Download Unit 7 Review

Unit 7 Review
Completion
Complete each sentence or statement.
1. Growth occurs through cell enlargement and cell ____________________.
2. Following replication of its DNA, each chromosome contains two ____________________, which are
attached to each other by a centromere.
3. A(n) ____________________ is a segment of a DNA molecule that carries the instructions for producing a
specific trait.
4. Chromosomes that are not involved in sex determination are called ____________________.
5. In humans, the genotype XX results in a(n) ____________________.
6. In humans, the specific condition caused by an extra chromosome 21 is called ____________________
____________________.
7. Loss of control and regulation of the ____________________ ____________________ can result in the
development of cancer.
8. “Cables” made of microtubules that extend from the poles of a cell to the centromeres during cell division are
called ____________________ ____________________.
9. Chromosomes coil up and become visible during ____________________.
10. Chromatids migrate toward poles as spindle fibers shorten during ____________________.
11. In many eukaryotic cells, ____________________ takes place after the nucleus divides.
12. After a new nuclear membrane forms during telophase of mitosis or meiosis, the ____________________
divides, resulting in two cells.
13. The four haploid cells formed in the male at the end of meiosis 2 develop a tail and are called
____________________.
14. The separation of a parent into two or more individuals of about equal size is called ____________________.
15. The process in which sperm and egg cells join is called ____________________.
16. The diploid phase in the life cycle of plants is called the ____________________.
17. A DNA subunit composed of a phosphate group, a five-carbon sugar, and a nitrogen-containing base is called
a(n) ____________________.
18. Errors in nucleotide sequencing are corrected by enzymes called ____________________
____________________.
19. A protein that prevents transcription by blocking the path of RNA polymerase along a molecule of DNA is
called a(n) ____________________.
20. Transcription begins when an enzyme called ____________________ ____________________ binds to the
beginning of a gene on a region of DNA called a promoter.
21. A(n) ____________________ is a harmless version of a disease-causing microbe that can stimulate a
person’s immune system to ward off infection by the infectious form of the microbe.
22. Watson and Crick determined that DNA molecules have the shape of a(n) ____________________
____________________.
23. Enzymes called ____________________ are responsible for unwinding the DNA double helix by breaking
the hydrogen bonds that hold the complementary strands together.
24. The nitrogen-containing base that is only found in RNA is ____________________.
25. The form of ribonucleic acid that carries genetic information from the DNA to the ribosomes is
____________________.
26. Cells must regulate gene expression so that genes will be ____________________ only when the proteins are
needed.
27. Portions of genes that actually get translated into proteins are called ____________________.
Essay
28. Refer to the illustration above. Identify the structure in the drawing and discuss its importance during
eukaryotic cell division.
29. Explain the mechanism of sex determination in humans.
30. Describe Down syndrome and its cause.
31. Discuss how a karyotype can be used to diagnose Down syndrome.
32. What would happen if the chromosome number were not reduced before sexual reproduction?
33. Briefly describe the five stages of the cell cycle.
34. What would happen if the chromosome number were not reduced before sexual reproduction?
35. Compare the features of mitotic metaphase, meiotic metaphase I, and meiotic metaphase II.
36. Identify three ways in which genetic recombination results during meiosis.
37. Explain why crossing-over is an important source of genetic variation.
38. What are the two things that might happen to a bud?
39. What are at least two advantages of asexual reproduction?
40. The DNA molecule is described as a double helix. Describe the meaning of this expression and the general
structure of a DNA molecule.
41. Describe how a molecule of DNA is replicated.
42. Identify the three types of RNA and briefly describe the function of each.
43. What is the evolutionary significance of the genetic code?
44. Describe the physical structure of the lac operon.
45. In a mutant strain of Escherichia coli, lactose fails to bind to the repressor on the operator portion of the lac
operon. What is likely to be the result of this failure?
