Unit 3 Dynamic Study Mode Flashcards
In preparing pyruvate to enter the citric acid cycle, pyruvate is _____ and _______, and the removed electrons are used to reduce an NAD+ to an NADH.
In preparing pyruvate to enter the citric acid cycle, pyruvate is oxidized and decarboxylated, and the removed electrons are used to reduce an NAD+ to an NADH.
The energy from the electrons in NADH and FADH2 fuel what process in the electron transport chain?
The pumping of H+ across the cristae of the mitochondrion
Oxygen is_______ in the electron transport chain.
reduced to water (not oxidized)
The electrons in _____ and _____ are the primary energy source for the electron transport chain.
The electrons in NADH and FADH2 are the primary energy source for the electron transport chain.
In the _____, The movement of H+ through ATP synthase produces ATP.
ETC -Electron Transport Chain
_______ is the process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesis of ATP.
Chemiosmosis
The ATP synthase in a human cell obtains energy for synthesizing ATP directly from the flow of H+ across the _____ _____ ______through the ATP synthase enzyme.
The ATP synthase in a human cell obtains energy for synthesizing ATP directly from the flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme.
______ ______ = Most ATP
It's the main ATP-producing stage of cellular respiration. Powered by redox reactions in the electron transport chain (ETC).
Oxidative Phosphorylation = Most ATP
It's the main ATP-producing stage of cellular respiration. Powered by redox reactions in the electron transport chain (ETC).
*Glycolysis produces ___ net ATP.
*The citric acid cycle produces ____ net ATP.
*Substrate-level phosphorylation includes both glycolysis and the citric acid cycle and produces only ____ net ATP.
Glycolysis produces only two net ATP.
The citric acid cycle produces only two net ATP.
Substrate-level phosphorylation includes both glycolysis and the citric acid cycle and produces only four net ATP.
During aerobic respiration, molecular oxygen (O2) is used for what purposes?
At the end of the electron transport chain to accept electrons and form H2O
Muscle tissues make lactate from pyruvate to _____ _____ so glycolysis can continue.
regenerate NAD+
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________.
NADH
What is the role of oxygen in the electron transport chain?
It is reduced to form water.
Most of the ATP in cellular respiration is produced by the process of chemiosmosis. How does this process produce ATP?
H+ flows across the inner mitochondrial membrane through the enzyme ATP synthase.
ATP is produced by the oxidation of pyruvate during the ____ _____cycle.
citric acid
______ occurs during glycolysis, the citric acid cycle, and fermentation.
Substrate-level phosphorylation
Electrons from_____and ______ are used to drive the electron transport chain.
Electrons from NADH and FADH2 are used to drive the electron transport chain.
Cells regulate cellular respiration through feedback inhibition of ______
glycolysis.
In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced.
glucose; oxygen
Most of the NADH that delivers electrons to the electron transport chain comes from which of the following processes?
The citric acid cycle
Mitosis includes five phases during which a variety of events occur.
1.
2.
3.
4.
5.
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
–the cytokinesis
- During prophase, chromatin condenses into distinct chromosomes, the nucleolus disappears, and the mitotic spindle apparatus begins to form. In addition, centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them. This structure is responsible for maneuvering the chromosomes around the cell during mitosis.
During prophase, chromatin condenses into distinct chromosomes, the nucleolus disappears, and the mitotic spindle apparatus begins to form. In addition, centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them. This structure is responsible for maneuvering the chromosomes around the cell during mitosis.
- In prometaphase of mitosis, the nuclear envelope fragments and the kinetochores attach to microtubules.
In prometaphase, the nuclear envelope fragments and the kinetochores attach to microtubules.
- During metaphase, the mitotic spindle aligns the chromosomes at the metaphase plate, a region along the equator of the cell.
During metaphase, the mitotic spindle aligns the chromosomes at the metaphase plate, a region along the equator of the cell.
- In anaphase, the centrioles are at opposite ends of the cell. The paired centromeres of each chromosome are separated by spindle microtubules, liberating the sister chromatids, which begin moving toward opposite poles of the cell.
In anaphase, the centrioles are at opposite ends of the cell. The paired centromeres of each chromosome are separated by spindle microtubules, liberating the sister chromatids, which begin moving toward opposite poles of the cell.
