Questions and Answers of Human Biology

Look back at the discussion of aging and DNA repair in Chapter 17 and Chapter 21, then propose an explanation of the observation that higher rates of cancer are associated with increasing age.
In the diagram above, summarize the main events in meiosis.
Define and describe the main features of the following developmental stages: fertilization, cleavage, gastrulation.
Development cannot proceed properly unless each of the following processes is successfully completed before the next begins, starting with ________.a. Gamete formationb. Fertilizationc. Cleavaged.
How accurate is the statement “A pregnant woman must do everything for two”? Give some specifics to support your answer.
Define cell differentiation and morphogenesis, two processes that are critical for development.
A renowned developmental biologist, Lewis Wolpert, once observed that birth, death, and marriage are not the most important events in human life—rather, Wolpert said, the most important moment in
During cleavage, the ________ is converted to a ball of cells, which in turn is transformed into the ________.a. Zygote; blastocystb. Trophoblast; embryonic diskc. Ovum; embryonic diskd. Blastocyst;
Summarize the development of an embryo and a fetus. When are body parts such as the heart, nervous system, and skeleton largely formed?
In the week following implantation, cells of the ________ will give rise to the embryo.a. Blastocystb. Trophoblastc. Embryonic diskd. Zygote
One of your best friends tells you that she and her husband think she might be pregnant. She feels she can wait until she’s several months along before finding an obstetrician. You think she could
Label the early development stages shown in the following diagram.
The complications of ectopic pregnancy (Section 17.2) are life-threatening for the mother, and in fact each year in the United States a few pregnant women die when their situation is not diagnosed in
The developmental process called ________ produces the shape and structure of particular body regions.
________ is the gene-guided process by which cells in different locations in the embryo become specialized.a. Implantationb. Neurulationc. Cell differentiationd. Morphogenesis
Match each developmental stage with its description. cleavage gamete formation organ formation cell differentiation gastrulation fertilization a. egg and sperm mature in parents b. sperm, egg nuclei
In a human zygote, the cell divisions of cleavage produce an embryonic stage known generally as a ________.a. Zona pellucidab. Gastrulac. Blastocystd. Larva
Of the four extraembryonic membranes, only the ________ is not needed in order for an embryo to develop properly.a. Yolk sacb. Allantoisc. Amnion because all are neededd. Chorione. This is a trick
All of the following apply to the birth process (labor) except ________.a. It consists of four main stages.b. Hormones from the fetus trigger it.c. In a newborn, breathing air triggers the
Of the following, ________ cannot cross the placenta.a. Alcoholb. The mother’s antibodiesc. Antibioticsd. Toxic substances in tobacco smokee. All can cross the placenta
Define somatic cell and germ cell.
DNA, packaged in chromosomes, is distributed to daughter cells by _______ or _______.
Normally you can’t inherit both copies of a homologous chromosome from the same parent. Why? Assuming that no crossing over has occurred, how likely is it that one of your non-sex chromosomes is an
Each kind of organism contains a characteristic number of _______ in each cell; each of those structures is composed of a _______ molecule and proteins.
Suppose you have a way of measuring the amount of DNA in a single cell during the cell cycle. You first measure the amount during the G1 phase. At what points during the remainder of the cycle would
Define somatic cell and germ cell.
A pair of chromosomes that are similar in length and the traits they govern are called _______.a. Diploid chromosomesb. Mitotic chromosomesc. Homologous chromosomesd. Germ chromosomes
Adam’s maternal and paternal chromosomes have alternate forms of a gene that influences whether a person is right-handed or left-handed. One form says “right” and its partner says “left.”
Name the four main stages of mitosis, and describe what happens in each stage.
Somatic cells have a _______ number of chromosomes.
Fresh out of college, Maria has her first job teaching school. When she goes for a pre-employment chest X-ray required by the school district, the technician places a lead-lined apron over her
Interphase is the stage when _______.a. A cell ceases to functionb. A germ cell forms its spindlec. A cell grows and duplicates its DNAd. Mitosis takes place
In a paragraph, summarize the similarities and differences between mitosis and meiosis.
