Help clarify my knowledge? Cell cycle & reproduction

[Merlyn]

Hello, my teacher bombarded me with a whole heap of information last week, and I'd really appreciate it if anyone could clarify what I've learnt (because I'm a bit confused and klafsjew;iifdsfajlgkfha).

Cell cycle:
It involves mitosis, cytokinesis, gap 1 which consists of cell growth and development, the 's' phase which is occurs during DNA replication and gap 2 which is when chromosomes begin condensing (interphase? )
What I know about DNA replication is that it involves Helicase, which is an enzyme that unzips DNA and polymerase, which puts the correct nucleotides to the bases. So now there are 2 double stranded DNA molecules - one strand of the original DNA and one strand that was just newly synthesised. These 2 DNA molecules rewind into the double helix by wrapping around proteins called histones.

Meiosis
During prophase 1:
the cell starts off with 2 pairs of single stranded homologous chromosomes
they replicate and become double stranded
the homologous pairs synapse and exchange segments of their chromosomes
Metaphase 1:
The chromosomes line up across the equator of the cell
anaphase 1:
the homologous chromosomes are separated as their centromeres are pulled to opposite sides of the cell
During telophase 1:
There are now 2 nuclei, each comprising of 2 double stranded chromosomes
Prophase 2:
these double stranded chromosomes disjoin to become single stranded
Anaphase 2:
They move to opposite directions
telophase 2:
There are now 4 cells, each with 2 single strands of chromosomes.

Some questions:
Is there no metaphase 2? And was the prophase 2 that I described correct?
Are there any details that I am missing?

For Binary fission
I just know that it's a form of asexual reproduction for prokaryotes and involves the cell elongating, the DNA replicating and the cell splitting. Is that amount of detail sufficient?

As for mitosis,
Prophase - DNA condenses into chromosomes, they become double stranded and the nuclear envelope disintegrates
Metaphase - Spindle fibres organise the chromosomes along the equator of the cell
anaphase - Centromeres divide as the spindle fibres pull each chromatid to opposite ends of the cell
telophase - nuclear envelope forms for the 2 new nuclei, and a cleavage furrow/cell plate forms

Cytokinesis - the cytoplasm splits to form 2 separate cells.

Haha... so here it is, I'll appreciate anyone who help fix me up. Thanks in advanced!

[Ancora_Imparo]

Pretty much on the money there! Just a few minor details...

Interphase is considered to be everything other than Mitosis. So G1 (Gap 1), S (Synthesis or DNA replication) and G2 (Gap 2) all fall under Interphase.

With DNA replication, I don't know how much detail your teacher has gone into, but you should be able to use terms like 'leading strand', 'lagging strand', 'replication fork', 'Okazaki fragments' and 'semi-conservative'. If you don't know these things yet, don't worry because you'll learn about it soon. However, the process you described was essentially correct.

There is a phase called Metaphase II and it's exactly the same as Metaphase I except that occurs in the daughter cells and there is no pairing of chromosomes. Also, the name for the process you described in Prophase I where genetic information is exchanged is called 'crossing over' or 'genetic recombination'.

Everything else sounds good!

[Yacoubb]

Hello, my teacher bombarded me with a whole heap of information last week, and I'd really appreciate it if anyone could clarify what I've learnt (because I'm a bit confused and klafsjew;iifdsfajlgkfha).

Cell cycle:
It involves mitosis, cytokinesis, gap 1 which consists of cell growth and development, the 's' phase which is occurs during DNA replication and gap 2 which is when chromosomes begin condensing (interphase? )
What I know about DNA replication is that it involves Helicase, which is an enzyme that unzips DNA and polymerase, which puts the correct nucleotides to the bases. So now there are 2 double stranded DNA molecules - one strand of the original DNA and one strand that was just newly synthesised. These 2 DNA molecules rewind into the double helix by wrapping around proteins called histones.
Just note that Interphase = G1 Phase + S phase + G2 Phase, and then Metaphase, Anophase and Telophase makes up the the remaining parts of the cell-cycle. Its probably best to know that human cells contain 46 chromosomes. At some stage, this needs to double in order for each daughter cell to have an equal number of the same chromosomes (i.e. 46 chromosomes each). This occurs during the S phase -> someone correct me if I'm wrong :\