- In telophase, a new nuclear envelope begins to synthesize, the mitotic spindle breaks down, the chromatin uncoils, and cytokinesis begins.
In telophase, a new nuclear envelope begins to synthesize, the mitotic spindle breaks down, the chromatin uncoils, and cytokinesis begins.
_____ involves the replication and division of a single chromosome, whereas _____ involves the division of multiple, replicated chromosomes.
Binary fission involves the replication and division of a single chromosome, whereas mitosis involves the division of multiple, replicated chromosomes.
Binary fission involves the division of a single chromosome, and mitosis involves the division of multiple chromosomes.
A cell plate forms across the middle of a plant cell, not a bacterial cell.
Binary fission does not involve microtubules, but mitosis does.
Binary fission involves the division of a single chromosome, and mitosis involves the division of multiple chromosomes.
A cell plate forms across the middle of a plant cell, not a bacterial cell.
Binary fission does not involve microtubules, but mitosis does.
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
Cytokinesis
Separation of the sister chromatids occur during ______ of mitosis.
anaphase
Duplication of the chromosomes occurs during the __ phase of interphase.
Growth of the cell occurs during the __ and__ phases of interphase.
Duplication of the chromosomes occurs during the S phase of interphase.
Growth of the cell occurs during the G1 and G2 phases of interphase.
structures that are part of the mitotic spindle?
*Nonkinetochore microtubules
*Kinetochore microtubules
*Centrosome
*The aster
Many of the events of mitosis depend on the mitotic spindle, which begins to form in the cytoplasm during ____
Many of the events of mitosis depend on the mitotic spindle, which begins to form in the cytoplasm during prophase.
Cytokinesis refers to __________.
division of the cytoplasm
A cell contains 40 chromatids at the beginning of mitosis. How many chromosomes will it contain at the completion of cytokinesis?
20
DNA replication occurs in __________.
the S phase of interphase in both somatic and reproductive cells
The nuclear envelope disappears during _____ of mitosis.
The nuclear envelope disappears during prometaphase of mitosis.
The chromosomes condense during _____ of mitosis.
The chromosomes condense during prophase of mitosis.
The sister chromatids are pulled apart toward opposite sides of the cell during _____ of mitosis.
The sister chromatids are pulled apart toward opposite sides of the cell during anaphase of mitosis.
he nuclear envelope forms again during _____ of mitosis.
The nuclear envelope forms again during telophase of mitosis.
The mitotic spindle forms during _____ of mitosis.
The mitotic spindle forms during prophase of mitosis.
You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________.
it had formed a cell plate
What phase of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?
Telophase
During interphase, the genetic material of a typical eukaryotic cell is __________.
dispersed in the nucleus as long strands of chromatin
The mitotic spindle forms during prophase of mitosis.
The chromosomes condense during prophase of mitosis.
The nucleoli disappear during prophase of mitosis.
The centrosomes move away from each other during prophase of mitosis.
Each duplicated chromosome appears as two identical sister chromatids during prophase of mitosis.
The mitotic spindle forms during prophase of mitosis.
The chromosomes condense during prophase of mitosis.
The nucleoli disappear during prophase of mitosis.
The centrosomes move away from each other during prophase of mitosis.
Each duplicated chromosome appears as two identical sister chromatids during prophase of mitosis.
IF the egg (ovum) of a rabbit contains 22 chromosomes. There will be __ chromosomes in the somatic (body) cells.
IF the egg (ovum) of a rabbit contains 22 chromosomes. There will be 44 chromosomes in the somatic (body) cells.
A pair of genetic structures carrying genes that control the same inherited characters are called __________.
homologous chromosomes
sister chromatids are located on the same chromosome
sister chromatids are located on the same chromosome
____ are the product of fertilization.
zygotes are the product of fertilization.
somatic cells contain two sets and are diploid.
somatic cells contain two sets and are diploid.
Somatic cells in animals differ from gametes in that somatic cells are
all of the cells of the body except for the gametes and their precursors.
A clone is the product of __________.
asexual reproduction and mitosis
The process called __________ reduces the chromosome number by __________.
meiosis; two consecutive cell divisions
What is the result when a diploid cell undergoes meiosis?
Four haploid cells
What occurs in meiosis, but not mitosis?
Homologous chromosomes separate.
