Biology Exam 3: Chapters 12-14 Cell Cycle and Genetics

What do we mean when we use the terms "monohybrid cross" and "dihybrid cross"?

A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.

Which of the following statements about the meiosis are correct?

Crossing over occurs between non-sister chromatids. Sister chromatids are not homologous chromosomes.

In eukaryotic cells, chromosomes are composed of _____.

DNA and proteins

Independent assortment of chromosomes occurs during _____.

Meiosis I only

Which of the following statements about meiosis and mitosis is true?

Meiosis II is similar to mitosis in that sister chromatids of each chromosome separate.

Which processes lead to most genetic variation in sexually reproducing organisms?

crossing over independent assortment of chromosomes in meiosis random fertilization

Mitosis separates chromosomes. The cytoplasm is divided between two daughter cells by ________.

cytokinesis

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?

different possible assortment of chromosomes into gametes

An advantage of asexual reproduction is that it _____.

enables the species to rapidly colonize habitats that are favorable to that species

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

environmental factors such as soil pH

Meiosis II typically produces _____ cells, each of which is _____.

four; haploid

When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.

gametes; progeny

What makes sexually reproduced offspring genetically different from their parents?

genetic recombination during meiosis

When drawing a Punnett square, the ___________ are listed on the outside edges.

genotypes of the parents' gametes

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have _____.

half the number of chromosomes and one-fourth the amount of DNA.

After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.

haploid, and the chromosomes are each composed of two chromatids

Replicated chromosomes line up at the metaphase plate in ______ pairs (tetrads).

homologous

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The flower color trait in radishes is an example of which of the following?

incomplete dominance

During _____ the cell grows and replicates both its organelles and its chromosomes.

interphase

Meiosis I produces _____ cells, each of which is _____.

two; haploid

Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?

25%

What is the ploidy of organisms that have two sets of chromosomes?

2n

In Mendel's experiment with round- and wrinkled-seed plants, the F1 plants, which produced only round seeds, matured and were allowed to self-fertilize. What was the ratio of round to wrinkled seeds in the F2 generation?

3 round-seed producing plants: 1 wrinkled-seed producing plant.

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?

38

Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white.(a) What is the most probable genotype of each parent?(b) Based on your answer in (a) above, what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols: G = gray and g = white.)

(a) Gg × Gg; (b) genotypic = 1:2:1, phenotypic = 3:1

Difference between mitosis and meiosis

-Mitosis : diploids(two identical) -Meiosis : haploids(four genetically different)

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?

0

If a purple-flowered, heterozygous plant were crossed with a white-flowered plant, what is the expected ratio of genotypes among the F1F1 offspring? Suppose PP is a dominant allele for a flower color and pp is a recessive one.

1 PpPp : 1 pp

A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits?

1/2

What proportion of chromosomes in a man's skin cell are maternal chromosomes?

1/2

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first child will be an albino?

1/4

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first female child will have albinism?

1/4

Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring?

1/8

A cell in G1 phase has 6 unreplicated chromosomes. How many DNA double helices does the cell have after chromosome replication?

12

If a cell has 24 chromosomes, how many chromosomes would each of its four daughter cells have after meiosis?

12

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. If 1000 F2 offspring resulted from a dihybrid cross, approximately how many of them would you expect to have red, terminal flowers?

190

When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded plants, what genotypic ratio was expected?

1:1

Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?

2

After S phase, what makes up a single chromosome?

2 sister chromatids

How many double-helical DNA molecules will be present in the sperm and egg cells of dogs that are diploid animals that contain 78 replicated chromosomes in each cell that enters meiosis?

39. There would 78 replicated chromosomes at the start of meiosis I, each with two molecules of DNA. The number of replicated chromosomes is reduced to 39 at the end of meiosis I. During meiosis II, the sister chromatids of the replicated chromosomes are separated to become individual daughter chromosomes, each with one molecule of DNA. This means that each of the daughter cells at the end of meiosis contains 39 unreplicated chromosomes and 39 molecules of double-stranded DNA.

In tigers, a recessive allele causes a white tiger (absence of fur pigmentation). If one phenotypically normal tiger that is heterozygous is mated to another that is phenotypically white, what percentage of their offspring is expected to be white?

50%

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

50%

A cell begins G1 phase with 6 unreplicated chromosomes. This cell undergoes S, G2, and M phases. How many chromosomes will the daughter cells contain?

6

A cell has 6 unreplicated chromosomes. How many replicated chromosomes does the cell have after chromosome replication?

6

Radish flowers may be red, purple, or white. The part of the radish we eat may be oval or long. A cross between a red-flowered long radish plant and a white-flowered oval radish plant yields all-purple long radish offspring. Then the F1 are crossed. In the resulting F2 generation, which of the following phenotypic ratios would be expected?

6:3:3:2:1:1

The chromosome number of hexaploid wheat, Triticum aestivum, can be represented as _____.

