Cell division, Genetics, and Molecular Biology Flashcards
(35 cards)
Explain why there is a limit to how large a cell can grow
If a cell continued to grow, its plasma membrane would be too small to meet its metabolic needs.
The cell must stop growing once it reaches a certain size. . New growth, therefore must come from addition of new cells.
Define the term “cell cycle”
A single cell cycle is defined as the sequence of events from one cell division to the next.
Summarize how advances in technology led to the new theories about the origin of cells
Researchers had begun to identify some cell structures many others- including genetic material - appeared transparent under a microscope. These structures were impossible to differentiate, even at high magnifications. Although scientists could observe the division of cells, they could not infer how distinct cellular processes work .
What is the central feature of the cell cycle?
the way that genetic material is duplicated and then passed
- from the original cell, called parent cell
- to each new cell, called daughter cell.
This process is made possible by the highly organized arrangement of genetic material within a cell
In what structures us the genetic information of a cell contained? Where are these structures located?
DNA “deoxyribonucleic acid” - a molecule of nucleic acid that governs processes of hereditary in the cells of organisms.
DNA is found in each chromosome of a cell. A chromosomes is a length of DNA and its associated proteins.
What is a centromere and where would you find it?
Centromere - the constricted ( pinched-in) region in the condensed chromosome is a specialized region
Centromere is located at by forming pairs of identical chromosomes joined.
How many chromosomes are there in the somatic cells of humans?
Human somatic cells have 46 chromosomes
What are homologous chromosomes?
Homologous chromosomes “similar-looking chromosomes) - organized into 22 pairs; known as autosomes.
Autosomes - two sex chromosomes that may or may not be homologous pair; are numbered 1 through 22.
Why are the X and Y chromosomes know as the sex chromosomes?
The sex chromes determine the sex of an individual .
- A human female has two X chromosomes.
- a human male has one X and one Y chromosome.
By convention, the sex chromosomes are counted as a pair even though X and Y are not homologous.
Clearly differentiates these terms diploid, haploid, polyploid.
Diploid - A cell that contains pairs of homologous chromosomes is said to be diploid. 46 or 23 pairs
Haploid - A cell that contains unpaired chromosomes is said to be haploid
- Human gametes, or reproductive cells (egg and sperm cells)
- The haploid number of chromosomes in a species is designated as n.
Polypoid - they have sets of more than two homologous chromosomes
What is karyotype?
Karyotype - set of chromosomes that an individual possesses called the individual’s karyotype.
Describe how the 22 autosomes and the sex chromosomes are distinct from one another.
- Their overall length,
- the location of the centromere,
- their staining properties/banding pattern
Each chromosomes has a distinct pattern of banding when stained.
Three characteristics are the same in homologous chromosomes,
Scientists can use these characteristics to identify individual chromosomes and to match pairs of homologous chromosomes.
What are the main phrases of the cell cycle?
Describe each phase.
G1 phase “Growth 1”/”Gap 1” -
- can’t identify any specific activities taking place during phase 1.
- know that important growth processes are occurring; the cell grows quickly
S Phase “Synthesis”
- midway through interphase, the cell’s DNA is copied exactly.
- DNA in the chromatin replicates to create a second identical set of DNA
- two identical chromosomes called sister chromatids, joined at the centromere,
- New genetic material is synthesized during the phase
G2 “Growth 2”/ “Gap 2”
- Cells that have completed the S phase then enter the last segment of interphase
- DNA replication in the S phase has consumed a great deal of energy , so this second growth stage lets the cell rebuild its reserves of energy to prepare for division.
- Cell manufactures proteins and other molecules to make structures required for division of the nucleus and cell.
Name the three important functions of mitosis and cytokinesis.
- Growth: they enable organisms to grow from a single-celled zygote into a mature organism that may contain hundreds of trillion of cells
- Maintenance: They produce new cells to replace worn out or dead cells.
