Lecture 8 Flashcards
Name 4 important structures in cell division
- nucleus
- nucleolus
- chromatin (chromosomes)
- centrosomes (+ microtubules)
What does cell division mean? (2)
the ability of organisms to reproduce
+ the continuity of life is based on the reproduction of cells (cell division)
3 roles of cell division
- Reproduction
- Growth and development
- Tissue Renewal and repair (skin, cells…)
Between chromatin and chromosomes, which one is tightly coiled and which is loosely arranged?
Chromatin: loosely arranged DNA
Chromosomes: tightly coils around protein
which protein are we talking about?
histones
Between chromatin and chromosomes, which one is used for dividing?
Chromosomes
Chromatin -> DNA when the cell is not dividing (b/c it’s loose)
What controls characteristics like hair, skin, or flower color?
they are controlled by genes
Where are genes located?
on the chromosomes
TRUE OR FALSE:
Each chromosome is a huge molecule of DNA
(+ protein)
TRUE
TRUE OR FALSE:
Each chromosome has DNA made up of nucleotides
TRUE
TRUE OR FALSE:
Each chromosome contains a very small number of genes
FALSE
contains a LARGE number of genes
TRUE OR FALSE:
Each gene occurs on a SPECIFIC chromosome.
TRUE (similar to an address)
How many chromosomes do we have?
46 chromosomes (23 pairs)
In humans, how many different kinds of chromosomes do we have?
23 different kinds of chromosomes
(23 mom + 23 dad = 46)
What is a karyotype?
an organized profile of a person’s chromosomes
How are the chromosomes arranged?
chromosomes arranged by size
(from largest to smallest)
What are autosome chromosomes?
An autosome is any chromosome that is not a sex chromosome
How many autosomes do we have?
22 autosomes (non-sex chromosomes)
How many sex chromosomes de we have?
only 1 sex chromosome
Why are Karyotypes useful and important?
Karyotypes can be checked for irregularities in the number or structure of chromosomes
(important for scientists to quickly identify chromosomal alterations)
What does it mean if there is an Abnormal Number of Chromosomes?
= Genetic Diseases
What are Non-reproductive chromosomes called?
autosomal or autosomes
(they don’t code for sex characteristics (ex. male/female))
Where can autosomes be found?
in somatic cells (non-gametic cells)
AND gametes (but in different quantities)
Where can we find sex chromosomes (X & Y)?
also in somatic cells (non-gametic cells) AND gametes (but in different quantities)
What is a zygote?
a fertilized egg
what is a fertilized egg?
when a sperm cell and egg cell unite (nuclei fuse forming 1 nucleus)
How many chromosomes in total does the new individual get?
46 CHROMOSOMES (1 complete set of 23 chromosomes from each parent)
Sexual reproduction creates what?
genetically unique individuals
How do individuals grow?
by increasing cell number (cell divides into 2 - 4 - 8…)
TRUE OF FALSE:
An exact copy of every chromosome is distributed to each cell in the division process
TRUEEE
What is the cell cycle?
time between when a cell is formed and when it divides
(forms 2 new daughter cells)
What are the 2 types of cell division?
Mitosis and Meiosis
IN MITOSIS:
1. what are the results:
2. it occurs during what?
- Results in identical body cells
- Occurs during growth and repair
IN MEIOSIS:
1. Gives rise to what?
2. same or different # of chromosomes?
Gives rise to gametes that have HALF the number of chromosomes as the original cell
Let’s analyze and understand everything about mitosis…
what is mitosis?
(somatic) cell division
-> division of cells that aren’t gametes
What is the result of mitosis?
resulting in 2 daughter
cells, each with the same
# of chromosomes as the
parent cell
The cell cycle is divided into different stages, name the 3 general ones
- Growth of the cell following division
- Copying of genetic info
- Distribution of copies of daughter cells
There are 2 main stages in the cell cycle, name them
1) Interphase (environ 95%)
2) Mitotic phase (much shorter environ 5%)
How many phases are in interphase? and when does it occur?
3 phases of interphase + occur b/w the time a cell is formed and when it begins the division process
name all 3 phases of interphase:
G1: (Growth 1)
S: DNA Synthesis
G2: (Growth 2)
when does G1Phase begin?
as soon as daughter cell formed
G1Phase: synthesis or growth?
GROWTH
period of active growth
What generally happens in G1?
the cell grows physically larger, copies organelles
What comes after G1?
S phase
What generally happens in S phase?
DNA replication
(the cell synthesizes a complete copy of the DNA in its nucleus)
Copied chromosomes are referred to as what?
sister chromatids
TRUE OR FALSE:
sister chromatids both contain the SAME genetic info?
