A single piece of DNA coiled and organized along with RNA and proteins found in the cell.

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Maintenance of Diploid chromosome number at mitosis

I'm just not understanding this: A regular human cell is diploid - because it has 46 chromosomes, in 23 pairs. So that means that when the cell undergoes mitosis, it will still have the full ...
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1answer
24 views

Why does meiotic recombination disrupt the independent assortment of genes on the same chromosome?

There are many sources that say that genes that are "linked" by being on the same chromosome assort with each other -- that when an allele is passed on that the gamete containing said allele will also ...
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2answers
39 views

What is the length of the centromeric repeat sequence in a human?

I'm looking for the lengths of the centromeres of human chromosomes. The best I could come up with so far has been: The length of individual centromeric arrays was found to range from an average of ...
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31 views

Is complete linkage found in all four chromosomes or only Y-chromosome of Drosophila? [duplicate]

Male Drosophila shows complete linkage. Is it observed for all four chromosomes or only the Y chromosome?
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1answer
141 views

Why are mice with a single X chromosome and no Y chromosome males?

I was searching online and I read this article Mice can be male without Y chromosome and this is a part of it: The experiments demonstrate that there are multiple ways to make males, says Richard ...
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19 views

Why is down syndrome more common than other trisomies? [duplicate]

Why is Down syndrome more common than say trisomy 18? Is chromosome 21 easier to replicate? Or is it because those babies are more viable?
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3answers
59 views

Whole Genome Sequencing and B Chromosomes

Do whole genome sequencing techniques detect B chromosomes if such chromosomes are present? My understanding is as follows: How the DNA material in a B Chromosome is mapped depends on the reference ...
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807 views

How are 23 chromosomes in human sperm chosen?

I'm not biologist and I have just a basic knowledge. I've been thinking for a long time about the following question: How does the body choose which 23 chromosomes should be active in human sperm and ...
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20 views

What would the resulting karyotype be if someone with Klinefelter syndrome fertilized an “empty” egg?

Endoreduplication: is a form of nuclear polyploidization that results in multiple, uniform copies of chromosomes. This process is common in plants and animals, especially in tissues with high ...
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Why are published chromosome counts for polyploids often incorrect by an integer multiplication factor of the original diploid like count?

Why are published chromosome counts (done using techniques such as root smashes) for polyploidy flowering plants often incorrect by a multiplication factor of 2 or 3 from the original diploid like ...
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137 views

Why do humans have 46 chromosomes? [duplicate]

Humans have approximately 25000 genes. Why are these genes on 46 chromosomes? Why not 40 or 50?
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959 views

recombination frequency problem

Three loci C, D and E are located on the same chromosome in this order. We found that the frequency of recombinants between C and D is 10% and that between D and E it is 20%. Assuming that ...
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206 views

Why does size decrease across the sequence of human chromosomes?

The following graph shows a decrease in the amount of base pairs per chromosome across the sequential set of human chromosomes: Is this because chromosomes were originally numbered by their size on ...
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Are both chromosomes transcribed and translated? [duplicate]

Or is it somehow regulated if both or only one chromosome is transcribed/translated?
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72 views

When does a chromatid become a chromosome?

When chromosomes lie on the metaphase plate, they have the characteristic X shape. But these are actually two chromatids that are held together at the centromere. If separation fails and both ...
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86 views

What is the relation between chromomere & nucleosome?

I've been lately studying structure of chromosome where I got these two terms. I got many definitions of them. Nucleosome: The basic structural sub-unit of chromatin, consisting of $\sim 200$ base ...
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103 views

Clarification on the “orientation” of chromosomal rearrangements

I need some clarifications on the concept of "orientation" in case of chromosomal rearrangements. Given a deletion event on a chromosome for example, is the resulting DNA at the breakpoint always in ...
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1answer
156 views

Which of the two chromosomes in a pair is expressed?

I have completely dummy question. I have 23 pairs of chromosomes in the cells 23 single coming from my mother and 23 single from my father. So how my cell choose which chromosome, mother's or ...
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22 views

Mitotic chromosome condensation screen

If I want to screen for mutant yeast (S. cerevisiae) colonies that have defects in mitotic chromosome condensation, can I screen for colonies arrested in Mid-M phase? Would that work?
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31 views

Transcription when Chromosomes are Condensed

Are genes transcribed just as well when chromosomes are condensed? I want to design a screen that depends on genes not transcribed when chromosomes are condensed (to identify cells that can't ...
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1k views

Chromosome 2 fusion?

I read this article by Jeffrey Tomkins and Jerry Bergman claiming to debunk chromosome 2 fusion. Is there anything wrong with these conclusions? " 1.The reputed fusion site is located in a ...
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1answer
110 views

What is a holocentric chromosome?

I was doing this question that asked: "How many centromeres does a typical chromosome have?" I thought one and the answer was:"One, except for holocentric chromosomes." So then what are ...
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89 views

Whole Genome Sequencing and Chromosome Counts

In general, do standard whole genome sequencing techniques rely more on known chromosome counts, independently arrive at chromosome counts, and/or not directly address issues such as base number, ...
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78 views

How do we know Denisovans had 46 Chromosomes

What allows sequencers to conclude that Denisovans had 46 chromosomes rather than merely knowing Denisovans had the crossover material arranged in 48 or say 44 chromosomes? See ...
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4answers
5k views

Why is polyploidy lethal for some organisms while for others is not?

Polyploidy is the multiplication of number of chromosomal sets from 2n to 3n (triploidy), 4n (tetraploidy) and so on. It is quite common in plants, for example many crops like wheat or Brassica forms. ...
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55 views

Differing Flow Cytometry Genome Sizes and Sexual Mating Implies Differing Chromosome Counts

Do the fundamental principles of genetics strongly suggest the following is a derived conjecture? If 2 flowering plant species A and B have widely differing genome size (at a minimum a 50% ...
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275 views

How does the molecular machinery choose where to cut a chromosome for recombination?

