Genetically speaking, the aardvark is a living fossil, as its chromosomes are highly conserved, reflecting much of the early eutherian arrangement before the divergence of the major modern taxa.

By some estimates, this might account for most of the internal radiation damage, as the recoil nuclei are typically heavy metals which preferentially collect on the chromosomes.

Most multicellular organisms have two sets of chromosomes, that is, they are diploid.

These chromosomes are referred to as homologous chromosomes.

Thus, ocular albinism occurs more frequently in males as they have a single X and Y chromosome, unlike females, whose genetics are characterized by two X chromosomes.

Some of these are challenging to sequence because they have more than two haploid ( n ) sets of chromosomes, a condition known as polyploidy, common in the plant kingdom.

The genes within these chromosomes are the cell's nuclear genome.

The interior of the nucleus does not contain any membrane-bound subcompartments, its contents are not uniform, and a number of subnuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes.

Typically, eukaryotic cells ( cells with nuclei ) have large linear chromosomes and prokaryotic cells ( cells without defined nuclei ) have smaller circular chromosomes, although there are many exceptions to this rule.

In eukaryotes, nuclear chromosomes are packaged by proteins into a condensed structure called chromatin.

In a series of experiments beginning in the mid-1880s, Theodor Boveri gave the definitive demonstration that chromosomes are the vectors of heredity.

A and B chromosomes are very similar, forming right-handed helices, while Z-DNA is a more unusual left-handed helix with a zig-zag phosphate backbone.

The physical strength of chromatin is vital for this stage of division to prevent shear damage to the DNA as the daughter chromosomes are separated.

M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's chromosomes are divided between the two sister cells, and cytokinesis, in which the cell's cytoplasm divides in half forming distinct cells.

It is now believed that this complex is mostly released from chromosome arms during prophase, so that by the time the chromosomes line up at the mid-plane of the mitotic spindle ( also known as the metaphase plate ), the last place where they are linked with one another is in the chromatin in and around the centromere.

During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes.

In fact, Dobzhanksy, for instance, worked quite a bit on so-called lethal chromosomes which are highly successful in one combination, and lethal in another.

Recent DNA analysis have revealed that Y chromosomes, tracing male descent, are 87 % Scandinavian.

Three DNA types are of particular interest: mitochondrial DNA that we all possess and that is passed down with only minor mutations through the matrilineal ( direct female ) line ; the Y-chromosome, present only in males, which is passed down with only minor mutations through the patrilineal ( direct male ) line ; and the Autosomal DNA, which is found in the 22 non-gender specific chromosomes ( autosomes ) inherited from both parents, which can uncover relatives from any branch of the family.

In 1911, Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies.

A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes.

This single set of chromosomes is duplicated in the egg, which develops parthenogenetically.

In G < sub > 1 </ sub > stage each of the chromosomes consists of a single ( very long ) molecule of DNA.

Even changes in the number of chromosomes can be accounted for by intermediate stages in which a single chromosome divides in generational stages, or multiple chromosomes fuse.

Well-studied biological nucleic acid molecules range in size from 21 nucleotides ( small interfering RNA ) to large chromosomes ( human chromosome 1 is a single molecule that contains 247 million base pairs ).

The number of chromosomes in a single ( non-homologous ) set is called the monoploid number ( x ), and is distinct from the haploid number ( n ).

Haploid individuals of this species have a single chromosome, and diploid individuals have two chromosomes.

Strasburger used diploid to refer to an organism with twice the number of chromosomes of a haploid organism, hence " double " and " single ".

This is distinct from the monoploid number ( x ), which is the number of unique chromosomes in a single complete set.

( A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.

This image shows haploid ( single ), diploid ( double ), triploid ( triple ), and tetraploid ( quadruple ) sets of chromosomes.

Meiotic recombination allows a more independent selection between the two alleles that occupy the positions of single genes, as recombination shuffles the allele content between homologous chromosomes.

Introgression involves the crossing of closely related plant relatives, and results in the transfer of ' blocks ' of genes, i. e. larger segments of chromosomes compared to single genes.

Polyploid cells have multiple copies of chromosomes and haploid cells have single copies.

# Squashing the preparation on the slide forcing the chromosomes into a single plane

By contrast, mosses and other bryophytes have only a single set of chromosomes and so are haploid ( i. e. each chromosome exists in a unique copy within the cell ).

When they separate ( during anaphase of mitosis and anaphase 2 of meiosis ), the strands are called daughter chromosomes ( although having the same genetic mass as the individual chromatids that made up its parent, the daughter " molecules " are still referred to as chromosomes much as one child is not referred to as a single twin ).

( The gametes of diploid organisms contain only single unpaired chromosomes and are called haploid.

A multicellular generation with a single set of chromosomes – the haploid gametophyte – produces sperm and eggs which fuse and grow into a multicellular generation with twice the number of chromosomes – the diploid sporophyte.

It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes.

Eukaryotes ( cells with nuclei such as those found in plants, yeast, and animals ) possess multiple large linear chromosomes contained in the cell's nucleus.

In addition, most eukaryotes have a small circular mitochondrial genome, and some eukaryotes may have additional small circular or linear cytoplasmic chromosomes.

In contrast, eukaryotes have longer linear chromosomes and initiate replication at multiple origins within these.

However, the process of binary fission is very much different from the process of mitosis, because of the non-involvement of nuclear dynamics and lack of linear chromosomes.

For example, bacterial chromosomes, plasmids, mitochondrial DNA and chloroplast DNA are usually circular double-stranded DNA molecules, while chromosomes of the eukaryotic nucleus are usually linear double-stranded DNA molecules.

Tree-like representations are explored in genetic programming and graph-form representations are explored in evolutionary programming ; a mix of both linear chromosomes and trees is explored in gene expression programming.

These complex computer programs are encoded in simpler linear chromosomes of fixed length, which are afterwards expressed as expression trees.

The human genome is organized into chromosomes ( very large linear DNA molecules contained within the cell nucleus ) and the small mitochondrial DNA ( a comparatively tiny circular DNA molecule ).

Telomeres are repetitive nucleotide sequences located at the termini of linear chromosomes of most eukaryotic organisms.

A small fraction of bacterial chromosomes ( such as those in Streptomyces and Borrelia ) are linear and possess telomeres, which are very different from those of the eukaryotic chromosomes in structure and functions.

The known structures of bacterial telomeres take the form of proteins bound to the ends of linear chromosomes, or hairpin loops of single-stranded DNA at the ends of the linear chromosomes.

Telomerase is a reverse transcriptase that lengthens the ends of linear chromosomes.

And gene expression programming successfully explores a genotype-phenotype system, where the genotype consists of linear multigenic chromosomes of fixed length and the phenotype consists of multiple expression trees or computer programs of different sizes and shapes.

* Gene expression programming-Like genetic programming, GEP also evolves computer programs but it explores a genotype-phenotype system, where computer programs of different sizes are encoded in linear chromosomes of fixed length.

Each of these genomes forms a chromosome with a linear structure, unlike most bacterial genomes, which exist in the form of circular chromosomes.