Unit 8 Flashcards
Why do cells divide?
- reproduction of cells
- unicellular organisms can reproduce an entire organism
- growth
- repair
What are the stages and what occurs during these stages?
INTERPHASE
- growth 1/growth, increase in cytoplasm
- synthesis/ duplication of chromosomes
- growth 2/ growth, preparation for division
MITOTIC PHASE
-division of the nucleus
Why must the cell cycle be controlled?
Because without control, cells would divide uncontrollably and produce tumors which can have serious health effects
What are growth factors ?
A protein secreted by certain body cells that stimulates other cells to divide
What is anchorage dependency?
Cells must be in contact with a solid surface to divide
What is density dependent inhibition?
A phenomenon where crowded cells stop dividing
Characteristics of a cancer cell
Divide rapidly often in the absence of growth factors
Do not divide by the rules of cell division (ex density Dependence)
Cell checkpoints
Control points where signals regulate the cell cycle
G1 checkpoint
Allows entry into the S phase or causes the cell the leave the cycle entering a non dividing g0 phase
What is cancer ?
A disease of the cell cycle when the cells do not respond normally to the cell cycle control system, these cells divide excessively and invade other tissues of the body
What is tumor
An abnormally growing mass of body cells
Malignant
Cells spread into neighboring tissues or other parts of the body and infect normal tissues
Benign
The abnormal cells stay at the original site
how many parents in asexual reproduction?
1
how many parents in sexual reproduction?
2
traits in asexual and sexual reproduction?
asexual: identical to original cell or offspring
sexual: Offspring are similar to parents, but show VARIATION in traits
what do unicellular organisms use cell division for?
to reproduce an entire organism
what is the cell cycle?
*The cell cycle is an ordered sequence of events for cell division
what are the two stages of the cell cycle?
interphase
mitotic phase
what stage takes up most of the cell cycle?
interphase
*What happens to the cell during interphase?
*Interphase:
* 90% of time
*GROWING phase
*Duplication of cell contents
•G1—growth, increase in cytoplasm
•S—duplication of chromosomes
•G2—growth, preparation for division
*What are the 3 sub-phases of interphase?
G1, S, and G2
Mitotic phase
10% of time
define Mitosis—
division of the nucleus
*Mitosis progresses through a series of stages (list the phases)
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis – division of cytoplasm
*Mitotic spindle (spindle fibers)
- composed of microtubules
- produced by centrosomes, structures in the cytoplasm that
- Organize microtubule arrangement
- Contain a pair of centrioles in animal cells
*Cytokinesis in Animal Cells:
Cleavage furrow
*Cytokinesis in plant cells:
cell plate formation
*WHY must cell division be controlled?
- allows for normal growth and development of tissue
* without control, cells can divide too much, invading normal tissues
What is a growth factor?
- Growth factors are proteins that stimulate division
- Different cell types respond specifically to certain growth factors
- Cancer cells divide rapidly, often in the absence of growth factors
Density dependent inhibition
when crowded cells stop dividing
Anchorage dependency
cells must be in contact with a solid surface to divide
*In cancer cells, growth is not inhibited by other cells, and tumors form
What is the cell cycle control system?
A set of molecules (ex: growth factors) that trigger and coordinate the cell cycle
What are cell cycle checkpoints:
*Control points where signals regulate the cell cycle
What are the 3 major checkpoints?
- G1 checkpoint allows entry into the S phase , or causes the cell to leave the cycle, entering a nondividing G0 phase (ex: nerve and muscle cells)
- G2 checkpoint
- M checkpoint
Describe what is happening at the G1 checkpoint
- A growth factor binds to a receptor on the cell membrane
- Within the cell cytoplasm, a signal transduction pathway sends the signal through a series of relay molecules
- The signal reaches the cell cycle control system (in the nucleus) to allow cell to enter S phase (replication)
What is cancer?
*Too much cell division
What is a tumor?
An abnormal mass of body cells, due to uncontrolled cell division
What is the difference between benign & malignant tumors?
- Benign: tumors that remain at the original site
* Malignant: tumors that spread to nearby tissue (metastasize), disrupting normal organ function
what do multicelular organisms use cell decision for?
development
growth
repair
Cells arise from…….
preexisting cells
where does binary fission occur
prokaryotic cells
what is dna like in prokaryotic cells
circular and not w/in nucleus
differences between eukaryotic and prokaryotic organisms?