Meiosis
During prophase 1:
the cell starts off with 2 pairs of single stranded homologous chromosomes
they replicate and become double stranded
the homologous pairs synapse and exchange segments of their chromosomes
Metaphase 1:
The chromosomes line up across the equator of the cell
anaphase 1:
the homologous chromosomes are separated as their centromeres are pulled to opposite sides of the cell
During telophase 1:
There are now 2 nuclei, each comprising of 2 double stranded chromosomes
Prophase 2:
these double stranded chromosomes disjoin to become single stranded
Anaphase 2:
They move to opposite directions
telophase 2:
There are now 4 cells, each with 2 single strands of chromosomes.

Some questions:
Is there no metaphase 2? And was the prophase 2 that I described correct?
Are there any details that I am missing?

For Binary fission
I just know that it's a form of asexual reproduction for prokaryotes and involves the cell elongating, the DNA replicating and the cell splitting. Is that amount of detail sufficient?

As for mitosis,
Prophase - DNA condenses into chromosomes, they become double stranded and the nuclear envelope disintegrates
Metaphase - Spindle fibres organise the chromosomes along the equator of the cell
anaphase - Centromeres divide as the spindle fibres pull each chromatid to opposite ends of the cell
telophase - nuclear envelope forms for the 2 new nuclei, and a cleavage furrow/cell plate forms

Cytokinesis - the cytoplasm splits to form 2 separate cells.

Haha... so here it is, I'll appreciate anyone who help fix me up. Thanks in advanced!

A handy acronym to remember:
I-P-MAT
I = interphase
P = prophase
M = metaphase
A = anaphase
T = telophase.

* Learn to identify what is occuring in diagrams. For example, in Metaphase, the centrioles form a spindle fibre along the equator of the cell and the chromosomes line up along the equator. Plenty of MC and even short answer questions asking you to identify what stage is occuring.

* A table of differences between mitosis and meiosis is helpful (e.g. mitosis is asexual and results in identical (2) daughter cells, whereas meiosis is sexual and results in non-identical (4) daughter cells.

* I'm being really meticulous but say Interphase I, Interphase II (i.e. use roman numerals)

* Know that random combinations and recombinations in meiosis result in variation in the genetic make-up of the daughter cells.

You're good to go

LOL I just realised Ancora_Imparo beat me! Woops ! Hope I helped too though!

[ealam2]

I                (Interphase)
P-refer        (Prophase)
M-ice          (Metaphase)
A-nd           (Anaphase)
T-alking      (Telophase)

C-ats          (Cytokineses)

 

[Merlyn]

Thank you all! ^^
My teacher explained briefly the 'leading strand', 'lagging strand', 'replication fork' and 'Okazaki fragments' but she said it wasn't that important.. She lied. D: Again. I'll have to do some research myself... unless someone could help explain it? Much appreciated.

[Eugenet17]

http://www.youtube.com/watch?v=pOsAbTi9tHw

GENIUS

[AbominableMowman]

http://www.youtube.com/watch?v=pOsAbTi9tHw

GENIUS

I always thought it was 'MITOSIS, CHROMOSOMES ARISE'
But its actually 'Mitosis, chromosomal ride'

[ggxoxo]

Thank you all! ^^
My teacher explained briefly the 'leading strand', 'lagging strand', 'replication fork' and 'Okazaki fragments' but she said it wasn't that important.. She lied. D: Again. I'll have to do some research myself... unless someone could help explain it? Much appreciated.

Hi Merlyn; these two sources helped me understand DNA replication when I was doing Biol:

http://www.youtube.com/watch?v=4PKjF7OumYo

http://www.courses.fas.harvard.edu/~biotext/animations/replication1.swf

Hope these help you!

[Merlyn]

Thanks for all the help! Much appreciated ^^