After mitosis, each daughter cell contains genetic instructions that are _______ and _______ chromosome number of the parent cell.a. Identical to the parent cell’s; the sameb. Identical to the
All of the following are stages of mitosis except _______.a. Prophaseb. Interphasec. Metaphased. Anaphase
A duplicated chromosome has _______ chromatids.a. Oneb. Twoc. Threed. Four
Crossing over in meiosis _______.a. Occurs between sperm DNA and egg DNA at fertilizationb. Leads to genetic recombinationc. Occurs only rarely
Match the stage of mitosis with the following key events. metaphase prophase telophase anaphase a. sister chromatids separate and move to opposite poles b. chromosomes condense and a microtubular
Because of the _______ alignment of homologous chromosomes during meiosis, gametes can end up with _______ mixes of maternal and paternal chromosomes.a. Unvarying; differentb. Unvarying; duplicatec.
Alleles are _______.a. Alternate forms of a geneb. Different molecular forms of a chromosomec. Always homozygousd. Always heterozygous
One gene has alleles A and a. Another has alleles B and b. For each genotype listed, what type(s) of gametes can be produced? (Assume independent assortment occurs.)a. AABBc. Aabbb. AaBBd. AaBb
Some people have proposed that all nuclear power plants in the United States be phased out over the next 20 years. Explain why you agree or disagree
Define somatic cell and germ cell.
Explain the difference between a primate and a hominin.
A heterozygote has _______.a. Only one of the various forms of a geneb. A pair of identical allelesc. A pair of contrasting allelesd. A haploid condition, in genetic terms
Define the difference between.(a) Gene and allele.(b) Dominant allele and recessive allele.(c) Homozygote and heterozygote.(d) Genotype and phenotype.
Cancer cells _______.a. Lack normal controls over cell divisionb. Secrete the growth factor angiogeninc. Display altered surface proteinsd. Are not inhibited by contact with other cellse. All of the
So far as we know, carcinogenesis is not triggered by _______.a. Breakdowns in DNA repairb. A breakdown in immunityc. Radiation defectsd. Protein deficiencye. Inherited gene
Using the diagram below as a guide, indicate the major steps in cancer metastasis.
_______ is the definitive method for detecting cancer.a. Blood testingb. Physician examinationc. Biopsyd. Medical imaging
The most common therapeutic approaches to treating cancer include all of the following except _______.a. Chemotherapyb. Irradiation of tumorsc. Surgery to remove cancerous tissued. Administering
Still referring to Problem 1, what will be the possible genotypes of offspring from the following matings? With what frequency will each genotype show up?a. AABB x aaBBb. AaBB x AABbc. AaBb x aabbd.
State the theory of segregation. Does segregation occur during mitosis or during meiosis?
The observable traits of an organism are its _______.a. Phenotypeb. Pedigreec. Genotyped. Multiple allele system
Go back to Problem 1, and assume you now study a third gene having alleles C and c. For each genotype listed, what type(s) of gametes can be produced?a. AABBCCb. AaBBccc. AaBBCcd. AaBbCcProblem
What is probability, and how is it applied in genetic analysis?
Offspring of a cross AA x aa are _______.a. All AAb. All aac. All Aad. 1/2 AA and 1/2 aae. None of the above
The young woman shown at right has albinism—very pale skin, white hair, and pale blue eyes. This phenotype is due to the absence of melanin, which imparts color to the skin, hair, and eyes. It
What is independent assortment? Does independent assortment occur during mitosis or during meiosis?
We say a gene is expressed when _______.a. A parent passes it to offspringb. A cell makes the protein coded by the gene’s chemical instructionsc. Its chemical instructions are “read out” in a
When you decide to breed your Labrador retriever Molly and sell the puppies, you discover that two of Molly’s four siblings have developed a hip disorder that is traceable to the action of a single
Assuming complete dominance, offspring of the cross Aa x Aa will show a phenotypic ratio of _______.a. 1:2:1b. 1:1:1c. 9:1d. 3:1
The ABO blood system has been used to settle cases of disputed paternity. Suppose, as a geneticist, you must testify during a case in which the mother has type A blood, the child has type O blood,
Which statement best fits the principle of segregation?a. Units of heredity are transmitted to offspring.b. Two genes of a pair separate from each other during meiosis.c. Members of a population
Soon after a couple marries, tests show that both the man and the woman are heterozygotes for the recessive allele that causes sickling of red blood cells; they are both HbA/ HbS. What is the
Crosses involving parents that are heterozygous for two traits (AaBb x AaBb) lead to offspring with phenotypic ratios close to _______.a. 1:2:1b. 1:1:1:1c. 3:1d. 9:3:3:1
A man is homozygous dominant for ten different genes that assort independently. How many genotypically different types of sperm could he produce? A woman is homozygous recessive for eight of these
Reasons that many phenotypes can’t be predicted with certainty include:a. There is continuous variation in a gene’s effects.b. A trait is shaped by more than one gene and by some aspect of a
Match each genetic term appropriately. cross involving two traits cross involving one trait homozygous condition heterozygous condition a. Aa x Aa b. Aa c. AABB X aabb d. aa
As is the case with the mutated hemoglobin gene that causes sickle-cell anemia, certain dominant alleles are crucial to normal functioning (or development). Some are so vital that when the mutant
Bill and Marie each have flat feet, long eyelashes, and “achoo syndrome” (chronic sneezing). All are dominant traits. The genes for these traits each have two alleles, which we can designate as
You decide to breed a pair of guinea pigs, one black and one white. In guinea pigs, black fur is caused by a dominant allele (B) and white is due to homozygosity for a recessive allele (b) at the
How do X and Y chromosomes differ?
