highly complex organs it was very susceptible to mutation. Explain?
(How many basepairs in the reading frame?) 4 - different nucleotides. 4^x = 61? Log4 61 = x, (Log 61)/(Log 4) = X, X= 3 A reading frame of 3, just like us No redundancy in the genetic code, each unique reading frame codes for a different amino acid. No wobble position.
b. In which parent and in which cells must this spontaneous mutation occur for it to be inherited? (hint: what happens if the mutation occurs in the heart.)
-Must occur in the mother, -in the oocyte/germline
)Sickle cell anemia and albinism are both recessive traits in humans. Imagine that a couple, already pregnant with fraternal twins, has just learned that they (the couple) are both heterozygous for both of these traits. As the couple's genetic counselor, the couple asks you what is the probability of having both of the twins be albino and have sickle-cell anemia
1 twin = ¼ * ¼ =1/16 2 twins = 1/16 * 1/16 =1/256= 0.004
Jim has an inherited mitochondrial disease caused by a mutation in the mitochondrial gene MT-JP, but nobody in his long family lineage also displayed such a disease, indicating it is likely a spontaneous mutation. Jim has 1 child who is unaffected, what is the probability his next child will be affected, assuming he marries an unaffected woman.
100%
Albinism in humans is inherited as a simple recessive trait. A normal male and an albino female have 6 children, all normal. What is the probability all the children are heterozygous
100%, however, father could also be heterozygous
With incomplete dominance, what is the ratio of phenotypes resulting from a monohybrid cross? What is the ratio of genotypes? a. What would it be for co-dominance? Phenotype and Genotype?
1:2:1, 1:2:1 1:2:1, 1:2:1
Name 1 way in which the concept of linkage disequilibrium is applied outside of the academic setting?
23andMe - find biogeographic admixture of individuals
Consider an organism that has a haploid-diploid lifecycle. If the diploid form has 54 chromosomes, how many homologous chromosome pairs does one of it's cells have prior to disjunction in anaphase I of meiosis?
27
Drosophila flies have 4 chromosome pairs, while mice have 18 chromosome pairs. How much total possible genetic variation can flies generate via independent assortment compared to mice?
2^4 (16) vs 2^18 (262,144)
If a typical somatic cell has 64 chromosomes, how many chromosomes are expected in each gamete of that organism?
32
10. Jeremy notices that his friend Dan (the son of Robyn, a single parent) has the same laugh and dimples as the longtime mailman. Ignoring ethical and privacy concerns, Jeremy decides that since he has just learned about PCR in class, he will perform a paternity test on the side during his BISC 336 lab to determine whether Mike is related to the mailman. He obtains hair samples from all three. >10 million DNA molecules are needed to analyze or sequence a polymorphism. Jeremy was only able to collect 5 cells from each individual. What is the minimal number of PCR cycles Jeremy will need to perform
5(2x) = 10,000,000; X = 21 cycles; (Log2 2,000,000 = X, X = 20.9)
You discovery a pre-maturely bald male mouse in your colony. Interested in the possible commercial funding opportunities in male-pattern baldness research. Your first task is to understand how this mutation is related to gender. What would you do to distinguish between a gene influenced by gender and one determined by a sex chromosome?
A trait influenced by gender will always show in males and never in females - A trait influenced by a sex chromosome will depending on the cross show in females
In a single PCR cycle consisting of 15 seconds at 94°C, 30 seconds at 50°C, and 1 min at 72°C, what 2) is happening in the step run at 50°C?
Annealing
What are the allele frequencies in a population for two independent loci, if (a) the first locus has just one allele, and (b) the second locus has four alleles?
B) p = 1.0; (b) p + q + r + s = 1.0
Each of the following situations would lead to pre-zygotic reproductive isolation, except for the situation when ______.
