What is cell division
The process by which a cell divides to create daughter cells.
What are the two possible products of cell division? (What kinds of cells are generated)
The process can produce either genetically unique cells, or genetically identical cells.
What is the purpose of creating genetically unique cells?
•So that offspring have a better chance of survival.
•Variation increases the chances of survival.
What is the purpose of creating genetically identical cells?
In the event that a cell is damaged or dies, a new cell may take its place.
When a parental cell undergoes cell division, what are the resulting cells called?
What does asexual reproduction imply/mean? Hint: (____ Organism)
It implies a new organism. Offspring will be exact genetic copies of the parent.
What does a bacterial chromosome consist of?
A circular piece of DNA, that is many times larger than the cell. It is compressed. This is wrapped around a histone protein.
When does the process of Binary Fission begin? In other words, what event signifies the beginning of this process?
It starts when the DNA of the bacterial chromosome begins to replicate at a specific location.
What is the specific location that Binary Fission starts?
The Origin of Replication
What occurs in Binary Fission? (The basic events)
• Starts when the DNA of the bacterial chromosome begins to replicate at a specific location called the origin of replication.
• The two copies of the DNA move apart to opposite ends of the cell
• While the DNA is being replicated the cell grows in size.
• When DNA replication is finished the cell membrane grows inward and the new cell wall is formed.
• Two daughter cells are formed.
What are some characteristics of Eukaryotic Chromosomes?
•A Eukaryotic cell may have multiple chromosomes.
•Every species has a specific characteristic number.
•They have a linear shape.
What are some characteristics of Prokaryotic Chromosomes?
•A Prokaryotic cell only has one chromosome.
•It is circular.
What must a cell do before it can divide?
It must first replicate its DNA.
What is a cell required to do when it undergoes cell division, in terms of the number of chromosomes?
The number of chromosomes must be the same.
What is responsible for the replication and distribution of DNA in terms of manageability? (Hint: It allows for the DNA to be tightly packed)
What is Chromatin? (What is it composed of, what does it look like?
Chromatin is essentially used to describe DNA strands that are loosely coiled around histone proteins.
What is Chromatin in relation to Chromosomes?
Chromosomes are essentially two chromatin fibers compressed.
What does a Chromosome look like? What is it composed of?
The Chromosome is an x-shaped arrangement of two identical sister Chromatids.
When do Chromatids come into play?
•Chromatids are essentially two identical instances of a chromosome.
•This is because before division, all chromosomes are replicated in the Synthesis phase.
Where do the sister chromatids join together?
At the centromere. Refer to the picture of a chromosome.
What are the two stages or functions that any Eukaryotic cell will be performing?
Carrying out its specific function (protein synthesis)
Mitotic cell division is an integral part of the cell cycle; or the _____ of a cell.
What are the two main phases of the cell cycle?
The M Phase
About how much is the Interphase responsible in terms of the cell cycle? What happens in this phase? What are the sub-phases?
•The Interphase accounts for 90% of the cell cycle.
•The cells either perform their function or prepare for cell division.
•The subphases are g1, s1, and g2.
What occurs in the G1 phase?
Cell performs its function or prepares for cell division.
In preparation for cell division during the G1 phase, what occurs?
Cells grow on the site, and the organelles are copied.
What occurs in the S stage (Synthesis)?
DNA synthesis occurs. Chromosomes are copied.
What occurs in the G2 stage?
•The cell continues to grow.
•Proteins that aid in cell division are synthesized.
What occurs in the M phase?
Active cell Division
What are the two processes of the M phase?
Mitosis and Cytokinesis
What occurs in Mitosis?
•Nuclear division (content of the Nucleus is divided)
•Identical chromosomes are separated
What are the 4 stages of Mitosis?
Prophase, Metaphase, Anaphase, Telaphase
What occurs in Cytokinesis?
•Division of cytoplasm
•Process is different in plants and animals
•Two identical daughter cells are present in the end.
