Bio 12 Flashcards
(19 cards)
What is the structure formed when chromatin condenses during cell division?
Chromosomes
Chromosomes are rod-shaped organelles composed of DNA and chromosomal proteins.
What are the two forms in which chromosomes can exist?
Replicated or unreplicated
Replicated chromosomes contain two chromatids, while unreplicated chromosomes consist of a single chromatid.
What is one half of a replicated chromosome called?
Chromatid
Two chromatids are connected by a centromere.
How many chromosomes are found in human somatic cells?
46 chromosomes (23 pairs)
This includes 23 maternal chromosomes and 23 paternal chromosomes.
What does the letter ‘n’ represent in terms of chromosome number?
Haploid number (23)
Cells with 2n chromosomes are diploid (46), such as somatic cells.
What are the pairs of chromosomes called that carry matching genetic information?
Homologous chromosomes or homologs
They carry the same sequence or alleles.
What are the two main periods in the cell life cycle?
Interphase and mitosis
Interphase is a non-division period, while mitosis involves cell division.
What occurs during the G1 phase of interphase?
Increase in protein synthesis, microvilli, pinocytosis, and organelle synthesis
This prepares the cell for DNA synthesis.
What is characterized by DNA synthesis in the cell cycle?
S phase
This phase results in 46 replicated chromosomes (92 chromatids).
What is the process of nuclear division called?
Karyokinesis
This occurs during mitosis.
List the four main stages of mitosis.
- Prophase
- Metaphase
- Anaphase
- Telophase
These stages represent the orderly changes during nuclear division.
What happens during prophase of mitosis?
Chromosomes become visible, centrioles move to opposite poles, and the nuclear membrane disintegrates
The nucleolus also disappears at this stage.
What is the role of spindle fibers during metaphase?
They attach to the centromeres of each chromosome
This helps align the chromosomes at the cell’s equator.
What occurs during anaphase?
Centromeres divide and chromatids are pulled to opposite ends of the cell
Each chromatid becomes a full-fledged chromosome.
What marks the beginning of cytokinesis?
Constriction of the cell at the equator
This occurs during telophase and can result in a cleavage furrow in animal cells or a cell plate in plant cells.
What is the key difference between meiosis and mitosis?
Meiosis reduces the chromosome number by half
It results in haploid cells, whereas mitosis maintains the diploid chromosome number.
What is crossing-over in meiosis?
Exchange of genetic information between homologous chromosomes during prophase I
This increases genetic variability in gametes.
What is the final product of meiosis?
Four haploid cells
These cells are genetically unique due to crossing-over.
What happens at fertilization?
Sperm (n) meets ovum (n) to produce a diploid zygote (2n)
The genetic makeup of the zygote is different from both parents.