TRUE
sister chromatids are physically attached by what?
a centromere
are chromosomes condensed at this stage?
NOOO
chromosomes are not condensed yet, they are simply linked to the sister copy/clone
when are the sister chromatids condensed?
in PROphase
what happens to the number of chromatids/chromosomes during mitotic chromosome replication?
chromatid number is 2x number of chromosomes
23pairs => 46 pairs of chromatids = 92 sister chromatids
RECAP:
46 chromosomes and 46 chromatids TO 46 chromosomes and 92 chromatids
What do we call the final stage of Interphase?
G2 Phase (occurs after S phase of interphase)
What generally happens in G2?
the cell increases slightly + begins preparation for the mitotic phase of the cycle
What do we have at the end of Interphase (3)?
- chromosomes have been copied
- centrosomes duplicated
- spindles have formed
Mitotic phase is a series of steps that results in what?
a distribution of EXACT copies of chromosomes to each developing daughter cell
name all steps of mitosis (5)
ia. Prophase (early)
ib. Prometaphase (late)
ii. Metaphase
iii. Anaphase
iv. Telophase
Pmat
What comes after telophase that isn’t part of the cell division septs?
Cytokinesis
First of all, what happens in prophase (early)?
DCC/ NE/ DCS/ MXA
DCC: DNA compacts/condenses
NE: Nuclear Envelope breaks
DCS: Duplicated Centrosomes (G2) separate
MXA: Microtubule fibers extend b/w centrosomes
In prophase (early), how does the DNA stay? Are they still called sister chromatids?
DNA will STAY in this chromosome form until the end of telophase
YES, they are still called sister chromatids
In prophase (early), the duplicated centrosomes separate and begin to move around what organelle?
around the nucleus
In prophase (early), the microtubule fibers extend b/w centrosomes forming WHAT?
forming the mitotic spindle
What comes after prophase (early)?
Prometaphase (late prophase)
What happens in Prometaphase (late prophase)?
NEB/ CO/ MAK/ ND
NEB: Nuclear Envelope broken down
CO: Centrosomes at Opposite ends of the cell
MAK: Microtubules to attached to Kinetochores
ND: Nucleoli disappear
What is kinetochore?
centromere region
What comes after Prometaphase?
Metaphase
When does Metaphase happen?
when all of the chromosomes are ALIGNED along the CELL MIDLINE (metaphase plate)
What happens in Metaphase?
each chromosome attached to protein fibers coming from opposite poles (with overlapping non-kinetochore microtubules)
What comes after metaphase?
anaphase (a = apart)
What is the main thing that happens during anaphase?
the sister chromatids SEPARATE
So how do they separate?
the centromeres break which separate the chromatids
How are the chromatids called now?
chromosomes
Are they still clones of each other or not?
THEY STILL ARE CLONES, but they are no longer attached at the
centromere / kinetochore
Where are the chromosomes pulled to?
to the opposite ends of the cell (using microtubules as tracks)
Does the cell elongate or not?
it does elongate
At the end of anaphase, what should we see from each pole of the cell?
each pole has a COMPLETE set of chromosomes
little note: so once chromatids are no longer attached to their duplicates, how do we call them?
chromosomes
before 1 chromosome (2 chromatids)
then 2 chromosomes
What comes after Anaphase
Telophase
How are the chromosomes at the end of anaphase and the beginning of telophase?
One copy of each Chromosome
present in at opposite ends of the
cell
What disappear?
the spindle fibers
What forms around the chromosomes?
nuclear membrane forms
what REappears?
the nucleolus
Chromosomes start to “relax”. What does this mean?
unwind/ less compact (return to chromatin form/state)
Recap of telophase:
SFD/ NMF/ NA/ CX
SFD: the spindle fibers disappear
NMF: nuclear membrane forms
NA: Nucleolus REappears
CX: Chromosomes relax
+ light indentation (not fully separated)
Does Telophase mark the end of mitosis?
YESs, even if cell
the division is not entirely
complete
What comes after telophase?
Cytokinesis
What happens in cytokinesis?
Cell gradually pinches in
along midline
What does this form?
forms a cleavage furrow
What is the result of cytokinesis?
