Question: The period between meiosis I and meiosis

> Let’s suppose a recessive allele encodes a completely defective protein. If the functional allele is dominant, what does that tell you about the amount of the functional protein that is sufficient to cause the phenotype? What if the allele shows incomple

> Huntington disease is a rare dominant trait that causes neurodegeneration later in life. A man in his thirties, who already has three children, discovers that his mother has Huntington disease though his father is unaffected. What are the following proba

> What is the difference between the G0 and G1 phases?

> Wooly hair is a rare dominant trait found in people of Scandinavian descent in which the hair resembles the wool of a sheep. A male with wooly hair, who has a mother with straight hair, moves to an island that is inhabited by people who are not of Scandi

> What would be the sex of a human with each of the following sets of sex chromosomes? A. XXX B. X (also described as X0) C. XYY D. XXY

> Assuming that such a fly would be viable, what would be the sex of a fruit fly with the following chromosomal composition? A. One X chromosome and two sets of autosomes B. Two X chromosomes, one Y chromosome, and two sets of autosomes C. Two X chromos

> What is meant by a gene interaction? How can a gene interaction be explained at the molecular level?

> A woman with an abnormally long chromosome 13 (and a normal homolog of chromosome 13) has children with a man with an abnormally short chromosome 11 (and a normal homolog of chromosome 11). What is the probability of producing an offspring that will have

> Three coat-color patterns that occur in some breeds of horses are termed cremello (beige), chestnut (brown), and palomino (golden with light mane and tail). If two palomino horses are mated, they produce about 1/4 cremello, 1/4 chestnut, and 1/2 palomino

> A sex-influenced trait in humans affects the length of the index finger. A short allele is dominant in males and recessive in females. Heterozygous males have an index finger that is significantly shorter than the ring finger. The gene affecting index fi

> In humans, a very rare dominant allele that causes the little finger to be crooked has a penetrance of 80%. In other words, 80% of heterozygotes carrying the allele will have a crooked little finger. If a homozygous unaffected person has children with a

> Compare phenotypes at the molecular, cellular, and organism levels for individuals who are homozygous for the hemoglobin allele, HbA HbA, and the sickle cell allele, HbS HbS.

> Let’s suppose you have pedigree data from thousands of different families involving a particular genetic disease. How would you decide whether the disease is inherited as a recessive trait as opposed to one that is dominant but shows incomplete penetranc

> What is the function of the FtsZ protein during binary fission?

> What type of bonding is responsible for the formation of the two types of secondary structures?

> The pedigree shown here involves a trait determined by a single gene (affected individuals are shown in black). Which of the following patterns of inheritance are possible for this trait? A. Recessive B. X-linked recessive C. Dominant D. Sex-influenc

> Based on the pedigree shown here for a trait determined by a single gene (affected individuals are shown in black), state whether it would be possible for the trait to be inherited in each of the following ways: A. Recessive B. X-linked recessive C. D

> The trait of feathering in fowls is a sex-limited trait controlled by a single gene. Females always exhibit hen-feathering, as do HH and Hh males. Only hh males show cock-feathering. Starting with two heterozygous birds that are hen-feathered, explain ho

> In cats, a temperature-sensitive allele produces the Siamese phenotype, in which the cooler extremities are dark and the warmer trunk area is lighter. A Siamese cat that spends most of its time outside was accidentally injured in a trap and required seve

> Discuss the differences among sex-influenced, sex-limited, and sex-linked inheritance. Give examples.

> In rabbits, the color of body fat is controlled by a single gene with two alleles, designated Y and y. The outcome of this trait is affected by the diet of the rabbit. When raised on a standard vegetarian diet, the dominant Y allele confers white body fa

> Scurs in cattle is a sex-influenced trait. A cow with no scurs whose mother had scurs had offspring with a bull with scurs whose father had no scurs. What are the probabilities of each of the following combinations of offspring? A. The first offspring wi

> Incontinentia pigmenti, a rare, X-linked dominant disorder in humans, is characterized by swirls of pigment in the skin. If an affected female, who had an unaffected father, has children with an unaffected male, what are the predicted ratios of affected

> Hemophilia is an X-linked recessive trait in humans. If a heterozygous woman has children with an unaffected man, what is the probability of each of the following combinations of children? A. An affected son B. Four unaffected offspring in a row C. An

> A human disease known as vitamin D–resistant rickets is inherited as an X-linked dominant trait. If a male with the disease produces children with a female who does not have the disease, what is the expected ratio of affected and unaffected offspring?

