Genetics: Chapter 8
_____% of genes escape transcriptional silencing in X inactivation
15
Approximately _____% of all recognize pregnancies in human beings end in ____ ______, and in about _____ of all spontaneous abortion, the fetus has a major _____ _____.
15 spontaneous abortion half chromosome abnormailty
For all organisms with XX-XY sex determination, there is a problem of the dosage of genes on the X and Y chromosome, because females have ____ copes of this chromosome whereas males have only _____. There is less of a problem for Y-linked genes because the Y chromosome is largely _____ and carries relatively _____ genes. In most organisms, a mechanism of ____ _____ had evolved in which the unequal dosage in the sexes is corrected either by _____ activity of genes in the X chromosome in the males or by ______ the activity of genes in X chromosome in females.
2 1 heterochromatic few dosage compensation increasing reducing
A Robertsonian translocation can join chromosome _____ to any other ______ chromosome
21 acrocentric
The standard human karyotype consists of a ____ pairs of ______ and _____ pair of ______ chromosome.
22 autosome 1 sex
Approximately _____% of males have some form of red-green color blindness. It is a typical _____ -linked inheritance. Affected males have _____ sons and _____ daughters, and the ______ daughter have ______ % affected sons and ____ % percent carrier daughter.
5 X normal carrier carrier 50 50
4 Chromosome structural aberrations
Deletion Duplication Inversion Translocation
pseudoautosomal regions
PAR
mosaic phenotype due to variation in the level of expression of a gene in different cell lineages owing to its position in the genome.
PEV
Telomerase contains an internal _____ template
RNA
DNA polymerase can not initiate DNA synthesis by itself, but instead requires an _____ ____ . At the end of a chromosome, the primer terminates the _____ end of the Newly synthesized DNA. When the primer is removed, the end has a short ___-____ nt.
RNA PRIMER 5' 8-12
In female mammals, one of the two _____ chromosomes is inactivated. This is a mechanism of _____ _____.
X dosage compensation
A chromosome that lacks a centromere is _____ chromosome.
acentric
Human ancestors had 24 pairs of chromosomes rather than 23. Two ______ chromosomes fused to create human chromosome 2
acrocentric
species have complete sets of chromosome from two or more diferent ancestral species
allopolyploids
_____ is when two (or more) different genomes are duplicated.
allopolyploidy
refers to a cell or organism in which the chromosome number is not an exact multiple of the haploid number
aneuploid
refers to a condition in which particular genes or chromosomal regions are present in extra or fewer copies compared with wildtype.
aneuploidy
______ is when all the genomes are the same.
autopolyploidy
all chromosome in the polyploidy species derive from a single diploid ancestral species through sexual or asexual polyploidization.
autopolyploidy
Two ways to form deletions: One is by chromosome ____ and ______. The other is that deletion can be also created by ______ recombination between _____ DNA sequences present at different sites along the DNA, a process known as ____ _____.
breakage reunion homologous repeated ectopic recombination
Genes near the _____ of chromosomal rearrangement become ______ in the genome and flanked by new neighboring genes. In many cases, the repositioning of a gene affects its level of expression or, in some cases, its ability to function, this is called _____ ______.
breakpoints repositioned position effect
specific region of the eucharyotic chromosome that becomes visible as a narrow constriction along the condensed chromosome.
centromere
The _____ serves as a central component of the kinetochore, the complex of DNA and proteins to which the spindle fibers attach in order to move the chromosomes in both mitosis and meiosis. The ______ is also the site at which the spindle fibers shorten, causing the chromosome to move toward the poles. Electron microscopic analysis has shown that in some organisms, _____ spindle-protein fiber is attached to centromeric chromatin. Most other organisms have _______ spindle fibers attached to each centromeric region.
centromere kinetochore single many
Structure of a yeast centromere: centromere DNA has four _______ _____ ____ (______)
centromere determining elements
Creation of a diploid from a nondiploid can be done by treatment with _____, which inhibits formation of the ____ _____.
