Chapter 2: Chromosomes and Cellular Reproduction Flashcards
How does prokaryotic DNA differ from eukaryotic DNA?
- Prokaryote: DNA is floating within the cell
- Eukaryote: DNA is complexed with histone proteins to form chromatin; much more organized; packed tightly and compartmentalized within the nucleus
How does the cell diameter of prokaryotic cells differ from eukaryotic?
- Prokaryote: small (1 to 10 um)
- Eukaryote: large (10 to 100 um)
How does the genome of prokaryotic cells differ from eukaryotic?
- Prokaryote: one circular DNA molecule
- Eukaryote: multiple, linear DNA molecules
What structures are present in eukaryotic cells, but absent in prokaryotic?
- Membrane-bound organelles
- Cytoskeleton
Why aren’t viruses considered to be “alive”?
- Do not possess a plasma membrane
- Are extremely small
- Do not possess a sufficient number of genes to replicate without a host
- Do not possess metabolic factors
What is a virus?
- Protein coat surrounding a piece of nucleic acid
- They are neither cells, nor primitive forms of life, nor are they “alive”
What are the three fundamental events for cell reproduction?
1) Genetic information must be copied.
2) The copies of genetic information must be separated from each other
3) The cell must divide
Describe prokaryotic cell replication.
- The single circular chromosome replicates.
- The origins segregate to opposite sides.
- The origins are anchored to opposite sides of the cell.
- The cell divides (cytokinesis). Each new cell has an identical copy of the original chromosome.
- This process is called binary fission
Differentiate diploid and haploid organisms.
- Diploid organism: has two sets of chromosomes organized as homologous pairs
- Haploid organism: carries one set of genetic information
How are homologous chromosomes similar?
- Look alike
- Have the same length and centromere position
- Have a similar banding pattern when stained
Where are the members of a homologous chromosome inherited from?
- One from the male parent
- One from the female parent
Define alleles.
A location on one homologue contains genes for the same trait that occurs at this locus on the other homologue, although the genes may code for different variations of that trait
What are centromeres?
The attachment point for spindle microtubules and the constricted region where the kinetochores form
What are telomeres?
The tips of a linear chromosome; the stable ends of chromosomes
How do you determine the number of chromosomes?
Count the number of functional centromeres
How do you determine the number of sister chromatids?
The number of sister chromatids = the number of telomeres
What are the four major types of eukaryotic chromosomes (depending on the position of the centromere)?
- Metacentric
- Submetacentric
- Acrocentric
- Telocentric
What are the two important processes of cellular reproduction?
- Growth: involves the duplication of the cells’ DNA and contents (interphase)
- Cell division: involves the separation of the cells’ DNA and content into daughter cells (mitotic phase)
Define mitosis.
The division of the nuclear material (DNA)
Define cytokinesis.
The division of the cytoplasm and its contents
What are the six steps to mitosis?
- Interphase
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What happens during the G1 phase of interphase?
The cell grows; synthesis of proteins necessary for cell division
What is the G0 phase in interphase?
The cells may enter a non-dividing phase
What happens during the M phase of interphase?
Mitosis and cytokinesis can take place
What happens during the S phase of interphase?
The DNA duplicates
What happens during the G2 phase of interphase?
The cell prepares for mitosis
What is the G2/M checkpoint in interphase?
After the checkpoint, the cell can divide
What happens during the M phase of interphase?
Mitosis and cytokinesis can take place
What are the three fundamental events of cell reproduction?
- Genetic information must be copied.
- The copies of genetic information must be separated from each other.
- The cell must divide.
Why do the processes that lead to cell reproduction differ in prokaryotic and eukaryotic cells?
Because of their structural differences
How do prokaryotic cells reproduce?
Simple division
Define meiosis.
- Production of haploid gametes
- Meiosis reduces the chromosome number by half, and includes two cell divisions
Define fertilization.
Fusion of haploid gametes.
Genetic variation is the consequence of ________.
meiosis