1.
The centromere is a region in which:
Correct Answer
A. Chromatids are attached to one another.
Explanation
The centromere is a region in which chromatids are attached to one another. During cell division, the chromosomes replicate and each chromosome consists of two identical chromatids held together at the centromere. This attachment is crucial for the proper separation of chromatids during mitosis or meiosis. The centromere plays a vital role in ensuring that each daughter cell receives the correct number of chromosomes.
2.
What is a chromatid?
Correct Answer
B. A replicated chromosome
Explanation
A chromatid refers to a replicated chromosome, which is formed during the S phase of the cell cycle when DNA replication occurs. Each chromatid contains an identical copy of the DNA molecule and is held together at the centromere with its sister chromatid. During cell division, the sister chromatids separate and become individual chromosomes. Therefore, a chromatid is not a chromosome in G1 of the cell cycle, a chromosome found outside the nucleus, a special region that holds two centromeres together, or another name for the chromosomes found in genetics.
3.
A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei containing how many chromosomes?
Correct Answer
D. 46
Explanation
During metaphase of mitosis, each chromosome consists of two sister chromatids. Therefore, if a cell contains 92 chromatids at metaphase, it means it has 46 chromosomes (92 chromatids divided by 2 chromatids per chromosome). At the completion of mitosis, each of the two resulting daughter cells will contain the same number of chromosomes as the parent cell, which is 46 chromosomes.
4.
The somatic cells derived from a single-celled zygote divide by which process?
Correct Answer
B. Mitosis
Explanation
The somatic cells derived from a single-celled zygote divide by mitosis. Mitosis is a process of cell division in which a single cell divides into two identical daughter cells, each containing the same number of chromosomes as the parent cell. This process is responsible for growth, development, and tissue repair in multicellular organisms. Unlike meiosis, which is involved in the formation of gametes (sex cells), mitosis is responsible for the division of non-reproductive cells. Replication refers to the duplication of DNA, while cytokinesis alone refers to the separation of the cytoplasm after cell division. Binary fission is a process of cell division in prokaryotes.
5.
What is a genome?
Correct Answer
A. The complete complement of an organism's genes
Explanation
A genome refers to the complete complement of an organism's genes. It includes all the genetic material present in an organism, including both coding and non-coding regions of DNA. Genes are the units of inheritance that determine the traits and characteristics of an organism, and the genome encompasses all of these genes. Therefore, the correct answer is "the complete complement of an organism's genes."
6.
Asexual reproduction and sexual reproduction are different in that
Correct Answer
E. All of the above
Explanation
Asexual reproduction and sexual reproduction are different in multiple ways. Asexual reproduction involves a single parent, while sexual reproduction involves two parents. Asexual reproduction results in offspring that are genetically identical to the parent, while sexual reproduction gives rise to genetically distinct offspring. Additionally, individuals reproducing asexually transmit 100% of their genes to their progeny, whereas individuals reproducing sexually only transmit 50%. Lastly, asexual reproduction only requires mitosis, while sexual reproduction always involves meiosis. Therefore, all of the above options correctly describe the differences between asexual and sexual reproduction.
7.
What is a karyotype?
Correct Answer
E. A display of every pair of homologous chromosomes within a cell, organized according to size and shape
Explanation
A karyotype is a display of every pair of homologous chromosomes within a cell, organized according to size and shape. It provides a visual representation of an individual's chromosomes, allowing for the identification of any abnormalities or genetic disorders. By examining the karyotype, geneticists can determine the number, size, and structure of chromosomes present in an individual's cells. This information is useful in diagnosing and studying genetic disorders, as well as in understanding the genetic makeup of an individual.
8.
The human X and Y chromosomes are
Correct Answer
D. Called "sex chromosomes" because they determine an individual's sex.
Explanation
The human X and Y chromosomes are called "sex chromosomes" because they determine an individual's sex. This is because females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). The presence of the Y chromosome determines the development of male characteristics. Therefore, the correct answer is that the X and Y chromosomes are called "sex chromosomes" because they determine an individual's sex.
9.
If the liver cells of an animal have 24 chromosomes, how many chromosomes do its sperm cells have?
Correct Answer
B. 12
Explanation
Sperm cells are haploid, meaning they contain half the number of chromosomes as the somatic cells. In this case, since the liver cells have 24 chromosomes, the sperm cells would have half of that, which is 12 chromosomes.
10.
Which of the following is true of a species that has a chromosome number of 2n = 16?
Correct Answer
C. There are 8 homologous pairs.
Explanation
A species with a chromosome number of 2n = 16 means that it has 16 chromosomes in total, with each chromosome having a homologous pair. Therefore, there are 8 homologous pairs in this species.
