41 Questions
What is the complex of DNA and proteins referred to as?
Chromatin
What forms when DNA slightly coils around histones?
Nucleosome
Which structures assist in organizing the DNA inside the nucleus by forming bead-like units?
Histones
Which phase of the eukaryotic cell cycle involves the synthesis and replication of DNA?
S phase
What is the final result of cell division in eukaryotic cells?
Two nearly identical daughter cells
What are the two main reasons that a cell divides?
The cell becomes less efficient in nutrient and waste exchange and places increasing demands on its DNA.
Which factor does NOT affect the rate of exchange of substances in and out of a cell?
The genetic material inside the nucleus.
How does the surface area to volume ratio change as a cell grows larger?
The ratio decreases, making exchange processes less efficient.
What primarily dictates the traffic problems faced by larger cells?
The volume and surface area ratio constraints.
What role does DNA play in limiting cell size?
It serves as the library of information, making it difficult to meet increasing cellular demands as the cell grows.
Which stage is characterized by the separation of sister chromatids?
Anaphase
Which structures are responsible for organizing spindle fibers in plant cells?
Centrosomes
What occurs during prophase in eukaryotic cells?
Genetic material condenses and duplicated chromosomes become visible
What is the primary function of the centromere during mitosis?
Attaching sister chromatids together
Which phase of mitosis is typically the longest and may take up half of the total time to complete mitosis?
Prophase
In which phase do the centromeres of duplicated chromosomes line up across the center of the cell?
Metaphase
Which structure forms in plant cells during cytokinesis to separate the two daughter cells?
Cell plate
What happens to the cell membrane in animal cells during cytokinesis?
It is drawn inward until the cytoplasm is pinched into two parts.
Which regulatory proteins respond to events inside the cell?
Internal regulators
What role do growth factors play in regulating the cell cycle?
They stimulate the growth and division of cells.
How do cells respond to tissue injury in terms of cell division?
Cells at the edge of the injury are stimulated to divide rapidly.
What prevents a cell from entering anaphase until spindle fibers have attached to each chromosome?
An internal checkpoint
What is an advantage of asexual reproduction?
Quick reproduction when conditions are right
Which of the following statements is true about prokaryotic chromosomes?
They are single circular DNA molecules
What is a disadvantage of sexual reproduction?
Requires more time to find a mate and develop offspring
What role do histones play in eukaryotic chromosomes?
Binding tightly to DNA
What is a key consequence of lack of genetic diversity in asexual reproduction?
Population may be unable to adapt to changing conditions
Which organisms primarily rely on cell division as their only form of reproduction?
Single-celled organisms
How do offspring produced by sexual reproduction differ from those produced by asexual reproduction?
They inherit genetic information from two parents
Where is the genetic information of prokaryotic cells primarily located?
In the cytoplasm
What role does the cell cycle play in the organism?
It is essential for embryonic development and wound healing.
Which regulatory influence is particularly associated with the cell cycle?
External regulatory proteins
Which mechanism can halt the cell cycle?
DNA replication errors
During wound healing, why is the cell cycle significant?
It enables rapid cell division to replace damaged cells.
How do other external regulatory proteins affect the cell cycle?
They can either stimulate or inhibit cell division.
Which cell type is capable of developing into any type of cell in the body?
Totipotent cells
At what developmental stage do human cells begin to specialize?
Blastocyst stage
What are embryonic stem cells specifically capable of producing?
All adult cell types
What types of cells do adult stem cells primarily differentiate into?
Cells within the tissues where they are found
Which of the following statements about pluripotent cells is accurate?
Pluripotent cells generally cannot form tissues surrounding the embryo
In a Punnett square prediction of genotype frequencies for a monohybrid cross between parents with PP and Pp genotypes, what percent of the offspring is expected to be heterozygous?