In meiosis, __________ of __________ cross over and form __________.
nonsister chromatids; homologous pairs; chiasmata
Somatic cells in humans differs from gametes in that human somatic cells __________.
contain two sets of each of the 23 chromosome types
Regardless of whether an organism is an animal, a plant, a fungus, or an algal cell, all zygotes are __________ and are formed during the __________ of two __________ gametes.
diploid; fertilization; haploid
Sister chromatids differ from nonsister chromatids in that sister chromatids __________.
are products of the S phase of the cell cycle and are two copies of one chromosome
During meiosis II, ____ holds sister chromatids together along their lengths as the second meiotic spindle forms.
During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms.
Genetic diversity requires __________.
sexual reproduction, nonindependent assortment, crossing over between nonsister chromatids of homologous chromosomes, and random fertilization
Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?
16
They have genes for the same traits at the same loci.
Homologous chromosomes
A pair of genetic structures carrying genes that control the same inherited characters are called __________.
homologous chromosomes
In meiosis, __________ of __________ cross over and form __________.
nonsister chromatids; homologous pairs; chiasmata
Unselected
Allelic variation is an important source of __________ in a population.
genetic diversity
How many genes are present in the human genome?
Tens of thousands
The genome is an organism’s entire complement of DNA, the molecule that carries the genes. Each chromosome has hundreds or thousands of genes; the entire human genome has on the order of 20,000 to 25,000 genes.
The major contribution of sex to evolution is that __________.
it provides a method to increase genetic variation
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
The hydrogen (H+) concentration gradient across the membrane holding ATP synthase.
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
gylcolysis
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
Oxygen (O2)
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
Most CO2 from catabolism is released during the
citric acid cycle
A molecule becomes more oxidized when it __________.
loses an electron.
During oxidation, an electron is removed.
When a molecule is reduced, you can also say:
*It has been reduced.
*It has ____ electrons (often hydrogen ions).
*It is the _____ agent
When a molecule is reduced, you can also say:
*It has been reduced.
*It has gained electrons (often hydrogen ions).
*It is the oxydizing agent (because it causes another molecule to be oxidized).
_____ means the molecule has gained electrons (and often hydrogen atoms), which ____ its overall charge. It often occurs alongside _____, which is the loss of electrons, in what’s called a _____ reaction.
reduction means the molecule has gained electrons (and often hydrogen atoms), which reduces its overall charge (hence the term “reduction”). It often occurs alongside oxidation, which is the loss of electrons, in what’s called a redox reaction.
In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced.
glucose; oxygen
In cellular respiration, _____ and _____ are removed from glucose and added to oxygen.
In cellular respiration, electrons and hydrogen are removed from glucose and added to oxygen.
_____ _______: After hydrogen ions are pumped into the mitochondrial intermembrane space, they flow back through ATP synthase, which produces most of the ATP associated with cellular respiration.
Oxidative phosphorylation
During glycolysis, glucose is metabolized into two molecules of _____ with a net yield of only two ___.
During glycolysis, glucose is metabolized into two molecules of pyruvate with a net yield of only two ATP.
The events of cellular respiration in proper sequence?
Oxidation of glucose to pyruvate; oxidation of pyruvate; citric acid cycle; oxidative phosphorylation
The high electronegativity of the oxygen atom is the reason that oxygen is such a strong oxidizing agent.
The high electronegativity of the oxygen atom is the reason that oxygen is such a strong oxidizing agent.
The function of cellular respiration is to __________.
extract usable energy from glucose
In cellular respiration, glucose is _____ (resulting in the production of carbon dioxide) and oxygen is _____ (resulting in the production of water).
In cellular respiration, glucose is oxidized (resulting in the production of carbon dioxide) and oxygen is reduced (resulting in the production of water).
The oxidation of organic molecules produces carbon dioxide, and as the exergonic process of cellular respiration is not 100% efficient, some energy is lost to the environment as heat.
The oxidation of organic molecules produces carbon dioxide, and as the exergonic process of cellular respiration is not 100% efficient, some energy is lost to the environment as heat.
A small amount of ATP is made in glycolysis by the transfer of a _____ group from a fragment of ____ to ADP by substrate-level ______
Transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation
Glucose is phosphorylated at the beginning of ______.
glucose is phosphorylated at the beginning of glycolysis.