11.
Which of the following is the term for a human cell that contains 22 pairs of autosomes and two X chromosomes?
Correct Answer
D. A female somatic cell
Explanation
A female somatic cell is the correct answer because it is the only option that fits the description of having 22 pairs of autosomes and two X chromosomes. An unfertilized egg cell and a sperm cell each contain only half of the genetic material, so they do not have 22 pairs of autosomes. A male somatic cell would have one X and one Y chromosome, so it also does not fit the description. Therefore, the correct answer is a female somatic cell.
12.
Which of these statements is false?
Correct Answer
D. At sexual maturity, ovaries and testes produce diploid gametes by meiosis.
Explanation
At sexual maturity, ovaries and testes produce haploid gametes by meiosis, not diploid gametes. Meiosis is the process by which diploid cells undergo two rounds of division to produce haploid gametes with half the number of chromosomes. Therefore, the statement that ovaries and testes produce diploid gametes by meiosis is false.
13.
In animals, meiosis results in gametes, and fertilization results in
Correct Answer
C. Zygotes.
Explanation
Meiosis is a type of cell division that occurs in animals to produce gametes, which are reproductive cells like eggs and sperm. Fertilization is the process where two gametes, one from each parent, combine to form a zygote. The zygote is the initial cell of a new individual and has the potential to develop into a complete organism. Therefore, the correct answer is zygotes.
14.
After telophase I of meiosis, the chromosomal makeup of each daughter cell is
Correct Answer
D. Haploid, and the chromosomes are composed of two chromatids.
Explanation
After telophase I of meiosis, the chromosomal makeup of each daughter cell is haploid, meaning they contain half the number of chromosomes as the parent cell. The chromosomes in each daughter cell are composed of two chromatids, which are identical copies of each other formed during the S phase of interphase. This is because during meiosis I, homologous chromosomes separate, but sister chromatids remain attached. Therefore, each daughter cell ends up with a haploid set of chromosomes, each consisting of two chromatids.
15.
Which of the following terms belongs with the words synapsis, tetrads, and chiasmata?
Correct Answer
B. Crossing over
Explanation
The term "crossing over" belongs with the words synapsis, tetrads, and chiasmata because it is a process that occurs during meiosis where genetic material is exchanged between homologous chromosomes. This process leads to genetic recombination and the creation of new combinations of alleles, contributing to genetic diversity. Synapsis, tetrads, and chiasmata are all associated with meiosis and the formation of gametes, and crossing over is a key event that occurs during this process.
16.
Which of the following is true of the process of meiosis?
Correct Answer
C. Four haploid cells result.
Explanation
During the process of meiosis, the cell undergoes two rounds of division, resulting in four daughter cells. These daughter cells are haploid, meaning they contain half the number of chromosomes as the original diploid cell. This is achieved through the separation of homologous chromosomes during the first division and the separation of sister chromatids during the second division. Therefore, the correct answer is that four haploid cells result from the process of meiosis.
17.
Crossing over occurs during which phase of meiosis?
Correct Answer
A. PropHase I
Explanation
Crossing over occurs during prophase I of meiosis. This is the phase where homologous chromosomes pair up and exchange genetic material through a process called crossing over. This genetic exchange increases genetic diversity and plays a crucial role in the formation of new combinations of alleles. The other phases mentioned, anaphase I, telophase I, prophase II, and metaphase II, do not involve crossing over.
18.
When comparing prophase I of meiosis with prophase of mitosis, which of the following occurs only in meiosis?
Correct Answer
B. Tetrads form.
Explanation
During prophase I of meiosis, tetrads form, which refers to the pairing of homologous chromosomes. This is a unique event that occurs only in meiosis and allows for the exchange of genetic material between homologous chromosomes through a process known as crossing over. In prophase of mitosis, the chromosomes also condense, the nuclear envelope disassembles, a spindle forms, and each chromosome is composed of two chromatids. However, the formation of tetrads is specific to meiosis.
19.
Independent assortment of chromosomes is a result of
Correct Answer
A. The random and independent way in which each pair of homologous chromosomes lines up at the metapHase plate during meiosis I.
Explanation
Independent assortment of chromosomes refers to the random and independent alignment of homologous chromosomes during meiosis I. This means that each pair of homologous chromosomes can line up in any combination at the metaphase plate, leading to a random distribution of genetic material into the daughter cells. The other options mentioned, such as the random nature of fertilization and the distribution of sister chromatids, are not directly related to independent assortment. Therefore, the correct answer is the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.
20.
Which of the following statements about crossing over is incorrect?
Correct Answer
B. Crossing over plays a role in both sexual and asexual reproduction.