B. the progeny that result from mating are sterile
In an exotic species of bird, the difference between smooth feathers and ruffled feathers is controlled by a single gene: birds with a dominant allele, R, have smooth feathers, and birds homozygous for the recessive allele, r, have ruffled feathers. Birds with a dominant allele for a pigment gene, B, have black feathers and homozygous recessive bb birds have blue feathers. a. How would you set up a dihybrid cross between a black bird with smooth feathers (which happens to be homozygous for the dominant alleles of both genes), and a blue bird with ruffled feathers? Show the phenotypes and genotypes of the parents and F1 progeny.
BB (black) RR (smooth) X bb (blue) rr (ruffled) ---> F1 all Bb (black) Rr (smooth)
Why are Randomized controlled Trials not useful for identifying alleles/variants underlying the genetic basis of disease?
Because can't change an individual's DNA
Why does a small population lead to genetic drift? Does this lead to increased or decreased allelic diversity, why?
Because stochastic/random semi-low probable events can lead to homozygous allele fixation.
Explain why you would expect polymorphisms physically (on the chromosome) near to an allele under directional selection to not display random variation?
Because the closer a polymorphism is to another, the less chance of recombination happening to separate them.
How does the CAP regulate the lac Operon?
CAP and cAMP together bind to the promoter and help to recruit RNA polymerase. Without cAMP CAP doesn't bind to the promoter and RNA polymerase is not efficiently recruited to the promoter
What is different about Crispr/Cas9 and microRNAs?
Cas9 targets DNA, found in prokaryotes. Argonaute targets RNA, found in eukaroytes
Describe post-zygotic isolation. Give an example
Changes that occur after a zygote is formed that prevent genetic exchange through reproduction. For example, hybrid sterility or failure of hybrids to develop.
What 3 pieces of other scientist's data did Watson and Crick use to create their model of DNA.
Chargoff's rules of nucleotide ratios A:T, G:C 1:1, 1:1, G-C and A-T don't occur at the same ratio • Levene's structure of the sugars, phosphates, and bases(A, T, G, C) in nucleic acids • Franklin's X-ray crystallography of DNA- showing a helical structure
Lots of scientists were interested in understanding why children look like their parents? This question drives to the heart of our understanding of one of the important facets of life- how it passed from one generation to another. However, the data is very confusing, some children look very much like their fathers, while other children don't look like any of their parents. What were Mendel's breakthroughs that allowed him to answer this question.
Chose simple either/or traits Took a reductionist approach only examining one trait at a time Reciprocal crosses to isolate variables Counted lots of progeny
a. Why did Cell Biologists think Chromosomes could form the basis of genetic inheritance?
Chromosomes halved their number Chromosomes had paired structures
Many of the color varieties of summer squash are determined by several interacting loci: Wildtype squash are white, a recessive allele, a, causes yellow squash, while another recessive allele b, causes green squash. a) How would you test if these alleles are mutations in the same gene? And what result would you expect if they are not in the same gene.
Complementation test: a/+ x b/+, look at a/b plants. If they are not the same gene a/b plants would be white. They would complement each other.
In an exotic species of bird, the difference between smooth feathers and ruffled feathers is controlled by a single gene: birds with a dominant allele, R, have smooth feathers, and birds homozygous for the recessive allele, r, have ruffled feathers. Birds with a dominant allele for a pigment gene, B, have black feathers and homozygous recessive bb birds have blue feathers. d. What cross could you do to determine whether the chosen bird from part c is BB or Bb (assume that birds of all genotypes mentioned so far in this problem are available for crosses)? Indicate what the expected results would be if the bird is BB and if it is Bb.
Could do testcrosses, as follows: If BB: BB X bb (blue) ---> expect all Bb (black) If Bb: Bb X bb (blue) ---> expect 1/2 Bb (black), 1/2 bb (blue) Or could do crosses using the Bb F1 progeny generated in part a: If BB: BB x Bb —> expect all progeny black If Bb: Bb X Bb ---> expect 3/4 black, 1/4 blue
Having a BRAC mutation greatly increases your risk for breast cancer. However, individual BRAC mutations are rare. 23andMe gained authorization from the FDA to test for 3 BRAC mutations: -185delAG in BRAC1 -5382insC in BRAC1 -6174delT in BRAC2 a. What kind of physical mutation are these? (How do they affect the protein formed) b. What kind of functional effect will these mutations likely have? Why?
