Biology 7&9
A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA in one of the grasshopper daughter cells?
100 units
At the end of telophase I of meiosis, as cytokinesis occurs, there are _____.
2 haploid cells
How many pairs of autosomes do humans have?
22
n humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing _____ different gametes.
2^23
The directions for each amino acid in a polypeptide are indicated by a codon that consists of ________ nucleotide(s) in an RNA molecule.
3
An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?
4
What is the typical result when a diploid cell undergoes meiosis?
4 Haploid cells
Each cell in an individual with Down syndrome contains _____ chromosomes.
47
In a cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing _____ chromosomes.
5
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. There are _____ chromatids.
92
Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?
Extra copies of the other somatic chromosomes are probably fatal.
At which point do centrosomes begin to move apart to the opposite poles of the cell in a dividing human liver cell?
Prophase
Crossing over occurs during _____.
Prophase 1
During which stage of meiosis do synapsis and crossing over occur?
Prophase 1
Synapsis occurs during _____.
Prophase 1
RNA polymerase links nucleotides to form mRNA.
RNA polymerase links nucleotides to form mRNA.
Chromatids form _____.
S Phase of Interphase
An example of a cell that is 2n is a _____.
Somatic Cell
Which of the following is a key difference between meiosis and mitosis?
Synapsis occurs.
hich event occurs only during prophase I of the first meiotic division?
Synapsis of homologous pairs occurs
Looking through a light microscope at a dividing cell, you see two separate groups of chromosomes on opposite ends of the cell. New nuclear envelopes are taking shape around each group. The chromosomes then begin to disappear as they unwind. You are witnessing
Telophase
Which events occur during prophase?
The nuclear envelope breaks down. Chromosomes condense and are attached to spindle fibers.
which of the following conditions would result in inhibition of cell division due to density-dependent factors?
being completely surrounded by other cells
In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____.
chiasma
A cleavage furrow forms in an animal cell during _____.
cytokinesis
Meiosis starts with _____ cells and produces _____ gametes.
diploid ... haploid
In bacterial cells, binary fission involves _____.
distribution of a copy of the single parental chromosome to each daughter cell
Cytokinesis refers to _____.
division of the cell outside the nuclear material
Observations of cancer cells in culture support the hypothesis that cancer cells _____
do not exhibit density-dependent inhibition
The diploid phase of the human life cycle begins with _____.
fertilization
Cytokinesis _____.
finishes mitosis by dividing the cytoplasm and organelles of the original parent cell into two separate daughter cells
Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with _____.
formation of a cleavage furrow
ou can determine this is a plant cell rather than an animal cell because it has _____.
formed a cell plate
The function of meiosis is to make _____.
four cells with a haploid number of chromosomes
During asexual reproduction, yeast cells can produce _____.
genetically identical offspring
In sexually reproducing multicellular organisms, the main functions of mitosis are _____.
growth and development and Repair
Fertilization joins _____ to produce a _____.
haploid gametes ... diploid zygote
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
The _____ separate in meiosis I; the _____ separate in meiosis II.
homologous chromosomes ... sister chromatids.
In anaphase I, _____.
homologous chromosomes move toward opposite poles
During anaphase I, _____.
homologues separate and migrate toward opposite poles
Chromatids are _____.
identical copies of each other if they are part of the same chromosome
In eukaryotic cells, the RNA is processed before it leaves the nucleus. This processing _____.
includes the addition of a cap and tail, which protect the mRNA molecule from enzymatic attack, and the removal of introns
During _____, the cell carries out its normal functions and the chromosomes are thinly spread out throughout the nucleus.
interphase
If a chromosome fragment breaks off and then reattaches to the original chromosome, but in the reverse direction, the resulting chromosomal abnormality is called a(n)
inversion.
When we say that an organism is haploid, we mean that _____.
its cells each have one set of chromosomes
n some organisms such as certain fungi and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would be the consequence of this?
large cells containing many nuclei
In humans, the _____ determines the sex of the offspring because _____.
male ... the male can contribute either an X or a Y chromosome
If it weren't for _____, chromosome number would double with every generation of sexual reproduction.
meiosis
Looking through a light microscope at a cell undergoing meiosis, you see that the chromosomes have joined into XX-shaped tetrads. These tetrads are lined up along a plane that runs through the center of the cell. This cell is in _____.
meiosis I
At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?
metaphase
During which phase of mitosis do the chromosomes line up on a plane equidistant from the two spindle poles?
metaphase
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
Which of the following is a correct representation of an event that occurs in mitosis?
metaphase—chromosomes line up on the equatorial plane.
