Principle of Biology Chapter 4a
Compete the following sentence: The role of tautomerism in causing mutations relates to the fact that the process ultimately affects the...
hydrogen bonding affinities of the base.
If one parent plant produces white flowers and the other purple flowers, what does the theory of blended inheritance predict the offspring's flowers should look like?
The theory of blended inheritance predicts that these crosses will produce offspring with pale purple flowers.
In Figure 42.7, which allele represents a sex-linked trait? Which alleles represent linked traits?
The w allele represents a sex-linked trait because it is carried on the X chromosome. Its associated phenotype will only appear in males with the allele or in females homozygous for the recessive allele. The G C and g c alleles represent linked traits because the genes for G/g and C/c are located very close to each other on the same chromosome. These alleles are likely to be inherited together.
How are sickle-cell anemia and cystic fibrosis related?
They are both due to mutations in a single gene.
What are the main similarities and differences between the male gametes in flowering plants and mammals?
They are both haploid cells that fuse with the egg to produce a diploid zygote. However, in animals, male sperm are motile and move to the egg. In flowering plants, the male gametes are non-motile and are contained within pollen that has to be deposited on the carpel, either by animals or wind/water pollination.
You breed a female fruit fly that shows the wild-type phenotype but is heterozygous for two traits with a male expressing mutations in both those traits. After many repetitions of the same cross, half the offspring show the wild-type phenotype, and half show both mutations. What can you conclude about the genes for the two traits?
They are on the same chromosome and probably close together.
How are sexual and asexual reproduction alike?
They can both occur in multicellular organisms.
Why did Meselson and Stahl transfer E. coli from media containing 15N to media containing 14N?
They needed to ensure that all newly synthesized DNA would contain the same marker.
Although Morgan didn't see any white-eyed females in his F2 generation, female fruit flies can display white eyes. What would the genotype of a white-eyed female be? What would her parents' genotypes and phenotypes be?
To display the recessive, X-linked trait of white eyes, a female fruit fly would have to have the genotype XwXw (homozygous recessive). She could get this genotype from a father carrying one Xw allele and an XWXw (heterozygous) mother. This father would have white eyes, and since red eyes are dominant to white eyes, the mother would have red eyes. A female fruit fly with white eyes can also have a white-eyed mother with the genotype XwXw and a white-eyed father with one Xw allele.
When a heterozygous pea plant self-fertilizes, the offspring may have any of four possible phenotypes. If the parent is RrYy, what are the possible offspring genotypes? R = round, r = wrinkled, Y = yellow, y = green.
YYRR (1), YYrr (1), yyRR (1), yyrr (1), YYRr (2), YyRR (2), Yyrr (2), yyRr (2), YyRr (4).
Which of the following would NOT be expected as a result of a point mutation?
a duplicated chromosome
What is the "Philadelphia chromosome"?
a modified chromosome 22, produced as a result of chromosome translocation
In fruit flies, brown body color ( B) is dominant to black body color ( b). A brown fruit fly is crossed with a black fruit fly. Both flies are purebred. What will the offspring's genotypes be?
all Bb
Meiosis in ferns directly produces...
spores.
Which of the following is the correct sequence for alternation of generations in a fern?
sporophyte → spores → gametophyte → gametes → zygote
Which of the following is the best definition of genetic fitness as applied to a mammal?
the ability of the animal to survive and reproduce with changes to the environment that may kill or reduce the reproductive ability of other members of the population
Which of these statements about genetic disorders is false?
All genetic disorders follow Mendelian inheritance patterns.
A boy is colorblind, although neither of his parents is. Colorblindness is an X-linked recessive trait. If his parents have a daughter, what is the probability that she will be colorblind?
0
If both parents are heterozygous for a trait, what is the probability that a given offspring of theirs will display the recessive trait? Assume the gene for the trait is not sex-linked.
1/4
How many chromosomes are there in a human sperm?
23
According to the data in Table 37.1, what is the ratio of round to angular (wrinkled) seeds? Based on this ratio, what was the genotype of the parents?
