Exam #4 Mastering Questions

Part complete Crossing over of chromosomes during meiosis shuffles parental chromosomes, resulting in a genetically unique child. Select the three true statements about crossing over.

-During meiosis II, sister chromatids separate into four different gametes. -A hybrid chromosome that has crossed over will contain pieces of both the maternal and paternal chromosomes. -During prophase I of meiosis I, homologous paternal and maternal chromosomes pair up and undergo crossing over.

Use the Punnett square from the introduction and the ones you drew for Part A to select the three statements that are true about the inheritance of this form of deafness.

-If a deaf child is born to hearing parents, both parents must be Dd. -If a deaf man and a hearing woman have a deaf child, the mother's genotype must be Dd. -The child of a deaf man and a DD hearing woman will definitely have hearing.

Which processes lead to most genetic variation in sexually reproducing organisms? Select all that apply.

-independent orientation of chromosomes in meiosis -random fertilization -crossing over

Which of the following events have not yet occurred? Select all that apply.

-separation of sister chromatids into distinct cells -production of four haploid gametes

In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?

1 AB : 1 aB

Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is a MendAlien with orange eyes and white skin. If Sam and Carole were to mate, the predicted phenotypic ratio of their offspring would be _____.

1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin

An individual heterozygous for eye color, skin color, and number of eyes mates with an individual who is homozygous recessive for all three characters; what would be the expected phenotypic ratio of their offspring? [Hint: B = black eyes, b = orangeeyes; G = green skin, g = white skin; C = two eyes, c = one eye]

1 black eyes, green skin, two eyes : 1 black eyes, green skin, one eye : 1 black eyes, white skin, two eyes : 1 black eyes, white skin, one eye : 1 orange eyes, green skin, two eyes : 1 orange eyes, green skin, one eye : 1 orange eyes, white skin, twoeyes : 1 orange eyes, white skin, one eye

Flower color in snapdragons is an example of incomplete dominance. If a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the expected progeny plants will be __________.

25% red, 50% pink, and 25% white

A woman with type O blood is expecting a child. Her husband is type A. Both the woman's father and her husband's father had type B blood. What is the probability that the child will have type O blood?

50%

What must happen before a cell can begin mitosis?

The chromosomes must be duplicated.

If the gene for seed color that Mendel studied exhibited pleiotropy, how might a green pea be different from a yellow pea?

With pleiotropy, there would be other differences between the peas - for example, green peas may also be larger, ripen earlier, and be more sensitive to frost.

If you are a male, the Law of Independent Assortment indicates that your gametes contain _____.

a random mix of the chromosomes you inherited from each parent

At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.

cytokinesis

Mendel observed that pairs of alleles were separated or segregated in gametes and that they were rejoined in fertilization. We know that pairs of _____ are segregated in _____ and then are rejoined through fertilization.

homologous chromosomes ... meiosis

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

metaphase II

Looking through a light microscope at a cell undergoing division, you see that the condensed chromosomes have lined up along the midline of the cell. The homologous pairs are NOT joined in tetrads. Each chromosome takes its own place in line, independent of its homolog. You are witnessing _____.

metaphase of mitosis

Chromosomes become visible during _____.

prophase

Synapsis occurs during _____.

prophase I

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

Spindle fibers attach to kinetochores during _____.

prometaphase

Terms

1. A (benign tumor) is a lump of abnormal cells that, although growing out of control, remains at its original site. 2. A (malignant tumor) is an abnormally growing mass of cells that is actively spreading through the body. 3. (Metastasis) is the spread of cancer cells from their site of origin to other sites in the body. 4. An individual with a malignant tumor is said to have (cancer.) 5. The most common type of cancer is a (carcinoma) ; this type always originates in tissues that line organs.

Terms

1. A (character) is an inherited feature that varies from individual to individual. 2. A (trait) is one particular variation of a character. 3. A genetic cross involving parents that differ in a single character is called a (monohybrid cross). 4. Most human genes come in alternate versions called (alleles). 5. If an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the (dominant) allele. 6. If an organism has two non-identical versions of a gene, the one that is not expressed in the organism is called the (recessive allele). 7. The physical traits of an organism are called it's (phenotype). 8. The (genotype) is the genetic makeup of an organism.