46. Describe two types of mutations and their effects.
Unit 7 Review
Answer Section
COMPLETION
1. ANS: division
DIF: I
2. ANS: chromatids
OBJ: 6.1.1
STO: Bio 4A, TAKS 2 Bio 4B, Bio 6E
DIF: I
3. ANS: gene
OBJ: 6.1.2
STO: TAKS 2 Bio 6A, Bio 6E
DIF: I
4. ANS: autosomes
OBJ: 6.1.2
STO: TAKS 2 Bio 6A, Bio 6E
DIF: I
5. ANS: female
OBJ: 6.1.3
STO: TAKS 2 Bio 6A, Bio 6E
DIF: I
OBJ: 6.1.3
6. ANS: Down syndrome
STO: TAKS 2 Bio 6A, Bio 6E
DIF: I
7. ANS: cell cycle
STO: TAKS 2 Bio 6C, Bio 6F
OBJ: 6.1.5
DIF: II
OBJ: 6.2.3
8. ANS: spindle fibers
STO: TAKS 2 Bio 4B, TAKS 2 Bio 6C,
DIF: I
9. ANS: prophase
OBJ: 6.3.1
STO: TAKS 2 Bio 4B, Bio 6E
DIF: I
10. ANS: anaphase
OBJ: 6.3.2
STO: TAKS 2 Bio 4B, Bio 6E
DIF: I
11. ANS: cytokinesis
OBJ: 6.3.2
STO: TAKS 2 Bio 4B, Bio 6E
DIF: I
12. ANS: cytoplasm
OBJ: 6.3.3
STO: TAKS 2 Bio 4B, Bio 6E
DIF: I
13. ANS: sperm
OBJ: 6.3.3
STO: TAKS 2 Bio 4B, Bio 6E
DIF: II
14. ANS: fission
OBJ: 7.1.3
STO: TAKS 2 Bio 4B, Bio 6E
DIF: II
15. ANS: fertilization
OBJ: 7.2.2
STO: Bio 6E
DIF: II
16. ANS: sporophyte
OBJ: 7.2.4
STO: TAKS 2 Bio 4B, Bio 6E
DIF: II
17. ANS: nucleotide
OBJ: 7.2.4
STO: TAKS 2 Bio 4B, Bio 6E
DIF: I
OBJ: 9.2.1
18. ANS: DNA polymerases
STO: TAKS 2 Bio 6A
DIF: II
19. ANS: repressor
STO: TAKS 2 Bio 6B (11th), TAKS 2 Bio 6C
OBJ: 9.3.2
DIF: I
OBJ: 10.2.1
20. ANS: RNA polymerase
STO: TAKS 2 Bio 6A, TAKS 2 Bio 6B (11th)
DIF: II
21. ANS: vaccine
OBJ: 10.2.2
STO: TAKS 2 Bio 4B, TAKS 2 Bio 6B (11th)
DIF: I
22. ANS: double helix
OBJ: 9.1.1
STO: TAKS 1 Bio/IPC 2C, Bio 3F
DIF: I
23. ANS: helicases
OBJ: 9.2.2
STO: TAKS 2 Bio 6A
DIF: II
24. ANS: uracil
OBJ: 9.3.1
STO: TAKS 2 Bio 6B (11th)
DIF: I
25. ANS: mRNA
OBJ: 10.1.1
STO: TAKS 2 Bio 6A
DIF: I
26. ANS: transcribed
OBJ: 10.1.3
STO: TAKS 2 Bio 6B (11th)
DIF: I
27. ANS: exons
OBJ: 10.2.1
STO: TAKS 2 Bio 6A, TAKS 2 Bio 6B (11th)
DIF: I
OBJ: 10.2.3
STO: Bio 4A, TAKS 2 Bio 6A
ESSAY
28. ANS:
This is a chromosome, the structure where the DNA in eukaryotic cells is found. The chromosome is formed
right before a eukaryotic cell divides. Chromosomes are made of two chromatids attached at the centromere.
During mitosis, the nucleus of a cell divides into two nuclei, each containing a complete set of the cell’s
chromosomes. Thus, each new cell formed during cell division contains identical DNA.
DIF: III
29. ANS:
OBJ: 6.1.2
STO: TAKS 2 Bio 6A, Bio 6E
A female parent donates one X chromosome. A male parent donates either an X or a Y chromosome. If an
egg is fertilized by a sperm containing an X chromosome, the resulting zygote will be XX, and the new
individual will be female. If an egg is fertilized by a sperm containing a Y chromosome, the resulting zygote
will be XY, and the new individual will be male.
DIF: III
OBJ: 6.1.3
STO: TAKS 2 Bio 6A, Bio 6E
30. ANS:
Down syndrome is a disorder characterized by short stature, a round face, upper eyelids that cover the inner
corner of the eye, and varying degrees of mental retardation. This syndrome results from an extra copy of
chromosome 21.
DIF: III
OBJ: 6.1.5
STO: TAKS 2 Bio 6C, Bio 6F
31. ANS:
A karyotype is a photograph that shows the collection of chromosomes found in an individual’s cells.
Analysis of this collection of chromosomes can reveal abnormalities in chromosome number. Down
syndrome is associated with trisomy 21—an extra chromosome 21 in the cells of a person. Such an
abnormality can be detected by observing a karyotype of an affected person.
DIF: III
OBJ: 6.1.5
STO: TAKS 2 Bio 6C, Bio 6F
32. ANS:
The number of chromosomes in the offspring would be double the number in the parents. The number and
characteristics of chromosomes in cells determine the traits of the organism. The organism would almost
certainly not survive the doubling of its chromosomes, and even if it did survive and reproduce, then the
number of chromosomes would become unmanageably large after only a few generations.
DIF: III
OBJ: 6.1.5
STO: TAKS 2 Bio 6C, Bio 6F
33. ANS:
The G1 stage of the cell cycle is the phase of cell growth. This is followed by the S stage, during which DNA
is copied. G2 involves the cell preparing for cell division. The nucleus of a cell is divided into two nuclei
during the mitosis phase. The cell cycle concludes with cytokinesis, during which the cytoplasm divides. The
newly formed cells then enter into a new cell cycle, repeating these stages again.