336/101 = 3.3, or approximately 3:1. The parents were both heterozygous for seed shape, meaning both of them had the genotype Rr.
How many autosomal chromosomes are present in an individual with Klinefelter syndrome?
44
A couple's first son is colorblind, though neither parent is. Colorblindness is an X-linked recessive trait. What is the probability that the couple's second son will be colorblind?
50%
What was unusual about Morgan's results when he crossed two red-eyed flies heterozygous for the trait of white eyes?
Only the males had white eyes.
Huntington's disease, a progressive nervous system disorder, is inherited as a dominant trait. The songwriter Woody Guthrie died of Huntington's disease. If he was heterozygous for the trait and his wife did not carry it, what was the probability that their son would develop Huntington's disease?
50%
In humans, dry earwax is recessive to wet earwax. Consider a woman with dry earwax and her male partner who has wet earwax. If he is heterozygous for the trait of wet earwax, what is the probability that their child will have wet earwax?
50%
In Mendel's experiments, the F2 generation produced 705 purple-flowered plants and 224 white-flowered plants. What is the ratio of the more common form to the less common form?
705 purple/224 white flowers = 3.15. This means that the ratio of purple to white flowers was approximately 3:1. Put another way, three of every four plants had purple flowers.
How does a karyotype differ from a family pedigree?
A family pedigree is useful in identifying inherited diseases, but a karyotype is usually not.
What result showed up in the F 1 generation of Mendel's first monohybrid crosses that countered prevailing ideas about inheritance?
All the plants looked like just one of the parents.
According to the blended inheritance theory, what would the offspring of a true-breeding tall plant and a true-breeding short plant look like?
All would be of medium height.
Why would you expect males to be more often affected by an allele carried on the X chromosome that codes for a recessive trait?
Any male who inherits the allele that codes for the recessive trait would display the trait because there is no second X chromosome in males to mask the trait. Although females may exhibit an X-linked trait, their father would have to be affected, and their mother would have to be either affected or a carrier of the allele.
What types of inheritance patterns would you expect human monogenic diseases to exhibit, assuming simple Mendelian inheritance?
Autosomal recessive and dominant disorders and sex-linked disorders. Sex-linked disorders may be linked to the X chromosome or the Y chromosome.
Consider the genotypes in Table 39.2. What is the dominance relationship for the Lf, lf, Lfd and lfa alleles?
Because a homozygote for Lfd (Lfd Lfd) and any heterozygote with at least one Lfd allele (Lfd Lf, Lfd lf, or Lfd lfa) will flower in the latest time period, we know that Lfd is the allele that is dominant over all others. Likewise, because the homozygote for lfa (lfa lfa) is the only genotype that flowers earliest, we can infer that it is the allele that is recessive to all others. Finally, because the heterozygote Lf lf expresses the same phenotype (later flowering) as the Lf Lf homozygote, Lf is dominant over lf. As a result, the dominance series is Lfd > Lf > lf > lfa.
How does sexual reproduction give rise to genetic variation?
Because genes from two different individuals, the male and female parents, are present in the fertilized egg, each offspring has two different sets of alleles, one from each parent, which in many cases will be different. Each time reproduction occurs, the process is repeated and acquisition of other alleles will take place.
X-ray measurements of DNA by Franklin and others showed that the distance between the sugar-phosphate backbones was uniform all along the DNA molecule. Explain why this measurement implies that pyrimidines bond with purines in complementary base pairs, rather than pyrimidines bonding with other pyrimidines and purines bonding with other purines.
Because pyrimidines and purines have different sizes, pairings between purines and pyrimidines always have similar width. If pairs of pyrimidines bonded together (C + T), they would have a different width than pairs of purines (A + G), and the double helix would not have a uniform width along its length.
In Figure 38.5, what are the possible genotypes that could produce a brown phenotype? What about a black phenotype?