Glycolysis occurs in the _____.
Glycolysis occurs in the cytosol.
The name of the process that oxidizes glucose to pyruvate and produces ATP and NADH is _____.
glycolysis.
The processes that generates most of the NADH that delivers electrons to the electron transport chain?
The citric acid cycle
Most of the NADH is produced during the citric acid cycle, along with some FADH2.
One molecule of CO2 is formed when pyruvate is converted to acetyl CoA, and two molecules of CO2 are produced in the citric acid cycle.
One molecule of CO2 is formed when pyruvate is converted to acetyl CoA, and two molecules of CO2 are produced in the citric acid cycle.
In preparing pyruvate to enter the citric acid cycle, Pyruvate is ——, and a molecule of carbon dioxide is —–. The electrons removed in this process are used to reduce NAD+ to NADH.
In addition to these events, a molecule of coenzyme A is attached to the resulting acetyl group.
In preparing pyruvate to enter the citric acid cycle, Pyruvate is oxidized, and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH.
In addition to these events, a molecule of coenzyme A is attached to the resulting acetyl group.
Why is the citric acid cycle called a “cycle”?
The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle.
In the citric acid cycle, for each pyruvate that enters the cycle, __ ATP, __ NADH, ___ FADH2 are produced.
In the citric acid cycle, for each pyruvate that enters the cycle, Two ATP, six NADH, two FADH2 are produced.
Where do the reactions of the citric acid cycle occur in eukaryotic cells?
The matrix of the mitochondrion
How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen?
4
There is a net gain of two ATP from glycolysis and one from each molecule of acetyl CoA oxidized in the citric acid cycle for a total of four per glucose.
the major energy-related accomplishment of the citric acid cycle,
Formation of NADH and FADH2
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________.
NADH
The citric acid cycle produces three NADH per turn of the cycle.
The release of CO2 and synthesis of NADH accompanies the conversion of pyruvate to acetyl CoA before the citric acid cycle.
The carboxyl group of pyruvate is removed as a carbon dioxide molecule. The remaining two-carbon fragment is oxidized to acetate and NAD+ is reduced to NADH.
The release of CO2 and synthesis of NADH accompanies the conversion of pyruvate to acetyl CoA before the citric acid cycle.
The carboxyl group of pyruvate is removed as a carbon dioxide molecule. The remaining two-carbon fragment is oxidized to acetate and NAD+ is reduced to NADH.
The energy given up by electrons as they move through the electron transport chain is used in the process of
Pumping H+ across a membrane.
Many of the electron transport molecules in the mitochondrion pump a _____ _____ into the intermembrane space when they pass an electron along the chain.
Many of the electron transport molecules in the mitochondrion pump a hydrogen ion into the intermembrane space when they pass an electron along the chain.
Energy for synthesizing ATP is obtained by ATP synthase directly from the flow of ___across the inner mitochondrial membrane through the ATP synthase enzyme
Energy for synthesizing ATP is obtained by ATP synthase directly from the flow of ___across the inner mitochondrial membrane through the ATP synthase enzyme
_____ ____ flow along an electrochemical gradient across the inner mitochondrial membrane. The gradient is the source of the energy for ATP production.
Hydrogen ions flow along an electrochemical gradient across the inner mitochondrial membrane. The gradient is the source of the energy for ATP production.
During aerobic respiration, molecular oxygen (O2) is used
at the end of the electron transport chain to accept electrons and form H2O
ADP is converted to ATP during _____ _____, and ____ functions as the terminal electron acceptor in oxidative phosphorylation.
ADP is converted to ATP during oxidative phosphorylation, and oxygen functions as the terminal electron acceptor in oxidative phosphorylation.
NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.
NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.
In eukaryotic cells, the components of the electron transport chain are located in or on __________.
the inner membrane of the mitochondrion
Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________.
enables the cell to recycle the reduced NADH to oxidized NAD+
In glycolysis in the absence of oxygen, cells need a way to regenerate which compound?
NAD+
Muscle tissues make lactate from pyruvate to
regenerate NAD+
If muscle cells in the human body consume O2 faster than it can be supplied, Muscle cells would not be able to produce enough ATP to meet demands, oxidative phosphorylation would stop, and muscle cells would consume glucose at an increased rate.