Deletions: Deletions of 2 or 1 bps will affect the reading frame; likely leading to premature stop codons Loss-of-function: Frame shifts that are likely to cause nonsense = hypomorphs or amorphs
If one is testing the goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the Chi-square analysis?
Df= number of observation-expectations pairs (classes) assessed - 1 = 3
She does not have the disease, what other data and information is going to allow you to give her the most definitive answer?
Does her spouse have any family history of the disease? (Partial credit - Genetic testing)
What non-coding DNA elements work in cis to control transcription?
Enhancers, Promoters, 3' UTRs, Operators, Histone modifications, methylation
Why are diseases related to heart cells not ideal for ex vivo gene therapy approaches?
Ex vivo gene therapy requires you to take cells out, grow and manipulate them and then put them back so they can resume normal function. One can not take heart cells out and just put them back
Name one cause of DNA mutations AND What type of mutation might this method create?
Example: X-rays = double strand breaks = insertions or deletions = frameshifts => nonsense UV = Thymine dimers, if repaired wrongly => missense alleles => depends on position - hypomorphs most likely, but could be silent or premature stop - nonsense. -Other causes of DNA mutations - polymerase mistakes, polymerase repeats, Base-analogs, ENU-mutagenesis, etc.
What major world problem would you use Crispr/Cas9 to solve? a. Name one obstacle you would have to overcome to implement your solution?
Examples we talked about in class included mosquitos - using gene drives, and Duchene muscular dystrophy In these cases: making sure crispr/cas9 is efficiently propagated to the next generation, via homologous recombination in the first case. Or getting crispr/cas9 into somatic cells in the second case.
b. She wants to find her ethnic ancestry? How will you advise her? Why?
Genetic sequencing does not reveal ethnic ancestry; just biogeographical admixture.
Specific pediatric cancers are caused by mutations creating a unique sequence in a proto-oncogene change that gene to an oncogene. a. What type of physical and genetic mutation most likely underlie this change?b. Is this disease suitable for gene therapy-using a transgenic technique? c. What technique might this disease be suitable for? What is a drawback of this second technique that you would have to watch out for? d. Cancers are not simply about growth, mutations in what type of cell biological pathways often underlie Cancer?
Genetic: Hypermorphic Physical: Missense No, adding a wildtype copy of a proto-oncogene will not decrease the amount or activity of that gene, it would make it worse. Crispr/Cas9 - You could target the mutation specifically and thus not affect the wild-type copy. This would disable the oncogene, by making a indel. -You would have to watch out for possible off-target effects. Defects in survelliance pathways - such as DNA repair or cell cycle checkpoints, or apoptosis
Shh, Gli3 and IFT (ll) are all part of a signaling pathway which is a dependent pathway. Can you further describe the relationship between shh and g
Gli3 is downstream of Shh
The recessive sonic-hedgehog mutation (shh) causes a phenotype called syndactyl in which a human hand only grows 1 finger (called a digit). While another recessive mutation in gli3 causes a phenotype called polydactyl in which too many fingers form on a single hand (>5). The recessive mutation ling-ling (ll) in a gene important for cilia also causes polydactyl. a) You intercross shh/+ x gli3/+ animals; and then intercross the double heterozygous F1 animals (shh/+; gli3/+ x shh/+; gli3/+) your double mutants from this cross (shh/shh; gli3/gli3) cause polydactyl. What is the relationship between shh and gli3?
Gli3 is epistatic to Shh
b. How did Morgan prove genes are on chromosomes
He used sex chromosomes to show that the white allele is X-linked. Based on the nonmendelian ratio
16)Mendel postulated inheritance occurring through paired unit factors. What is the physical basis of paired unit factors? Explain.
Homologous chromosomes. Mendel postulated pairs of unit factors, homologous chromosomes represent those pairs.