Because the brown allele (B) is dominant, the brown phenotype could be the result of a homozygous (BB) genotype or a heterozygous (Bb) genotype. The recessive black allele (b) can only produce the black phenotype when the individual is homozygous recessive (bb); that is, the black phenotype only occurs when the offspring has inherited a recessive allele from each parent.
Imagine that two heterozygous plants, each with one dominant allele and one recessive allele, are mated with each other. Since a plant has a 50% chance of inheriting a particular allele from each parent, what is the probability that the offspring of the two plants will inherit two copies of the allele coding for the recessive trait?
Because these events are independent, one may calculate probability using the multiplication rule. The probability of inheriting the allele coding for the recessive trait from both parents is ½ * ½ = ¼ = 25%.
If neither of the parents displays the symptoms of an autosomal recessive Mendelian disorder that runs in their families, what is the likelihood that their child will develop the disease?
Children inherit one of the two possible alleles from each parent. An autosomal recessive disorder only manifests itself if the child inherits the allele coding for the recessive disease from both parents. There is a 25% chance the child will inherit the disease if both parents are carriers of the disease allele. And there is a 0% chance the child will inherit the disease if only one parent, or neither parent, is a carrier.
Explain how observations of the behavior of chromosomes during meiosis and fertilization provide evidence that chromosomes are carriers of genetic information.
Chromosome pairs are present in diploid cells before meiosis. During meiosis, chromosome pairs separate and form gametes with only one of each kind of chromosome. Fertilized cells again contain pairs of chromosomes, implying that chromosomes in the gametes from each parent contribute one set of chromosomes to the total number of chromosomes in a zygote.
Can you think of a situation in which the breaking and rejoining of DNA molecules does not normally lead to a mutation and is beneficial to the individual?
Crossing over during meiosis is responsible for introducing genetic variability and does not normally lead to a mutation because the breaking and rejoining of chromosomes occur at homologous locations along the chromosomes.
Why must the lagging strand be produced in discontinuous Okazaki fragments?
DNA polymerase III only adds nucleotides to a growing strand in the 5′ to 3′ direction. In the leading strand, an RNA primer is synthesized by DNA primase, and the new complementary DNA strand is synthesized continuously as the polymerase follows the direction of the opening replication fork. In the lagging strand, DNA polymerase III adds nucleotides in the direction away from the replication fork, so RNA primers must be added frequently and nucleotides added until they meet the previous primer.
Why are polar bodies formed? If meiosis in a male produces four sperm, why doesn't meiosis in a female produce four eggs?
Developing egg cells have evolved to split asymmetrically during meiosis, producing one large egg cell and three smaller polar bodies once meiosis is complete. This process ensures that the single, surviving egg cell receives as much cytoplasm as possible from each division of meiosis. A large amount of cytoplasm is needed to nourish the growing embryo during early development.
What did Michael Dougherty, the director of education at the American Society of Human Genetics, suggest regarding the teaching of Mendelian inheritance?
Dougherty suggested that teachers should talk about gene variation before they introduce Mendel.
If an animal egg were fertilized by many sperm, there would be many copies of the organism's chromosomes in the egg. What prevents this from happening?
Egg activation, which involves biochemical reactions, prevents more than one sperm from entering the egg.
Which of the following best characterizes the implications of the reintroduction of wolves to the Yellowstone food web?
Elk changed their behavior and foraged less near stream banks, but the trophic cascade did not extend to trees.
Why have so many genetic experiments been done on fruit flies? Name two characters that make fruit flies a good model organism.
Fruit flies reproduce and mature rapidly, lay many eggs, are relatively easy to maintain, and show alternate forms of several characteristics but have few genes compared with many other organisms.
Which of these statements about genetic disorders are true?
Genetic disorders may occur at the single-gene level. Mitochondrial DNA mutations may cause genetic disorders. Changes in number of complete chromosomes may be involved in genetic disorders. Parts of chromosomes may be translocated to other chromosomes in genetic disorders.
How did Mendel determine the basic principles of inheritance?
He used experimentation, observation, and mathematical analysis.
What happens at the origin of replication?