colchicine mitotic spindle
Monoploid is sterile can be converted into a homozygous diploid by treatment with the substance _____. This chemical is an inhibitor of the formation of the ____ ____. Most of cells are killed, but many of the now-diploid cells can develop into a complete plant, such plant which are completely homozygous, are fertile ad produce normal seeds.
colchicine mitotic spindle
The inactivation process is one of chromosome ______ initiated at a site called _____ (_____-_____ _____) near the ______.
condensation XIC X-inactivation center centromere
No ____ _____ within an inversion allows normal chromosome separation
crossing over
Unequal crossing over can lead to an increase or _____ in the number of ______.
decrease repeats
Ectopic recombination between direct repeats in the same DNA molecule results in _____ of the material between the repeats
deletion
Ectopic recombination can create ______.
deletions
an inability to perceive green
deuteranopia
A chromosome that has two centromeres is said to be ______.
dicentric
The products of the crossing over include a ____ and an _____ chromosomes. Neither the dicentric chromosome nor the acentric chromosome can be included in a ______ gamete. When there is a crossover take place in the inversion loop, the only chromatids that can be recovered in the gametes are the chromatids that did ____ participate in the crossover.
dicentric acentric normal not
Crossing over in a paracentric inversion creates _____ and ______ chromosomes
dicentric and acentric
A mechanism regulating X-linked genes such as that their activities are equal in males and females.
dosage compensation
male; taller than average, slighly impaired mental function, at a high risk of committing crimes
double Y (47,XXX)
Unequal crossing over of tandem repeats
duplication
Some abnormal chromosomes have a regions that present twice, which is a ______. _____ duplication are able to produce even more copies of the duplicated region by means a process called ____ _____ ____.
duplication tandem unequal crossing over
Most structural abnormalities in chromosome are _____, ____, ____, and ____.
duplication deletions inversions translocations
recombination between homologous DNA sequences present at nonhomologous sites in the genome.
ectopic recombination
In polyploidy, the ______ chromosome complement is multiplied
entire
PEV usually results form a chromosome aberration that moves a wildtype gene from a position in ______ to a new position in or near ______.
euchromatin heterochromatin
refers to a cell or organism having a chromosome number that is an exact multiple of the haploid number such as triploid, tetraploid etc.
euploid
The symbol rob refers to the translocation and the + and - sign designates a an ____ copy or a ______ copy of the entire chromosome.
extra missing
Unequal crossing over can occur in ____ ____ genes
eye pigment
Human chromosome 2 may have arisen by _____ of two shorter chromosomes
fusion
chromosome set is the set of chromosomes present in a gamete, irrespective of the chromosome number in the species.
haploid
Some chromosome are composed of primarily ______ (e.g. Y chromosome in D. melanogaster.
heterochromatin
chromatin that remains condensed and heavily stained during interphase.
heterochromatin
commonly present adjacent to the centromere and in the telomeres of chromosomes.
heterochromatin
An organism that is ______ for a reciprocal translocation usually produces only about ______ as many offspring as normal- a condition called _______. The reason for the _____ is production of unbalanced gametes in meiosis. When meiosis take place in a ______ heterozygote, the normal and translocated chromosomes must undego synapsis, as shown.
heterozygous half semisterility semisterility transclocating
appear to have centromeric sequences spread throughout their length (also called a ____ ____).
holocentric centromere (diffuse centromere)
a protein complex which is recruited to the X chromosome which decreases the level of transcription of each X chromosome by half.
in females of C' elegans
a complex including at least one male-specific protein is recruited to the x-chromosome, which alters it s chromatin structure, most likely by acetylation of a specific lysine in histone H4. This results in an increase in the transcriptional activity of the single X chromosome in males a level equal to the sum of that both X chromosome in females.
in males of drosophila
Probability of a child with Down syndrome _____ with mother's age.
increases
Translocation can be formed by an _____ of parts between two _____ chromosomes or by _____ ______ between copies of repeated DNA sequences
interchange broken ectopic recombination
Another important type of chromosome abnormality is an ______, a chromosome in which the linear order of a group of genes is the reverse of the normal order.
