chapter 5
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proteins _: they _
perform most of the cell’s functions: serve as building blocks for cell structures; they form the enzymes that catalyze the cell’s chemical reactions; they regulate the activity of genes; and they enable cells to move and to communicate with one another.
chro- mosomes contain both _ and _
DNA protein
DNA, after all, is simply a _ composed of _, which are _.
long polymer only four types of nucleotide subunits chemically very similar to one another
DNA=
deoxyribonucleic acid (DNA)
the two strands are held together by _ bonds
hydrogen
With the exception of the _ (_) and highly special- ized cells that _ (such as _), human cells each contain two copies of every chromosome, one inherited from the mother and one from the father.
gametes sperm and eggs lack DNA entirely mature red blood cells
Each chromosome can be “_” a different color using _
painted _ sets of chromosome-specific DNA molecules coupled to different fluorescent dyes.
An earlier and more traditional way of distinguishing one chromosome from another involves _.
staining the chromosomes with dyes that bind to certain types of DNA sequences _ These dyes mainly distin- guish between DNA that is rich in A-T nucleotide pairs and DNA that is G-C rich, and they produce a predictable pattern of bands along each type of chromosome. The resulting patterns allow each chromosome to be identified and numbered.
An ordered display of the full set of _ human chromosomes is called the human _
46 karyotype
_ analyze karyotypes to detect chromosomal abnormalities that are associated with some _ (Figure 5–9) and with certain types of _
Cytogeneticists inherited disorders cancer
A gene is often defined as a _
segment of DNA that contains the instructions for making a particular protein or RNA mol- ecule.
Together, the total genetic information carried by a complete set of the chromosomes present in a cell or organism constitutes its _.
genome
the total number of genes is about _ for the simplest bacterium and about _ for humans.
500 24,000
However, chromosomes from many eukaryotes—includ- ing humans—contain, in addition to genes and the specific nucleotide sequences required for normal gene expression, a large _
excess of interspersed DNA
DNA must be able to be replicated, and the replicated copies must be separated and partitioned equally and reliably into the two daughter cells at each cell division. These processes occur through an ordered series of events, known collectively as the _.
cell cycle
_, when chro- mosomes are duplicated, and _, the much more brief stage when the duplicated chromosomes are distributed, or segregated, to the two daughter nuclei.
interphase mitosis
One type of nucleotide sequence, called a _, is where DNA replication begins; eukaryotic chromosomes contain _ to _
replication origin many replication origins allow the long DNA molecules to be replicated rapidly
Another DNA sequence forms the _ that mark the ends of each chromosome. Telomeres contain _ that are required for the ends of chromosomes to be _.
telomeres repeated nucleotide sequences fully replicated
telomeres also serve as a _ that keeps the chromosome tips from _.
protective cap _ being mistaken by the cell as broken DNA in need of repair.
Eukaryotic chromosomes also contain a third type of specialized DNA sequence, called the _, that allows duplicated chromosomes to be separated during M phase (see Figure 5–14). During this stage of the cell cycle, the DNA coils up, adopting a more and more compact structure, ultimately forming highly compacted, or condensed, mitotic chromosomes
centromere
The proteins that bind to DNA to form eukaryotic chromosomes are traditionally divided into two general classes: the _ and the _ chromosomal proteins. The complex of both classes of protein with nuclear DNA is called _.
histones nonhistone chromatin
Histones are responsible for the first and most fundamental level of chromatin packing: the formation of the _.
nucleosome
The interphase nucleus is the _
nucleus of a cell when it is not dividing
Eukaryotic cells have several ways to adjust rapidly the local structure of their chromatin. One way takes advantage of a set _. These protein machines use the energy of ATP hydrolysis to change the position of the DNA wrapped around _
of ATP-dependent chromatin-remodeling complexes _ nucleosomes