Helicase separates the strands of DNA.
meiosis I
Homologous chromosomes are pulled apart during anaphase I. Meiosis I results in the creation of two genetically unique daughter cells. During metaphase I, chromosomes are aligned along the metaphase plate.
Examine Figure 38.8. In a cross between a brown female fly and a black male fruit fly, if half of the offspring are black, what is the female's genotype? What if all of the offspring are brown?
If half the offspring are black, the female is heterozygous for the brown allele (Bb). If they are all brown, she is homozygous for brown allele (BB).
If the final sequence of DNA cannot be added to the 5′ end of the lagging daughter strand during replication, how would you expect this to affect the length of a molecule of DNA with each round of replication?
If the final sequence of DNA cannot be added to a linear DNA molecule, this would mean that with each successive round of replication, the molecule would get shorter and shorter.
A heterozygous fly (Bb Vv) with a black body and normal wings is crossed with a homozygous recessive fly with a grey body and vestigial wings (bb vv). The parents of the heterozygous fly (Bb Vv) had the following genotypes: BB VV and bb vv. If the genes for body color and wing type are unlinked, which phenotypes will appear and in what ratio? What if the genes are tightly linked on the same chromosome?
If the genes are unlinked, the four phenotypes (gray body, normal wings; black body, vestigial wings; gray body, vestigial wings; and black body, normal wings) will appear in a 1:1:1:1 ratio. If the genes are tightly linked, the offspring will receive only b v or B V gametes, so they will have only one of two phenotypes — gray body, normal wings, or black body, vestigial wings — and these phenotypes will appear in a 1:1 ratio.
How many genotypes result from the cross presented in Figure 39.5? And how many phenotypes result?
In Figure 39.5, the cross results in nine genotypes (CCBB, CCBb, CCbb, CcBB, CcBb, Ccbb, ccBB, ccBb, and ccbb) and three phenotypes (black, brown, and white).
A DNA sequence is as follows: 5′ - CCT ACT GAG GTG - 3′, and it codes for Pro-Thr-Glu-Val. If a tautomeric change occurs in the first thymine base in this sequence, what would be the new base sequence on the strand produced after this DNA strand undergoes replication? Also, how would the sequence produced when the daughter strand itself replicates differ from the sequence shown above? Based on the genetic code, what effect do you think this mutation will have on the gene product?
In making the daughter strand, the first T would pair with G instead of A, so the sequence of the complementary strand after replication would be 3′ - GGG TGA CTC CAC - 5′, and in the next replication using this strand as the template, the complementary strand would be 5′ - CCC ACT GAG GTG - 3′. The difference would therefore be in the first codon, which would now read CCC instead of CCT. However, because both CCC and CCT code for the amino acid proline, there should be no effect on the gene product in this case.
Compare the DNA molecules produced after the first and second rounds of replication in the conservative model and the semi-conservative model. What are you able to predict about the DNA produced after each round of replication based on each model?
In the conservative model, the original parental DNA remains intact after replication, and the daughter DNA contains two new strands. In the dispersive model, the parental DNA is broken into smaller fragments, which are then copied and pieced back together to form the daughter DNA molecules. As a result, each strand would contain a mixture of original and newly synthesized DNA. In the semi-conservative model, the first round of replication produces DNA with one complete original strand and one complete newly synthesized strand.
Albinism, the trait of being albino, is recessive. What can you accurately predict about an albino mouse?
It is homozygous recessive for albinism.
What is the role of DNA polymerase I in the replication of E. coli DNA?
It replaces RNA nucleotides with DNA nucleotides.
What distinguishes keystone species from other species in a community?
Keystone species have an influence on their communities that is greater than either their collective biomass or abundance would suggest.
Female guppies seem to find males with orange spots to be more desirable mates than males without the orange color. How might the frequency of orange spots change over several guppy generations? Why? Give a reason you might not see this outcome.
