10
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What is the point of Meiosis II, considering Meiosis I already produced haploid cells?
After meiosis I, those n=23 chromosomes have two chromatides. Meiosis II just separates them into single chromatides.
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8
votes
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How do gene locations change during crossing over events?
It depends on the regions of sequence homology between the two chromosomes. Crossing over occurs through pairing of homologous regions. If there's a substantial stretch of chromosome without a ...
- 1,699
7
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No. of meiotic divisions to produce specific no. of seeds
Assuming that you have studied megasporogenesis and microsporogenesis. To produce a seed, you require the production of pollen(n) and egg(n) and their fusion.
Let's start with pollen grain(n):
4 ...
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6
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Mitosis versus Meiosis I: What's the difference?
At the start, all the cells are 2n, diploid cells. By far the largest difference between meiosis I and mitosis is that mitosis results in genetically identical, diploid somatic cells. Meiosis, in it's ...
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6
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Do the eggs for larger litters come from the same meiosis events, or different ones?
I'm not sure about the ubiquity of this but, in many animals, each primary oocyte that undergoes oogenesis only produces one mature egg. The other products of meiosis are polar bodies, which are not ...
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6
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When are a female's eggs created?
Oocytes, or immature female eggs, develop in the fetus's ovaries during pregnancy. This graph (U. New South Wales) shows the oocyte population over time in a human female:
Although the x-scale is ...
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6
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How does the molecular machinery choose where to cut a chromosome for recombination?
In humans and mice anyway ,a lot of it boils down to the recognition of a specific sequence that marks recombination hotspots by PRDM9.
http://www.sciencemag.org/content/327/5967/836
Edit - I'm ...
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5
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How does the molecular machinery choose where to cut a chromosome for recombination?
The question is very broad and complicated, since the situation may differ in prokaryotes and eukaryotes. Nevertheless, I'm citing a good paper that is closely related to your question:
Studies in ...
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5
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Why isn't meiosis II called mitosis (as the chromosome number doesn't half)?
Well, in my opinion, the entirety of the meiosis is a process (reproduction of sex cell) in which two levels of division occur, it's all kind of one process. Though meiosis II may seem to have many ...
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4
votes
How do I identify the different stages of meiosis under microscope?
ID characteristics that can help you recognize diplotene better:
diplotene :
the only difference between this phase and Diakinesis is that The centrosomes reach the poles.
you can see the photos ...
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4
votes
Do the eggs for larger litters come from the same meiosis events, or different ones?
While your question asking about birds, reptiles and fish (oh my!) may be too broad, hopefully looking at frog oogenesis can show some differences in large offspring number v. small offspring number. ...
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4
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How can a haploid plant be bisexual?
Meiosis does not determine sexual form. Eukaryotes use meiosis and fertilization to recombine genes to form new combinations. Meiosis does produce haploid cells from diploid cells, but that has ...
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4
votes
How are germ cells not reduced in number?
In case of gametogenesis (let us talk about spermatogenesis) gametes are formed from meiotic division of Primary spermatocytes.
In Primates Primary spermatocytes are cells that that are formed from ...
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4
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No. of meiotic divisions to produce specific no. of seeds
For producing $x$ number of seeds (or say zygote) $x$ number of egg cells must fuse with $x$ number of male gametes.
In angiosperms, 1 meiotic division of Megaspore mother cell leads to formation of ...
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4
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When in the cell cycle is the number of chromosomes normally reduced?
It is the other way around. Meiosis I (or reductional division) splits chromosome pairs so each cell gets half of the chromosomes of the parent. Meiosis II (or equational division) splits double-...
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3
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How do two parents, recessive and dominant genes and two complimentary nucleotides end up in one DNA?
I will talk about humans only and I will not talk about the special case of sexual chromosomes (and anomalies such as trisomy 21) from the answer just to keep things easy. There is a lot to say, so I ...
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3
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How do two parents, recessive and dominant genes and two complimentary nucleotides end up in one DNA?
I think you really need to go back to the very basics and try to understand the DNA molecule, what a chromosome is, DNA replication and mitosis, what homologous chromosomes are, what non homologous ...
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3
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How are germ cells not reduced in number?
"How are germ cells not reduced in number?"
It does happen. Germ cells do eventually run out. It is called menopause in women. And age related infertility in men.
As for your question of where do ...
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3
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During what phase is the cell polyploid?
I assume that you mean phase of cell division. First off all i will write down a definition of word polyploid. Polyploid is cell which has two or more pairs of homologus chromozoms. There are two ...
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3
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How could a cell only have chromosomes from father or from mother?
That graphic is just confusing you.
The cell doesn't keep track of all the chromosomes from Mother versus all the chromosomes from Father so it can sort them out later. That I know of! [I don't ...
- 2,367
2
votes
How do nuclear membranes form during Telophase of Mitosis/Meiosis?
According to this book, during disassembly of the nuclear envelope, the nuclear membranes are broken down into vesicles. The nuclear membranes reform at the end of mitosis as the vesicles bind to the ...
- 2,834
2
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Formula for number of divisions required to form x number of cells (Mitosis and Meiosis)
For a male, one primary spermatocyte produces two secondary spermatocytes through meiosis I, which in turn produce two spermatids each through meiosis II. So one primary spermatocyte produces four ...
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2
votes
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What are chiasmata?
We need to make a distinction between the genetic map of a chromosome, which is usually built up from meiotic recombination frequencies between linked genetic markers, the physical map of a chromosome,...
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Mechanics of Chromosomal Crossover
How does the cell select where to to make the break on both chromosomes?
There are proteins that direct the selection of a site where a double strand break will be made on one chromatid.
...
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2
votes
Doesn't meiosis form two pairs of similar cells and two pairs of opposite cells?
Great question - I think there are two misconceptions in your question that are interfering with your understanding.
First, crossing-over occurring at just the "tips" is just for clarity in textbooks ...
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2
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Do Gametes contain mitochondria/chloroplasts from their parent cell?
Is this DNA found in the mitochondria and chloroplasts coded for in the host's (animal's or plant's) DNA.
No, the DNA contained in these organelles it not a subset of the nuclear genome. However, ...
- 1,135
2
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Does chromosome cross occur over male and female or vice versa?
The question is unclear to me but hopefully that will help a little bit.
My understanding is homologous chromosome pair, which means male and female chromosome
There is no male and female ...
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2
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Aneuploidy in meiosis
From Study.com >>
On the off chance that nondisjunction happens amid anaphase II of meiosis II, it implies that no less than one set of sister chromatids did not isolate.
In this situation, two ...
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2
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Why do some organelle (like ER and Golgi complex) cannot be seen under microscope during cell division?
A cell when undergoes the process of cell division there are structures known as spindle fibres that are required to pull the chromosomes off to the poles of the cell so that it can be segregated into ...
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