biology test 3

In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos?

Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.

A tetrahybrid cross is one involving four characters that assort independently. You want to estimate the outcomes of such a cross in your pet fruitflies. How will you estimate the frequencies of genotypes in the offspring?

Set up each monohybrid cross, calculate the probabilities for each allele pair in that cross, then multiply the probabilities together. Your denominator will be 256.

Which of the following is an INCORRECT statement regarding sex-linked genes?

Sex-linked genes determine only the sex of the organism.

It's your 10-year high school reunion. Everyone seems to have grown and changed so much—except Ralph. He still lives in the same place, drives the same old car, and tells the same old tired jokes. Because you are a biology major who understands the cell cycle, you say which of the following to Ralph?

"Oh, Ralph! You're stuck in G0!"

If one parent is blood type AB and the other is type O, what fraction of their offspring is expected to have blood type A?

0.5

A red snapdragon (RR) is crossed with a white snapdragon (rr). R is known to be incompletely dominant to r. Members of the F1 generation are then crossed. What is the ratio of flower colors in the F2 generation?

1 red: 2 pink: 1 white

The human X chromosome has about ______ genes. The Y chromosome has about ____ genes. The fruit fly has ____ chromosomes.

1,110: 78: 8

The existence of rare XY individuals who are phenotypically normal women was instrumental in learning about human sex determination. Maleness is determined by the SRY gene found on the Y chromosome. How is it possible to be an XY woman

The SRY locus of the Y chromosome is deleted.

According to one hypothesis, the high prevalence of the sickle-cell allele in some people of African descent has a selective advantage. How does this work?

The malarial parasite triggers sickling in red blood cells, causing the body's defense system to destroy both the cells and the parasite.

what is the order to events that happen when a growth factor causes a cell to begin dividing

1. growth factor is present in extracellular fluid 2. growth factor binds to receptor protein 3. intracellular proteins relay signal to cell cycle control system 4. cell cycle control system overrides G1 checkpoint 5. cell proceeds to S phase

Filomena is a carrier for albinism, a recessive genetic disorder. Javier is also a carrier for this trait. They fall in love and marry. What is the probability that two of their children will have albinism?

1/16

High levels of LDL cholesterol in the bloodstream can be the result of familial hypercholesterolemia, an inherited condition that displays incomplete dominance. In a family with a severely affected father and an unaffected mother, what percentage of their children are expected to have higher than normal blood cholesterol?

100%

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

16

There are over 100 alleles known for the gene associated with cystic fibrosis. With current technology, it is possible to determine exactly which allele or alleles is/are carried by a person. What is the maximum number of different alleles that any person can carry?

2

Normal human gametes carry _____ chromosomes.

23

In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different gametes.

2^23

For any species with two or more chromosomes, the total number of chromosome combinations that can be produced in meiosis is _____.

2n, where n = the haploid number of chromosomes

On average, what percentage of infants born to 45-year-old mothers have Down syndrome?

3%

In Labrador retrievers, black coat is dominant to chocolate, normal vision is dominant to progressive retinal atrophy (PRA), and normal hip joint is dominant to hip dysplasia. The alleles for all of these traits assort independently. Two dogs that are heterozygous for alleles of all three genes are crossed. Using the rules of probability (not a Punnett square), what is the chance that the first pup born to these dogs will be black, have PRA, and have hip dysplasia?

3/64

In pea plants, the yellow seed allele (Y) is dominant over the green seed allele (y). What is the phenotypic ratio of yellow seeds to green seeds in the F2 generation resulting from a cross between two true-breeding parents, one with YY and one with yy?

3:1

A somatic human cell that is preparing to divide has ____ chromosomes and _____ chromatids. Each resulting daughter cell has ____ chromosomes.

46 duplicated; 92; 46 single

A woman who is a carrier of hemophilia marries a man affected with hemophilia. What percentage of their sons and daughters is expected to have hemophilia?

50% of sons and 50% of daughters

Huntington's disease (HD) is a dominant genetic disorder with an onset in the late 30s, when many people have already started their families. What is the probability that a child born to a man with the HD allele (H) and a woman without this allele (h) will have Huntington's disease? Will the children who do not develop the disease be carriers of the HD allele?

