Chapter 6: Chromosomes And Cell Division Flashcards
Telomere
A section of non-coding DNA that serves as a protective cap and is located at each tip of every chromosome
Chromatin
A linear DNA strand bound to and wrapped tightly around proteins called histones
Histones
Which keep the DNA from getting tangled and enable it to be tightly and efficiently packed in an orderly manner inside the nucleus
Binary Fission
Means division in two. Genetic information is carried by a single chromosome that is attached at one site to the cell membrane
Replication
The method by which a cell creates an exact duplicate of each chromosome
Parent Cell
The original cell
Daughter Cells
The parent cell is divided into two new cells which are completely identical
Cell Cycle
The alternation of activities between processes related to growth and processes related to cell division
Somatic Cells
Are the cells forming the body of the organism
Gametes
The sex cells. Sperm and egg cells that give rise to the rest of the cells
Interphase
Where the cell grows and prepares to divide
Mitotic Phase
During which first the nucleus and genetic material within the cell divide and then the rest of the cellular contents divide
First Step of Interphase: Gap 1
A cell may grow and develop as well as performing its various cellular functions. Most cells spend most of their time in Gap 1.
Second Step of Interphase: DNA Synthesis
The cell begins to prepare for cell division. First, by creating an exact duplicate of each chromosome by replication. After replication each chromosome has a pair of DNA held together near the center
Third Step of Interphase: Gap 2
Usually characterized by significant growth, as well as high rates of protein synthesis in preparation for division
Gap 1 vs Gap 2
Gap 2 is different because genetic material has now been duplicated
Mitosis
A process in which the parent cells nucleus, including its chromosomes divides.
Cytokinesis
The cytoplasm is divided into two daughter cells which have a complete set of the parents cells DNA and other cellular structures
Checkpoints
Critical points in the cell cycle at which progress is blocked until specific signals trigger continuation of the process
Growth Factors
Provide feedback about the cells environment and can signal that division is appropriate
First Checkpoint: Assessing DNA Damage and Cell Growth
Occurs at the end of Gap 1 when the cell decides if it will proceed to the DNA synthesis phase or delay cell division
Checkpoint 2: Assessing DNA Synthesis
Is a mitosis readiness assessment that indicates that if no DNA damage is detected and if it passes it initiates the process of mitosis
Checkpoint 3: Assessing Anaphase Readiness during Mitosis
Assesses whether the chromosomes have aligned properly at the metaphase plate and whether there is appropriate pull on them
First Step of Chromosome Replication: Unwinding and Separation
The DNA molecule unwinds and separates into two strands.
Second Step of Chromosome Replication: Reconstruction and Elongation
Each of the single strands becomes a double strand as the appropriate complementary base of a nucleotide pairs with the exposed base
Growth in Mitosis
Growth happens in part through the creation of new cells.
Replacement in Mitosis
Cells must be replaced when they die.
Apoptosis
Some cells need to be replaced in a planned process of cell suicide
Sister Chromatids
The chromosomes replicate becoming two identical linear DNA molecules
Condensation
Where the sister chromatids coil tightly and become compact prior to replication
Interphase
In preparation for mitosis, the chromosome replicates. Where sister chromatids are formed and are held together at the centromere
Prophase
Following replication, the sister chromatids condense. The spindle forms and the nuclear envelope breaks down
Metaphase
The chromatids congregate at the cell center. After condensing the sister chromatids line up at the cells center
Anaphase
The chromatids separate and move in opposite directions. The spindle pulls each chromatid in the sister chromatids pairs toward opposite poles of the cell
Telophase
New nuclear membranes form around the two complete chromosome sets. The parent cell is prepared to divide into two genetically identical cells
Cancer
Unrestrained cell growth and division that can damage adjacent tissues.
Features of Cancer Cells
Cells lose their contact inhibition, cells can divide indefinitely, cells have less adhesiveness
Meiosis
A process that enables organisms to make special reproductive cells which have only half as many chromosomes as the rest of the cells in the organisms body
Diploid
Refers to cells that have two copies of each chromosome
Haploid
Refers to cells that have one copy of each chromosome
Outcomes of Meiosis
It reduces the amount of genetic material in gametes and produces gametes that differ from one another with respect to the combinations of alleles they carry
Homologous Pair
A maternal copy and a paternal copy of each of the 22 pairs of chromosomes
Interphase in Meiosis
In preparation for meiosis, the chromosomes replicate.
Prophase I
Chromosomes condense and crossing over occurs. The sister chromatids do something that makes every sperm or egg cell genetically unique
Crossing Over
Some of the genes inherited from your mother get swapped onto the strand of DNA inherited from your father and vice versa
Metaphase I
All chromosomes line up along the center of the cell. After crossing over each pair of chromosomes move to the center of the cell and are pulled together to form the metaphase plate
Anaphase I
Homologues are pulled to either side of the cell. One of the two sister chromatids goes to one pole and the other goes to the other pole.
Telophase I and Cytokinesis
Nuclear membranes reassemble around sets of sister chromatid pairs, and two daughter cells form. Each daughter cell has the genetic material for each of the 23 chromosomes
Prophase II
Chromosomes recondense. The genetic material in each of the two daughter cells once again could tightly. No crossing over occurs
Metaphase II
Sister chromatid pairs line up at the center of the cell.
Anaphase II
Sister chromatids are pulled to opposite sides of the cell. When finished each will become 4 daughter cells
Telophase II and Cytokinesis
Nuclear membranes reassemble and the two daughter cells pinch into four haploid gametes.
Advantages of Sexual Reproduction
Combining alleles from two parents at fertilization, crossing over during the production of gametes, and shuffling and reassortment of homologous during meiosis
Disadvantages of Sexual Reproduction
Dangers of mating, inefficient DNA transfer, and can make organisms vulnerable predation and disease
Advantages of Asexual Production
Fast and easy, efficient, and genetically identical
Disadvantages of Asexual Reproduction
The less likely the offspring will be suited to the environment when it changes
X and Y Chromosomes
Human sex chromosomes
Female Sex Determination
2 X chromosomes
Male Sex Determination
One X and One Y chromosome
Karyotype
A visual display of the complete of chromosomes
Turner Syndrome
Some females carry only 1 X Chromosome. XO
Klinefelter Syndrome
An individual who carries 2 X chromosomes and one Y chromosome
XYY Males
Super males. Relatively tall with severe acne with slightly lower intelligence
XXX Females
Metafemales. Sterile but no other physical or mental problems