During the Interphase, how do the G1, G0, and G2 phases compare visually?
They look the same.
What occurs in the Interphase/what are the characteristics of this phase?
•It is a period of cell growth where DNA is replicated.
•DNA exists in chromatin form and it is housed in the nucleus.
•The organelles are copied.
•The nucleus remains intact.
•Centrioles located close to the nucleus.
•The nucleolus is present.
What occurs in the Prophase?
•The Chromatin coils and condenses into chromosomes.
•This is the first time that chromosomes are visible under a light microscope.
•The centrioles move to opposite poles.
•The spindle fibers begin to grow from the centrioles/centrosomes
•The nucleoli disappear.
What occurs in the Prometaphase?
•The nuclear envelope fragments.
•The spindle fibers attach to the sister chromatids.
What occurs in the Metaphase?
•Chromosomes line up in a single file at the metaphase plate.
What occurs in the Anaphase?
•The spindle fibers pull the sister chromatids apart.
•The sister chromatids move to opposite ends.
•Chromatids represent full-feldged chromosomes.
What occurs in the Telaphase?
•The nuclear envelope and nucleoli reappear.
•Chromosomes begin to uncoil.
•Spindle fibers disappear.
What occurs in Cytokinesis?
The end of the cycle results in two daughter cells.
It begins during the Telaphase.
When Cytokinesis occurs in Animals, what is used?
A cleavage furrow is introduced. This is simply a hollow grove in the cell along the metaphase plate.
What Cytokinesis occurs in Animals, what forms at the furrow? What do these formed objects do?
The microfilaments contract and the furrow deepens until the cell splits in two.
When Cytokinesis occurs in plants, what is involved?
A cell plate is produced.
During Cytokinesis in plants, what is formed from the Golgi that help contain cell wall material?
Vesicles come together to form a cell wall in the middle of a cell.
What is a cell plate?
A cell plate is a arrangement of vesicles that fuse in the middle of a plant cell.
What kinds of factors can influence cell division? (Two Types)
•Chemical and physical factors can influence cell division.
What is released by cells that is a growth factor? How many different types of growth factors have been identified? How do cells respond to growth factors? (All the same or differently?)
•Proteins are released by certain cells that stimulate other cells to divide.
•50 different growth factors have been identified.
•Different cells respond specifically to certain growth factors.
What is Density - dependent inhibition?
•Essentially, in this condition crowded cell stop growing.
•Availability of nutrients decreases and prevents continued cell growth and division.
What is Anchorage Dependence?
•In order to divide, most animal cells must be attached to the extra-cellular matrix of a tissue.
•Rogue cells cannot divide.
What is Cancer? How do cells behave in this state? Do the cells respond to the body's mechanisms? What do these cells not exhibit?
•The cells essentially undergo a period of uncontrolled cell growth/division.
•Cancer begin when a single cell in a tissue undergoes DNA mutations.
•Cancer cells do not respond normally to the body's control mechanisms.
•They don't exhibit density dependent inhibition, anchorage dependence, or stop dividing when growth factors are depleted.
What do cancer cells do that is harmful to tissues?
•They divide excessively and invade other tissues.
When cancer cells are left to spread indefinitely, what will ultimately occur to the organism?
•The organism will eventually die.
What do cancer cells ultimately result in the development of?
•The development of a tumor.
What is a tumor?
•A tumor is an abnormal mass of cell.
What are the two types of tumors?
•A benign tumor and a malignant tumor.
What occurs with a benign tumor?
•Abnormal cells remain at the original site and resemble normal cells in appearance.
•They typically do not cause problems.
What occurs with a malignant tumor?
•Cancer cells have a different physical appearance from normal cells.
•Cancer cells invade neighboring tissue.
•Impair the functions of one or more organs.
•Spread through the lymph nodes to other parts of the body.
