2.2 Cell Division Flashcards
What is the cell cycle?
The sequence of dividing and non-dividing stages of the life of a cell
What is interphase of the cell cycle?
It is the non-dividing stage and the longest stage
What are the main stages of the cell cycle?
G1 phase = cell growth
S phase = DNA replication
G2 phase = prep for mitosis
Cell division = mitosis
What does diploid mean?
2 sets of chromosomes with homologous pairs
1 paternal set and 1 maternal set
What does haploid mean?
1 set of chromosomes no homologous pairs
A mix of paternal and maternal chromosomes
What type of cells are diploid?
Somatic cells= human cells
What type of cells are haploid?
Gametes
How can you tell if a cell has not undergone cytokinesis?
They have multiple nuclei because the nuclear division has taken place but the cytoplasm hasn’t split
What is a chromosome?
Condensed chromatin
What is chromatin?
DNA double helix that is bound to histones
If an haploid organism undergoes mitosis what type of cell (hap/dip) does it produce?
Haploid
What type of cells does mitosis take place in?
Eukaryotic
What is mitosis?
Nuclear division in eukaryotic cells that produces 2 genetically identical daughter cells
Are the daughter cells haploid or diploid in mitosis?
Diploid
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What happens during interphase of mitosis?
The cell makes a copy of its DNA - DNA replication
Cell growth
The chromosomes are not visible ATP synthesis
Synthesis of organelles
What happens during prophase of mitosis?
Chromosomes condense and shorten and become visible
Spindle fibres form from each pair of centrioles
Chromosomes attach to spindle fibres by their centromere
Nucleolus disappears
Nuclear envelope breaks down, chromosomes are free in the cytoplasm
What happens during metaphase of mitosis?
Chromosome are pulled along the spindle fibres and align themselves across the equator of the cell
The centromeres divide into two
What happens during anaphase of mitosis?
Spindle fibres contract and shorten, pulling sister chromatids apart
Chromosomes are pulled to opposite poles
What do mitochondria do in anaphase?
Mitochondria located around the spindle fibres provide ATP for contractions
What happens during telophase of mitosis?
Chromosomes reach their respective poles
Nuclear envelope and nucleoli reform
Spindle fibres disintegrate
Chromosomes become elongated becoming less visible
What happens during cytokinesis during mitosis?
Cell membrane pinches inwards separating the cytoplasm
Cytoplasm divides to produce two new cells
What is the importance of mitosis?
Responsible for cell growth for tissues and organisms
Tissue repair
Asexual reproduction in single cells eukaryotes
How would you identify prophase from a diagram?
The chromosomes are random and have no specific arrangement and they are visible
What is an advantage of genetically identical offspring to parents?
In an unchanging environment, successful parents rapidly produce successful offspring
What is a disadvantage of having genetically identical offspring to parents?
The offspring are more vulnerable to changes in the environment like disease
How do you calculate t he mitotic index?
No. Of cells undergoing mitosis: total no. Of cells
Why do you use a root in the root tip squash prac?
It is the growth region where mitosis occurs
no dividing cells more than 5mm from tip
to get soft tissue to squash
so it will fit under the cover slip
Why is a stain necessary in the root tip prac?
So the chromosomes become visible to view under the microscope
Why is the root tip added to HCl?
To soften the cell wall so the stain can enter the cell quickly
What stain is used in the root tip prac?
Acetic orcein
Why is the watch glass with the root and HCL placed in a hot water bath?
It speeds up the movement of the stain and the softening of the cell walls
Why do you need to squash the root tip?
Makes it thin to get a single layer of cells to see the chromosomes under the microscope
What is the root tip prac?
- Cut 5mm off garlic root tip
- Add one drop of 1M HCl and place in waterbath for 10mins
3.put 10 drops of acetic orcein stain - Add the root tips
- Using forceps, remove a root tip and place it on a microscope slide. Place a cover slip over the top
- Immediately place filter paper over the cover slip then use thumb to gently squash the root tip
How do prokaryotes divide?
Binary fission
What is the process of binary fission?
- Circular DNA replicates and both copies attach to cell membrane. Plasmids also replicate
- Cell membrane begins to grow between two DNA molecules
- Cell membrane begins to pinch inwards dividing the cytoplasm
- A new cell wall forms between the two molecules of DNA fully dividing the original cell
- Two new identical daughter cells formed with a single copy of the circular DNA and a variable no. Of plasmids
What is the process of replication in viruses?
- The virus attaches to the host cell with the attachment proteins. Then they inject their nucleic acids into the host cell
- The genetic code of injected viral nucleic acids is read by the host cell
- Host cell starts to produce viral components: nucleic acids, enzymes, structural proteins
- These components are then assembled into new viruses
How do cells stop dividing in healthy cell division?
Differentiated cells loose their ability to divide and there are genes present that can program cell death
What is apoptosis?
The cell deaths that occur in healthy cell division
What is a tumour?
A mass of cells that can become cancerous
How is cancer formed from cell division?
Uncontrolled mitosis:
Genes that regulate cell division and cell death are mutated
Mutation passes onto daughter cells
Mutations accumulate
Describe the arrangement of chromosomes in interphase of mitosis
Chromosomes (are) becoming visible/distinct
Because (still) condensing; chromosomes are condensed
Chromosomes (arranged) at random/not lined up
Because no spindle (activity);
What does sterile mean?
not able to produce children
Why would an offspring procuced be sterile?
Too many/extra set/three copies of chromosomes
(Homologous) chromosomes do not pair
(So) no meiosis
Why would preventing spindle fibres forming prevent the cell cycle?
- Chromosomes/centromeres cannot attach (to spindle)
Chromosomes cannot line up (on spindle) - (So, no) metaphase
- Chromatids cannot separate (on spindle);
What do you do to improve accuracy of an experiment?
repeats
How is growth prevented by preventing mitosis?
Prevents anaphase
Disrupts formation of spindle fibres
So preventing the separation of sister chromatids
No new cells are formed
What are evidence that chromosomes are undergoing mitosis?
The individual chromosomes are visible because they have condensed
Each chromosome is made up of two chromatids because DNA has replicated
The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis
How does a chromosome’s structure differ along its length?
Differences in base sequences
Differences in histones
Differences in condensation coiling