Eukaryotic
- More complex
- Ex: human cells carry about 25,000 genes
- DNA found in the nucleus
- DNA in the form of chromosomes
Prokaryotic
- Unicellular
- Ex: typical bacterium carry only 3,000 genes
- DNA floating in cytoplasm (no nucleus)
- DNA in coiled/circular form
what type of organism has a more complex cell division?
eukaryotic
what are eukaryotic chromosomes composed of
chromatin
dna + proteins
chromatin
Highly compacted chromatin; this occurs when cell is preparing to divide.
chromosome
chromosome has two copies called _______
sister chromatids
area where 2 chromatids are
centromere
Why must cell division be controlled?
Allows for normal growth and development of tissue. Without control, cells can divide too much, invading normal tissues.
Proteins that stimulate division
Growth factors
When crowded cells stop dividing
Density dependent inhibition
Cells must be in contact with a solid surface to divide
Anchorage dependency
A set of molecules that trigger and coordinate the cell cycle
Cell cycle control system
Control points where signals regulate the cell cycle
Cell cycle checkpoints
Checkpoint that allows entry into the S phase
G1 checkpoint
Nondividing phase
G0 phase
Too much cell division
Cancer
Abnormal mass of body cells, due to uncontrolled cell division
Tumor
Tumors that remain at the original site
Benign tumor
Tumors that spread to nearby tissue(metastasize), disrupting normal organ function
Malignant tumor
Types of cancers
Carcinoma, sarcoma, leukemia, lymphoma
what happens to the sister chromatids as the cell divides
they separate
Once separated from its sister, each chromatid is called a
chromosome
what are changes in an organisms dna
mutations
what causes genetic variation?
a mutation arises and is reshuffled between genes
How does the orientation of homologous chromsomes effect the gametes and lead to genetic variation?
There is 50/50 chance of the maternal (red) or paternal (blue) chromosome facing a given pole
•What is a tetrad?
A pair of homologous chromosome
•Where does each chromosome come from?
one from each parent
Define Crossing over:
exchange of segments of chromosomes within a homologous pair (tetrad)
what is a chiasma
the site of crossing over
Genetic recombination:
production of new combinations of genes due to CROSSING OVE
How does crossing over lead to genetic variation?
*One parent contributes the genes for brown coat (C) with black eyes (E)
*The other parent donates the genes for white coat (c) with pink eyes (e)
*Crossing over occurs
*Four genetically different chromosomes are produced:
•2 parental (original) versions carrying genes for brown coat with black eyes and white coat with pink eyes
t/f errors happen in meiosis
true
*What is a karyotype?
an ordered display of magnified images of an individual’s chromosomes arranged in pairs, starting with the longest
how can chromosomal abnormalities be detected?
karyotyoe
how is a karyotype prepaired?
- Lymphocytes (white blood cells) are treated with a chemical to stimulate mitosis
- WBCs are treated with another chemical to arrest mitosis at metaphase
- At this stage, chromatin is condensed and each chromosome is easy to see
how many chromosomes do humans have? how many pairs
46 organized to 23 pairs
which pairs are autosomes?
1-22
what number is the sex chromosome?
23
female gamete?
XX
male gamete?
XY
what is the most common human chromosome abnormality?
trisomy 21
characteristics of down syndrome?
characteristic facial features susceptibility to disease shortened life span mental retardation variation in charcateristics
t/f the younger a mother is the more likely their child is to get down syndrome
false
the older
how are gametes different from gametes?
crossing over(which leads to genetic recombination) and orientation
homologous chromosomes
pairs of chromosomes that are matched in length, centromere position, gene locations
autosomes
pairs of chromosomes that have the same size and the same genes; 22 pairs of chromosomes that are not sex chromosomes
sex chromosomes
the x and y chromosomes that determine an individual’s sex
diploid
cells that have 2 homologous sets of chromosomes(2n and somatic)
hapoid cells
cells that have 1 set of chromosomes (half the # of chromosomes) (n) (gametes - sperm and egg)
diploid and haploid number for humans
diploid- 46 chromosomes
haploid- 23 chromosomes
how does mitosis fit into the life cycle?
the zygote can develop into a multicellular adult
how does meiosis fit into the lift cycle
it creates gametes: eggs in females, sperm in males
how are the stages of meiosis 1 different from meiosis 2?
there are 2 pairs of homologous chromosomes starting in meiosis 1, and 1 pair in meiosis 2.
meiosis 1 splits one cell into 2, meiosis 2 splits 2 cells into 4.
meiosis 1 is 2n=46, meiosis 2 results in n= 23
what are the chromosomes doing in each stage of meiosis?