What is Asexual Reproduction? What kinds of organisms practice it? What is produced?
•Asexual reproduction is when a single parents passes all of its genes to its offspring.
•This produces clones.
•It is practiced by all prokaryotes, and some eukaryotes.
•An individual receives a unique combination of genes from two parents.
•These two different cells from two different individuals unite to form the first cell of a new organism.
•Only practiced by Eukaryotic organisms.
The two general types of cells found in sexually reproducing organisms?
Somatic cells and gamete cells.
What is a somatic cell?
A somatic cell is generally taken to mean any cell forming the body of an organism. This excludes the other type, gamete cells.
What is a gamete cell?
Two cells that unite during sexual reproduction to form a zygote.
They are used for sexual reproduction only.
Gamete cells are created by meiosis.
Human Somatic Cells
Contain 46 chromosomes, which are actually only 23 pairs.
Each pair composed of one chromosome from each parent.
These pairs are called homologous chromosomes.
A chromosome with the same gene sequence as another. One is from the father, one is from the mother.
How are genes positioned for homologous chromosomes in terms of location?
The same trait is carried at the same location.
How do the homologous chromosomes compare? Are they identical?
Nearly identical in length and centromere position. They are not identical as they have different alleles.
What is an allele?
A different form of a gene.
What are the two types of chromosomes?
What are Autosomes?
Non-sex chromosomes. Identical in both males and females. Found in all sexually reproducing organisms. Account for all but one pair of homologous chromosomes.
What are Sex Chromosomes?
Chromosomes that determine gender. There is a single pair. In humans gender is determined by the absence or presence of a y chromosome.
Which arrangement of chromosomes is that of a male?
Which arrangement of chromosomes is that of a female?
What are diploid cells?
Cells that contain homologous pairs.
They carry two genes for every trait.
They are symbolized as 2n.
All somatic cells are diploid cells.
Created by mitosis.
Diploid # for an organism is the total number of chromosomes.
For humans, 2n would be 46.
What are haploid cells?
A cell that contains one complete set of chromosomes, or half the number of total chromosomes. They are utilized for sexual reproduction.
What is fertilization?
Only occurs in sexual reproduction.
2 haploid cells (gametes) are joined to restore the diploid number in humans.
egg(23) + sperm(23) = 46
What is Meiosis? How many stages is it broken down to?
Type of cell division that produces gametes/haploid cells
Results in genetically unique daughter cells
Only occurs in the reproductive organs
Broken down into two phases
What main event occurs in Meiosis 1?
Homologous chromosomes are seperated
What main event occurs in Meiosis 2?
The sister chromatids are separated.
What does the Meiosis process look like?
Ultimately 4 haploid cells are produced.
What sub-phases make up Meiosis 1?
Interphase(2n), Prophase I (2n), Metaphase I (2n), Anaphase I (2n), Telophase I (n), Interkinesis (N). (TO EDIT)
What occurs in the Interphase?
G, S, and G2 phase occur. DNA is copied.
What occurs during Prophase 1?
This is the most complex stage. DNA coils into a chromosome, the nucleus disappears. The nuclear membrane fragments. Centrioles move to opposite poles. Synapsis occurs. This causes tetrads to form.
What is Synapsis?
The pairing of homologous chromosomes.
What is Cross Over?
Overlaping of chromosomes and exchanging of genes.
How many sites can there be in crossover?
There can be multiple sites of overlap in a single tetrad.
What are the sites of overlap and exchange called?
What does crossover produce?
New genetic combinations.
What does the Meiosis 1 Process look like in its phases?
What occurs during Metaphase I?
Homologous chromosomes line up along the middle.
What occurs during Anaphase I?
Spindle fibers pull homologous chromosome pairs apart.
What occurs during Telophase I?