_______segregate during _______.a. Homologues; mitosisb. Genes on one chromosome; meiosisc. Homologues; meiosisd. Genes on one chromosome; mitosis
If a couple has six boys, what is the probability that a seventh child will be a girl?
What is a “carrier” of a genetic trait?
The alleles of a gene on homologous chromosomes end up in separate _______.a. Body cellsb. Gametesc. Nonhomologous chromosomesd. Offspringe. Both b and d are possible
Human sex chromosomes are XX for females and XY for males.a. With respect to an X-linked gene, how many different types of gametes can a male produce?b. If a female is homozygous for an X-linked
What evidence indicates that a trait is coded by a dominant allele on an autosome?
Genes on the same chromosome tend to stay together during _______ and end up in the same _______.a. Mitosis; body cellb. Mitosis; gametec. Meiosis; body celld. Meiosis; gametee. Both a and d
People with Down syndrome have an extra copy of chromosome 21, for a total of 47 chromosomes. However, in a few cases of Down syndrome, 46 chromosomes are present. This total includes two
Explain the difference between an X-linked trait and a sex-influenced trait.
The probability of a crossover occurring between two genes on the same chromosome _______.a. Is unrelated to the distance between themb. Increases the closer they arec. Increases the farther apart
If a trait appears only in males, is this good evidence that the trait is due to a Y-linked allele? Explain why you answered as you did.
Explain what nondisjunction is, and give two examples of phenotypes that can result from it.
A chromosome’s structure can be altered by _______.a. Deletionsb. Duplicationsc. Translocationsd. All of the above
A woman unaffected by hemophilia A whose father had hemophilia A marries a man who also has hemophilia A. If their first child is a boy, what is the probability he will have the disorder?
Nondisjunction can be caused by _______.a. Crossing over in meiosisb. Segregation in meiosisc. Failure of chromosomes to separate during meiosisd. Multiple independent assortments
About 4 percent of people of Northern European descent have a cystic fibrosis allele, but only about 1 in 2,500 of these people actually has the disorder. What is the most likely reason for this
The following pedigree shows the pattern of inheritance of red–green color blindness in a family. Females are shown as circles and males as squares; the squares or circles of individuals affected
A gamete affected by nondisjunction could have _______.a. A change from the normal chromosome numberb. One extra or one missing chromosomec. The potential for a genetic disorderd. All of the above
Genetic disorders can be caused by _______.a. Gene mutationsb. Changes in chromosome structurec. Changes in chromosome numberd. All of the above
Match the following chromosome terms appropriately. crossing over deletion nondisjunction translocation gene mutation a. a chemical change in DNA that may affect genotype and phenotype b. movement of
A person who is a carrier for a genetic trait _______.a. Is heterozygous for a dominant traitb. Is heterozygous for a recessive traitc. Is homozygous for a recessive traitd. Could be either a or b
Which mutation would be more harmful: a mutation in DNA or one in mRNA? Explain your answer.
Why is DNA replication called “semiconservative”?
Nucleotide bases, read ______ at a time, serve as the “code words” of genes.
Jimmie’s Produce put out a bin of tomatoes having beautiful red color and looking “just right” in terms of ripeness. A sign above the bin identified them as genetically modified produce. Most
Name one kind of mutation that produces an altered protein. What determines whether the altered protein will have beneficial, neutral, or harmful effects?
DNA contains genes that are transcribed into ______.a. Proteinsb. MRNAsc. RRNAsd. TRNAse. B, c, and d

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