p1- 2 pairs of homologous chromosomes
m1- homologous chromosomes line up at the middle , creating tetrads
a1- chromatids are pulled apart
t1- total split into 2 cells, no duplication
p2- 2 separate cells w 2 chromosomes
m2- chromosomes are lined up
a2- chromatids are pulled apart
t2- split into 4 cells w 2 separate chromatids
similarities btw mitosis and meiosis
one duplication of chromosomes
differences btw meiosis and mitosis
mitosis : 2 genetically identical cells w the same # of chromosomes as the original
meiosis : 4 genetically different cells w 1/2 the chromosome # as the original
What are the 2 types of cell division?
Mitosis and Meiosis
What are the major differences between asexual and sexual reproduction?
Asexual - genetically identical offspring from one parent without the participation of sperm and egg
Sexual - resemble parents but not identical, offspring inherits a unique combination of genes, two parents, participation of cell and egg
Why does cell division occur in unicellular organisms?
To reproduce an entire organism
Why does cell division occur in multicellular organisms?
To reproduce asexually (such as plants grow from cuttings)
What is binary fission?
A type of cell division/means of asexual reproduction in which a parent organism, often a single cell, divides into 2 individuals of about equal size
How does binary fission occur?
- Duplicating of chromosome and separation of copies
- Continued elongation of the cell and movement of copies
- Division into 2 daughter cells
What are the major differences between eukaryotic and prokaryotic cell division?
Eukaryotic - all chromosomes duplicate before the cell divides
Prokaryotic - does not duplicate before dividing
What is chromatin?
Complex of DNA and proteins that constitutes eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing
What is a chromosome?
A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis
What is a chromatid?
Half of a chromosome, have identical DNA/genetic material
What is a centromere?
Between sister chromatids, hold them together
An occasional mishap in which the members of a chromosome pair fail to separate.
Nondisjunction
Nondisjunction in Meiosis I: A pair of homologous chromosomes does not separate, resulting in gametes ending up with abnormal numbers of chromosomes: two gametes have three, the other two have only one each.
Nondisjunction in Meiosis II: One pair of sister chromatids fails to move apart, resulting in two abnormal gametes and two normal gametes.
The differences between nondisjunction in Meiosis I and II
If a fragment of a chromosome is lost, the remaining chromosome will have this
Deletion
If a fragment from one chromosome joins to a sister chromatid or homologous chromosome, it will produce this
Duplication
If a fragment reattaches to the original chromosome but in the reverse direction, this results
Inversion
The attachment of a chromosomal fragment to a nonhomologous chromosome
Translocation
what is mitosis
the division of a single nucleus 2 genetically identical daughter nuclei. part of mitotic phase
what is cytokinesis
the division of the cytoplasm into 2 separate daughter cells. occurs during telophase and is part of the mitotic phase
what are the stages of mitosis? what are the chromosomes doing during each?
interphase- chromosomes are duplicated
prophase- chromosomes become discrete due to chromatin fibers becoming more tightly coiled and folded
prometaphase- chromosomes are highly condensed and attached to spindles
metaphase- chromosomes align in middle
annaphase- chromosomes come apart and split sister chromatids
telophase- chromatin of chromosomes uncoils
cytokinesis- chromosomes in different cells
how do plant and animal cells differ in cytokinesis?
animal cells- involved cleavage furrow which pinches the cell in 2
plant cells- forms a cell plate that grows outward and eventually becomes part of plasma membrane and cell wall
how does independent orientation of chromosomes provide variation in gametes?
there is a 50% chance that a particular daughter cell will get the maternal chromosome of a certain homologous pair and a 50% chance it will receive the paternal chromosome.
how does crossing over provide variation in gametes?
crossing over creates recombinant chromosomes having a combination of genes that were originally different, though homologous chromosomes
what is a karyotype?
karyotype- ordered display of magnified images of an individual’s chromosomes arranged in pairs, starting with the longest
what information does a karyotype give you?
it can show errors that occurred in meiosis that lead gametes to containing chromosomes in abnormal numbers or with major alterations in structure. it can show things such as trisomy 21
what is trisomy 21? how does it occur?
trisomy 21 is when one has 3 #21 chromosomes and has 47 chromosomes. it is known as Down Syndrome. it occurs due to nondisjunction, when the members of chromosomes fail to separate
How are types of cancers categorized & what are some of these categories?
- Based on their site of origin
* EX: carcinoma, sarcoma, leukemia, lymphoma