DIF: III
OBJ: 6.2.1
STO: TAKS 2 Bio 4B, Bio 6E
34. ANS:
The number of chromosomes in the offspring would be double the number in the parents. The number and
characteristics of chromosomes in cells determine the traits of the organism. The organism would almost
certainly not survive the doubling of its chromosomes, and even if it did survive and reproduce, then the
number of chromosomes would become unmanageably large after only a few generations.
DIF: III
OBJ: 7.1.1
STO: TAKS 2 Bio 4B, Bio 6E
35. ANS:
During metaphase of mitosis, the diploid number of chromosomes of the cell line up single file across the
equator of the cell. Meiotic metaphase I is characterized by the homologous chromosomes lining up as pairs
(double file) along the equator. Metaphase 2 of meiosis appears similar to mitotic metaphase, except that the
number of chromosomes is the haploid number rather than the diploid number. These chromosomes line up
single file across the cell equator.
DIF: III
36. ANS:
OBJ: 7.1.1
STO: TAKS 2 Bio 4B, Bio 6E
Genetic recombination results when crossing-over occurs between homologous chromosomes, when
homologous pairs separate independently in meiosis I, when sister chromatids separate independently in
meiosis II, and when the zygote that forms a new individual is created by the random joining of two gametes.
DIF: III
OBJ: 7.1.2
STO: TAKS 2 Bio 4B, Bio 6E
37. ANS:
Crossing-over occurs when two homologous chromosomes exchange reciprocal segments of DNA during
prophase I of meiosis. This results in chromosomes in which the two chromatids no longer have identical
genetic material. When meiosis is completed, the resulting gametes carry new combinations of genes.
DIF: III
OBJ: 7.1.2
STO: TAKS 2 Bio 4B, Bio 6E
38. ANS:
It may break from the parent and become an independent organism, or it may remain attached to the parent
and eventually give rise to many individuals.
DIF: III
OBJ: 7.2.2
STO: Bio 6E
39. ANS:
1. It is less complex than sexual reproduction.
2. In a stable environment, it allows organisms to produce many offspring in a short period of time.
3. Organisms do not need to use energy to produce gametes or to find a mate.
DIF: III
OBJ: 7.2.3
STO: Bio 6E
40. ANS:
DNA molecules are composed of two complementary strands of nucleotides arranged in a pattern resembling
a spiral staircase. Each nucleotide consists of a sugar molecule, a phosphate group, and one of four possible
bases. The double helix arrangement is maintained by the formation of hydrogen bonds between
complementary bases. Within the base pair adenine and thymine, as well as within the base pair guanine and
cytosine, equal numbers of molecules are present.
DIF: III
OBJ: 9.2.2
STO: TAKS 2 Bio 6A
41. ANS:
To begin the replication process, enzymes called helicases break the hydrogen bonds that hold the two
complementary strands of the DNA double helix together, allowing the helix to unwind. The complementary
strands are held apart by additional protein molecules. At the replication fork, the point at which the double
helix separates, a molecule of DNA polymerase attaches and begins to add nucleotides to the exposed bases
according to the base-pairing rules. This continues until the DNA polymerase reaches a nucleotide sequence
that signals it to detach, having completed the replication of the DNA strand.
DIF: III
OBJ: 9.3.1
STO: TAKS 2 Bio 6B (11th)
42. ANS:
Three types of RNA are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
Messenger RNA carries hereditary information from the DNA in the nucleus to the site of translation on the
ribosomes. tRNA carries amino acids to the ribosomes for assembly into proteins. rRNA is a structural
molecule, becoming part of the ribosomes upon which translation occurs.
DIF: III
OBJ: 10.1.3
STO: TAKS 2 Bio 6B (11th)
43. ANS:
The fact that the genetic code is the same in all organisms and is nearly universal suggests that all life-forms
have a common evolutionary ancestor with a single genetic code.
DIF: III
OBJ: 10.1.4
STO: TAKS 2 Bio 6B (11th)
44. ANS:
The lac operon consists of three segments. These include a promoter, an operator, and three
lactose-metabolizing genes. In addition, a regulator gene lies close to the lac operon.
DIF: III
OBJ: 10.2.1
STO: TAKS 2 Bio 6A, TAKS 2 Bio 6B (11th)
45. ANS:
The failure of lactose to bind to and remove the repressor will prevent the lac operon from functioning. As a
result, RNA polymerase will not transcribe the lactose-metabolizing genes of the lac operon, and the enzymes
that normally break down lactose will not be produced.
DIF: III
OBJ: 10.2.1
STO: TAKS 2 Bio 6A, TAKS 2 Bio 6B (11th)
46. ANS:
Gene rearrangements are mutations that move an entire gene to a new location. Changes in a gene's position
often disrupt the gene's function because the gene is exposed to new regulatory controls in its new location.
Gene alterations are changes in a gene itself. These include a change in one or many nucleotides in a gene.
Point mutations, insertions, and deletions are examples of gene alterations. These types of mutations can
disrupt a gene's function. (Students might also describe point mutations, insertions, deletions, or
transpositions in response to this question.)
DIF: III
OBJ: 10.2.4
STO: TAKS 2 Bio 4B, TAKS 2 Bio 6A, TAKS 2 Bio 6C,