6n

In humans, male-pattern baldness may be assumed to be controlled by an autosomal gene that occurs in two allelic forms. Allele B determines nonbaldness, and allele b determines pattern baldness. In males, because of the presence of testosterone, allele b is dominant over B. If a man and woman both with genotype Bb have a son, what is the chance that he will eventually be bald?

75%

The egg of a fruit fly has 4 individual chromosomes. How many chromosomes are in a somatic (body) cell of a fruit fly?

8

A black guinea pig crossed with an albino guinea pig produced twelve black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for this genetic situation?

Albino is recessive; black is dominant.

What is the difference between heterozygous and homozygous individuals?

All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.

In meiosis, homologous chromosomes are separated during ________.

Anaphase I

Centromeres split and sister chromatids migrate to opposite poles in ________ of meiosis.

Anaphase II

Which of the following stages of meiosis is correctly matched to chromosome composition at that stage?

Anaphase I−−two sister chromatids

If you followed a woman's cells through meiosis, at what stage of meiosis would the amount of DNA in one of these cells be equal to the amount of DNA in one of her G1 phase (before DNA replication) kidney cells?

At the end of meiosis I. In a kidney cell before DNA replication, there are pairs of each chromosome, with one double-helical molecule of DNA per chromosome; at the end of meiosis I, each cell has only one of each type of chromosome, but each chromosome has two double-helical molecules of DNA.

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation and have one child out of three who is albino (without melanin pigmentation). What are the genotypes of the albino's parents?

Both parents must be heterozygous.

Mendel's experimental method involved using true breed parental plants for each of the traits he studied in the monohybrid cross. Why was this vital to the outcomes of the experiment?

By starting with a true breed pure line, Mendel could better understand the inheritance of the traits as only due to the result of the cross.

Which structure is directly correlated with the production of genetic variability in the daughter cells produced during meiosis?

Chiasma

The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid. Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II. During anaphase of both meiosis I and meiosis II, the DNA content (number of copies of chromosomes) in a cell is halved. However, the ploidy level changes only when the number of unique chromosome sets in the cell changes. This occurs only in meiosis I (where separation of homologous chromosomes decreases the ploidy level from 2n to n and produces daughter cells with a single chromosome set).

What is occurring during the S phase of the cell cycle?

DNA is synthesized

The alleles found in haploid organisms cannot be dominant or recessive. Why?

Dominance and recessiveness describe which of two possible phenotypes are exhibited when two different alleles occur in the same individual.

Mendel crossed plants that produced only round seeds to those that produced only wrinkled seeds. In the next generation, all the pea plants produced only round seeds. Which term describes how the round-seed allele is inherited?

Dominant

Since independent assortment can occur in different ways during meiosis, two people could come up with different color-combinations of chromosomes in their drawings of gametes, and both be correct.

False

True or false? A haploid organism has one pair of homologous chromosomes.

False

If the cell continues toward the completion of mitosis, which of the following events would occur next?

Formation of telophase nuclei

The somatic cells of a privet shrub each contain 46 chromosomes. How do privet chromosomes differ from the chromosomes of humans, who also have 46?

Genes of privet chromosomes are significantly different from those in humans.

Which statement about the difference between homologous chromosomes and sister chromatids is correct?

Homologous chromosomes contain the same genes but often different alleles. Sister chromatids contain the same genes and the same alleles.

Which of the following happens at the conclusion of meiosis I?

Homologous chromosomes of a pair are separated from each other.

A key difference between mitosis and meiosis is

Homologs pair up and crossing over happens during meiosis I but does not happen in mitosis

During which phase of the cell cycle is the cell actively participating in the functions of a multicellular organism as well as undergoing all the preparation for cell division?

Interphase. It's the "time between phases" when the cell is carrying out tissue functions and preparing for division.

Malignant tumor cells possess the ability to cause metastatic tumors a great distance from the primary tumor site. How do tumor cells cause this to happen?

Malignant cells break free of the primary tumor and travel through the bloodstream and lymphatic system.

Crossing over normally takes place during which of the following processes?

Meiosis I

During _____ chromosomes align single file along the equator of a haploid cell.

Metaphase II

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?

One allele was dominant.

What is the composition of a tetrad at the beginning of prophase I?

One pair of homologous chromosomes

In humans, blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait. A woman with blue eyes and normal color vision whose father was color-blind marries a man who also has normal color vision. He has brown eyes, but his mother had blue eyes. Which of the following would you expect to be TRUE for their sons?

One-fourth of their sons will be color-blind and have blue eyes, one-fourth of their sons will be color-blind and have brown eyes, one-fourth of their sons will have normal color vision and blue eyes, one-fourth of their sons will have normal color vision and brown eyes.

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their twenties. How likely is it for a woman to have this condition?

One-half of the daughters of an affected father and a carrier mother could have this condition.

Mendel studied seven different traits in the garden pea. What genetic term is used to describe an observable trait, such as those studied by Mendel?