Male guppies with orange spots will be favored and father more offspring because the females find these males to be more desirable mates (known as sexual selection, which is similar to natural selection, but is driven by mate choice). Their male offspring will inherit the father's Y chromosome and will also have orange spots and as a result, the prevalence of orange spots would likely increase through time. However, natural selection could reduce the changes of this outcome. For instance, males with bright orange spots or other traits that might make them more desirable mates might also make them more visible to predators and then more likely to be killed prior to reproduction. In this case, the trait's prevalence might not increase over time.
Why can't Mendelian inheritance explain the inheritance patterns of all genes?
Mendelian inheritance does not take into account all of the factors that determine inheritance. For example, a gene may have more than two alleles, or there may be no clear dominant or recessive allele. Alleles may also not assort independently, or their inheritance may be affected by epigenetic factors. All of these would be considered forms of non-Mendelian inheritance.
Which statement about meiosis and mitosis is true?
Mitosis produces daughter cells with the same number of chromosomes as the parent cell.
How were technological improvements important in development of the chromosomal theory of inheritance?
More powerful microscopes and novel staining techniques allowed researchers to view the processes of mitosis and meiosis.
How did Morgan's work expand on Mendel's principles of inheritance?
Morgan discovered that not all alleles are sorted into gametes independent of all other alleles.
How did Morgan's data from the monohybrid cross challenge Mendel's principle of independent assortment?
Morgan's data suggested that alleles did not separate as independent entities during meiosis. Instead an allele was part of a chromosome, and the whole chromosome was sorted into a gamete. That idea suggested that two alleles in a dihybrid cross would follow Mendel's principle of independent assortment only if they happened to be on different chromosomes. By chance, Mendel studied alleles of genes that were located on different chromosomes.
Which of these observations would support the idea that some alleles are linked?
Most people who have freckles also have red hair.
Explain how crossing over increases genetic variation.
Non-sister chromatids from homologous chromosomes exchange genetic information, usually at two or more locations per chromosome depending on the size.
What is the phenotypic ratio among the offspring of the dihybrid cross shown in Figure 38.6?
Of the 16 possible genotypes, we would expect on average the following probable breakdown: 9 brown body, red eye; 3 brown body, brown eye; 3 black body, red eye; and 1 black body, brown eye. Thus, we would expect a 9:3:3:1 phenotypic ratio.
Which of these disorders is not a result of aneuploidy?
Prader-Willi syndrome
Explain the importance of radioactive isotopes in the design of the Hershey-Chase experiments.
Radioactive isotopes were used to independently track the movement of proteins and DNA in the Hershey-Chase experiment. Radioactively labeled phosphorus (32P) was used to track DNA, while radioactively labeled sulfur (35S) was used to track protein.
In the study on desert rodents and plants, what was the cascade of interactions after the kangaroo rat was removed?
Removal of kangaroo rats led to lower plant diversity because kangaroo rats eat dominant large-seeded species, allowing annual plants to flourish.
What is one way that the replication of eukaryotic DNA generally differs from the replication of prokaryotic DNA?
Replication shortens the lagging strand in eukaryotic DNA.
In most female mammals, one X chromosome is active and one is inactive in each adult cell. What determines which chromosome is the active one?
Researchers do not know yet.
Look at the first 10 plants from Mendel's data in Table 37.1. Which trait is dominant? How can you tell?
Round peas are dominant, and the angular (wrinkled) trait is recessive. This is because there are more round seeds on average, even though there is also considerable variation among individuals.
Which of the following is NOT true of a tautomeric shift?
Shifts involve damage to bases by free radicals.
Which of the following is true of a tautomeric shift?
Shifts may occur in either purine (A or G) or pyrimidine (C or T) bases. Shifts may occur in any base position in a codon. Shifts in thymine may occur from the keto to the enol form. Shifts may be spontaneous or induced.
What repair mechanisms does the cell use when it detects damage to its DNA?
Single nucleotides may be replaced, if incorrectly paired, by mismatch repair enzymes. If DNA is damaged by ultraviolet light or chemicals, leading to the formation of large bulky DNA lesions, these mutations may be removed by nucleotide excision repair, where the section of DNA containing the lesion is excised by nucleases, replaced by DNA polymerase, and reconnected to the existing DNA by DNA ligase, using the undamaged strand as a template.