Would gene therapy using a transgenic approach be suitable to treat Huntington's disease? If not what technique would?
Huntington's disease is a dominant gain-of-function disease, in which increased number of repeat causes neurodegeneration. Increase the amount of endogenous gene is not going to help in this case, because it doesn't reduce the number of repeats.
In cats, having extra ears is a recessive autosomal trait. A population of cats in Hardy-Weinberg equilibrium for this trait has dominant allele frequency (p) of 0.9. If there are 100 cats in the next generation, how many will have extra ears?
If p = 0.9, then q = 0.1. If the population is at equilibrium, the allele frequencies do not change from generation to generation. To figure out how many cats would have the recessive trait: q2×(# of cats) = (0.1)2× (100) = 1
A child often has traits that look like a blending of both our parents, instead of just one parent. This observation appears to go against Mendel's rules of inheritance? Name one explanation.
Incomplete dominance multiple genes important for a trait
Name two evolutionarily significant benefits of meiosis that are not present in mitosis
Independent assortment and recombination create variability
A woman comes to you a genetic counselor and indicates that she might be color blind., she just doesn't know. Something about this makes you suspicious, especially since you know that colorblindness is X-linked and thus very rare in women- what is the one question you want to ask her family.
Is her father colorblind
8. How could you test whether a non-coding RNAs is a lncRNA vs a microRNA
Is its function Dicer-dependent?
A spontaneous mutation occurs in one of the copies of MT-TK, a gene found in mitochondrial DNA. MT-TK generates a tRNA required to make proteins for mitochondrial function. a. Since there are many copies of MT-TK and only 1 contains a mutation, what about this mutation would allow it to cause a phenotype?
It can be dominant
How does acetylation to the histone tail affect transcription?
It helps to increase transcription by opening up DNA.
What elements act in Cis?
Lac Operator, Lac Promoter
Which elements are expressed in the presence of glucose and lactose
LacI
The following regulatory and non-regulatory elements are involved in the lac Operon: LacI, Lac operator, Lac Promoter, LacZ, Lac A, LacY a. Which elements are expressed in the presence of lactose
LacI, LacZ, LacZ, LacY
Name 1 way in which scientists use concept of linkage disequilibrium to identify disease alleles?
Linkage disequiplibrium means that polymorphic markers are closer to a disease allele and thus will tend to co-segregate with that allele. Thus, one can look for polymorphic markers that segregate with disease alleles greater than unlinked alleles, therefor identifying the approximate location of the disease allele.
Jim has an inherited mitochondrial disease caused by a mutation in the mitochondrial gene MT-JP, but nobody in his long family lineage also displayed such a disease, indicating it is likely a spontaneous mutation. a) In which parent (Mother, Father or both) did this mutation occur? Why?
Mother, mitochondrial genes are always inherited from mother
A certain type of congenital deafness in humans is caused by a rare autosomal recessive gene. In a mating involving a deaf man and a deaf woman, could some of the children have normal hearing? Explain your answer.
No, since both man and woman must be homozygous recessive.
What happens during nondisjunction?
Not all chromosomes separate properly/evenly
What is one argument for Junk DNA not being important. How would you prove that argument
Onions have variable amount of junk dna, some large and some small, yet it still makes an onion. • Remove all the junk DNA and see what happens? • Transfer the extra DNA into the small genomed onion
After graduating, your family calls you with any random science question. One day your Aunt asks you if she should use 23andme to sequence her DNA. a. She wants to find out if she's at risk for breast cancer. How will you advise her? Why? Any other information you want to know?
Only makes sense if she has information to suggest she might have one of the three variants. For example, they are most prevalent in Ashkenazi population. Otherwise, unlikely to be informative
Why were true breeding plants important to Mendel
Otherwise he might have had a mixed population homozygous and heterozygous dominant hybrids
in class we discuss a series of experiments examining the genetic basis for LDL levels. Researchers examining families with hypercholestemia (high LDL levels) found missense alleles in PCSK9. While researchers examining individuals with very low LDL levels found nonsense alleles in PCSK9. How does PCSK9 regulate LDL levels? Explain your reasoning?
