chapter 10 part 1 Flashcards
(88 cards)
1
Q
genome content, chromosome number, and relative size/shape of each chromosome are __________________
A
species-specific
2
Q
closely related species have _________ numbers of chromosomes
A
similar
3
Q
do chromosomes occupy the same territory in each nucleus?
A
no
4
Q
once confined to a territory, what happens to a chromosome
A
chromosome doesn’t leave until the M phase is initiated
5
Q
what do chromosomes do within their territories
A
active and move, turn during transcription and DNA replication
6
Q
how do chromosomes appear to be anchored to their territories?
A
by their centromeres
7
Q
inter-chromosomal domains
A
regions between territories
8
Q
what do inter-chromosomal domains act as?
A
channels for movement of proteins, enzymes, and RNA molecules
9
Q
larger, more gene-rich chromosomes are usually found where?
A
center of the nucleus
10
Q
smaller, less gene-rich chromosomes are usually found where?
A
near periphery of nucleus
11
Q
what do karyotypes allow for
A
recognition of abnormalities in chromosome number or structure
- also comparison between species
12
Q
what elements can be easily identified in a karyotype
A
- extra/missing chromosomes
- rearrangements (insertions, deletions)
13
Q
in situ hybridization
A
uses molecular probes (DNA/RNA sequences) labeled with fluorescent to detect their target sequences
14
Q
first-generation methods used nucleotide probes labeled with
A
P32
15
Q
fluorescent in situ hybridization (FISH)
A
use multiple fluorescently colored labeled so each labeled chromosome can be identified with different wavelengths
16
Q
short arm of chromosome
A
p
17
Q
long arm of chromosome
A
q
18
Q
metacentric
A
centromere is near the middle of the chromosome
19
Q
submetacentric
A
centromere is between the center and the tip
20
Q
acrocentric
A
centromere is close to one end
21
Q
telocentric
A
centromere is at tip of chromosome and there is no p arm
22
Q
acentric
A
piece of DNA without a centromere
23
Q
heterochromatin
A
- more condensed
- silenced genes (methylated)
- stains darker
- more repetitive DNA
24
Q
euchromatin
A
- less condensed
- actively expression genes (acetylated)
- stains lighter
- less repetitive DNA
25
chromosome banding allows cytogeneticists
cytogeneticists can identify each chromosome in a karyotype
26
standard for human chromosome banding
G (Giemsa) banding - patterns distinct and reproducible
27
how many genes in human genome
22,000
28
2000 Giemsa bands
- average of 11 genes/band (both light and dark)
- assume all bands have equal number of genes
29
light Giemsa bands =
euchromatin
30
dark Giemsa bands =
heterochromatin
31
how are designations stated
1q3.2.3
- numbering begins at the centromere and progresses outward in each direction
32
chromosome nondisjunction
failure of homologous chromosomes or sister chromatids to separate as they normally do during cell division
33
what can chromosome nondisjunction result in
- abnormalities in chromosome number (aneuploidy)
- somatic cells: one daughter w extra chromosome (2n+1) and other missing (2n-1)
34
mitotic nondisjunction
- if at 1st division (zygotic) all cells aneuploid
- if later in development, aneuploid sectors in an organism
35
meiotic nondisjunction
- aneuploid haploid organisms (n+/-1)
- aneuploid gametes (n+/-1) leading to aneuploid zygotes
- increased frequency if crossing-over fails
36
result of nondisjunction in germ-line cells
aneuploid gametes that can produce aneuploid zygotes
37
nondisjunction in meiosis I results from
failure of homologs to separate
38
gametes produced from nondisjunction in meiosis I
n+1 or n-1
39
fusion of n+/-1 gametes with normal n gametes produces...
trisomic (2n+1) or monosomic (2n-1) offspring
40
nondisjunction in meiosis II results from
failure of sister chromatids to separate normally
41
gametes produced from nondisjunction in meiosis II
- 2 normal gametes
- one (n+1)
- one (n-1)
42
what do changes in gene dosage lead to
imbalance of gene products from the affected chromosome relative to the unaffected chromosome
43
aneuploidy laters the dosage of what?
all the genes on the affected chromosome
44
how much more product is produced in trisomies
50% more
45
how much less product is produced in monosomies
50% less
46
do animals or plants tolerate gene dosage changes more readily?
