Biology slides 8
What is the primary purpose of the cell cycle?
To create new cells and enable growth through regular cycles of division.
What are gametes?
Special cells produced for sexual reproduction.
What are two major phases of the cell cycle?
Mitosis (cell division) and interphase (cell growth and function).
What occurs during the G1 phase of the cell cycle?
Cells grow, obtain energy, and produce new proteins.
What happens during the S phase of the cell cycle?
The full genome of the organism is replicated.
What is the focus of the G2 phase?
Further growth and preparation for cell division, including organelle and protein production.
What is the M phase of the cell cycle?
The phase where mitosis and cytokinesis occur, resulting in the division of the cell.
What is the G0 phase?
A resting phase where some cells stop dividing and just maintain their functions.
What are the checkpoints in the cell cycle?
Regulatory points that ensure a cell is ready to proceed to the next phase.
What is the role of DNA during the S phase?
DNA is replicated to ensure each daughter cell receives an identical copy.
What is a chromosome?
A double-stranded DNA molecule that contains coding and noncoding DNA.
How many chromosomes do most human somatic cells contain?
46 chromosomes, inherited from both biological parents.
What are homologous chromosomes?
Pairs of chromosomes that are similar but not identical, containing different alleles.
What are base pairs in DNA?
Hydrogen bonds that form between adenine and thymine or cytosine and guanine.
What is a replication fork?
The area where the DNA strands separate during replication.
What is the semi-conservative nature of DNA replication?
Each new DNA molecule consits of one original strand and one newly synthesized strand.
What is the role of DNA polymerase during replication?
To build complementary strands of DNA using one strand as a template.
What are sister chromatids?
Identical copies of a chromosome that are joined at the centromere.
What happens to sister chromatids during mitosis?
They are separated and distributed into daughter cells.
What is the error rate during DNA replication?
Approximately 1 in 100,000, with proofreading reducing it to about 1 in 10 billion.
What is chromatin?
The hierarchical organization of DNA wrapped around histone proteins.
What is the significance of the centromere?
It is the region where sister chromatids are attached and later separated during cell division.
What is the function of histone proteins in DNA structure?
To help organize DNA into a compact, structured form called chromatin.
What is the purpose of cell division?
To produce two identical daughter cells from one parent cell.
What is the role of organelles during the G2 phase?
New organelles are produced to prepare for cell division.
What does the term 'cytokinesis' refer to?
The process of cytoplasm division that follows mitosis.
What is the significance of the cell cycle in human biology?
It is essential for growth, development, and tissue repair.
What is the role of the centomere in a chromosome?
The centromere is the region of a chromosome where it can attach to its sister chromatid and is where they attach after replication.
What is the purpose of mitosis?
Mitosis produces two identical daughter cells from a single parent cell.
How many stages are there in mitosis?
There are five stages in mitosis: prophase, prometaphase, metaphase, anaphase, and telophase.
What happens during prophase?
During prophase, DNA condenses to form chromosomes, and the centrosomes move away from each other.
What is the metaphase plate?
The metaphase plate is the imaginary line where pairs of sister chromatids align at the center of the cell during metaphase.
What occurs during anaphase?
During anaphase, the kinetochores pull the sister chromatids apart towards opposite centrosomes.
What is cytokinesis?
Cytokinesis is the process where the cytoplasm divides to form two separate daughter cells after mitosis.
What is the difference between diploid and haploid cells?
Diploid cells have two sets of chromosomes (2n), while haploid cells have one set of chromosomes (n).
What is the role of meiosis?
Meiosis is responsible for producing haploid gametes from diploid germ cells.
What is a tetrad in meiosis?
A tetrad is a group of four chromatids formed by the synapsis of homologous chromosomes during prophase 1.
What is crossing-over?
Crossing-over is the exchange of genetic material between homologous chromosomes at chiasmata during meiosis.
What is the significance of gametes?
Gametes are haploid cells that combine during sexual reproduction to form a zygote.
What happens during telophase?
During telophase, chromosomes reach the centrosomes, and a nuclear envelope begins to form around each set of chromosomes.
What is the function of the kinetochore?
The kinetochore is a protein that holds the centromere onto the cell's microtubules during cell division.
What is the outcome of meiosis?
Meiosis results in four genetically diverse haploid cells from one diploid cell.
What are nonkinetochore microtubules?
Nonkinetochore microtubules are microtubules that do not attach to kinetochores and help elongate the cell during mitosis.
What is the role of the contractile ring during cytokinesis?
The contractile ring helps to form the cleavage furrow that divides the cell into two daughter cells.
What is the significance of the cleavage furrow?
The cleavage furrow is the indentation that begins the process of cytokinesis in animal cells.
What is the difference between somatic cells and gametes?
Somatic cells are diploid and make up most of the body's tissues, while gametes are haploid and involved in reproduction.
What is the result of fertilization?
Fertilization results in the formation of a zygote, which is a diploid cell formed from the fusion of two haploid gametes.
What occurs during late prophase?
During late prophase, the nuclear membrane disappears and kinetochores attach chromosomes to spindle fibers.
How does the cell prepare for mitosis?
The cell prepares for mitosis during the G2 phase of interphase by duplicating its DNA and organelles.
What is the importance of the synaptonemal complex?
The synaptonemal complex helps bind homologous chromosoes tightly together during prophase 1 of meiosis.
What happens to the nuclear envelope during mitosis?
The nuclear envelope breaks down during prophase and re-forms during telophase.
What is the process called where DNA is swapped between homologous chromosomes?
Crossing-over.
What are the structures called where crossing-over occurs?
Chiasmata.
What happens to sister chromatids during meiosis 1?
They separate from each other (disjunction).
What type of cells are produced at the end of meiosis 1?
Haploid cells with 23 chromosomes.
What is the result of meiosis 2?
Four haploid daughter cells containing unduplicated chromosomes.
How many divisions occur in meiosis?
Two divisions.
What is the difference between the daughter cells produced by mitosis and meiosis?
Mitosis produces two diploid cells, while meiosis produces four haploid cells.
What is gametogenesis?
The formation of gametes.
How many gametes are produced in oogenesis?
One gamete (egg) and three polar bodies.
When does spermatogenesis begin?
At puberty.
When does oogenesis begin?
During fetal development.
What is nondisjunction?
The failure of homologous chromosomes or sister chromatids to separate properly during cell division.
What is aneuploidy?
A condition where there is an abnormal number of chromosomes in cell.
What is karyotype?
A visual representation of an individual's chromosomes arranged side-by-side.
What is the significance of crossing-over during meiosis?
It increases genetic variability among gametes.
What is the diploid number represented as in the example provided?
2n = 6.
What happens to the other cells produced during oogenesis?
They do not fully develop and are destroyed.
What is the role of meiosis in the animal body?
To produce gametes and reduce the number of chromosomes by half.
What is the timing of meiosis 2 in oogenesis?
It stops at Metaphase 2 until fertilization.
What is the result of independent assortment during meiosis?
Each human can produce 2^23 different gametes.
What occurs during prophase 1 of meiosis?
Synapsis of homologous chromosomes and crossing over.
What is the main difference between mitosis and meiosis regarding genetic composition?
Mitosis produces genetically identical cells, while meiosis produces genetically diverse cells.
What is the outcome of meiosis in terms of chromosome number?
It reduces the chromosome number by half.
What is the significance of the cleavage furrow during meiosis?
It indicates the division of the cytoplasm during telophase and cytokinesis.
What happens to the sister chromatids during anaphase 2 of meiosis?
They separate and move toward opposite poles.
What is the role of the spindle apparatus during meiosis?
To help segregate chromosomes during cell division.