PCSK9 promotes LDL levels -A Nonsense allele will remove function. While a missense allele could be anything from amorph to hypomorph to hypermorph (which is most likely in this situation considering it has the opposite phenotype as the nonsense allele).
Sasha is studying a Holt-oram syndrome; a type of congenital heart disease that is caused by a few genes usually just 1 mutant gene. What type of analysis should she use to study this disease? Why?
Pedigree - monogenic, large effect size
What types of alleles/variants are identified in pedigrees compared to GWAS experiments?
Pedigrees: Strong, rare alleles GWAS: Weak, more common alleles
Polydactyly is a phenotype in which an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly?
Pp x pp = Pp, pp 1:1 50%, probability of individual child does depend on previous children
What is a possible weakness of the Hershey Chase experiment have?
Proteins stuck to DNA -replication and increased protein synthesis might have diluted out the signal.
.A polymorphism or polymorphic marker in a genetic sense usually represents a site along a chromosome where a specific nucleotide sequence exists. Name 3 different types of polymorphic markers?
RFLP SSLP/STR SNP
Explain what an STR is? (Don't just write the acronym)
STRs are like SSLPs - simple sequence length polymorphisms, containing short repetitive sequences. The number of repeats varies within different human populations. Allowing the combination of different STRs to be used to genetically identify an individual.
reverse genetics
Targeting of a specific gene for analysis.
a. If you reject the null the hypothesis; what can you conclude?
That the deviation of observed from expected is unlikely to occur due to randomness
A highly prized breed of chickens has a mixture of light and dark feathers, a plumage known as "Erminette". You cross a set of male and female Erminette chickens and find that their F1 progeny include 130 with Erminette plumage, 62 with purely light plumage, and 64 with purely dark plumage. a. Assuming that this trait is determined by a single gene, formulate a hypothesis for the genetic basis of the Erminette phenotype. Calculate the chi-square value for the observed data to evaluate your hypothesis.
The Erminette phenotype could result from either incomplete dominance or codominance (either interpretation is feasible). If you denote the dark allele as A and the light allele as a, then Erminette would be Aa and the cross Aa x Aa would give AA:Aa:aa in 1:2:1 ratio. The expected numbers based on this model are 64:128:64. chi-square value = (4/128) + (4/64) = 0.093
What is one thing similar about Crispr/Cas9 and microRNAs?
The both have a RNA/Protein complex RNAs in both are ~21 base pairs Both cleave nucleotides
Why is it more correct to say identifying alleles/disease variants underlying disease than to say identifying genes underlying disease?
The gene exists in all individuals, it's how it is different (the allele) that's important
Concisely, describe the particular features of Creighton's and McClintock's experiment that allowed them to prove Morgan's hypothesis that coupling and repulsion results from the physical exchange of DNA between homologous chromosomes?
The knob and extra-length of DNA on one chromosome allowed them to trace the DNA on that chromosome, visualizing recombination or the exchange of information (cell biology). That cell biology was matched with how the pattern of traits changed.
What would have been the result and what would Avery, McCarthy and Macleod have been able to conclude if instead of using a ribonuclease they used a nuclease that digests all types of nucleic acids?
The nuclease would have inhibited transformation. However, they would have been unable to distinguish between RNA and DNA
Leeuwenkoek- the famous cell biologist - tried his hand at genetics to prove his theory of inheritance; in which males determine inheritance because a tiny little human being exists in the sperm. He crossed a gray male rabbit to a female white rabbit and got all gray rabbits. You are the reviewer of his paper, what experiment will you make him do before he can publish? Explain.
The reciprocal cross - white male rabbit x grey female rabbit. In his single cross he didn't isolate the sex variable from the grey allele.
What is the approximate p value corresponding to this chi-square value? (You can give this as a range of values, such as x<p<y.) Can you reject your hypothesis on the basis of this value.
