Exam 4: mastering biology

What is crossing over? 1)the movement of genetic material from one chromosome to a nonhomologous chromosome 2)making an RNA copy of a DNA strand 3)a direct consequence of the separation of sister chromatids 4)also referred to as the "independent assortment of chromosomes" 5)the exchange of homologous portions of nonsister chromatids

1)the exchange of homologous portions of nonsister chromatids

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? 75 100 25 50

25

What do we mean when we use the terms monohybrid cross and dihybrid cross? 1)A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. 2)A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio. 3)A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents. 4)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.

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.

What is the difference between heterozygous and homozygous individuals? 1)Heterozygotes carry two copies of a gene while homozygotes only carry one. 2)The homozygote will express the dominant trait and the heterozygote will express the recessive trait. 3)All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ. 4)Homozygotes have one chromosome while heterozygotes have two similar chromosomes.

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

When homologous chromosomes cross over, what occurs? 1)Corresponding segments of non-sister chromatids are exchanged. 2)Two chromatids get tangled, resulting in one re-sequencing its DNA. 3)Two sister chromatids exchange identical pieces of DNA. 4)Maternal alleles are "corrected" to be like paternal alleles and vice versa.

Corresponding segments of non-sister chromatids are exchanged.

Which of the following can occur by the process of meiosis but not mitosis? 1)Haploid cells multiply into more haploid cells. 2)A diploid cell combines with a haploid cell. 3)Haploid cells fuse to form diploid cells. 4)Diploid cells form haploid cells.

Diploid cells form haploid cells.

True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait. True False

False

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? 1)Privet sex cells have chromosomes that can synapse with human chromosomes in the laboratory. 2)Genes of privet chromosomes are significantly different than those in humans. 3)Privet cells cannot reproduce sexually. 4)Privet shrubs must be metabolically more like animals than like other shrubs.

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

If a cell has completed meiosis I and is just beginning meiosis II, which of the following is an appropriate description of its contents? 1)It has half the chromosomes but twice the DNA of the originating cell. 2)It is identical in content to another cell formed from the same meiosis I event. 3)It has one-fourth the DNA and one-half the chromosomes as the originating cell. 4)It has half the amount of DNA as the cell that began meiosis.

It has half the amount of DNA as the cell that began meiosis.

If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb? 1/2 None 1/4 3/4

None

What is a major difference between mitosis and meiosis I in a diploid organism? 1)Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis II. 2)Only meiosis I results in daughter cells that contain identical genetic information. 3)DNA replication takes place prior to mitosis, but not before meiosis I. 4)Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.

Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I

Which of the following occurs during meiosis but not during mitosis? 1)A spindle apparatus forms. 2)Chromosomes condense. 3)Chromosomes migrate to opposite poles. 4)Synapsis occurs. 5)Chromosomes align at the metaphase plate.

Synapsis occurs.

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants? 1)Recessive genes occur more frequently in the F1 generation than do dominant ones. 2)Traits are inherited in discrete units and are not the results of "blending." 3)There is considerable genetic variation in garden peas. 4)Genes are composed of DNA.

Traits are inherited in discrete units and are not the results of "blending."

True or false? The same phenotype can be produced by more than one genotype. 1)True 2)False

True

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes? 1)46 2)about 8 million 3)23 4)about 1000

about 8 million

What is an allele? 1)a type of chromosome 2)a variety of pea plant used by Mendel 3)the recessive form of a gene 4)an alternative version of a gene 5)the dominant form of a gene

an alternative version of a gene

In meiosis, homologous chromosomes are separated during _____. anaphase II mitosis prophase I anaphase I

anaphase I

Centromeres split and sister chromatids migrate to opposite poles in meiosis _____. anaphase I telophase I telophase II anaphase II

anaphase II

When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______. 1)gametes, progeny 2)progeny, gametes 3)gametes, parents 4)parents, gametes

gametes, progeny

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have _____. 1)the same number of chromosomes and half the amount of DNA. 2)half the amount of cytoplasm and twice the amount of DNA. 3)half the number of chromosomes and half the amount of DNA. 4)half the number of chromosomes and one-fourth the amount of DNA.

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 _____. 1)haploid, and the chromosomes are each composed of a single chromatid 2)diploid, and the chromosomes are each composed of two chromatids 3)haploid, and the chromosomes are each composed of two chromatids 4)diploid, and the chromosomes are each composed of a single chromatid

haploid, and the chromosomes are each composed of two chromatid

Independent assortment of chromosomes occurs during _____. 1)meiosis I only 2)mitosis and meiosis I 3)mitosis and meiosis II 4)meiosis II only

meiosis I only

Sister chromatids separate from each other during _____. 1)mitosis and meiosis II 2)meiosis I only 3)meiosis II only 4)mitosis and meiosis I

mitosis and meiosis II

Which of the following occurs in meiosis but not in mitosis? 1)chromosome replication 2)synapsis of chromosomes 3)condensation of chromosomes 4)alignment of chromosomes at the equator

synapsis of chromosomes

Independent assortment of chromosomes is a result of _____. 1)the random distribution of the sister chromatids to the two daughter cells during anaphase II 2)the diverse combination of alleles that may be found within any given chromosome 3)the random combinations of eggs and sperm during fertilization 4)the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)? TtPp TTpp ttpp TTPP

ttpp

Mitosis results in the formation of how many cells; meiosis results in the formation of how many cells? 1)two diploid cells ... two haploid cells 2)two diploid cells ... four haploid cells 3)four haploid cells ... two diploid cells 4)two diploid cells ... two diploid cells 5)four diploid cells ... four haploid cells

two diploid cells ... four haploid cell