Haploid set of chromosomes at each pole
Nuclear membrane begins to re-appear
Chromosomes begin to uncoil
Intermediate stage that is a combo of modified interphase and true cytokinesis (no DNA replication)
Begins during telophase
2 Haploid daughter cells formed. (Chromosomes contain 2 chromatids)
What does the cell cycle look like?
Essentially mitosis without the Interphase.
Acts upon both newly created haploid cells simultaneously
What occurs in Prophase II?
DNA coils into chromosomes
Nuclear membrane fragments
Centrioles move to opposite poles
What occurs in Metaphase II?
Chromosomes line up along the middle
Spindle fibers attach to sister chromatids
What occurs in Anaphase II?
Spindle fibers pull sister Chromatids apart
Chromatids move to opposite poles
What occurs in Telophase II?
The nuclear membrane begins to reappear
Chromatids move to opposite poles
What occurs in Cytokinesis?
4 Haploid Gamete cells are created.
Are the mechanisms of genetic variation unique to sexual or asexual reproduction?
What occurs with crossover?
New genetic combinations are created.
What is independent assortment?
The random orientation of homologous pairs during metaphase of meiosis 1.
Each homologous pair arranges itself along the metaphase plate independent of their pairs.
What is random fertilization?
Random nature of gamete selection during fertilization.
What is Nondisjunction?
Errors in meiosis that result in a cell with abnormal chromosomes
If these errors occur when homologous pairs fail to segregate during meiosis then all 4 gamete cells are affected.
If errors occur when sister chromatids fail to segregate during meiosis 2 then only 2 gamete cells are affected.
What is a Karyotype?
•A diagnostic tool used to detect errors in meiosis.
•It is essentially photograph of an individuals homologous pairs.
•Must use a diploid cell (somatic) that is actively dividing.
What are Human Karyotypes able to do?
They are able to be utilized to detect gender.
Homologous chromosomes are # 1-22 in descending order based on size
Pairs # 23 are the sex chromosomes.
What are chromosomal Abnormalities?
Fertilization of altered gametes results in offspring with chromosomal abnormalities.
What is Trisomy 21? What is it commonly known as? Give some statistics/information.
It is commonly called Down Syndrome.
It is caused by an extra copy of chromosome #21.
It is the most common chromosome abnormality.
Occurs in 1/700 births.
Afflicted individuals have characteristic facial features, short stature, varying degrees of mental retardation and united fertility.
Results in nondisjunction in either the sperm or egg.
What is the klinefelter syndrome?
The klinefelter syndrome is a gender disorder.
Results in a male with abnormal body proportions.
Underdeveloped testes, is sterile and usually of normal intelligence.
Caused by nondisjunction.
What is the Turner Syndrome?
Results in a female that is short in stature, has no sexual maturity, sterile, has web skin between neck and shoulders, and usually of normal intelligence.
Caused by nondisjunction
What is the Jacob syndrome?
Affects 1/2000 births
Results in a normal male -> tall
Is caused by nondisjunction
What is the metafemale?
Results in a normal female that has limited fertility
It is caused by nondisjunction
What are alterations to the chromosomal structure? What kinds of cells do they affects?
During cell division chromosomes may break and lead to various rearrangements. This may lead to mutations.
May occur in the gametes or somatic cells.
What is inversion?
Gene order is inverted in a chromosome.
(1) A B C D E F G H I [Before]
(2) A B C F E D G H I [After]
What is translocation?
•Genes are added from nonhomologous chromosomes.
•Crossing over between nonhomologous chromosomes
(1) H I J K L
(2) A B C D E F G
(1) + (2) H I D E F G A B C J K L
What is deletion?
A portion of a chromosomes genes are lost
(1) A B C D E F
(2) A B C F
What is duplication/insertion?
A portion of the chromosomes are repeated or genes are insterted.
(1) A B C D E F G
(2) A B C D E D E F G
(3) A B C D E D E F G
What are the three things that Scientists use to differentiate chromosomes?
Scientists use size, banding pattern, and centromere position.