50%; no

Polyploidy is involved in which of the following examples?

A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes

Which of the choices most accurately summarizes Mendel's law of segregation as expressed using modern genetic terminology?

Alleles separate from each other (segregate) during gamete formation.

Imagine that a mutant strain of Drosophila undergoes crossing over at half the normal rate. How would a genetic map prepared for this mutant differ from a genetic map prepared for a normal (wild type) fly?

The order of genes would be the same in both strains, but the distances measured between genes in the mutant would be half those of the wild type

Imagine that four genes on a single chromosome in a mutant phenotype of Drosophila cross over at half the normal rate as in the wild-type phenotype. How, if at all, would genetic maps of that chromosome differ between this mutant and the wild-type fly?

The order of genes would be the same, but the four genes in the mutant would be closer together than in the wild type.

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?

Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

Consider the photograph of a karyotype. This is _____.

a photograph of all a person's chromosomes

Which of the following is the best definition of a "wild-type" trait?

a trait that is most common in nature

Which of the following choices lists correct information about trisomy 21 and characteristics of people with this disorder?

affects about 1/850 children; short stature; susceptible to leukemia

Nondisjunction during meiosis I results in a situation where _______. Nondisjunction during meiosis II results in a situation where _______.

all gametes are abnormal; some gametes are abnormal

In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this?

cancer cells continuously secrete growth factors into the cell culture medium

Chemotherapy affects the ______ of cancer cells. These drugs can produce nausea because they affect ______ cells, which divide ______.

cell cycle; intestinal; rapidly

Which of the following is an event that occurs during metaphase of mitosis in a dividing somatic cell?

centrosomes of sister chromatids line up

Fur color in dogs is a/an ________. Black fur on a Labrador retriever is a/an ______. The black fur is the result of the interaction between two _____.

character; trait; alleles of a gene

Crossing over occurs at _______

chiasmata

telophase and cytokinesis

chromosomes become less condensed and new nuclear envelope forms. in cytokinesis, the cytoplasm divides

Which of the following statements about clones is NOT correct?

clones can be produced by sexual reproduction

Meiosis differs from mitosis in that _____ only occurs in meiosis.

crossing over

A cell is treated with a drug that prevents the formation of vesicles. Which of the following processes depends on the formation of vesicles and would therefore be blocked?

cytokinesis in a plant cell

Which of the following would you expect to observe in normal cells, but not in cancer cells?

density dependent inhibition and anchorage dependence

An organism that is heterozygous for a gene has _________. Imagine a cross between two plants heterozygous for seed shape where R = round seeds and r = wrinkled seeds. Which of the following states the genotypes that will be produced from this cross?

different alleles of the gene: 1/4 RR: 1/2 Rr: 1/4 rr

A human karyotype is constructed from chromosomes visualized in a ____ cell. The autosomes are arranged from _____ and numbered ______. Each chromosome consists of two ______.

diploid; metaphase; largest to smallest; from 1 to 22; sister chromatids

In metaphase of mitosis, _______ line up at the metaphase plate. In metaphase I of meiosis I, _______ line up at the metaphase plate.

duplicated chromosomes; tetrads of homologus chromosomes

What are the main signs or symptoms of the most common lethal genetic disorder in the United States?

excess mucous production that affects the lungs, liver, and other organs

Recombinant chromosomes result from which of the following?

exchange of genetic material between homologus chromosomes

Which of the following statements about the sex chromosomes is INCORRECT?

females do not have homologus sex chromosomes

Eye color in fruitflies is an X-linked character with red eyes (R) dominant to white eyes (r). The Y chromosome does not have a gene locus for eye color. What is the outcome of a mating between a red-eyed male (XRY) and a red-eyed heterozygous female (XRXr)?

females: 100% have red eyes; males: 50% have red eyes and 50% have white eyes

Consider the photograph shown below. You can determine this is a plant cell rather than an animal cell because it has __________

formed a cell plate

meiosis starts with a diploid cell and produces what

four haploid cells

Which of the following events DOES NOT OCCUR during interphase of a dividing cell's cell cycle?