- Repair: They can regenerate damaged tissues.
Why must each daughter cell have the correct genetic information?
-Each daughter cell must have the correct genetic information.
- The genetic material of the parent cell must be replicated
- The replicated chromatin must be condensed and organized as chromosomes in the nucleus
- One complete set of chromosomes must be divided into each of two new nuclei.
- The cell cytoplasm must divide to produce two complete and functional daughter cells.
What are the four phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
List the key events that happens to chromosomes in each phase.
Prophase
- DNA chromatin condenses into tightly packaged visible chromosomes
- Nucleolus disappears & nuclear envelope breaks down releasing chromosomes into cytoplasm
- Centrioles move to opposite poles & radiate spindle fibres which attach to centromere of chromosomes
- Spindle Fibers (made of microtubule subunits) guide chromosomes during cell division)
- Homologus Chromosomes DO NOT pair up.
Metaphase (Middle)
- Spindle fibres guide chromosomes to middle equator
- Thick, coiled chromosomes are lined up in the centre of the cell in the metaphase plate. Spindle Fibres are attachment to the chromosomes.
Anaphase (Apart)
- The chromosomes have separated and are moving toward the poles
- Spindle fibers shorten (removal of microtubule subunits) splitting centromeres apart & sister chromatids separate to opposite poles
- At same time, other spindle fibres lengthen forcing poles away from each other elongating the cell
Telophase (Two Cells)
- Two masses of chromosomes unwind into 2 less visible chromatin masses
- Spindle fibers dissolve, nucleolus & nuclear envelope reforms around each mass of chromatin
- Telophase followed by actual division of cytoplasm called cytokinesis
- Animal cells form an indentation along cell equator & eventually pinches into two new daughter cell
- Plant cells from rigid cell plate between 2 chromatin masses that becomes the cell wall.
How do mitosis and cytokinesis differ in plant cells and animal cells?
- Plant cells do not have centrioles, but they do form a spindle apparatus
- The rigid cell of wall of a plant cell is much stronger than the membrane of an animal cell. The cell wall does not furrow and pinch in during cytokenesis
- Instead, a membrane called a cell plate forms between the two daughters nuclei.
- The cell plate extends across the diameter of the cell, and it is then reinforced by the addition of cellulose and proteins to create a new cell wall.
Describe the two key outcomes of meiosis.
-Reduction division: Meiosis is sometimes referral to as a reduction division because it is a form of cell division that produces daughter cells with fewer chromosomes than the parent cells.
Recombination: The products of meiosis have different combinations of genes. Genetic recombination gives rise to offspring that are genetically distinct from one another and their parents.
In what ways does meiosis serve a different function than mitosis?
- Mitosis produces two diploid (2n) somatic cells that are genetically identical to each other and the original parent cell,
- Meiosis produces four haploid (n) gametes that are genetically unique from each other and the original parent (germ) cell
Where does meiosis take place?
Meiosis or reduction division occurs during gametogenesis in the formation of gametes (sperm and ova). Meiosis occurs in the testes and ovaries of males and females, respectively, in the primordial germ cells.
Describe the phases of meiosis 1 and meiosis 2.
- Meiosis I begins with one diploid parent cell and ends with two haploid daughter cells, halving the number of chromosomes in each cell.
- Meiosis II starts with two haploid parent cells and ends with four haploid daughter cells, maintaining the number of chromosomes in each cell.
How is the outcome of meiosis different from the outcome of mitosis?
Cells divide and reproduce in two ways, mitosis and meiosis.
- Mitosis results in two identical daughter cells.
- Meiosis results in four sex cells.
Distinguish independent assortment from crossing over.
Independent assortment of genes is due to the random orientation of pairs of homologous chromosomes in meiosis I.
Chiasmata formation between non-sister chromatids can result in an exchange of alleles.
Crossing over is the exchange of DNA material between non-sister homologous chromatids.
