Chapter 6 Flashcards
complete genome sequences involve???
genomes are larger and more complex: most eukaryotes– prokaryotes. Genome size does no appear to be related to genetic complexity. most eukaryotic genomes contain large amounts of noncoding DNA
bacteria, yeast, many plants, animals, including humans
Differences in sizes of eukaryotic genomes primarily reflects differences in amounts of ____ DNA
noncoding
noncoding sequences play roles in regulation of gene expression, and expanding coding potential by allowing genes to be expressed in __________-
alternate ways
A _____ is a segment of DNa that is expressed to yield a functional product
gene
noncoding DNA is found within most eukaryotic genes. Coding sequences in genes___ are separated by non coding sequences ____________
exons
introns
the entire gene is transcribed to RNA and the introns are then removed by _____, so only exon are included in the mRNA
splicing
Introns make up more than 90% of the average human gene. Introns are present in most,but not all, genes of complex eukaryotes.
almost all _____ lack introns
Introns are _____ in most gens of simple eukaryotes, such as yeast
introns are present in _______
most introns are conserved in genes of both plands and animals
almost all HISTONE GENES lack introns
introns are NOT FOUND in most gens of simple eukaryotes such as yeasts
introns are present in RARE GENES OF PROKARYOTES
Many introns encode functional products- proteins or noncoding RNAs.
introns allow exons of a gene to be joined in different combinations, resulting in different proteins from the same gene__________
alternative splicing
simple sequence repeats:???
These can be separated by equilibrium centrifugation in CsCl density gradients: AT-rich sequences are less dense than GC-riched sequences
such repeat- sequence DNAs band as “satellites” separate from the main band of DNA, and thus are called _____________
they are not transcribed but some play important roles in chromosome structures
tandem arrays of short sequences; 1-500 nucleotides.
satellite DNAs
Gene families are though to have arisen by duplication of an original ancestral gene, followed by mutation and divergence of different family members Results include:
- proteins optimized for different functions
- some mutation results in loss of function
prokaryotes have _________ chromosomes, ____ DNA
single chromosomes and circular DNA
eukaryotes has ____ chromosomes, a ______ molecule of DNA
multiple chromosomes, linear of DNA
The basic structure of chromosomes is the same in all eukaryotes (true or false)
true
define Chromatin:
a complex of DNA and proteins (major proteins are histones)
what are the five major types of chromatin?
H1, H2A, H2B, H3, H4 ; these are very similar among different species of eukaryotes
chromatin also contains many other proteins involved in activites such as ___________ and _________-
replication and gene expression
chromatin also contains many other proteins involved in activites such as ___________ and _________-
replication and gene expression
the __ is the basic structural unit of chromatin
nucleosome
the DNA is wrapped around histones in _______ and sealed by ___________. nonhistones proteins bind to linker DNA between nucleosome core particles
nucleosomes core particles
sealed by histone H1
147 base pairs of DNa is wrapped around a histone core to form ______. Histone H1 is bound to DNA where it enter the core particle—–this forms a ________________________-
nucleosomes core particles
chromatosome
the ________ contains ++++ base pairs of DNA wrapped 1.67 turns around a histone core consisting of TWO EACH of H2A, H2B, H3, and H4 (the core hstones)
nucleosome core particles
contain 147 base pairs
a ________ consists of 166 base pairs of DNA (2 full turns) wrapped around the histone core and held in place by H1 (a linker histone)
chromatosome
______ of DNA with histones yields a chromatin fiber approximately 10 nm in diameter, which shortens in length about sixfold.
it is further condensed by coiling into 30 nm fibers ,resulting in a total condensation of fityfold
packaging of DNA
an interphase (nondividing) cells, most of the chromatin (called ____________) is relatively decondensed and distributed throughout the nucleus
euchromatin
about 10% of interphase chromatin (called ____________) is in a very highly condensed state that resembles the chromatin of cells undergoing mitosis
heterochromatin
Heterochromatin: transcriptionally ____ and contains highly repeated DNA sequences
inactive
as cells enter mitosis, their chromosomes become ________________
highly condensed
at metaphase, the DNa has been ____ nearly ten-thousandfold
condensed
does transcripion occur during mitosis?
NO
what is the centromere?
it is a specialized region of a chromosome that helps ensure the correct distribution of duplicated chromosomes to daughter cells during mitosis
describe the breakdown of mitosis and what happens
- DNA is replicated during interphase, resulting in two copies of each chromosome
2 metaphase chromosomes consist of two identical sister chromatids, held together at centromere
- microtubules of the mitotic spindle attach to the centromere, and the two sister chromatids separate and move to opposite poles
- then the nuclear membrane reforms, and the chromosomes decondensed
each daughter nuclei contains one copy of each parental chromosomes
each daughter nuclei contains ___ copy of each parental chromosome
one
Centromeres are DNA sequences to which proteins bind, forming a ________
kinetochore
spindle microtubules bind to the _________
kinetochore
proteins associated with the kinetochore act as “____________” to drive the movement of chromosomes along the spindle fibers
molecular motors
what are telemeres
they are sequences at the end of chromosomes, and are required for the replication of linear DNA molecules
the ends of linear chromosomes cant be replicated by DNA polymerase. ________ uses reverse transcriptase activity to replicate telomeric DNA sequences
telomerase
maintenance of telomeres:
determines the life spand and reproductive capacity of cells
maintenance of telomeres:
determines the life spand and reproductive capacity of cells