> How are homologs similar to each other and how are they different?

> Propose the most likely mode of inheritance (autosomal dominant, autosomal recessive, or X-linked recessive) for the following pedigrees. Affected individuals are shown with filled (black) symbols. I-1 I-2 Il-1 II-2 II-3 II-4 III-1 III-2 III-3 III-4

> In chickens, the Leghorn variety has white feathers due to an autosomal dominant allele. Silkies have white feathers due to a recessive allele in a second (different) gene. If a true-breeding white Leghorn is crossed to a true-breeding white Silkie, what

> In Shorthorn cattle, coat color is controlled by a single gene that can exist as a red allele (R) or a white allele (r). The heterozygotes (Rr) have a color called roan that looks less red than the RR homozygotes. However, when examined carefully, the ro

> A type A woman is the daughter of a type O father and a type A mother. If she has children with a type AB man, what are the following probabilities? A. A type AB child B. A type O child C. The first three children with type AB D. A family composed of

> A woman with type B blood has a child with type O blood. What are the possible genotypes and blood types of the father?

> Describe the differences among dominance, incomplete dominance, codominance, and overdominance.

> A cell is diploid and contains three chromosomes per set. Draw the arrangement of the chromosomes during metaphase of mitosis and metaphase of meiosis I and II. In your drawing, make one set dark and the other lighter.

> Identify the key events during meiosis that result in a 50% reduction in the amount of genetic material per cell.

> For the following events, specify whether they occur during mitosis, meiosis I, or meiosis II: A. Separation of conjoined chromatids within a pair of sister chromatids B. Pairing of homologous chromosomes C. Alignment of chromatids along the metaphase

> How does the attachment of kinetochore microtubules to the kinetochore differ in metaphase of meiosis I compared to metaphase of mitosis? Discuss what you think would happen if a sister chromatid was not attached to a kinetochore microtubule.

> How do you think the end results would be affected if the cells were not treated with a hypotonic solution?

> A species is diploid and has three chromosomes per set. Make a drawing showing what the chromosomes would look like in the G1 and G2 phases of the cell cycle.

> With regard to sister chromatids, which phase of mitosis is the organization phase, and which is the separation phase?

> What is a sister chromatid? Are sister chromatids genetically similar or identical? Explain.

> Three genes (A, B, and C) are found on three different chromosomes. For the following diploid genotypes, describe all of the possible gamete combinations. A. Aa Bb Cc B. AA Bb CC C. Aa BB Cc D. Aa bb cc

> Describe the timing of meiosis I and II during human oogenesis.

> At puberty, the testes contain a finite number of cells and produce an enormous number of sperm cells during the life span of a male. Explain why testes do not run out of spermatogonial cells.

> Describe the cellular differences between male and female gametes.

> Let’s suppose that a gene affecting pigmentation is found on the X chromosome (in mammals or insects) or the Z chromosome (in birds) but not on the Y or W chromosome. It is found on an autosome in bees. This gene exists in two alleles:&

> The arctic fox has 50 chromosomes (25 per set), and the common red fox has 38 chromosomes (19 per set). These species can interbreed to produce viable but infertile offspring. How many chromosomes would the offspring have? What problems do you think may

> Corn has 10 chromosomes per set, and the sporophyte of the species is diploid. If you performed a karyotype, what is the total number of chromosomes you would expect to see in each of the following types of cells? A. A leaf cell B. The sperm nucleus of

> Where is the information to make a polypeptide stored?

> List several ways in which telophase appears to be the reverse of prophase and prometaphase.

> What is a homolog? With regard to genes and alleles, how are homologs similar to and different from each other?