Which of the following is NOT true about meiosis I?
Sister chromatids are pulled apart from one another during anaphase I.
What is the chromosomal theory of inheritance?
The "heritable factors" of Mendel, which are genes or alleles, are located on the chromosomes.
Why does crossing true-breeding red and white snapdragons result in pink offspring?
The allele that codes for the red pigment trait has incomplete dominance.
Which of the following is a way a dominant species could impact community structure?
The species can outcompete others for a scarce resource. The biomass of the species can provide habitat to numerous other organisms. The activity of the species can alter the physical environment. The species can be the main food source of a keystone species.
How does the single genetic defect cause the phenotypes seen in cystic fibrosis?
The defective protein coded by the gene cannot transport molecules across the cell membrane.
Organisms like ferns and mosses that have this type of life cycle typically live in moist conditions. Do you have an idea about why this is so?
The dispersal of spores does not rely on the presence of moisture. However, fertilization depends on the sperm swimming to the egg, and this will only happen if the environment is moist enough for this to occur.
The "ridge" on a Rhodesian ridgeback dog, a line of fur along the spine growing in the opposite direction from the rest of the dog's fur, is caused by an allele coding for a dominant trait. Call this allele R and the allele coding for the recessive trait r. What are you able to conclude about the genotype of a dog whose phenotype shows a ridge?
The dog could be homozygous (RR, with two alleles coding for the dominant trait) or heterozygous (Rr, with one allele coding for the dominant trait and one allele coding for the recessive trait). It could not be homozygous for the allele coding for the recessive trait (rr).
Marfan syndrome is associated with tall height and a high risk of heart and eye problems. How does mutation of one gene cause all these symptoms?
The gene codes for a connective tissue protein used in many parts of the body.
What happens in overdominance?
The hybrid has a more extreme phenotype than either parent.
Explain how anaphase I might occur in a male rabbit's spermatocytes.
The microtubules connecting to each kinetochore begin to shorten, and the chromosomes are pulled away from the metaphase plate toward opposite poles.
What phenotypic ratio does the dihybrid cross in Figure 39.6 show? What is the genotype of the long squash? What are the genotypes of the sphere-shaped squashes?
The offspring occur in a ratio of 9 disk : 6 sphere : 1 long. The genotype that is homozygous for the recessive trait for both genes, aabb, is long. A homozygous genotype that codes for the recessive trait at either gene — aaBb, aaBB, Aabb, or Aabb — is sphere-shaped. A homozygous or heterozygous genotype that expresses both dominant traits, AABB or AaBb, is disc-shaped.
Examine Figure 39.1. What are the offspring genotypes? If one-half are pink, one-quarter are white and one-quarter are red, then which genotype matches which phenotype?
The offspring that are pink have the genotype Rr. The red-flowered offspring have the RR genotype, and the white-flowered offspring have the rr genotype.
Examine the data in Figure 41.5. If both parents had the same phenotype and genotype (Rr Vgvg), how many types of gametes did they produce? Explain the F1 phenotypic ratio.
The parents were both Rr Vgvg and showed the wild-type phenotypes of red eyes and normal wings. They produced four different types of gametes, depending on how the chromosomes sorted out during meiosis: R Vg, r vg, R vg, and r Vg. This illustrates Mendel's principle of independent assortment. The resulting phenotypic ratio is expected to be 9:3:3:1. Nine out of 16 offspring show both dominant traits (red eyes-normal wings), and 3 out of 16 show one recessive and one dominant trait (red eyes-vestigial wings), 3 out of 16 show the other recessive trait and the other dominant trait (rosy eyes-normal wings), and 1 out of 16 shows both recessive traits (rosy eyes-vestigial wings).
Analyze the karyogram in Figure 40.7 to determine what chromosomal abnormality the individual has. What genetic disorder is associated with this abnormality?