There are three phenotypic classes, and therefore two degrees of freedom, so 0.975<p<0.9. (Specifics may vary depending on which table you use.) The hypothesis cannot be rejected on this basis.
A major advance for PCR came with the discovery of bacteria living in hot springs (>95), from which one could isolate a thermostable Polymerase, why was this?
Thermostable polymerase allows polymerase to survive the cycling particularly the 95 degree step, otherwise polymerase is denatured every time strands are disassociated. And polymerase has to be added at each step.
Why are diseases related to blood cells ideal for gene therapy techniques? Or what is a particular challenge for gene therapy.
They are good because you can take an ex-vivo approach - removing them and putting them back. For gene therapy it is difficult to get the gene into the cells of interest
How do CAP (catabolite activating protein) levels change in response to glucose
They don't: Glucose regulates the levels of cAMP which couples with the CAP protein to bind to the promoter
What is the smallest number of individuals scientists can use to identify a disease-causing mutation? How would the concept of linkage disequilibrium apply in this case?
Trios: Mom, Dad, child It does not
In thinking about the genetic definition of a gene (a unit of inheritance), name two requirements.
Universal, replicated, encodes information, passed between generations
What would happen if too many (di-deoxynucleotides) ddNTPs were added to a Sanger sequencing reaction?
Very short sequences
Cystic fibrosis is a progressive genetic disease causing thick sticky secretions instead of think slippery secretions, this can be particularly harmful to the lungs and digestive system. This disease is most prevalent in Caucasians of Northern European descent. A woman from Britain fleeing Brexit comes to you - a genetic counselor - worried that her unborn child would have this disease. In order to give her a risk assessment a. What do you need to know about the disease?
What is the mode of inheritance of this disease? Family history of the disease?
We will be talking about a classic paper by Andrew Fire next week Titled "Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans" (which you can find on blackboard). Please read this short paper and answer the following questions. a. What question is this paper seeking to answer? b. What genetic methodologies that we've discussed in class are used in this paper? Sufficiency c. Andrew Fire and Craig Mello won the Nobel Prize for the work they did in this paper, why was the work so important?
What properties of RNA injection disrupt endogenous mRNA function? Sufficiency Reveals an dsRNA mechanism of RNA interference and implicates an entire mechanistic system within the cell, including a mechanism of epigenetic inheritance.
Explain why spontaneous mutations would or would not have a large effect on the allele frequencies in a large population?
Would not, because frequency of spontaneous mutation in the population is so low and to not cause a dramatic shift in allele frequencies - without selection.
Hair length and hair color are two traits in cats that are inherited in a Mendelian fashion. If White hair (W) is dominant over any other colored hair (w) and Long hair (L) is dominant over short hair (l), how many different phenotypes can you ever expect to see if: a white, long-haired male cat (heterozygous for hair color only) named JoJo makes little kittens with a black, short-haired cat named Bella?
WwLL x wwll = White, long; black, long = 2
Based on these requirements, could chromosomes function as the unit of inheritance? Why or why not?
Yes, from what we've learned so far (problem set 1) chromosomes fit the definition of a gene just as much as segments of DNA.
One criticism of the Avery, McCarty and Macleod experiment is that the ribonuclease (targeting RNA) they used was NOT very efficient and therefore did not digest all of the RNA in their experiment. Is this a legitimate criticism, why or why not?
Yes, if RNA was an important component of hereditary it wouldn't have been known since some RNA still would have been left-over in this experiment and thus would explain the reason why transformation still occurs when RNAse is added.
Is it important that individual STRs are unlinked from one another?
Yes, if STRs are linked than they won't vary randomly.
Dosage compensation in humans and mice requires X-inactivation in females. a. How could you test the role of the lncRNA Xist in X-inactivation? (Would using Crispr/Cas9 be good?) a. How could you test whether Xist acts in trans (not on the same chromosome) or in Cis (on the same chromosome on which its expressed.
