Cell division Flashcards
What is DNA?
Deoxyribonucleic acid - all genetic info of a cell
What is a chromosome?
A length of DNA and its associated proteins found in nucleus of Eukaryotic cell
What is a Histone?
Protein that helps condense DNA
What is chromotin?
DNA appears in this form during most of a cells life. Becomes condensed durng cellular devision.
slightly condensed DNA
What s the centromere?
Specilized constricted (pinched in) region in the condensed chromosome.
What are homologous cells?
Similar looking chromosomes that carry the same genes also known as autosomes
What are the 46 somatic chromosomes divided into?
22 pairs of homologous cells
and 2 sex cells that may or may not be homologous
What are the sex chromosomes?
X and Y (23rd pair)
What is a karyotype?
Picture of chromosomes - particular set of chromosomes that an individual posesses
What does the term Ploidy mean?
Measure of how many chromosomes
What does haploid mean?
One copy of each chromosome (sperm and eggs) | n
What does the term diploid mean?
Two copies of each chromosome (somatic cells)
What does the term polyploid mean?
More than two coppies of chromosomes (Some plants, genetic disorders)
What does n repersent?
The number of copies of each chromosome
Why do cells need to divide?
Repair, growth, sexual reproduction
What are the three stages of the cell cycle?
Interphase, Mitosis, Cytokenesis
What are characteristics of interphase?
Cell growth and normal function
Not dividing
Composed of 3 stages: G1, S, G2
What is the G1 stage?
Apart of interphase, normal cell function
What is the S stage (Synthesis)
Synthesis of DNA, makes a copy of each chromosome
What is the G2 stage?
Apart of interphase, growth of cell and preperation to divide
What is mitosis?
Cell division contains four steps:
Prophase
Metaphase
Ananphase
Telophase
What is cytokenesis
The splitting og cytoplasm, last step
What is G0?
Stage of interphase, not going to replicate DNA
Done by cells that dont divide (Neurons)
What is the purpose of contractile ring?
Pinches rhe cell into two during cytokenesis
What does a plant produce during cell division?
Cell plate, forms down middle of dividing cell, helps divide
What is the purpose of checkpoints in regulating the cell cycle?
To regulate the progression through the cycle.
What control the cell cycle?
Interactions between cyclins and cyclin-dependent kinases to control the cell cycle.
What may occur if a disruption interputs the cell cycle?
May result in cancer/and or programed cell death (apoptosis)
What are cell cycle checkpoints?
Where a cell decides to proceed with the next steps of the cell cycle.
What are the three most important checkpoints?
G1, G2, Spindle Checkpoint
What is the G1 checkpoint?
The main checkpoint for most cells
Usually after this checkpoint cells will divide completly
If a cell doesnt pass this ckecpoint it’s said to be in G0
What chekcs occur at G1?
Cell size - is it big enough
Nutrients
Growth Factors
DNA Damage
What occurs at the G2 checkpoint?
Checks for DNA damage - takes places after DNA replication
If the cell doesnt pass the G2 checkpoint what happens?
Apoptosis
What occurs at the spindle checkpoint?
Checks if sister chromatids are attached correctly to spindle microtubules
This is the transition checkpoint between metaphase and anaphase
What may occur if the spindle checkpint fails?
May result in down syndrome
What are cyclins?
Proteins that activate kinases
What are protein kinases?
Enzymes that activate or inactivate other proteins by phosphotlating them
Called Cyclin-dependent kinases or CDK
How do cell checkpoints work?
Cyclins partner with CDKs activating it as a kinases and CDK directs it’s activation to other proteins resulting in passing the checkpoint
What is MPF?
Maturation-promoting factor
A cyclin-CDK complex that was found in frog eggs
What is the role of MPF?
Breaks down the nuclear membrane (before mitosis/ M phase)
What makes cancer cells difer from othes?
Uncontrolled growth
Cells are undifferential and non-functional
No contact inhibition
Able to move (metastasis) through blood
What does the term cell potency refer to?
A cells ability to differentiate into other cells
What is a totipotent cell?
Cells that can form all other types of cells in a body and extracellular/placental cells
Are adult mammal cells totipotent?
No however cells of murola are
What are stem cells?
Unspecilized cells - cannot form whole body hoever can form a vareity of cells/tissues
What are pluripotent cells?
Cells that can become any type of cell exluding placenta/umbillical chord
What are multipotent cells?
Stem cells that are more restricted and can form a few types of tissues
ex: bone marrow cells becoming blood cells
What is meiosis?
The production of cells with only half of the necessary cells (gametes)
How does gametogensis work?
Through Ruduction division (Reduces DNA by half)
What is oogenesis?
Makes eggs - however only 1 of 4 becomes and egg the others become polar bodies
What are polar bodies?
Haploid cells that dont become eggs
What is spermatogensis?
Makes sperm, half of sperm get Y and other half get X
What is the purpose of the recombination of genes?
Increases variation - resuling in non-indentical daughter cells
What is the end result of meiosis?
4 Haploid cells
What is a tetred?
Homologous pair
At what point are haploid cells produced during meiosis?
After meiosis 1
What are the two ways that genetic variation may occur?
Independent assortment
Crossing over
What is independent assortment?
Creation of gametes that carry different combinations of maternal and paternak chromosomes
What is crossing over?
The exchange of genetic material between maternal and patternal chromosomes
What process results in independent assortment?
During metaphase I each homolgous pair lines up at the equator
In each pair the maternal and paternal homologues are randomly pulled to poles
This results in different combinations
What process results in crossing over?
During prophase I chromosomes will form a tetrad and swap genes
This produces recominants which are different from either parent
What is the site of crossing over called
Chiasma
What is non-disjunction?
The failure of homologous chromosomes or sister chromatids to seperate propery during cell division
What does the term synapsis refer to?
Coming together
What are life cycles?
The series of changes that the members of a species undergo as they pass from the beginning of a given developmental stage to the inception of that same developmental stage is a subsequent generation
What does a life cycle show?
When an orgnanism is haploid or diploid and how they reprodue
