36
votes
Accepted
Why is Chromosome 1 called Chromosome 1?
Chromosomes were first known about from karyograms (that's the word for chromosome pictures like these) sort of like this one (1)(2):
The scientists looking at these chromosomes didn't know much ...
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33
votes
Accepted
Do men and women have the same number of genes?
It is true that the Y chromosome is shorter than the X chromosome and that there are more genes on the X chromosome.
Do men have fewer genes?
One could (mis)understand three things in the ...
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26
votes
Accepted
Are there examples of cells with more than one nucleus?
Are there examples of cells with more than one nucleus?
Yes, they are called Multinucleate cells. There are two types of multinucleated cells
Syncytia
Coenocytes
I highly recommend having a look at ...
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17
votes
Human Evolution Chromosome 2: Fusion or Break?
The way you answer these sorts of questions is by looking at other, further relatives because that gives you more hints about what the "ancestral" trait is.
Since other apes (gorillas, ...
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13
votes
Accepted
Why does size decrease across the sequence of human chromosomes?
You nailed it!
Nomenclature
Autosomal chromosomes
Chromosomes are numbered based on their size (in base pairs).
Sexual chromosomes
Sexual chromosomes (when they exist) are defined as the largest ...
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13
votes
Accepted
Which of the two chromosomes in a pair is expressed?
The majority of normal autosomal genes have biallelic expression, i.e. the alleles on both chromosomes are used to make protein. This is why mutations in a gene which cause non-function of the product ...
- 156
11
votes
Accepted
Why does human chromosome 19 have the second highest number of protein-coding genes?
This Nature paper from 2004, by Jane Grimwood et al. goes at least a long way towards giving an answer to the question of the OP. In short: there were inordinately many duplications, especially during ...
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11
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Are there examples of cells with more than one nucleus?
There is a branch of life called the Diplomonads, most of which have two nuclei. They are single cell organisms and an early offshoot of the eukaryotic linage. A good example is Giardia lamblia.
https:...
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10
votes
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The human has 46 double chromosomes or simple chromosomes?
Your first picture shows a chromosome that has been (1) condensed and (2) undergone DNA replication. During G1 interphase (normal cell activity; not dividing), your chromosomes actually do not look ...
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8
votes
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Why are mice with a single X chromosome and no Y chromosome males?
Almost all mammals (including mice and humans) have two sexes where the males have a Y chromosome and an X chromosome (whereas females have two X and no Y chromosomes). This is not the only way ...
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8
votes
Interpretation of picture of human chromosomes
The picture can be a bit misleading because it represents 22 autosomes (autosome = non-sexual chromosome) while there are 22 pairs of autosomes (so the homologous chromosome is not represented). And ...
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8
votes
Accepted
Interpretation of picture of human chromosomes
Since I have used more than 1 image in my answer; with numbers starting from 1; I'll call your provided figure as figure-0
What is shown in following picture?
Though the image showing many things;...
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8
votes
Are there examples of cells with more than one nucleus?
According to this article The hairy beast with seven fuzzy sexes
Tetrahymena thermophila has two: a large macronucleus and a small micronucleus. The macronucleus controls the everyday functions of ...
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8
votes
Accepted
What causes cells to inactivate one X-chromosome?
Even a male cell can count the number of X chromosomes. (Lee et al. 1996; Cell 86: 83-84)
When X inactivation is getting started the two chromosomes "kiss" - a process that lasts for a couple of ...
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7
votes
Haploid eukaryotes?
Update: There are plenty of eukaryotes that occur in haploid stage as the dominant life cycle stage. See metagenesis in cnidarian animals and "alternation of generation" in algae, protists and fungi.
...
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6
votes
Accepted
Cousin Marriage from genetics point of view
The problem is that humans have 22 other pairs of chromosomes than just the sex chromosomes X and Y. Reproducing with your cousin (the son of your mother's brother is the son of your uncle which means ...
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6
votes
What are the ploidy levels in major groups of organisms?
Are all animals haploid (n=x) ?
No
Are all fungi haploid (n=x) ?
No
Are all plants diploid (2n=x) ?
No
Are all Protists diploid (2n=x) ?
No
Also, what is the ploidy of archaea and ...
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6
votes
How to disambiguate between chromosome and chromosome pair?
This is standard. For a typical human diploid cell there are two copies of chromosome 1, two copies of chromosome 2, etc; you'd have either two copies of the X chromosome or one X and one Y.
There's ...
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5
votes
Accepted
Do all chromosomes in one human body contains same genome?
Yes, all cells contains the same genome. This is because, for a given individual, all of its cells comes from the zygote, a singular cell formed after fecondation of the maternal ovum and paternal ...
- 1,145
5
votes
Haploid eukaryotes?
Some apicomplexans such as Plasmodium spp. are haploid during their asexual stages. The organism spends more time (at least in the human host) in the asexual stage than sexual. source
Plasmodium ...
- 151
5
votes
Does aneuploidy include the loss of chromosome arms?
To my knowledge aneuploidy regards to chromosome numerical change, not to losses within chromosomes.
Take a look at this paragraph from An Introduction to Genetic Analysis. 7th edition (Griffiths AJF, ...
- 647
5
votes
What is the X-chromosome responsible for?
Here is the list! There are about 900 protein coding genes and about 500 non-coding transcribed sequences. It is not going to be feasible to explain you the function of every single one of those genes....
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4
votes
Is complete linkage found in all four chromosomes or only Y-chromosome of Drosophila?
All chromosomes. There is no crossing over in males in Drosophila. Check out the related question Why doesn't recombination occur in male Drosophila? for sources and context.
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Explanation about cytogenetic notation
Those are the break points of the inversion. So chromosome 4 was cut at p13 and q22 and the fragment was reinserted in the reverse direction, giving a pericentric inversion.
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4
votes
Accepted
Is it ok if I define Genes this way in Biology?
The term gene has been defined (by Wilhelm Johannsen) much before we even knew about the structure of DNA (by Watson and Crick). As such, a gene is typically a vaguely defined functional unit in the ...
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4
votes
Accepted
Why are X-linked illnesses less common in females if females have X-chromosome inactivation anyway?
Barr bodies (X-chromosome inactivation) don't form in the initial fertilized embryo — it's not that one X-chromosome is inactivated, and then that same inactivation is passed down to daughter cells. ...
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4
votes
Will a person with two copies of the same set of chromosomes be normal?
It sounds like this person would be close to what you get with "pure lines", aka inbred strains in laboratory animals:
A population of identical homozygotes constitutes a pure line. Pure lines "...
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4
votes
Are there examples of cells with more than one nucleus?
When a "slime mold" enters the "plasmodium" phase n cells merge together to form one cell with n nuclei. This means plasmodiums can have thousands or tens of thousands of nuclei...
- 236
4
votes
Human genome, chromosomes
Do all chromosomes have the same DNA?
No. Not any more than each chapter of a book has the same words in the same order.
If so, does it mean that in different cells with different functions
...
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4
votes
How much shorter is the short arm of a chromosome? And why?
It varies from chromosome to chromosome and from species to species. In some cases, both arms are roughly the same length. In some cases, one arm is so short that it is almost inexistant. For ...
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