fragmentation of nuclear envelope

You love to eat frogs' legs and want to start raising frogs. Your friend tells you that the size of frogs' legs is inherited with incomplete dominance, with the L allele for great big legs dominant and ll frogs having tiny legs. You believe, however, that frog leg size is a polygenic trait. When you visit a neighboring frog farm to start your new career, what observation would prove that you are correct?

frogs with a wide range of leg sizes

Crossing over of genes on homologous chromosomes during meiosis leads to which of the following?

gametes that are different from the parental gametes

The chromosome theory of inheritance is based upon which of the following sets of observations?

genes segregate; chromosomes come in pairs

During anaphase I

homologous chromosomes separate and migrate toward opposite poles

Chromatids are _____

identical copies of each other if they are part of the same chromosome

Two identical twins are raised in different environments. They possess _____ genotypes and _____ phenotypes.

identical; variable

A cell preparing to undergo meiosis duplicates its chromosomes during

interphase

Our understanding of the role played by genes in many human characteristics is advancing rapidly in, for example, body size, performance on IQ tests, and personality traits. In this new genetic era, the role of the environment __________.

is to work with genes in complex and often unknown ways in the development of these traits

During binary fission, each copy of the duplicating chromosome moves to opposite ends of the cell. What does this achieve?

it ensures that each daughter cell receives a chromosome

What is the function of a cell plate in a dividing cell?

it will form the cell wall of a new plant

What is the difference between reciprocal translocations and crossing over?

reciprocal translocations occur between non-homologus chromosomes; crossing over occurs between homologus chromosomes

One version of a gene may encode __________, whereas a different version of the same gene may encode __________.

red eyes; white eyes

Which of the following events occurs in meiosis II?

separation of sister chromatids

anaphase

sister chromatids separate and become full fledged chromosomes that move to opposite poles

During anaphase II

sister chromatids separate and migrate toward opposite poles

Which of the following prenatal diagnostic tests involves the least risk to the mother or fetus AND is most informative regarding genetic disorders?

tests of fetal cells or DNA in mother's blood

When we say that an organism is haploid, we mean that _____

that its cells have one set of chromosomes

Which of the following did Mendel NOT investigate in his extensive studies of heredity?

the effects of the environment

during prophase 1 of meiosis

the homologus chromosomes stick together in pairs

metaphase

the mitotic spindle is fully formed and chromosomes are lined up in the middle of the cell

In people with sickle-cell disease, red blood cells break down, clump, and clog blood vessels. Blood vessels and broken cells accumulate in the spleen. Among other symptoms, this leads to physical weakness, heart failure, pain, and brain damage. Such a suite of symptoms can be explained by __________.

the pleiotropic effects of the sickle-cell allele

Two parents of mixed ethnicity have twins, one of which is born with very light skin and one of which is born with very dark skin. This is because of __________.

the polygenic nature of skin color genes

Sister chromatids have ______ DNA sequence(s). Homologous chromosomes can have _______ DNA sequence(s).

the same; different

Many genetic disorders can be detected before birth. Procedures include _____, which is noninvasive, or _____, which allows the chromosomes of the fetus to be examined. Alternatively, maternal blood samples can be taken and tested for _____.

ultrasound imaging ... chorionic villus sampling ... AFP

In a family pedigree to trace a trait of interest, an empty circle represents a/an _______. A blackened square represents a/an _______. ("Affected" means "has trait of interest"; "unaffected" means "Does not have trait of interest.")

unaffected woman: affected man

If the two characteristics that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located close together on the same chromosome, then the F2 generation __________.

would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment

We can better understand our ancestry by analyzing the __________ in males.

y chromosome

Although women with ductal carcinoma in situ (DCIS) are at relatively low risk of dying from that disease, one large, long-term study found that some patients are at higher risk than others. These higher-risk patients tend to be _______ or _______.

younger than 40; black

In Morgan's testcross of a gray-bodied, long-winged heterozygous female Drosophila with a homozygous recessive black-bodied, vestigial-winged male, the following offspring were obtained: 965 gray body, long wing; 944 black body, vestigial wing; 206 gray body, vestigial wing; 185 black body, long wing. Focusing only on the recombinant classes (gray body, vestigial wing and black body, long wing), the numbers of offspring of each type are similar (206 and 185). What accounts for the similar number of offspring of each recombinant phenotype?

