ch6-partI

A chart of chromosome cutouts arranged from largest to smallest, used to identify abnormalities in chromosome number and structure.

The wheat genome is roughly five times the size of the human genome.

The short arm is denoted by the letter p.

The long arm is denoted by the letter q.

To recognize each of the duplicated chromosomes by its size, shape, and banding pattern.

A body where all the centromeres congeal, with chromosome arms emanating out of it.

It is used to determine whether disease conditions are associated with chromosome abnormalities.

Feulgen’s reagent and aceto-carmine.

Giemsa stain is a mixture of dyes used to stain chromosomes after they are treated with trypsin. It interacts with the remaining proteins on the chromosomes to produce a reproducible pattern of bands.

Tetraploid zygotes, which survive because each parental set of chromosomes is balanced.

Larger grains, easier to harvest, and ability to grow in a wider range of conditions.

Polyploids created by hybridization between different species, where the contributing genomes are qualitatively different.

An ideogram is the pattern of bands within a chromosome.

Polyploidy is the condition of having extra sets of chromosomes.

It allows meiosis to proceed in good order, enabling the production of euploid gametes.

Because aneuploid pollen does not compete well with euploid pollen during pollen tube growth.

If their constituent genomes segregate independently.

A univalent is a solitary chromosome that is left without a partner during meiosis in a polyploid organism.

More than 17,000 varieties.

46 chromosomes—44 autosomes and two sex chromosomes (XX in females and XY in males).

A trivalent is a formation where all three homologous chromosomes synapse, each partially paired with the others.

The X chromosome is intermediate in size, and the Y chromosome is about the same size as chromosome 22.

Interphase.

Because chromosomes from different species are less likely to interfere with each other’s segregation during meiosis.

C. B. Bridges.

It causes cells to swell, diluting their contents and spreading out the chromosomes for easier analysis.

It is highly reproducible and specific for each chromosome, allowing cytogeneticists to identify particular chromosomes and determine if a chromosome is structurally abnormal.

21 chromosomes in the gametes and 42 in the somatic cells.

Triple-hybrid wheat contains the chromosomes of each of its progenitors, making it an amalgamation of the genomes of three different species.

Polyploids created by chromosome duplication within a single species, where a single genome has been multiplied to create extra chromosome sets.

A mechanism of asexual reproduction involving a modified meiosis that produces unreduced eggs, which then form seeds.

Because they undergo successive rounds of chromosome replication without cell division, producing large chromosomes.

Two of the three homologues synapse, leaving a univalent free to move to either pole during anaphase, or all three homologues synapse forming a trivalent.

Polyploids contain extra sets of chromosomes and are often sterile because their multiple sets of chromosomes segregate irregularly in meiosis.

About two-thirds of all grasses are polyploids.

In the Middle East, around 10,000 years ago.

More than 20 percent.

Duplicated chromosomes pile up next to each other, forming a bundle of strands aligned in parallel, resulting in polytene chromosomes.

About nine rounds of replication, producing approximately 500 copies in each cell.

DNA in only a few pairs of chromosomes.

About 850 bands.

It led to significant advancements in the study of chromosome number and structure.

Because chromosomes are most easily seen during this stage.

It has made it possible to study chromosomes in other types of cells, such as human white blood cells.

One-half of all known plant genera contain polyploid species.

Roses, chrysanthemums, and tulips.

Chromosome painting involves treating chromosome spreads with fluorescently labeled DNA fragments (probes) that bind to complementary DNA sequences in the chromosomes, creating colorful images that reveal the location of specific DNA sequences.

Triticum aestivum.

Chromosomes were arranged into groups according to size, with the largest classified as group A, the next largest as group B, and so forth.

Because zygotes formed by fertilization with aneuploid gametes are almost certain to die.

By propagating the species asexually through methods like cuttings, grafts, and bulbs.

The analysis of stained chromosomes.

They found that altered phenotypes were caused by dominant factors transmitted primarily through the female, and each mutant strain had an extra chromosome.

Aneuploidy is a numerical change in part of the genome, usually just a single chromosome.

48 chromosomes.

Polyploidy generally increases cell size.

Polyploid plants tend to produce larger seeds and fruits, providing greater yields in agriculture.

They do not allow a researcher to distinguish one chromosome from another unless the chromosomes are very different in size or in the positions of their centromeres.

A probe is a fluorescently labeled DNA fragment that binds to complementary DNA sequences in the chromosomes, labeling them with the fluorescent dye and revealing specific DNA sequences.

Syria, Iran, Iraq, and Turkey.

Chromosome 21.

An alphanumeric directory of sites along the length of each chromosome.

By chromosome duplication in a hybrid produced by crossing two different but related diploid species.

Euploid.

A condition where an organism has an extra chromosome, resulting in three copies of that chromosome.

The presence of extra chromosome sets.

Wheat, coffee, potatoes, bananas, strawberries, and cotton.

700 million metric tons.

Through two hybridization events followed by chromosome doubling, resulting in a hexaploid with three different chromosome sets.

Polytene chromosomes are bundles of aligned chromatin fibers, most spectacularly found in the salivary glands of Drosophila larvae.

Differential coiling along the length of the bundle causes variation in the density of the chromatin.

The denser chromatin stains more deeply, creating a pattern of dark and light bands.

Through mitosis without cytokinesis or altered meiosis producing unreduced gametes.

Because they contain two distinct sets of chromosomes, each duplicated, allowing regular meiosis.

Rapidly growing material such as animal embryos and plant root tips.

46 chromosomes.

Polyploid species tend to be larger and more robust than their diploid counterparts.

More than a billion people.

Chromosome 1.

The centromere divides each chromosome into long and short arms.

The centromeres of each of the chromosomes.

The banding pattern is highly reproducible, permitting detailed analysis of chromosome structure.

Nineteenth-century European biologists who discovered chromosomes and observed their behavior during mitosis, meiosis, and fertilization.

Euchromatin contains most of the genes and forms banded chromosome arms, while heterochromatin is gene-poor, surrounds the centromere, and does not become polytene.

Chromosome rearrangements are structural changes in chromosomes, such as a piece of one chromosome being fused to another or a segment within a chromosome being inverted.

To trap the chromosomes in mitosis, making them easier to see.

Polyploidy is rare in animals because it interferes with the sex-determination mechanism.

The resulting zygotes almost always die, leading to reduced fertility in polyploid species.

Quinacrine is a chemical relative of the antimalarial drug quinine. It stains chromosomes to show a characteristic pattern of bright bands on a darker background when exposed to ultraviolet (UV) light.

Chromosome painting with probes made from human DNA fragments labeled with different fluorescent dyes.

Banding and painting techniques.

It yields aneuploid cells.

A process that produces polyploid cells by chromosome duplication followed by separation of sister chromatids without cell division, resulting in extra chromosome sets within a single nucleus.

They pair precisely, point-for-point along their length, making the banding patterns of each perfectly aligned.

A numerical change in part of the genome, usually a change in the dosage of a single chromosome.

Hypoploid organisms have an underrepresented chromosome or chromosome segment, while hyperploid organisms have an overrepresented chromosome or chromosome segment.

Polyploidy is very common in plants but very rare in animals.

Extra sets of chromosomes may segregate irregularly in meiosis, leading to unbalanced (aneuploid) gametes.