If muscle cells in the human body consume O2 faster than it can be supplied, Muscle cells would not be able to produce enough ATP to meet demands, oxidative phosphorylation would stop, and muscle cells would consume glucose at an increased rate.
A gram of fat oxidized by respiration produces approximately twice as much ATP as a gram of carbohydrate. Fats are better electron donors to oxygen than are sugars.
Fats contain more hydrogen and less oxygen than sugars—it is the transfer of electrons from good donors such as hydrogen atoms to good acceptors such as oxygen that provides the energy in respiration.
____ occurs during S phase
replication of the DNA
The centromere is a region in which __________.
sister chromatids are attached to one another in prophase
The chromosome has a narrow “waist” at a specialized region called the centromere, where sister chromatids are attached.
A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with __________.
There would be 32 chromosomes present in each of the daughter cells.
“Cytokinesis” refers to __________.
the division of the cytoplasm that follows the mitotic division of the nucleus.
Chromatids are __________.
identical copies of each other if they are part of the same duplicated chromosome
If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle?
30.
In this case, mitosis starts with 30 chromosomes, each of which consists of two chromatids. At the completion of mitosis, each daughter cell will contain 30 chromosomes.
A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled __________.
between the G1 and G2 phases
Between these two phases of the cell cycle, the DNA is replicated during the S phase.
G2 follows S and that during the S phase, DNA is _____.
G2 follows S and that during the S phase, DNA is replicated.
During interphase, the genetic material of a typical eukaryotic cell is __________.
dispersed in the nucleus as long strands of chromatin
During interphase, the chromosomes cannot be distinguished individually because the chromosomes are still in the form of
During interphase, the chromosomes cannot be distinguished individually because the chromosomes are still in the form of loosely packed chromatin fibers.
If a human somatic cell is just about to divide, it has __________ chromatids.
92
Human somatic cells have 92 chromatids just prior to cell division due to the replication of the 46 chromosomes that occurred during the S phase.
Cells from an individual with Down syndrome would have 23 pairs of chromosomes plus an extra chromosome for a total of 47. At S phase, those chromosomes replicate to produce 94 sister chromatids.
Cells from an individual with Down syndrome would have 23 pairs of chromosomes plus an extra chromosome for a total of 47. At S phase, those chromosomes replicate to produce 94 sister chromatids.
Prokaryotes reproduce by a type of cell division called binary fission, which involves replicating the single chromosome and distributing the copies equally to two daughter cells.
Prokaryotes reproduce by a type of cell division called binary fission, which involves replicating the single chromosome and distributing the copies equally to two daughter cells.
At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?
Metaphase
The chromosomes convene on the metaphase plate, an imaginary plane that is equidistant from the spindle’s two poles.
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
Cytokinesis
Cytokinesis is usually well under way by telophase. In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two.
_____ begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called chromosomes) to move toward opposite poles of the cell.
Anaphase begins when the cohesins joining sister chromatids are cleaved, allowing the chromatids (now called chromosomes) to move toward opposite poles of the cell.
_____ begins when the cohesins connecting sister chromatids are cleaved, liberating the chromatids (now called chromosomes), which begin moving toward opposite poles of the cell.
Anaphase begins when the cohesins connecting sister chromatids are cleaved, liberating the chromatids (now called chromosomes), which begin moving toward opposite poles of the cell.
One event occurring during prophase is __________.
the beginning of the formation of a spindle apparatus
During prophase, the mitotic spindle begins to form.
The phase of mitosis during which the chromosomes move toward separate poles of the cell is __________.
Anaphase
Following cytokinesis in an animal cell, how many centrioles does each new daughter cell possess?
two
Each daughter cell inherits a single centrosome following cytokinesis, and each centrosome contains two centrioles.
Each daughter cell inherits a single centrosome following cytokinesis, and each centrosome contains two centrioles.
In a human skin cell that is going through the cell cycle, when do the centrosomes separate?
Prophase
The centrosomes move away from each other during _____, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them.
The centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them.
Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. How many sister chromatids are present in the early telophase of mitosis?
0
By telophase, the chromatids have separated, and the individual units of DNA (now called chromosomes) are arriving at the poles. There are no chromatids at this point.
In _____ the nuclear envelope fragments and the kinetochores attach to microtubules. During _____, fragments of the nuclear envelope begin to reassemble along with portions of the endomembrane system.