The person has three copies of chromosome 21 (trisomy 21). This condition results in Down syndrome.
How did the discovery of linked genes change the understanding of Mendel's principles?
The principle of independent assortment does not hold true for linked genes.
During metaphase I, the tetrads are aligned at the metaphase plate. How does their arrangement influence genetic variation? What is this concept called?
The random arrangement of chromosomes along the metaphase plate is called independent assortment. The number of possible chromosome combinations in gametes that could be produced through independent assortment is 2n where n = the number of chromosomes in a haploid cell of a given species. In humans, for example, there are 23 different chromosomes in a gamete. This means that there are almost 8.4 million chromosome combinations that could occur through meiosis.
Describe how independent assortment during meiosis increases genetic variation.
The random arrangement of chromosomes during metaphase I creates gametes that are genetically unique from one another.
Which of the following is not a way a dominant species could impact community structure?
The species could be rare with a low biomass but with a large impact on the distribution and biomass of other species.
Mutation can be described as...
changes in the genomic sequence.
Which of the following factors affects how many blood cells a person has?
contracting an infection the person's genes moving to a high altitude training for a triathlon
What type of genetic cross can demonstrate both the principles of segregation and independent assortment?
dihybrid cross
In which model of DNA replication does the parent DNA molecule break into fragments that are copied?
dispersive
a characteristic that makes Drosophila an ideal model organism
easily manipulated in a laboratory large numbers of offspring many well defined variations and mutations many online resources available
Which of these inheritance patterns involves interaction of more than one gene?
epistasis
Name a human trait that is no longer considered a classic Mendelian trait.
eye color
A frameshift mutation is one of the most severe types of mutations because...
frameshift mutations often result in stopping translation.
A person inherits two copies of the ___ that defines the consistency of their earwax, one from each parent. From her father, she inherits the ___ for dry earwax. From her mother, she inherits the ___ for wet earwax.
gene, allele, allele
In peas, yellow color and round shape are dominant to green color and wrinkled shape, which are recessive. If you have a round, yellow pea and want to know its genotype, what kind of pea should you breed it with?
green-wrinkled
Albinism is an autosomal recessive trait. An albino mother has an albino daughter by a healthy man. They plan on having several more children. On average, what proportion of the children are expected to be albino?
half of the sons and daughters
Which protein is responsible for synthesizing the new DNA strand during replication in prokaryotes?
helicase primase topoisomerase DNA polymerase I None of the answers are correct. <----
Which of the following would be expected as a result of a point mutation?
introduction of a premature stop codon production of a codon that codes for defective gene product production of a nonsense codon production of a codon that codes for the same amino acid sequence
Which of the following is the best tool for detecting aneuploidy?
karyotyping
Which of the following is NOT a characteristic that makes Drosophila an ideal model organism?
long generation time
Which one of the following is NOT the purpose of meiosis?
multiplication of somatic cells
Which of the following is an example of a dominant species?
mussels in Paine's intertidal community one year after ochre stars had been removed
Which of the following is NOT a type of chromosomal mutation?
nondisjunction
The growth factor bone morphogenetic protein-4 (BMP-4) was first identified as a bone-forming factor by its ability to form bone tissue when injected into muscle. However, it has since been found to also play important roles in neural development and the formation of a large variety of tissues. Mutations in the BMP-4 gene are therefore expected to cause a wide range of abnormalities. Which term best describes this phenomenon?
pleiotropy
Which of the following could drive a bottom-up force?
precipitation a nutrient input the availability of habitat an increase in solar input
purpose of meiosis
production of eggs production of sperm halving the number of chromosomes
Describe in order the four phases that occur during meiosis II.
prophase II, metaphase II, anaphase II, telophase II
The dominant traits in Mendel's pea plants were green pea pods ( G) and round peas ( R). Yellow pea pods ( g) and wrinkled peas ( r) were recessive. If you bred plants heterozygous for both characters, GgRr, with each other, how many more plants with green pea pods and round peas would result, on average, than plants with yellow pea pods and round peas?
three times as many