inversion
Ectopic recombination between inverted repeats results in _____
inversion
In organism that is heterozygous for an _____, one chromosome is wildtype and the other carries an inversion. There chromosome pass through _____ without difficulty, but maybe be a problem in ______.
inversion mitosis meosis
Homologous chromosome pairing in an inversion heterozygote... The loop formed is called an _____ ______.
inversion loop
A ______ shows arranged chromosome pairs
karotype
______ is the chromosome complement of a cell or organism; often represented by an arrangement of _____ chromosomes according to their length and the positions of their ______.
karotype metaphase centromere
male, tend to be tall, no sex maturation and sterile, enlargement of breast, mild mental impairment.
klinefelter syndrome (47,XXY)
______ centromere (conventional type) fall into two categories: _____ centromeres and ______ centromeres. In both cases, microtubules attach to a single region of the chromosome (the ______).
localized point regional kinetochore
In _____, at roughly the 64-128 cell stage of embryo, one and only one X chromosome in each, chosen at random, remains genetically active, and all the other x chromosomes undergo a process of x-inactivation.
mammals
Dosage compensation in ______ results from genetic inactivation of X chromosome at an early stage in ______ development. Some genes in the "inactive" X chromosome are not _____.
mammals embryonic inactivated
Remember that during _____, the homologous chromosomes pair up in the process of ______. In an inversion heterozygote, in order for gene-for-gene pairing to take place everywhere along the length of the chromosome, one or the other chromosome must ____ into to a ______ in the region in which the gene is inverted. The loop is called ____ _____. As long as no ____ ____within the inversion, the homologous chromosomes can separate normally at _____ I.
meiosis synapsis twist loop inversion loop crossing over anaphase
Major symptoms of down syndrome: ___ _____ _____ stature Poor ____ tone ______ life span Other abnormalities: _____ defects
mental retardation small muscle short heart
An inversion can be formed by a two-break event in a chromosome in which the _____ segment is reversed in orientation ______ the breaks are ______. An inversion can also be created by _____ _____ between DNA sequences what are inverted repeats.
middle before healed ectopic recombination
A ______ copy of a chromosome usually results in more harmful effects than an _____ copy of the same chromosome. In human fertilization, ______ zygotes are probably created more greater numbers than ______ zygotes. But ______ is not found among aborted fetuses because the abortion take place so early in development that the pregnancy goes unrecognized by the mother.
missing extra monosomic trisomic monosomy
Euchromatin is visible only in the ______ cycle.
mitotic
chromosome set is the basic set of chromosome that is multiplied in a polyploid series of species such as Chrysanthemum.
monoploid
An organism is _____ if it develops from a cell with a single set of chromosomes. _____ can not take place normally in the germ cells of a monoploid. Because each chromosome lacks a pairing partner, and hence monoploids are usually _____.
monoploid Meiosis sterile
refers to an otherwise diploid organism that has an missing copy of an individual chromosome.
monosomy
Most of _____ and ______ are incompatible with life. There are three exceptions: trisomy ____, _____, and _____/
monosomy and trisomy 13 18 21
an individual composed of two or more genetically distinct types of cells
mosaic
The short arm is designated with the letter ____, which stands for " ______", Within each arm the regions are numbered. The first digit indicate the ______ number, followed by ______ or _____ arm. The first digit after p or q is the major region, numbered consecutively proceeding from the _____ toward the ______; within each region, the second number by indicated by a _____ placed after a _____ is the next-smaller division, again numbered outward from the _______.
p petite chromosome short long centromere telomere digit decimal centromere
The short arm of a chromosome is called "_____" and the long arm "_____".
p q
On the other hand, when there is crossing over within the inversion loop, the chromatid involved in the crossing over become physically _____, and the result is the formation of chromosome containing large duplications and deletions. The inversion in which the centromere is not included in the inverted region is known as a ______ inversion.
paracentric
Crossing over in a ______ inversion does not create dicentric and acentric chromosomes
pericentric
When the inversion does include the centromere, it is called a ______ inversion, which means around the centromere. Although both products are monocentric, chromatids with ____ and ______ are created. These chromosome with duplication and deficiency can be included in a gamete, but normally they causes ______. So again only the chromatids _____ participating in the crossover is recovered in the gametes.
