AP Biology › Cellular Division
In a dihybrid cross of seed color and seed shape, Y (yellow) is dominant to y (green) and R (rounded) is dominant to r (wrinkled). An individual with genotype YyRr is crossed with an individual with genotype YYRr. The inheritance of the alleles for seed color does not affect inheritance of genes for seed shape. Which law supports this statement?
Law of segregation
Law of independent assortment
Law of random mating
Law of dominance
The law of independent assortment states that inheritance of one gene does not influence inheritance of another gene. Thus, inheritance of seed color does not affect the inheritance of seed shape.
In a dihybrid cross of seed color and seed shape, Y (yellow) is dominant to y (green) and R (rounded) is dominant to r (wrinkled). An individual with genotype YyRr is crossed with an individual with genotype YYRr. The inheritance of the alleles for seed color does not affect inheritance of genes for seed shape. Which law supports this statement?
Law of segregation
Law of independent assortment
Law of random mating
Law of dominance
The law of independent assortment states that inheritance of one gene does not influence inheritance of another gene. Thus, inheritance of seed color does not affect the inheritance of seed shape.
Which of the following is not a phase of mitosis?
Anaphase II
Prophase
Prometaphase
Telophase
The five phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase in that order. Since mitosis involves the production of two genetically identical diploid daughter cells from one parent cell, there is only one cell division. Thus, all phases that dictate a Roman numeral refer to meiosis, which involves the production of four nonidentical haploid daughter cells from one parent cell as the result of two cell divisions. During anaphase II of meiosis, the sister chromatids are pulled to opposite poles of the cell, and the second round of cytokinesis begins.
In preparation for cellular division, the cell must first duplicate its chromosomes. Each duplicated chromosome consists of two __________.
sister chromatids
centromeres
duplicates
chromatins
homologous chromosomes
Sister chromatids are two identical copies of the same chromosome. They are attached to each other at a region called the centromere. Homologous chromosomes are not identical. Rather, they are chromosomes that look alike, and have the same genes at the same loci, but not necessarily the same versions of those genes. For example, we all have two copies of chromosome number 1. Assume eye color is coded on this chromosome. One copy may have the brown allele, while the other copy might have the green allele. Both chromosomes have loci that code for eye color, but they are not identical since one came from each parent.
What is the purpose of chromatin?
To maintain structure of the chromosome and assist in controlling the activity of the genes
To maintain structure of the chromosome only
To assist in controlling the activity of the genes only
To hold the sister chromatids together
Chromatin serves as a scaffold for DNA and helps regulate gene activity. Chromatin can be condensed, as euchromatin, or loosely packed, as heterochromatin. The compactness of chromatin determines its level of activity. When it is loosely packed, it can be acted upon by DNA replication and/or transcription enzymes, and those genes may be expressed. Centromeres hold sister chromatids together.
A scientist takes a sample of human epithelial cells, injects it with a dye that highlights the genetic information, and places the sample under the microscope. What will the genetic information for the majority of the cells look like?
Uncondensed and restricted to the nucleus
Condensed into 46 discrete chromosomes and restricted to the nucleus
Condensed into 23 discrete chromosomes and restricted to the nucleus
Condensed into 23 discrete chromosomes and floating in the cytoplasm
Condensed into a single circular chromosome and floating in the cytoplasm
The DNA will appear uncondensed and restricted to the nucleus. This is because a majority of the cells found in the sample will be in interphase, the longest stage of the cell cycle. Since it is the longest phase in the cell cycle, a majority of cells will be undergoing this phase at any given sample time. It is a point when the cell is undergoing normal cell processes and preparing for replication. During this phase, the DNA is uncondensed, allowing for transcription and giving DNA replication enzymes easy access to the nucleotide sequence.
DNA is condensed into 46 discrete chromosomes and restricted to the nucleus during early prophase, which makes up only a short period of the cell cycle. DNA is never condensed into 23 discrete chromosomes in somatic cells (such as epithelium), since 23 chromosomes would indicate a haploid cell. In humans, haploid cells only exist in the gametes, or sex cells. While prokaryotes have a single circular chromosome floating in the cytoplasm, such structure for a eukaryotic genome is not possible.
Which of the following is not a phase of mitosis?
Anaphase II
Prophase
Prometaphase
Telophase
The five phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase in that order. Since mitosis involves the production of two genetically identical diploid daughter cells from one parent cell, there is only one cell division. Thus, all phases that dictate a Roman numeral refer to meiosis, which involves the production of four nonidentical haploid daughter cells from one parent cell as the result of two cell divisions. During anaphase II of meiosis, the sister chromatids are pulled to opposite poles of the cell, and the second round of cytokinesis begins.
What is the purpose of chromatin?
To maintain structure of the chromosome and assist in controlling the activity of the genes
To maintain structure of the chromosome only
To assist in controlling the activity of the genes only
To hold the sister chromatids together
Chromatin serves as a scaffold for DNA and helps regulate gene activity. Chromatin can be condensed, as euchromatin, or loosely packed, as heterochromatin. The compactness of chromatin determines its level of activity. When it is loosely packed, it can be acted upon by DNA replication and/or transcription enzymes, and those genes may be expressed. Centromeres hold sister chromatids together.
In preparation for cellular division, the cell must first duplicate its chromosomes. Each duplicated chromosome consists of two __________.
sister chromatids
centromeres
duplicates
chromatins
homologous chromosomes
Sister chromatids are two identical copies of the same chromosome. They are attached to each other at a region called the centromere. Homologous chromosomes are not identical. Rather, they are chromosomes that look alike, and have the same genes at the same loci, but not necessarily the same versions of those genes. For example, we all have two copies of chromosome number 1. Assume eye color is coded on this chromosome. One copy may have the brown allele, while the other copy might have the green allele. Both chromosomes have loci that code for eye color, but they are not identical since one came from each parent.
A scientist takes a sample of human epithelial cells, injects it with a dye that highlights the genetic information, and places the sample under the microscope. What will the genetic information for the majority of the cells look like?
Uncondensed and restricted to the nucleus
Condensed into 46 discrete chromosomes and restricted to the nucleus
Condensed into 23 discrete chromosomes and restricted to the nucleus
Condensed into 23 discrete chromosomes and floating in the cytoplasm
Condensed into a single circular chromosome and floating in the cytoplasm
The DNA will appear uncondensed and restricted to the nucleus. This is because a majority of the cells found in the sample will be in interphase, the longest stage of the cell cycle. Since it is the longest phase in the cell cycle, a majority of cells will be undergoing this phase at any given sample time. It is a point when the cell is undergoing normal cell processes and preparing for replication. During this phase, the DNA is uncondensed, allowing for transcription and giving DNA replication enzymes easy access to the nucleotide sequence.
DNA is condensed into 46 discrete chromosomes and restricted to the nucleus during early prophase, which makes up only a short period of the cell cycle. DNA is never condensed into 23 discrete chromosomes in somatic cells (such as epithelium), since 23 chromosomes would indicate a haploid cell. In humans, haploid cells only exist in the gametes, or sex cells. While prokaryotes have a single circular chromosome floating in the cytoplasm, such structure for a eukaryotic genome is not possible.