2 daughter cells with exact
same genetic information
Each daughter cell has 2 copies of each chromosome, we call them homologous pairs (what does this entail?)
homologous pairs = have genes for same traits, same size/shape
What can happen at the end?
the cell may enter G1 of Interphase (can repeat cycle)
GIVE A BRIEF SUMMARY OF ALL THE STEPS
- DNA replication (S phase of Interphase) + formation of 2 sister chromatids
- In Prophase, NM breaks down + spindle fibers assemble
- Metaphase: sister chromatids line up along the metaphase plate
- Anaphase: sister chromatids SEPARATE and move to opposite ends of the cells
- Telophase: Nuclear envelope reappears around chromosomes
- Cytokinesis: parent cell DIVIDES (forming 2 daughter cells)
- Each daughter cell has 2 copies of each chromosome (homologous pairs)
Is mitosis in plant cells similar or completely different?
it’s similar
What is the main difference?
there are no centrioles, but have microtubule organizing centers
+
major difference in cytokinesis: Cells can’t pinch in half like animal cells (daughter cells are separated by a cell plate)
What happens during cytokinesis for plant cells?
- vesicles from Golgi carry cell wall components and travel to the center of dividing cells
- Cell plate forms at the center and
proceeds to the cell membrane
What happens in Prokaryotic cells?
Binary fission
What is Binary fission?
division in half
It’s important to remember that most bacteria have a single ______ that forms the nucleiod
have a single circular chromosome
What is the result after the chromosome replicates?
the 2 resulting chromosomes migrate to polar ends of cell (which elongates the cell to provide room for both chromosomes)
What then happens to the plasma membrane?
the PM grows inward at the center of the cell (between the nucleoid region)
What is the result of this separation?
2 daughter cells
The cell cycle regulation has checkpoints… for what reason?
the cell cycle is VERY tightly controlled, at specific times, the cells check themselves to assess if everything is good (checkpoint)
What happens when everything is OK?
the cycle continues to the next stage
What happens when there is smt wrong?
the cycle does NOT continue until the error is fixed
If the error CAN NOT be fixed, the cell will ____ _____
undergo apoptosis
What is apoptosis?
programmed cell death
(cell suicide) (b/c it’s not a good idea to make a copy of a damaged cell)
How many checkpoints are there?
3 main checkpoints
name all 3 checkpoints:
G1 checkpoint
G2 checkpoint
M checkpoint
Tell me what G2 checkpoint is influenced by
- cell size
- DNA damage
- DNA replication
Tell me what G1 checkpoint is influenced by
G1 checkpoint:
- Growth factor proteins
- nutrients
- cell size
- DNA change
Tell me what M checkpoint (metaphase-anaphase) is influenced by
- chromosome attachments to spindle
What is the purpose of all these checkpoints?
- not a good idea to copy a damaged cell
- cancer prevention
Why cancer prevention?
cancer is a disease of the cell
a cancerous cell multiplies out of control (excessive cell growth and division)
the checkpoints are ignored
Is the cell under control?
NO, The cell is no longer under
the control of mechanisms
that normally regulate cell
growth and division.
(escape normal control methods)
Spontaneous mutations (by accident) during what?
during DNA replication
Mutagens can occur by what?
by various agents (chemical, radiation, etc.) that change the genetic info of an organism
= thus increases the frequency of mutations
What is called a mutagen?
anything that can bring about a mutation in DNA
Give an example of a mutagen
too much UV light exposure which damages the DNA
Cancer development is done in 2 ways, which ones?
Benign tumors and Malignant tumors
Tell me more about the Benign tumors:
- mass of cells (lump) that do not invade neighboring tissues (may grow very largre)
Are Benign tumors considered cancer
NO
Can they be removed?
yes
Can Benign tumors spread?
NO
Tell me more about Malignant tumors:
- a mass of cells that invade neighboring tissues
- can impair the functioning of one or more organs
Are Malignant tumors considered cancerous?
YES
Can Malignant tumors spread?
YES
the spread of cancer cells to locations distant from their original site, how do you call this?
metastasis (it’s the release of cancerous cells into the bloodstream)
Can Benin tumors metastasize?
NO, only malignant tumors can metastasize
What are the steps of cancer development of a malignant tumor?
- a tumor grows from a single cancer cell
- cancer cells invade neighboring tissue
- cancer cells spread through lymph and blood vessels to OTHER parts of the body
- a small % of cancer cells may survive and establish a NEW tumor in ANOTHER part of the body
name all 3 possible treatments
- Surgery
- High-energy radiation
- Chemotherapy
Which treatment would you use for a tumor that appears to be LOCALIZED?
High-energy radiation
What does High-energy radiation do?
- non-specific damage to DNA
- cancer cells have LOST their ability to repair DNA
Metastatic tumors are treated with what treatment?
Chemotherapy
What does chemotherapy do?
- damage to actively diving cells
- taxol freezes the mitotic spindle by preventing microtubule formation
What are some side effects of chemotherapy?
nausea, immune suppression, hair loss