Phenotype

Mendel studied the inheritance of several types of pea-plant traits, including seed color. Seed color is an observable trait of the plant and is termed a(n) ___________________ .

Phenotype

How is plant cell cytokinesis different from animal cell cytokinesis?

Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.

Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize the amino acid phenylalanine. This amino acid is not naturally produced by humans. Therefore, the most efficient and effective treatment is which of the following?

Regulate the diet of the affected persons to severely limit the uptake of the amino acid.

What is a major difference between mitosis and meiosis I in a diploid organism?

Sister chromatids separate in mitosis; homologous pairs of chromosomes separate in meiosis I.

checklist of tips for drawing chromosomes during independent assortment:

Start with replicated chromosomes. Decide which details to include. Line up pairs at the metaphase plate. Pair homologous chromosomes. Use maternal/paternal color codes.

Synapsis occurs during _____.

Synapsis, the pairing of homologous chromosomes, occurs during prophase I.

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

XnXn and XnY

Which of the following statements about independent assortment and segregation is correct?

The law of independent assortment requires describing two or more genes relative to one another.

How did Mendel's monohybrid cross with round and wrinkled seeds and other single traits tested, directly contradict the blending hypothesis?

The result of the cross between round and wrinkled pure breed cell lines was all round seeds in the F1 offspring, not partially round and wrinkled as blending theory would predict.

How does a homozygous round seed plant differ from a heterozygous round seed plant in the F2 generation?

The round seed heterozygote has a genotype with two different alleles (Rr) while the round seed homozygote has the same allele (RR).

What information can not be obtained from an individual's karyotype?

The sequence of bases of a particular gene

What major events occur during anaphase of mitosis?

The sister chromatids on replicated chromosomes separate, and the spindle poles are pushed farther apart; Anaphase completes the critical step of the separation of replicated chromosomes to opposite poles to ensure that each daughter cell receives the same complement of chromosomes.

Why is the pea wrinkled-seed allele a recessive allele?

The trait associated with the allele is not exhibited in heterozygotes.

Assume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of meiosis. If crossing over did not occur, which of the following statements about meiosis would be true?

There would be less genetic variation among gametes.

Which statement about the daughter cells following mitosis and cytokinesis is correct?

They are genetically identical to each other and to the parent cell.

Each chromatid contains a single molecule of double-stranded DNA.

True

Each chromatid within a chromosome contains the same set of genes.

True

Each chromosome contains both DNA and protein.

True

Homologous chromosomes migrate to opposite poles during _____.

anaphase I

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

anaphase I of meiosis

During _____ sister chromatids separate.

anaphase II

Sexual reproduction _____.

can produce diverse phenotypes that may enhance survival of a population in a changing environment

Homologous chromosomes _____.

carry information for the same traits

What are homologous chromosomes?

chromosomes that are similar in their size, shape, and gene content

For the duration of meiosis I, each chromosome _____.

consists of two sister chromatids joined by a centromere

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

length, centromere position, staining pattern, and traits coded for by their genes

Homologous pairs of chromosomes align opposite to each other at the equator of a cell during ________.

metaphase I of meiosis

Sister chromatids separate from each other during _____.

mitosis and meiosis II

A cell near the end of anaphase of mitosis will have ________.

no chromosomes in the center of the cell

The first gap in the cell cycle (G1) corresponds to ________.

normal cell growth and function

When does DNA replication take place regarding meiosis? DNA replication _____.

occurs before meiosis I begins

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?

pleiotropy

Which of the following describes the ability of a single allele to have multiple phenotypic effects?

pleiotropy

When we first see chiasmata under a microscope, we know that _____.

prophase I is occurring

During _____ a spindle forms in a haploid cell.

prophase II

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be expected to be which of the following?

purple and long

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6022 yellow and 2001 green (8023 total). The allele for green seeds has what relationship to the allele for yellow seeds?

recessive

Cell cycle

series of events that cells go through as they grow and divide

Which of the following is an example of polygenic inheritance?

skin pigmentation in humans

Which of the following occurs in meiosis but not in mitosis?

synapsis of chromosomes

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

telophase I

At the end of _____ and cytokinesis there are four haploid cells.

telophase II

A genetic cross of a parent who has a dominant phenotype, but an unknown genotype (R?Y?), with a parent who contains only recessive alleles (rryy) is known as ___________.

testcross

During _____ both the contents of the nucleus and the cytoplasm are divided.

the mitotic phase

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that _____.

the parents were both heterozygous for the particular trait

Taxol is an anticancer drug extracted from the Pacific yew tree that disrupts microtubule formation in animal cells. When Taxol is added to animal cells, cell division stops. Specifically, Taxol must affect ________.

the structure of the mitotic spindle

Mendel accounted for the observation that traits that had disappeared in the F1 generation reappeared in the F2 generation by proposing that ________.

traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1 generation