Mitosis and meiosis Flashcards
What is mitosis used for?
Asexual reproduction
Growth
Tissue repair
Repair cells
What happened in prophase in mitosis?
- The nuclear envelope and nucleolus breaks down
- The centrioles duplicate and go to opposite poles
- The DNA condenses into 2 identical chromatids
- Spindle fibres made from tubulin are made from the centrioles in animal cells
What happened in metaphase in mitosis?
- The chromatids move into the middle down the equator of the cell or the metaphase plate
- The spindle fibres attach to the centromeres on the chromatids
What happened in anaphase in mitosis?
- The centromere divides and the sister chromosomes are dragged to opposite poles.
What happened in telophase in mitosis?
- A nuclear envelope is made around the chromosomes and they unravel
- The cell membrane starts to split
What happens in cytokinesis after mitosis in animal cells?
The plasma membrane folds inwards and ‘nips in’ the cytoplasm
What is meiosis used for?
Sexual reproduction
What happened in prophase I in meiosis?
- The nuclear envelope and nucleolus breaks down
- The centrioles duplicate and go to opposite poles
- The DNA condenses
- Spindle fibres made from tubulin are made from the centrioles in animal cells
- The homologous pairs of chromosones form bivalents and exhange alleles
What happened in metaphase I in meiosis?
- The homologous pairs of chromosones are opposite to each other on the equator
- The spindle fibres connect to the centromeres of the chromatids
What happened in anaphase I in meiosis?
The homologous chomosones are dragged to the opposite poles by the motor proteins on the tubulin spindle fibres
What happened in telophase I in meiosis in animal cells?
- A nuclear envelope is made around the chromosomes and they unravel
- The cell membrane starts to split into 2 not genetically identical daughter cells with 1/2 the number of chromosomes from the original
What happened in telophase I in meiosis in plant cells?
- A nuclear envelope is made around the chromosomes and they unravel
- The cell membrane starts to split into 2 not genetically identical daughter cells with 1/2 the number of chromosomes from the original
What happens in telophase II in meiosis in plant cells?
- A nuclear envelope is made around the chromosomes and they unravel
- The cell membrane starts to split into a ‘tetrad’ of 4 haploid daughter cells with half the number of chromosomes as the 1st cell
What are the similarities between mitosis and meiosis?
Mitosis and meiosis 2 are similar in what happens
Both have the same interphase
What happens in cytokinesis in plant cells?
An end plate is formed from where the equator of the spindle was, and new plasma membrane and cellulose cell wall are laid down on either side along the end plate
What are the differences between mitosis and meiosis?
In mitosis the DNA isn’t exchanged
Mitosis only splits once, meiosis twice
Mitosis makes genetically identical daughter cells
Mitosis makes 2 cells, meiosis makes 4
What happens in cytokinesis after mitosis in plant cells?
An end plate forms at the equator and a new plasma membrane and cell wall material are laid down on either side along this plate
What is the benefit of the chromatids exchanging information in meiosis?
To achieve more diversity and to swap alleles
What is independant assortment?
When the homologous chromosome pairs line up on the equator independent of one another
What is independent assortment?
Each homologous pair lined up on the equator independently of all other pairs randomly.
How does variation occur in meiosis?
- Crossing over
- Mutation
- Random fertilisation
- independant assortment
Why is fertilisation random?
It isn’t known which sperm will fertilise the egg and which egg will come out
How do you find the number of variations in a cell without crossing over?
2 to the power of the number of pairs of chromosomes
Why is variation important?
To provide a wide variety of types of people to be able to adapt to different environments
Where is the genetic material crossed over in meiosis 1?
The chiasmata
What happens in cytokinesis after meiosis in plant cells?
An end plate is formed from where the equator of the spindle was, and new plasma membrane and cellulose cell wall are laid down on either side along the end plate
Homologous pair of chromosome meaning
a pair of chromosomes that code for the same genes but have different alleles
Sister pair of chromatids meaning
A pair of chromatids that are exactly the same. from the same chromatid
centromere meaning
Where two chromatids are attatched
Cytokinesis in plant cells
Due to the celll wall instead of the cell nipping in vesicles assemble where the equator was. The vesicles then fuse which splits the cell. The vesicles undergo lysis then wall is made.
bivalent
A pair of homolohous chromosones
chiasmata
the place where the homo chromosones are attatched when swapping.
Prophase II
The chromosones condense again and the sister pairs of chromatids pair up
all other things happen as normal e.g nucleolus bye
Metaphase II
the spindle fibres attatch to the centromere of each chromone.
independent assortment can happen because the sister chromatids can be randomly arranged so DNA can be different
anaphase II
The sister chromatids are pulled apart