During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____.
nondisjunction
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
Which of the following features likely accounts for the difference between plant and animal cell cytokinesis?
plants have cell walls
The term binary fission is best applied to _____.
prokaryotes
In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.
prophase
Crossing over occurs during _____.
prophase I
The exchange of parts between nonhomologous chromosomes is called _____.
reciprocal translocation
The function(s) of meiosis is/are _____.
reproduction (production of gametes)
Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called
sister chromatids
During anaphase II, _____.
sister chromatids separate and migrate toward opposite poles
The kinetochores are _____.
sites at which microtubules attach to chromosomes
Mitosis occurs in _____; meiosis occurs in _____.
somatic or body cells ... germ cells in the testes or ovarie
At a critical point in meiosis, the chromosomes do not replicate. This occurs between _____.
telophase I and prophase II
One event occurring during prophase is _____.
the beginning of the formation of the mitotic spindle Correct. During prophase, the mitotic spindle begins to form.
A gene is usually _____.
the information for making a polypeptide
Individual chromosomes are usually observed with a light microscope during mitosis, even though cells spend more time in interphase. This is because _____.
they have uncoiled to form long, thin strands
Meiosis is typically accomplished in _____.
three steps. All of the chromosomes are duplicated in a diploid cell, and then there are two cell divisions to produce a total of four haploid gametes.
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
During the process of translation, _____ matches an mRNA codon with the proper amino acid.
transfer RNA
Mitosis and cytokinesis result in the formation of _____; meiosis and cytokinesis result in the formation of _____.
two diploid cells ... four haploid cells
which of the following is a normal human female?
xx
Polyploidy is involved in which of the following examples?
A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes.
Which of the following statements regarding the function of mitosis is false?
Allow genetic diversity
What is the difference between a benign tumor and a malignant tumor?
Benign tumors do not metastasize; malignant tumors do.
Which of the following occurs during mitosis?
Chromatids separate.
Which of the following statements regarding the differences between mitosis and meiosis is false? Cells produced by mitosis are diploid, whereas cells produced by meiosis are haploid. In meiosis four daughter cells are produced, whereas in mitosis two daughter cells are produced. Crossing over is a phenomenon that creates genetic diversity during mitosis. In mitosis cytokinesis occurs once, whereas in meiosis cytokinesis occurs twice.
Crossing over is a phenomenon that creates genetic diversity during mitosis.
DNA replication occurs in _____.
S Phase of Interphase
Which of the following statements correctly describes the timing of DNA synthesis?
Single chromosomes enter the synthesis or S phase of interphase. At the end of this phase, after DNA replication, the chromosomes are double, each consisting of two sister chromatid
Down syndrome can be the result of _____.
nondisjunction of chromosome 21 during meiosis
Which of the following indicates Turner syndrome?
xo
Consider the cell cycle shown below. Cells will usually divide if they receive the proper signal at a checkpoint in the _____ phase of the cell cycle.
G1
Consider the two mice shown below. They have the same chromosomes, carrying genes for the same traits in the same loci, but specifying different versions of the same traits—for example, coat and eye color. These chromosomes are called _____.
Homologous chromosomes
ariation occurs when chromosomes are shuffled in _____.
Meisios
fter fertilization, the resulting zygote begins to divide by _____.
Mitosis
Which of the following statements regarding mitosis and meiosis is false? Meiosis only occurs in the ovaries and testes. Mitosis produces daughter cells with half the number of chromosomes as the parent cell. A normal human zygote has 46 chromosomes. All sexual life cycles involve an alternation of diploid and haploid stages.
Mitosis produces daughter cells with half the number of chromosomes as the parent cell.
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.
The term binary fission is best applied to _____.
Prokaryotes
If the diploid number of chromosomes in a certain animal is 6 (2n = 6), there are three sets of two homologous chromosomes each, or three pairs. How do these three pairs align and separate in meiosis?
They align and assort independently to form any of eight different combinations.
During cell division, what role do centrosomes play?
They organize the microtubules.
The transfer of genetic information from DNA to RNA is called
Transcription
Who is generally credited with discovering that the DNA molecule is constructed as a double helix?
Watson and Crick
consider the photograph of a karyotype. This is _____.
a photograph of all a person's chromosomes
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
Crossing over is important because it _____.
allows the exchange of genes between homologous chromosomes
Unless the chromosomes were stained to show band patterns, a karyotype would usually be unable to show _____.
an inversion
if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction, the resulting chromosomal abnormality is called _____.
an inversion
The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____.
anaphase
Single sister chromatids are found in cells at mitotic _____.
anaphase and telophase
The function of mitosis is to produce daughter cells that _____.
are genetically identical to the parent cell (assuming no mutation has occurred)
Why does a DNA strand grow only in the 5' to 3' direction?
because DNA polymerases can only add nucleotides to the 3' end of the growing molecule