> Explain why the products of meiosis may not be genetically identical, whereas the products of mitosis are.

> A diploid species has four chromosomes per set for a total of eight chromosomes in its somatic cells. Draw such a cell as it would look in late prophase of meiosis II and prophase of mitosis. Discuss how prophase of meiosis II and prophase of mitosis dif

> Nine-banded armadillos almost always give birth to four offspring that are genetically identical quadruplets. Explain how you think this happens.

> Why is it necessary for the chromosomes to condense during mitosis and meiosis? What do you think might happen if the chromosomes were not condensed?

> Eukaryotic cells must sort their chromosomes during mitosis so that each daughter cell receives the correct number of chromosomes. Why don’t bacteria need to sort their chromosomes?

> With regard to question C13, how would the phenomenon of crossing over affect the results? In other words, would the probability of a gamete inheriting only paternal chromosomes be higher or lower? Explain your answer. From C13: A cell has four pairs of

> A cell has four pairs of chromosomes. Assuming that crossing over does not occur, what is the probability that a gamete will contain all of the paternal chromosomes? If n equals the number of chromosomes in a set, which of the following expressions can b

> What is the difference between the X-Y and X-0 systems of sex determination?

> If a diploid cell contains six chromosomes (i.e., three per set), how many possible random arrangements of homologs could occur during metaphase of meiosis I?

> A eukaryotic cell is diploid and contains 10 chromosomes (5 in each set). In mitosis and meiosis, how many daughter cells will be produced, and how many chromosomes will each one contain?

> The arrangement of homologs during metaphase of meiosis I is a random process. In your own words, explain what this means.

> The process of binary fission begins with a single mother cell and ends with two daughter cells. Would you expect the mother and daughter cells to be genetically identical? Explain why or why not.

> Do you know the genotype of an individual with a recessive trait and/or a dominant trait? Explain your answer.

> In a cross between a heterozygous tall pea plant and a dwarf plant, predict the ratios of the offspring’s genotypes and phenotypes.

> Based on genes in pea plants that we have considered in this chapter, which statement(s) is/are not correct? A. The gene causing tall plants is an allele of the gene causing dwarf plants. B. The gene causing tall plants is an allele of the gene causing

> In your own words, describe Mendel’s law of segregation. Do not use the word segregation in your answer.

> How can you determine whether an organism is heterozygous or homozygous for a dominant trait?

> With regard to genotypes, what is a true-breeding organism?

> Let’s suppose a pea plant is heterozygous for three genes, Tt Yy Rr, and each gene is on a different chromosome. How many different ways could the three pairs of homologous chromosomes line up during metaphase of meiosis I?

> A true-breeding plant with round and green seeds was crossed to a true-breeding plant with wrinkled and yellow seeds. The F1 plants were allowed to self-fertilize. What is the probability of obtaining the following plants in the F2 generation: two that h

> A pea plant that is dwarf with green, wrinkled seeds was crossed to a true-breeding plant that is tall with yellow, round seeds. The F1 generation was allowed to self-fertilize. What types of gametes, and in what proportions, would the F1 generation make

> Describe the difference between genotype and phenotype. Give three examples. Is it possible for two individuals to have the same phenotype but different genotypes?

> Honeybees are unusual in that male bees (drones) have only one copy of each gene, but female bees have two copies of their genes. This difference arises because drones develop from eggs that have not been fertilized by sperm cells. In bees, the trait of

> On rare occasions, an organism may have three copies of a chromosome and therefore has three copies of the genes on that chromosome (instead of the usual number of two copies). For such a rare organism, the alleles for each gene usually segregate so that

> What are the expected phenotypic ratios from the following cross: Tt Rr yy Aa × Tt rr YY Aa, where T = tall, t = dwarf, R = round, r = wrinkled, Y = yellow, y = green, A = axial, a = terminal; T, R, Y, and A are dominant alleles. Note: Consider using the

> A true-breeding tall pea plant was crossed to a true-breeding dwarf plant. What is the probability that an F1 individual will be truebreeding? What is the probability that an F1 individual will be a true-breeding tall plant?

