Lecture 10 Flashcards
What is a genome
All genetic material in a cell
What happens to chromatin when it tightly coils around many proteins
It forms a chromosome
What does diploid mean
Two complete sets of chromosomes (one from each parent)
What is a karyotype
Person’s chromosomes arranged by and numbered by size
How many pairs of chromosomes in a somatic cell
23 (46 chromosomes)
What is the cell cycle
Time between when a cell forms and divides into 2 daughter cells
Stages in cell cycle
Interphase, mitotic phase
Phases of interphase
G1, S, G2
Which phase of interphase : begins as soon as daughter cell formed, active growth, synthesis of new organelles and reaches mature cell size
G1
Which interphase phase : dna replication, exact copy of each chromosome is made
S phase
What are sister chromatids
Copied chromosomes, attached to center by centromere
Number of chromatids during synthesis phase
92 (sister chromatids each with 46 chromosomes)
G2 phase :
2nd growth phase, prep for mitotic phase (centrosomes duplicate and spindle fibres form)
Mitosis stages
- Prophase (early and late)
- Metaphase
- Anaphase
- Telophase
What happens during early prophase
Chromatin compacts into chromosomes, nucleus still intact, spindle fibers extend
What happens during late prophase
Nuclear membrane breaks down, centrosomes at opposite side of cell, some chromosomes attach to spindles
What happens during metaphase
Chromosomes align at cell midline (metaphase plate)
What happens during anaphase
Sister chromatids separate, pulled to opposite ends of cell using microtubules as tracks, cell elongates, at the end the cell ends has complete set of chromosomes
How are sister chromatids pulled appart during anaphase
Proteins holding them broken down by enzyme
What happens during telophase
Chromatine fibers start to loosen up/becomes less coiled, spindles disappear, nuclear membrane forms, nucleoli reappear, end of mitosis
Cytokinesis (other stage of mitotic phase)
Cell pinches in half forming a cleavage furrow, results in twi daughters cells w same gene info, begins while still in telophase
When dies mitosis occur
Reproduction, growth and development, tissue renewal
How do prokaryotic cells divide
Binary fission (circular chromosomes replicate and got to opp ends, plasma membrane pinches at center and divides)
Which cell have the same genetic composition
Every somatic cell
Every cell in the body has some genes that are turned
Either on or off
Cells express different subsets of genes, only expressing those they require which makes each cell
Produce diff types of proteins
Cell division length
Actively dividing cells (intestines/skin) : 12h-24h
Unicellular organisms : 90min
G0 phase :
Pause between M and S phase in cell cycle
Examples of cells in G0 phase (liver)
Liver cells remain in it for a year, doing metabolism and detoxification before reentering cell cycle
Example of G0 phase cells
Those that form the lens of the eyes and nerve cells perpetually in G0 phase
What are checkpoints in cell cycle
When regulatory proteins in cell checks at specific times to make sure everything is ok in cc
If something is wrong in cell cycle during checkpoints
Doesn’t continue cycle until fixed, if error cannot be fixed -> apoptosis
What is apoptosis
Programmed cell death
What happens if damaged cell doesn’t undergo apoptosis
Keeps dividing, leads to cancer
What does cell differentiation mean
When a cell assumes its function in organism, takes in cell-specific characteristics
For homeostasis to be maintained, regulatory systems must
Ensure that cells don’t divide uncontrollably and differentiate at appropriate time
Cancer is when cells
Lose ability to respond to regulatory mechanisms (divide uncontrollably and indefinitely)
How can mutations occur
Copying errors in dna replication or induced by exposure to external elements
Most affected genes by cancer
Control cell cycle and code for proteins involved in cell division
(Those that regulate cell growth and division during cc)
What are mutagens
Agent that induces permanent dna change
Mutagens example
Radiation (x rays, uv)
Chemical (pollutants, metals, tobacco)
Biological (viruses and bacteria)
What are the twi different cancer stages
Bening and malignant
Bening tumors
Mass of cells that don’t invade neighbouring tissues (if large enough can impair function of organ, generally encapsulated)
Malignant cancer
Mass of cells that invade neighbouring tissues and creates metastasis
What is metastasis
Release of cancerous cells into bloodstream or lymph where they can travel and invade other tissues