50%
Study Notes
Cell Growth, Division, and Reproduction
- Limits to Cell Size
- Two main reasons for cell division: + Cell becomes less efficient in moving nutrients and waste materials + As a cell grows, it places increasing demands on its own DNA
- Problems of Size
- Rate of exchange between food, oxygen, and water to enter and waste products to leave depends on surface area of cell
- As cell grows, rate of exchange becomes less efficient, leading to cell division
Cell Division and Reproduction
-
Asexual
- Cell division is the only form of reproduction for many single-celled organisms
- The two cells produced are genetically identical to the cell that produced them
-
Sexual
- Involves fusion of two reproductive cells formed by each of two parents
- Offspring produced by sexual reproduction inherit some genetic information from each parent
Compare
-
Asexual
-
Advantages
- Can reproduce quickly, enabling them to compete successfully with other organisms
-
Disadvantages
- Lack of genetic diversity is a disadvantage when conditions change
-
Advantages
-
Sexual
-
Disadvantages
- Requires more time to find a mate and allows for growth and development of offspring
-
Advantages
- Produces genetic diversity
- If the environment changes, diversity in species may help ensure that the population contains the right combination of characteristics needed to survive
-
Disadvantages
Process of Cell Division
- Chromosomes
- Genetic information is bundled into packages of DNA called chromosomes
- Prokaryotic Chromosomes
- DNA molecules are found in the cytoplasm
- Most prokaryotes contain a single circular DNA chromosome containing all of the cell's genetic information
- Eukaryotic Chromosomes
- Chromosomes in eukaryotic cells contain DNA tightly bound to proteins known as histones
- The complex of DNA and proteins is referred to as chromatin
The Structure of DNA and Chromosomes
- DNA slightly coils around histones and together the DNA
Cell Division
-
G2: Preparing for cell division
- Synthesis phase: Many of the organelles and molecules required for cell division are produced
-
M Phase: Cell division
- Mitosis
- Cytokinesis
Mitosis
- 4 phases:
-
Prophase:
- Longest phase, may take up to half of total time to complete mitosis
- Genetic material inside nucleus condenses and duplicated chromosomes become visible
- Outside nucleus, spindle starts to form
-
Metaphase:
- Centromeres of duplicated chromosomes line up across the center of the cell
-
Anaphase:
- Sister chromatids separate and move to opposite ends of the cell
- Telophase
-
Prophase:
Cytokinesis
- Division of cytoplasm to form two separate cells
- Usually occurs at the same time as telophase
- In animal cells:
- Cell membrane is drawn inward until cytoplasm is pinched into two nearly equal parts
- In plant cells:
- Cell plate forms halfway between divided nuclei
- Cell plate gradually grows into cell membranes that separate the two daughter cells
Regulating Cell Cycle
-
Controls on Cell Division
- Cells at edges of injury are stimulated to divide rapidly
- New cells form, starting the process of healing
- When healing process nears completion, rate of cell division slows, controls on growth are restored, and normal activities return
-
Regulatory Proteins
- Dozens of proteins help to regulate
- Cell cycle is controlled by regulatory proteins both inside and outside the cell
Cell Differentiation
-
Adult Cells
- Generally reach a point at which their differentiation is complete - cannot turn into other types of cells
-
Stem Cells and Development
- Totipotent: Able to develop into any type of cell in the body
-
Human Development:
- After about four days of development, human embryo forms into a blastocyst
- At this stage, cells begin to specialize
- Outer cells form tissues that attach embryo to mother
- Inner cells are said to be pluripotent
-
Stem Cells
- Sit at base of branching “arm” of development from which different cell types form
- Stem cells are the unspecialized cells from which differentiated cells develop
-
Adult Stem Cells
- Pools of adult stem cells produce new cells to replace dead cells
- Limited to replacing cells in the tissues where they are found
- Pools of adult stem cells produce new cells to replace dead cells
-
Embryonic Stem Cells
- Capable of producing every cell type
This quiz covers the limitations of cell size, the reasons why cells divide, and the problems associated with increasing cell size.
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