Download DNA is a long thin molecule that

Name: ________________________
Biology Chapter 8 Vocabulary
1. ________________ is a long thin molecule that stores genetic information.
2. During cell division, the DNA in a eukaryotic cell’s nucleus is coiled into very compact structures called
________________. They are rod-shaped structures made of DNA and proteins.
3. – 4. The DNA in eukaryotic cells wraps tightly around proteins called ________________. They help
maintain the shape of the chromosome and aid in the tight packing of DNA. ________________ proteins are
generally involved in controlling the activity of specific regions of the DNA.
5. The chromosome consists of two identical halves. Each half of the chromosome is called a
________________. They form as the DNA makes a copy of itself before cell division.
6. The constricted area of each chromatid is called a ________________. It holds the two chromatids together
until they separate during cell division.
7. – 8. ________________ are chromosomes that determine the sex of an organism, and they may also carry
genes for other characteristics. All of the other chromosomes in an organism are called ________________.
9. The organism receives one copy of each autosome from each parent. The two copies of each autosome are
called ________________ chromosomes, or homologues. They are the same size and shape and carry genes
for the same traits.
10. A ________________ is a photomicrograph of the chromosomes in a dividing cell found in a normal
human.
11. Cells having two sets of chromosomes are said to be ________________. These cells have both
chromosomes for each homologous pair.
12. Human sperm cells and egg cells are ________________ cells. These cells contain only one set of
chromosomes.
13. ______________________ is the division of a prokaryotic cell into two offspring cells.
14. ________________ results in new cells with genetic material that is identical to that of the original cell.
15. ________________ reduces the chromosome number by half in new cells. The new cells join together later
in the organism’s life cycle to produce cells with a complete set of chromosomes.
16. The ________________ is the repeating set of events that make up the life of a cell. Cell division is one
phase of the cell cycle.
17. The time between cell divisions is called ________________. It is divided into three phases and cell
division is divided into two phases.
18. – 19. During cell division, the chromosomes and cytoplasm are equally divided between two offspring
cells. Cell division consists of mitosis and cytokinesis. During mitosis, or the ________________, the nucleus
of a cell divides. ________________ is the division of the cytoplasm of the cell.
20. Cells spend most of their lifetime in ________________. Following cell division, offspring cells are
approximately half the size of the original cell.
21. During the first stage of interphase— called the ________________ —offspring cells grow to mature size.
G1 stands for the time gap following cell division and preceding DNA replication.
22. After cells have reached a mature size, they typically proceed into the next phase of interphase, called the
________________. During this phase, the cell’s DNA is copied.
23. The ________________ represents the time gap following DNA synthesis (S phase) and preceding cell
division. This phase is a time during which the cell prepares for cell division.
24. Cells can also exit the cell cycle (usually from the G1 phase) and enter into a state called the
________________. During this phase, cells do not copy their DNA and do not prepare for cell division.
25. ________________ is the first phase of mitosis. It begins with the shortening and tight coiling of DNA into
rod-shaped chromosomes that can be seen with a light microscope.
26. – 27. Two pairs of dark spots called ________________ appear next to the disappearing nucleus. In animal
cells, each contains a pair of small, cylindrical bodies called ________________. Plant cells lack these.
28. – 29. In both animal and plant cells, the centrosomes move toward opposite poles of the cell. As the
centrosomes separate, ________________ made of microtubules radiate from the centrosomes in preparation
for mitosis. This array of spindle fibers is called the ________________, which serves to equally divide the
chromatids between the two offspring cells during cell division.
30. – 32. ________________ fibers attach to a disk-shaped protein—called a ________________ —that is
found in the centromere region of each chromosome. Kinetochore fibers extend from the kinetochore of each
chromatid to one of the centrosomes. ________________ extend across the dividing cell from centrosome to
centrosome.
33. ________________ is the second phase of mitosis. During metaphase, chromosomes are easier to identify
using a microscope than during other phases; thus, karyotypes are typically made from photomicrographs of
chromosomes in metaphase. During metaphase, the kinetochore fibers move the chromosomes to the center of
the dividing cell. Once in the center of the cell, each chromosome is held in place by the kinetochore fibers.
34. During ________________, the chromatids of each chromosome separate at the centromere and slowly
move, centromere first, toward opposite poles of the dividing cell. When the chromatids separate, they are
considered to be individual chromosomes.
35. ________________ is the fourth phase of mitosis. After the chromosomes reach opposite ends of the cell,
the spindle fibers disassemble and the chromosomes return to a less tightly coiled chromatin state. A nuclear
envelope forms around each set of chromosomes, and a nucleolus forms in each of the newly forming cells.
36. During telophase, the cytoplasm of the cell divides by a process called cytokinesis. The area of the cell
membrane that pinches in and eventually separates the dividing cell into two cells is called the
_______________________. The cleavage furrow pinches the cell into two cells through the action of
microfilaments.
37. In plant cells, vesicles formed by the Golgi apparatus fuse at the midline of the dividing cell, forming a
membrane-bound cell wall called the ________________. When complete, the cell plate separates the cell into
two cells.
38. In humans, meiosis produces haploid reproductive cells called ________________. Human gametes are
sperm cells and egg cells, each of which contains 23 (1n) chromosomes. The fusion of a sperm and an egg
results in a zygote that contains 46 (2n) chromosomes.
39. – 40. During prophase I, DNA coils tightly into chromosomes. As in the prophase of mitosis, spindle fibers
appear. Then the nucleus and nucleolus disassemble. Notice how every chromosome lines up next to its
homologue. The pairing of homologous chromosomes, which does not occur in mitosis, is called
________________. Each pair of homologous chromosomes is called a ________________. In each tetrad,
chromatids of the homologous chromosomes are aligned lengthwise so that the genes on one chromosome are
adjacent to the corresponding genes on the other chromosome.
41. – 42. Portions of chromatids may break off and attach to adjacent chromatids on the homologous
chromosome—a process called ____________________. This process permits the exchange of genetic
material between maternal and paternal chromosomes. Thus, crossing-over results in ________________
_____________________ by producing a new mixture of genetic material.
43. The random separation of the homologous chromosomes is called ________________ ________________.
Independent assortment of the chromosomes results in a random separation of the maternal and paternal
chromosomes, which results in genetic variation.
44. – 45. In the testes, meiosis is involved in the production of male gametes known as sperm cells or
spermatozoa. In the development of sperm cells, a diploid reproductive cell divides meiotically to form four
haploid cells called ________________. Each spermatid then develops into a mature sperm cell. The
production of sperm cells is called ________________.
46. – 47. ________________ is the production of mature egg cells, or ova. During oogenesis, a diploid
reproductive cell divides meiotically to produce one mature egg cell (ovum). The other three products of
meiosis, called ________________, degenerate.
48. ________________ reproduction is the production of offspring from one parent. Asexual reproduction
does not usually involve meiosis or the union of gametes.
49. ________________ reproduction is the production of offspring through meiosis and the union of a sperm
and an egg. Offspring produced by sexual reproduction are genetically different from the parents because
genes are combined in new ways in meiosis.