In prometaphase the nuclear envelope fragments and the kinetochores attach to microtubules. During telophase, fragments of the nuclear envelope begin to reassemble along with portions of the endomembrane system.
In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in __________.
Prophase
During prophase, we observe the formation of the spindle, the condensation of chromatin, and the disappearance of the nucleolus.
During what phase in the cell cycle would you find the most DNA per cell?
G2
Chromosomes are duplicated only during the S phase (“S” stands for synthesis of DNA). The phase following completion of the S phase is G2.
The DNA of the chromosomes is replicated in the S phase before mitosis.
The DNA of the chromosomes is replicated in the S phase before mitosis.
A human cell containing 22 autosomes and a Y chromosome is
a sperm
The two homologs of a pair move toward opposite poles of dividing cell during
Meiosis I
Meiosis II is similar to mitosis in that
sister chromatids separate during anaphase.
Although energetically more costly than _____ reproduction, _____ reproduction leads to different combinations of alleles that could provide adaptability in a changing environment.
Although energetically more costly than asexual reproduction, sexual reproduction leads to different combinations of alleles that could provide adaptability in a changing environment.
Independent assortment results from the random alignment of homologous pairs of chromosomes at metaphase I.
Independent assortment results from the random alignment of homologous pairs of chromosomes at metaphase I.
These three aspects of sexual reproduction increase genetic variation.
Random fertilization, independent assortment, crossing over
Meiosis involves two divisions that typically result in four daughter cells (instead of two). Each cell has half the number of chromosomes of the original parent cell and is, of course, not genetically identical to the parent cell.
Meiosis involves two divisions that typically result in four daughter cells (instead of two). Each cell has half the number of chromosomes of the original parent cell and is, of course, not genetically identical to the parent cell.
_____ _____ separate during anaphase I in meosis; this is the event that produces haploid cells.
Homologous chromosomes separate during anaphase I in meosis; this is the event that produces haploid cells.
Synapsis of homologous chromosomes occurs at _____ of meiosis I.
Synapsis of homologous chromosomes occurs at prophase of meiosis I.
An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?
4.
Because of the synapsis of homologous chromosomes, the number of tetrads in meiosis I will be the same as the haploid number of chromosomes.
Regions of chromosomes where nonsister chromatids cross over are called __________.
Chiasmata
Chiasmata are regions where crossing over has occurred.
Crossing over occurs during __________.
Prophase I
Crossing over, resulting in genetic recombination, occurs during synapsis in prophase I.
What is the function of meiosis?
To make cells with a haploid (half that of the parents) number of chromosomes
The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.
Cytokinesis normally accompanies both telophase I and telophase II as well as the telophase of mitosis.
Cytokinesis normally accompanies both telophase I and telophase II as well as the telophase of mitosis.
Cytokinesis is the __________.
division of the cytoplasm to create two cells
Homologs separate and migrate toward opposite poles during
Anaphase I of meiosis
Sister chromatids separate and migrate toward opposite poles during
Anaphase II
_____ is the pairing of homologous chromosomes during prophase I.
Synapsis is the pairing of homologous chromosomes during prophase I.
At the end of telophase I of meiosis and the first cytokinesis, there are __________.
two haploid cells
_____ results in cells that contain half the parental chromosome number
Meiosis
Somatic cells in humans contain __________ set(s) of chromosomes and are therefore termed __________.
two; diploid
Somatic cells in interphase contain the characteristic diploid chromosome number.
When we say that an organism is haploid, we mean that __________.
its cells have a single set of chromosomes
____ have genes for the same traits at the same loci.
homologous chromosomes
Sister chromatids are identical copies of each other formed through ___ ____ and participate in both ____ and ____.
Sister chromatids are identical copies of each other formed through DNA synthesis and participate in both mitosis and meiosis.
Humans have ___pairs of autosomes
Humans have 22 pairs of autosomes and one pair of sex chromosomes.
In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.
5
Haploid sex cells contain half as many chromosomes as diploid somatic cells.
In sexually reproducing species, the chromosome number remains stable over time because __________ and __________ always alternate.
meiosis; fertilization
Meiosis reduces the number of chromosomes by half, and fertilization restores the number to the diploid state.