You could move Xist to another chromosome (Sufficiency) Remove Xist altogether (requirement), using a KO. Crispr/Cas9 wouldn't work because it makes an indel, which disrupts a reading frame and lncRNAs don't have reading frames. You could move Xist to another chromosome and see if X-chromosomes are still inactivated
Name 3 ways a cell can stop a protein's function?
a. Close the chromatin around a gene, so that transcription factors can't bind b. Turn off transcription - via changes in transcription factors (trans-acting molecules) that function at the enhancer c. Degrade a mRNA transcript once it has been made, via microRNAs d. Sequester the mRNA from ribosomes e. Degrade the protein f. Stop the proteins function
How many genetically different gametes can be formed by individuals with the following genotypes? a. XxYy b. AaBB c. EeFfGghh
a. XxYy (2^2 = 4) b. AaBB (2) c. EeFfGghh (2^3 = 8)
b) You do a cross to determine the relationship between genes A and genes B. You find B is epistatic to A. What cross did you perform? What was the result finding that led you to this conclusion?
a/+; b/+ x a/+, b/+ (other crosses possible too, want to see a/a; b/b mutants). Analyze plants that are a/a; b/b. These plants would look like b/b plants, since B is epistatic to A.
Peas heterozygous for three independently assorting genes were intercrossed b.What proportion of the offspring will be homozygous for the recessive allele of at least one gene?
i. 37/64: aa occurs in ¼ of all cases (64 x 0.25) = 16, 1. rest 64-16= 48, ¼ of the rest will be bb (48 x 0.25) = 12. 2. Rest 48-12= 36, ¼ of the rest will be cc (36 x 0.25) = 9. 3. At least is additive 16 +12 +9 =37/64
In an exotic species of bird, the difference between smooth feathers and ruffled feathers is controlled by a single gene: birds with a dominant allele, R, have smooth feathers, and birds homozygous for the recessive allele, r, have ruffled feathers. Birds with a dominant allele for a pigment gene, B, have black feathers and homozygous recessive bb birds have blue feathers. c. From these F2 progeny, a black bird with smooth feathers is chosen at random.
i. What is the probability that this bird is homozygous BB? 1/3 ii. What is the probability that this bird is heterozygous Bb? 2/3 Note that due to the law of independent assortment, feather phenotype has no bearing on the answer. So the answer would have been the same if the black bird chosen had ruffled feathers, or if feather phenotype had not been specified.
In an exotic species of bird, the difference between smooth feathers and ruffled feathers is controlled by a single gene: birds with a dominant allele, R, have smooth feathers, and birds homozygous for the recessive allele, r, have ruffled feathers. Birds with a dominant allele for a pigment gene, B, have black feathers and homozygous recessive bb birds have blue feathers. b. From a mating between two of these F1 progeny, what proportion of the resulting F2 progeny are expected to be...
ii. black with smooth feathers? 9/16 iii. blue with smooth feathers? 3/16 iv. black with ruffled feathers? 3/16 v. blue with ruffled feathers? 1/16
7. What is the difference between lncRNAs and microRNAs
lncRNAs - are long non-coding RNAs (>200nt), they are not processed by dicer, drosha or argonaute - although their function is still pretty mysterious, they don't seem to target other RNAs. microRNAs - a short RNAs, that form a hairpin that is processed, by drosha and then dicer to a 21nt sequence that then complexes with argonaute to target endogenous mRNAs for degradation
According to the biological species concept, the major criterion for determining whether two populations are part of different species is _____.
reproductive incompatibility
forward genetics
unbiased analysis of mutations/ genes important for a specific process
In a Chi-square analysis, what condition causes one to reject (fail to accept) the null hypothesis?
when the probability value is less than 0.05
Peas heterozygous for three independently assorting genes were intercrossed a. What proportion of the offspring will be homozygous for all three recessive alleles?
¼ x ¼ x ¼ =1/64
15) Many people think Mendel got lucky? What meiotic event did Mendel's postulates not account for? What specifically would change
• Recombination and linkage, • Non-diploid organisms