Part complete Assume that in cattle a spotted coat is dominant to an even coat, short horns are dominant to long horns, and the traits for coat type and horn length assort independently. In a cross between cattle that are each heterozygous for both traits, what proportion of their offspring are expected to have long horns?

1/4

You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half the offspring trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents? A = big apples; a = small apples; R = red apples; r = yellow apples.

AArr and aaRr

The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?

Anaphase

In the following cross the genotype of the female parent is BbGg. What is the genotype of the male parent? [Hint: B = black eyes, b = orange eyes, G = green skin, g = white skin]

BBGg

Imagine that a deaf male has a child with a hearing female. You know that the male must have the genotype dd, but the female could be either Dd or DD. If the couple's first child has hearing, can you determine the mother's genotype? (Hint: Draw Punnett squares for the two possible crosses.)

Her genotype cannot be determined.

Cells will usually divide if they receive the proper signal at a checkpoint in the __________ phase of the cell cycle.

G1

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 one copy of the chromosome.

A BbGg x bbgg cross yields a phenotypic ratio of approximately 5 black eyes, green skin : 5 orange eyes, white skin : 1 black eyes, white skin : 1 orange eyes, green skin. Which of the following best explains these results?

Mendel's law of independent assortment is being violated.

The observed distribution of alleles into gametes is an illustration of _____.

Mendel's laws of segregation and independent assortment

The chromosomes line up in the center of the cell during which phase of mitosis?

Metaphase

How have Mendel's laws fared as we have learned more about cell biology and processes such as meiosis?

Our new knowledge has helped to explain some of the exceptions to Mendel's laws of inheritance.

Suppose we have a pea plant with purple flowers, determined by the dominant allele P. How might you determine whether the plant is homozygous (PP) or heterozygous (Pp)?

Perform a testcross: Cross the plant with a white one, which must be homozygous recessive (pp).

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?

Prophase

The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?

Telophase

Within one chromosome, what is the relationship between the sequence of bases in DNA of one sister chromatid compared to the other?

The sequences are identical.

Centromeres divide and sister chromatids become full-fledged chromosomes during _____.

anaphase

Homologous chromosomes migrate to opposite poles during _____.

anaphase I

During _____ sister chromatids separate.

anaphase II

In order to determine the genotype of a MendAlien with black eyes and green skin, you would cross this individual with a(n) _____ individual.

bbgg

A cell replicates its entire chromosomal DNA only __________.

before it is about to divide

Which of the following conditions would prevent cell division due to density-dependent factors?

being completely surrounded by other cells

A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.

both parents are heterozygous for both genes

A cross between two individuals with black eyes and green skin which results in an individual with orange eyes and white skin is an example of a _____ cross.

dihybrid

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

four ... haploid

DdEe pea plants can produce _____ type(s) of gametes, but a ddee plant can produce _____ type(s) of gametes.

four ... one

Fertilization joins _____ to produce a _____.

haploid gametes ... diploid zygote

During anaphase I, __________.

homologous chromosomes separate and migrate toward opposite poles

Nucleoli are present during _____.

interphase

A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change?

inversion

If it weren't for _____, chromosome number would double with every generation of sexual reproduction.

meiosis

Which of the following is a correct representation of an event that occurs in mitosis?

metaphase—chromosomes line up on the equatorial plane.

Mendel formulated his principles of inheritance based on _____.

observations on the outcomes of breeding experiments. The underlying processes were unknown at the time.

Duplication of the chromosomes to produce sister chromatids _____.

occurs in both mitosis and meiosis

During _____ a spindle forms in a haploid cell.

prophase II

Because it is passed essentially intact from father to son, Y chromosome research has been particularly useful in improving our understanding of __________.

recent human evolution

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

red eyes; white eyes

During anaphase II, __________.

sister chromatids separate and migrate toward opposite poles

An example of a cell that is 2n is a __________.

somatic cell

Mitosis occurs in _____; meiosis occurs in _____.

somatic or body cells ... germ cells in the testes or ovaries

Cytokinesis often, but not always, accompanies _____.

telophase

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

As we now understand it, the Law of Independent Assortment applies _____.

to pairs of genes that are on different chromosomes, but NOT to pairs of genes that are close together on the same chromosome

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

two ... haploid

During prophase a homologous pair of chromosomes consists of _____.

two chromosomes and four chromatids

At the end of telophase I of meiosis, as cytokinesis occurs, there are __________.

two haploid cells

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