> A true-breeding pea plant with round and green seeds was crossed to a true-breeding plant with wrinkled and yellow seeds. Round and yellow seeds are the dominant traits. The F1 plants were allowed to self-fertilize. What are the following probabilities f

> Marfan syndrome is a rare inherited human disorder characterized by unusually long limbs and digits plus defects in the heart (especially the aorta) and the eyes, among other symptoms. Following is a pedigree for this disorder. Affected individuals are s

> In people with maple syrup urine disease, the body is unable to metabolize the amino acids leucine, isoleucine, and valine. One of the symptoms is that the urine smells like maple syrup. An unaffected couple produced six children in the following order:

> At which stage do homologous chromosomes separate from each other?

> An individual has the genotype Aa Bb Cc and makes an abnormal gamete with the genotype AaBc. Does this gamete violate the law of independent assortment or the law of segregation (or both)? Explain your answer.

> For pea plants with the following genotypes, list the possible gametes that the plant can make: A. TT Yy Rr C. Tt Yy Rr B. Tt YY rr D. tt Yy rr

> A true-breeding tall plant was crossed to a dwarf plant. Tallness is a dominant trait. The F1 individuals were allowed to self-fertilize. What are the following probabilities for the F2 generation? A. The first plant is dwarf. B. The first plant is dwa

> What is the difference between cross-fertilization and self-fertilization?

> Albinism, a condition characterized by a partial or total lack of skin pigment, is a recessive human trait. If a phenotypically unaffected couple produce an albino child, what is the probability that their next child will be albino?

> In humans, the allele for brown eye color (B) is dominant to that for blue eye color (b). If two heterozygous parents produce children, what are the following probabilities? A. The first two children have blue eyes. B. A total of four children, two with

> A cross was made between a white male dog and two different black females. The first female gave birth to eight black pups, and the second female gave birth to four white and three black pups. What are the likely genotypes of the male parent and the two

> In cocker spaniels, solid coat color is dominant over spotted coat color. If two heterozygous dogs were crossed to each other, what would be the probability of the following combinations of offspring? A. A litter of five pups, four with solid fur and on

> Identical twins are produced from the same sperm and egg (which splits after the first mitotic division), whereas fraternal twins are produced from separate sperm and separate egg cells. If two parents with brown eyes (a dominant trait) produce one twin

> Ectrodactyly, also known as “lobster claw syndrome,” is a recessive disorder in humans. If a phenotypically unaffected couple produces an affected offspring, what are the following probabilities? A. Both parents are heterozygotes. B. An offspring is a

> Are all of the cell nuclei in the embryo sac haploid or is just the egg haploid?

> For the following pedigrees, describe what you think is the most likely inheritance pattern (dominant versus recessive). Explain your reasoning. Filled (black) symbols indicate affected individuals. I-1 I-2 II-1 II-2 II-3 II-4 II-5 III-1 III-2 III-3

> Describe the significance of nonparentals with regard to the law of independent assortment. In other words, explain how the appearance of nonparentals refutes a linkage hypothesis.

> A pea plant that is heterozygous with regard to seed color (yellow is dominant to green) is allowed to self-fertilize. What are the predicted outcomes of genotypes and phenotypes of the offspring?

> A cross is made between a pea plant that has constricted pods (a recessive trait; smooth is dominant) and is heterozygous for seed color (yellow is dominant to green) and a plant that is heterozygous for both pod texture and seed color. Construct a Punne

> Why did Mendel’s work refute the idea of blending inheritance?

> What is meant by the term diploid? Which cells of the human body are diploid, and which cells are not?

> Your textbook describes how the detrimental symptoms associated with the disease phenylketonuria (PKU) are caused by a faulty gene. Even so, a change in diet can prevent these symptoms. Pick a trait in your favorite plant and explain how genetics and the

> What is the cause of Down syndrome?

> What is meant by the term genetic variation? Give two examples of genetic variation not discussed in Chapter 1. What causes genetic variation at the molecular level?