Crossing over between chromosomes is reciprocal, so whenever a recombinant chromosome of one type is produced, there's a recombinant of the opposite type that is also produced.

An individual is heterozygous for a particular gene. Which of the following is true of this individual?

Different alleles of the gene are present at the same locus on homologous chromosomes.

Some insects, such as grasshoppers and roaches, have a sex determination system called "X-O." What are the characteristics of males and females in this system?

Females are XX: males are XO and half of their sperm lack a sex chromosome

When examining cells in the laboratory, you notice that a particular cell has half as much DNA as the surrounding cells. This observation can be explained if this cell's cell cycle halted at checkpoint _____.

G1

Immune system cells enter a resting phase after undergoing mitosis. When activated—for example, by an infection—they can reenter the sequence of events in the cell cycle that leads to cell division. What would be the correct cell cycle sequence of events for these reactivated cells?

G1, S, G2, M

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?

In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.

In breeding pure-breeding large and small strains of mice, you cross individuals of each strain and note that their offspring are intermediate in size. Two models (explanations) to account for this result are (1) that body size in these strains is due to one gene with alleles that show incomplete dominance and (2) that body size is a polygenic trait. How could you distinguish between these models?

Intercross the F1 and see if the F2 contains three size classes (consistent with the incomplete dominance model) or if there is a range of sizes (consistent with the polygenic model).

A person has the sex chromosomes XXXY. What is this condition called, and what is one of its symptoms?

Klinefelter syndrome; sterility

Why are lethal dominant alleles so much more rare than lethal recessive alleles?

Lethal dominant alleles are harmful whether they are carried in homozygous or heterozygous form, so there is always strong selection against these alleles.

Akin to urban legends, there are curious genetics legends - things like eye color being determined by one gene, with a brown eye allele being completely dominant to blue. The problem comes when simple myth meets the complex reality of how eye color and many other traits are transmitted. Why is the inheritance of so many traits difficult to explain using only Mendel's view of genetics?

Mendel was correct for the traits he investigated, but his principles must be extended (not discarded) to explain many more complex patterns of inheritance.

Maria, Susan, Josh, and LaShonda are exploring in a cave. Suddenly, Susan is injured by a rockslide and requires an immediate blood transfusion. Fortunately, all four are experienced medics and have all the equipment they need to perform a transfusion. Everyone knows his or her blood type. Who should volunteer to provide blood for Susan, and why? Here are the blood types: Susan: O Maria: AB Josh: A LaShonda: B

None of them, because people with Type O blood make antibodies against all other blood types.

Trisomy for most autosomes is fatal, yet trisomy or even tetrasomy (four copies) of the X chromosome is not. What is the explanation for this difference?

Only one copy of the X chromosome is functional within any given cell, regardless of the total number of X chromosomes.

John and Jane are planning a family, but each has a brother who has sickle-cell disease, so they are concerned that their children may develop sickle-cell disease. Neither John nor Jane nor their respective parents have the disease. They consult a genetic counselor who tells them that __________.

it's possible that they cannot produce a child with sickle-cell disease, but blood tests on them both will be required to make sure

Blue kernels in corn result from a dominant allele of a coloration gene, while white kernels result from a homozygous recessive allele of the same gene. A different gene has two alleles for shape, with smooth kernels being dominant to wrinkled. Plants heterozygous for both traits are crossed, with the following results: 1,447 blue smooth, 70 blue wrinkled, 25 white smooth, and 645 white wrinkled. What does this demonstrate?

linkage of the genes for kernel color and shape

Gametes are produced by _____.

meiosis

Variation occurs when chromosomes are shuffled in _____

meiosis

Malignant cells that spread beyond the site of origin exhibit _______. How are such cells spread

metastasis; via blood or lymph vessels

prophase

microtubules form the mitotic spindle and the nuclear envelope breaks up

interphase

most of the cells life is spent in interphase, which is when growth occurs. cells that are about to divide replicate their DNA

How many chromosomes does a typical bacterium have?

one

In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.

prophase

During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?

prophase 1

The correct order of events during meiosis is

prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.