pericentric deficiencies and duplications inviability not
_____ centromeres are found in a number of different yeasts including S. cerevisiae. Other eukaryotes have ______ centromeres that may contain hundreds of kilobases of repetitive DNA.
point regional
_____ organisms contain more than two compete sets of chromosome and is common in higher plants.
polyploid
_____` is often found in plants
polyploidy
a species has a genome composed of multiple complete sets of chromosome.
polyploidy
_____ _____ _____ (____) usually results from rearrangement that moves a gene.
position effect variegation (PEV)
If the crossover happens within mispaired red and green-pigment genes, a chimeric gene can be resulted in, which lead to _____ or _____.
protanomaly ceuteranomaly
an inability to perceive red
protanopia
Heterochromatin is highly _____ and low _____.
repetitive complexity
Creation of a _______ translocation: Two nonhomologous acrocentric chromosomes undergo fusion of their short arms
robersonian
Some genes in the inactivative X are not ______, some of genes that escape X inactivation have functional ______ in the Y chromosome, whereas others don't.
silenced homologs
Two reasons why extra sex chromosome have phenotypic effects that are relatively mild: The single active X principle results in the _____ of most X-linked genes Y chromosome contains relatively _____ functional genes. There are four most common types of sex chromosome abnormalities: Number _____ refers to the total number of chromosomes; ______ indicates that the person has three X chromosomes.
silencing few 47 XXX
A, B, C, etc. refer to grouping of chromosomes by _____ and ______ position.
size centromere
Replication of telomere DNA repeats by _____: RNA primer is removed, the complementary strand has a short _____-straned overhang at the ______ end. The single standed overhang is subject to degradation by _____. Without some mechaninism to restore the digested end, the DNA molecule in a chromosome would become slightly shorter with each replication. There is a mechanism for end restoration, which relies on an enzyme called ______. This enzyme works by adding tandem repeats of a simple sequence to the _____ end of a DNA strand.
telomerase single 3' exonuclease telomerase 3'
The RNA molecule in telomerase serves as the template for ______ DNA synthesis
telomere
Relatively few copies of the ______ repeats are necessary to prime the _______ to add more copies and form a telomere. Remarkably, the telomerase enzyme incorporates an essential RNA molecule, called a ___ _____, that contains sequences complementary to the telomere repeat and that serves as a template for ______ ______ synthesis and elongation. The complementary DNA strand of the telomere is synthesized exactly like the ______ strand in ordinary DNA replication.
telomere telomerase RNA guide telomere repeat lagging
Each end of a linear chromsome is composed of a special DNA-protein structure called a ______, which consists of the ____ ______ of simple sequences and associated proteins .
telomere tandem repeat
_____ are essential for chromosome stability.
telomeres
Two continuous regions that escape X inactivation are found at the ____ of the ____ and ____ arms. These are regions in which the _____ chromosome does remain functional homologous genes. These regions of homology enable X and Y chromosomes to synapse in _______, and a ______ takes place that holds the chromosomes together to ensure their proper segregation. The regions of shared X-Y homology define the _______ regions.
tips long short spermatogenesis crossover pseudoautosomal
A chromosome aberration resulting from the interchange of parts between nonhomologous chromosomes is called a _____.
translocation
has thee sets of chromosomes (total 69).
triploid
In a _____ organism, the segregation of chromosomes in _____ is upset because the ______ chromosome has two pairing partners
trisomic meiosis trisomic
refers to an otherwise diploid organism that has an extra copy of an individual chromosome.
trisomy
Chromosome abnormalities are an important cause of genetic disorders such as ____ _____ (down syndrome).
trisomy 21
____ _____ (Down syndrome; 1:750) is a viable condition, unlike most trisomies.
trisomy 21
female, mild mental impairment
trisomy X (47,XXX)
female, short in stature and without sexual maturation, normal mental abilities.
turner syndrome (45,X)