Lecture 13: The Cell Cycle Flashcards
What is heredity?
-All organisms come from other organisms
-All organisms resemble their parents
-Siblings are not identical
Why do children look like their parents?
Sperm and eggs are single cells that fuse together to become a zygote.
-This explains why you get features from both parents
How are organism made from one diploid cell?
Diploid cells divide many times to produce an organism(organisms are multicellular)
True or False: Every cell in your body derives from one single cell?
TRUE
What do daughter cells need to inherit from mother cells?
Daughter cells must inherit everything from the mother cells that they need to be successful
What is one very important thing that all daughter cells need?
Mitochondria
Cells contain multiple mitochondria, if a daughter cell only get one mitochondria from the mother cell how can it eventually get more?
Mitochondria can also divide
What are chromosomes?
-A package made up of one single double stranded DNA molecule
What are the two types of chromosomes?
Circular chromosome: Found in bacteria which have circular DNA
Linear Chromosome: Found in eukaryotes
Why are we able to see chromosomes under a microscope?
-When a cell is getting ready to divide the chromosomes condense by associating with proteins such as the histone protein
-That is what can be seen
What are the proteins that help chromosomes condense before dividing ?
Histones
So what is seen under a microscope when chromosomes are condensed?
DNA wrapped up in a tight knot around the histone proteins
What is a karyotype?
A way of organizing and identifying chromosomes
How to make a karyotype(DIY!)?
1.Take a cell in its process of dividing and put a cover slip on top of it and flatten it(mitotic squash)
2.This causes the cell to break open and the chromosomes spread out everywhere
3.The chromosomes are then stained and a photo of them is taken
4. Then line the chromosomes up into a pattern that you see
What does the karyotype reveal about chromosomes?
They come in pairs
What are pairs of chromosomes called?
Homologs
How many chromosomes do humans have?
23 pairs chromosomes(homologs), 46 individual chromosomes
What two chromosomes don’t appear to have pairs?
X and Y
True or False: The number of chromosomes depends on the organism/species?
TRUE
What happens to chromosomes right before division?
Each chromosome is replicated to produce two chromatids attached by a centromere
What is found in each chromatid?
Each chromatid has one double-stranded piece of DNA
After chromatids are formed, how many strands of DNA are found in each pair of homologous chromosomes?
4 strands of double stranded DNA
1 per chromatid, 4 chromatids
What is a mitotic chromosome?
Chromatids two identical pieces of DNA bound by a centromere
-It is called this because it is about to undergo division and must have two strands of DNA
What is a sister chromatid?
-Identical chromatids with duplicated genetic material
-There are two sister chromatids in a mitotic chromosome
How many chromosomes do daughter cells need?
Each daughter cell NEEDS one of each chromosome because they carry essential genetic material
Can daughters receive more than one of each chromosome?
No they cannot as this can cause problems such as Down syndrome
What extra chromosome causes down syndrome?
people with down syndrome have an extra chromosome 21
How do cells ensure that daughter cells receive only one of each chromosome and no more?
Make sure the chromosome is duplicated once before the cell divides
What is the first stage of cell division?
S phase - Chromosome DNA replication
What is the second stage of cell division?
Mitosis or Meiosis
What is mitosis?
Somatic cells make identical clones of themselves by creating daughter cells that inherit one chromosome
What is meiosis?
Process by which germ cells(reproductive cells) make non-identical copies of themselves by creating daughter cells that have one of each homolog
What is the third stage of cell division?
Cytokinesis: dividing the cytoplasm in two(optional)
What are the four stages of the cell cycle?
- Gap phase
- DNA Synthesis
- Gap 2
- Mitosis
What happens during the gap phase of the cell cycle?
-Cell grows
-Builds up mitochondria and ribosomes so that it can later give them to its daughter cells
What happens during DNA Synthesis of the cell cycle?
Creation of one and only one copy of the DNA
What happens during the gap 2 phase of the cell cycle?
Verification that DNA is properly ready and cell is ready for division
What happens during the mitosis stage of the cell cycle?
Chromosomes divide and cell splits in two daughter cells
How does the cell regulate the cell cycle?
-Cell has checkpoints to make sure the cell is ready to enter the next phase
What proof is there to prove that these checkpoints exist?
First, scientists added drugs into the chromosomes to ensure that the cell could not efficiently replicate the DNA. What they saw was that the cell stopped before it could undergo cell division
Then, scientist disabled the check point by adding caffeine then added the drug to stop replication and what they saw was the cell continued to undergo cell division
What are the check points?
The check points are proteins that make sure everything is ready to move to the next phase
-CDK and Cyclins
What proteins are important for the transition from G1 to S phase?
-Cyclin A
-CDK2
True or False: Little effort is used by cells to make sure each daughter cell inherits equally
True and False, simply making sure the
division occurs roughly in the middle of the cell seems to do the trick. However, cells do spend a lot of time dividing up their chromosomes
Why are karyotypes made with dividing chromosomes?
Only during division chromosomes are visible
What is the karyotype made of?
Mitotic Chromosomes
What is chromatin?
The combination of DNA and proteins before cell division
What is the order of the cell cycle?
- G1
- S
- G2
- M
Cytokinesis is not included as it it optional
What does interphase refer to ?
All stages of the cell cycle except for M phase
True or False: Most cells in your body have not divided in a long time?
True
In what phase do most cells stop cycling?
G1
What does the S to G2 checkpoint look for?
Internal signals that tell the cell that all of the DNA has been replicated
What does the G1 to S checkpoint look for?
External chemical signals from other cells
What is the basis of cancer? I
If something goes wrong with the checkpoint controls that regulate cell division, cells divide continuously and at the wrong time, this can cause cancer