I'm wondering about a few technicalities of crossover in meiosis. The point of crossover is to create new chromosomes that don't have the same allele combinations as the original two chromosomes. ...
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158 views

Explanation about cytogenetic notation

What is the correct meaning of cytogenetic notation "inv(4)(p13q22)" ? Inversions at chromosome 4, at the p arm 13 is inverted AND at q arm 22 is inverted OR Inversions at chromosome 4, the ...
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Are genes uniformly dispersed throughout the genome?

I think that telomeres and centromeres are regions with a very low gene content (= regions that contain few genes). To the exception of telomeres and centromeres, are genes uniformly distributed ...
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79 views

How does chromosome fusion get fixed in the population?

It's well known that one of human chromosomes is the result of fusion between two chromosomes in a primate ancestor. If we put anthropocentrism aside, it becomes clear that fusion events happened a ...
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77 views

Referencing the homologous chromosomes

There exist a co-ordinate system from chromosomes like "12p11.3". In this system, first integer range from 1 to 23 i.e it takes homologous chromosomes as a pair. If we want to distinguish among ...
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308 views

What determines the number of chromosomes an organism carries?

This is an extension of this question about What limits chromosomal length?. I am wondering what could be the specific reasons behind the number of chromosomes an organism carries. In other words, ...
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645 views

What does it mean to “map the human genome”

I know some elementary chemistry and biology. I also think I know what a gene is (it's a sequence of DNA which encodes a particular protein). I also know that on a chromosome there are sections of DNA ...
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3k views

Are human chromosomes connected or separate molecules?

Do the 46 human chromosomes form a single unbroken DNA helix? Or is it rather that a human's genome consists of 46 disconnected helices? If it is the former, does the common numbering scheme for ...
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3answers
1k views

Is the size of the genome across species roughly the same?

Chromosome number differs across species. Is the amount of DNA comparable between organisms, just being split into smaller chunks in those species with more chromosomes? Or do species have different ...
11
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1answer
143 views

What limits chromosomal length?

What are the upper and lower limits for chromosome length? Are these limits different in different species or kingdoms? If there is any limit, which cellular or molecular factors are reasons?
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118 views

From a computer science perspective, how is DNA compared for various purposes?

I am very interested in privacy preserving technolgies, such as Microsoft PINQ and would like to see if this is applicable to DNA comparison. Given that I don't have a background in biology, I ...
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147 views

Interlocus Contest Evolution means suicide?

I was reading Matt Ridley's "Genome" book. I am trying to understand the Interlocus Contest Evolution in his X-Y chapter. I do not understand why the X and Y chromosome would want to kill each other. ...
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134 views

Chromosome picture, how to interpret?

In this guide i was reading for annotations, there is a diagram of chromosomes of D.mel, I am confused as to why the chromosomes are all attached to one another, is this picture taken in a certain ...
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1answer
57 views

Why do genes with closely related functions often reside on different chromosomes?

Why do genes with closely related products are so often positioned on different chromosomes? To illustrate what I mean, here is an example from immunology: the invariant region of MHC is on ...
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90 views

Do the eggs for larger litters come from the same meiosis events, or different ones?

There are some species of animals that give birth to more than one pup at a time. In these species, are the fertilized eggs all from one or a limited group of meiosis processes, or are they from ...
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286 views

Why is it harder to sequence plant genomes than animal genomes?

Plants seem to be less complex organisms than animals, but despite that there are less plant genomes sequenced. Is that because plant genomes are more complex, for example in terms of regulatory ...
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1answer
59 views

What pattern can be learned from the data of RNA seq counts and HiC matrix? [closed]

I now have some data on the RNA seq counts and related Hi-C matrix of gene segment on a chromosome. My concern is, basically, what can we do with these data so as to establish the connection between ...
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188 views

Epistasis Across Chromosomes and Individuals 'Homozygous for Interactions'

Apologies for any failures in nomenclature. I'm a mathematician who is making a foray into genetics for a masters thesis. Specifically, I'm generating artificial diploid genetic sequence data and ...
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293 views

Barr body Giemsa staining

Why not all the female cheek cells show Barr Bodies when stained with Giemsa stain?? only 30 to 40 % female cells showed Barr Bodies . Why?
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How to engineer chromosomal duplications?

Specific genetic engineering of chromosomal aberrations like deletions, inversions and translocations are doable by using the CRISPR/Cas system or the other programmable nuclease systems. Insertions ...
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1answer
101 views

How was the origin of CTVT parasitic cancer determined?

The wikipedia article on CTVT says that the tumor cell has 57-64 chromosome while a normal dog has 78 chromosomes. Similarly while all chromosomes in dogs except the X and Y chromosomes are ...
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2answers
3k views

What effect does the Barr body have, in relation to female Turner syndrome?

Why do persons with Turner syndrome have developmental abnormalities, when normal XX-females do not, even though they only have 1 active X chromosome? From what I know, one X-chromosome is ...
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40 views

How much difference in genome is enough to prevent interbreeding? [closed]

I am not a biologist. I am a software developer interested in genetic algorithms therefore i am probably talking to biologists who also have a knowledge of genetic algorithms. I need to "breed" ...
4
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1answer
124 views

Does DNA analysis allow determining amount of chromosomes?

Nowadays it is possible to sequence the DNA of extinct species, such as the Neanderthals, the Denisovans, and others. Is it possible to determine, solely from the sequenced DNA or from known bone ...