Biology the Core 3rd Edition: Chapter 5
If a cell has 30 chromosomes before mitosis, how many does each daughter cell have afterward?
30
A human somatic (body) cell has ________ chromosomes.
46
According to the principle of segregation, the gametes of a heterozygous individual will contain ________.
50 percent dominant and 50 percent recessive alleles
What is the chromosome abnormality that causes Down syndrome?
A nondisjunction results in a person with an extra copy of chromosome 21. Extra: Down syndrome is sometimes referred to as trisomy 21.
What is the phenotypic ratio for the offspring of a cross between a homozygous dominant (ZZ) and a homozygous recessive (zz)?
All dominant
The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
Anaphase Extra: Sister chromatids separate and start their migration toward opposite poles during anaphase.
When are the chromosomes of a cell duplicated?
Before a cell divides Extra: Chromosomes replicate before cell division. This ensures that genetic material is appropriately distributed to the daughter cells.
What do the terms gene and allele have in common?
Both could refer to the same DNA sequence.
A cell preparing to undergo meiosis duplicates its chromosomes during
Chromosomes are duplicated during interphase.
At the end of the mitotic (M) phase, the cytoplasm divides in a process called
Cytokinesis Extra: Cytokinesis is the division of the cytoplasm that occurs in conjunction with telophase, the last phase in mitosis.
Chromosomes contain most of the cell's ____ which acts as the molecule of heredity.
DNA
What do we call a genetic cross that follows two separate characters, such as pea seed color and pea seed shape?
Dihybrid cross Extra: The law of independent assortment predicts that during a dihybrid cross each trait should be inherited separately.
Guar are increasingly rare wild oxen found in Asia. How would you clone this animal?
Fusing a guar cell nucleus with an egg cell from a domestic cow that has had its nucleus removedFertilizing an egg from a domestic cow that has no nucleus with a guar spermUsing stem cells from the umbilical cord of a guar calf Extra: This method successfully cloned a guar.
Imagine that five hypothetical genes are arranged on a chromosome in the following order: G--H--I--J--K. Which two genes are most likely to have a crossover occur between them?
G and K Extra: The probability of crossing over increases the farther the genes are from one another on the same chromosome.
In a Punnett square, what do the letters outside the little boxes represent?
Gamete genotypes
How does meiosis generate genetic diversity?
Homologous chromosomes cross over during prophase I; during metaphase I, chromosomes align randomly.
The cell cycle is a predictable sequence of events that makes up the lifetime of all cells. Sort the events to the phase of the cell cycle during which they occur.
Interphase The cytoplasm doubles, increasing the overall size and volume of the cell. Chromosomes are duplicated in preparation for cell division. Mitosis The duplicated chromosomes separate and are distributed to two offspring nuclei. Cytokinesis The cell divides into two offspring cells, each with a complete set of chromosomes from the parent cell. Extra: The function of mitosis is to generate more cells. For one cell to divide into two identical cells, chromosomes must be duplicated and then divided between the offspring cells. This process is what enables multicellular organisms to grow and repair their bodies.
Which of the following allows sexual reproduction to occur generation after generation?
Meiosis
Meiosis starts with a single diploid cell and produces
Meiosis produces four haploid cells.
The chromosomes line up in the center of the cell during which phase of mitosis?
Metaphase Extra: Metaphase occurs in the middle of mitosis, when the chromosomes line up in the middle of the cell.
Which of the following terms describes a failure of chromosomes to sort properly during meiosis?
Nondisjunction
Which of the following describes the ability of a single gene to cause multiple effects on an individual's phenotype?
Pleiotropy
Which of the following refers to the inheritance of traits that are controlled by two or more genes?
Polygenic
The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
Prophase Extra: Prophase is the first phase of mitosis, when the centrosomes begin moving toward opposite poles and the nuclear envelope breaks up.
What process involving cell division results in daughter cells that are NOT identical to the parent cell?
Sexual reproduction Egg and sperm cells have half the number of chromosomes as their parent cells.
As mitosis begins, __________ are linked together at the centromere.
Sister chromatids Extra: Sister chromatids are linked together until they are separated during cell division.
What is the difference between stem cells and other body cells?
Stem cells are adaptable and can give rise to other cell types.
The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
Telophase Extra: Telophase is the final phase of mitosis, when the chromosomes have arrived at the poles and the nuclear envelopes of the two new cells form.
What must happen before a cell can begin mitosis?
The chromosomes must be duplicated. Extra: Before mitosis can begin, the chromosomes, or genetic material, must be copied, which occurs during interphase.
What is the major difference between dominant and recessive alleles of the same trait?
When both are present in the heterozygote, only the dominant allele is expressed.
Most human genes come in alternate versions called
alleles
Recessive X-linked disorders ________.
are more common in males than females
Homologous chromosomes ________.
carry the same genes
A(n) ____ is an inherited feature that varies from individual to individual.
character
DNA and protein together form a complex called
chromatin
The DNA of every eukaryotic cell is stored in one or more ___ located in the ____
chromosomes nucleus
If an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the ____ allele.
dominant
No two gametes are exactly alike genetically, because ________.
each gamete has a different combination of parental chromosomes and is the result of crossing over
The ___ is the genetic makeup of an organism.
genotype
In humans, meiosis produces cells that are ________.
haploid, called gametes
The members of a homologous pair of chromosomes ________.
have the same genes but unique sets of alleles
A carrier of a human genetic disorder is ________.
heterozygous with one copy of the normal allele and one copy of the disease-causing allele
During prophase I of meiosis,
homologous chromosomes stick together in pairs.
If a woman with curly hair and a man with straight hair have a child with wavy hair, the gene for this characteristic of hair shows
incomplete dominance Extra: Incomplete dominance results in heterozygotes having phenotypes that are intermediate to the two homozygotes.
Random orientation of homologous pairs of chromosomes during meiosis I results in alternative arrangements that contribute to genetic variation in offspring. This is called
independent assortment Extra: Independent assortment is one of the processes that contribute to genetic variation.
A karyotype ________.
is a picture of chromosomes arranged in pairs
Diploid cells become haploid during ________.
meiosis I
Segregation ________.
occurs when alleles for the same trait separate during gamete formation
The physical traits of an organism are called its
phenotype
The correct order of events during meiosis is
prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.
During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?
prophase I.
If an organism has two non-identical versions of a gene, the one that is not expressed in the organism is called the ___ allele.
recessive
The sex of a human fetus is determined by the ________.
sex chromosome found in the sperm
Before a cell divides, it copies all of its chromosomes. While the two copies of a chromosome are attached they are called
sister chromatids
In meiosis II, ________.
sister chromatids are separated into different daughter cells
A duplicated chromosome remains tightly paired with its partner at a region called
the centromere
A gene is ________.
the unit of inheritance that codes for proteins or RNA
A(n) ____ is one particular variation of a character.
trait