plants
47
do aneuploids usually survive?
no
48
what trisomies are usually seen in newborn infants
13, 18, and 21
49
can sex chromosomes have viable monosomies or trisomies in humans
both
50
Pallister-Killian Syndrome
occurs due to presence of anomalous extra isochromosome 12p (short arm)
51
isochromosome
unbalanced structural abnormality in which the arms of the chromosome are mirror images of each other
52
what does Palliester-Killian syndrome lead to
development of Tetrasomy 12p
53
symptoms of Pallister-Killian syndrome
- hypotonia
- intellectual disability
- distinctive facial features
- sparse hair
- unusual skin coloring
- birth coloring
54
how is Pallister-Killian a mosaic condition
because not all cells have the extra isochromosome
55
what do studies that monitor human pregnancies indicate
half of all conceptions spontaneously abort during the first trimester
56
more than half of the spontaneously aborted pregnancies carry what?
abnormalities of chromosome number or structure
57
research has identified a link between trisomy 21 and what?
advanced maternal age (anyone over 35)
58
what are responsible for cognitive disabilities and heart abnormalities in trisomy 21?
small number of genes on chromosome 21
59
DSCR (Down Syndrome Critical Region)
correlated with majority of DS symptoms
60
DYRK
candidate gene known to produce dosage-sensitive learning defects in mice and flies, makes major contribution to down syndrome
61
DSCAM gene in mice and fruit flies
has homolog associated with formation of the heart and nervous system
62
Turner syndrome
monosomy of X chromosome with no second sex chromosome
63
what does Turner syndrome produce
phenotypically sterile females
64
SHOX gene in XO embryos
single copy of gene, which is not activated by dosage compensation, is insufficient to direct normal development (haploinsufficient)
65
what does mosaicism result from
mitotic nondisjunction early in embryogenesis
66
ex. of Turner syndrome and mosaicism
25-30% of cases occur in females mosaic w:
- 46 XX cells
- 45 XO cells
- 47 XXX cells
67
uniparental disomy
both copies of homologous chromosome pair arise from same parent
68
what was uniparental disomy first identified in connection with
- Angelman syndrome
- Prader-Willi syndrome
- caused by deletion of a small region of chromosome 15
69
possible mechanisms of uniparental disomy
- same chromosome (15) undergoes nondisjunction in both sperm and egg - when they unit, produce ind. w/ 2 copies of chromosome 15 from only 1 parent
- more often: nondisjunction occurs in one parent to produce gamete w/ 2 copies of chromosome - units with normal gamete to produce trisomic zygote - trisomy rescue
70
trisomy rescue
one copy of trisomy chromosome is randomly ejected in one of the first mitotic divisions after fertilization
- if 2 copies retained by zygote are from same parent, uniparental disomy results
71
polyploidy
presence of 3+ whole sets of chromosomes in the nucleus of an organism
72
autopolyploidy
duplication of chromosome sets within species
73
polyploidy in plants typically increases
fruit and flower size
74
allolpolyploidy
combining chromosome sets of different species
75
what do allolpolyploids result in
interspecific hybrid offspring that is infertile because the chromosome sets are not homologous
76
allopolyploidy involves sets of ________ homologous chromosomes
partially - homologous
77
how can a hybrid be fertile in allolpolyploidy
chromosome nondisjunction leads to cells with double the number of chromosomes, so now each chromosome has homolog for pairing
78
how do allopolyploids occur
naturally or via human manipulation
79
fertility is decreased in _____-numbered polyploids
odd (3n, 5n)
80
hybrid vigor
more rapid growth, increased fruit/flower production, improved resistance to disease of polyploids
81
Triticum aestivum
- bread wheat (2n = 42) = natural allolpolyploid
- appears to be hexaploid (6x=42) = six sets of similar chromosomes from at least 3 separate varieties
82
what are commercial bananas and seedless watermelons
triploids
83
plant monoploids can be induced to grow from what?
1n cells in anthers
84
G. Karpechencko
wanted plant with cabbage leaves and radish roots to solve world hunger
85
cabbage leaves/radish root plants
- each species has 18 chromosomes
- induced fusion of gametes generated sterile hybrids
- eventually produces seeds, had 36 chromosomes
86
why did the cabbage/radish plant have 36 chromosomes
derived from spontaneous doubling of chromosome number which allows proper pairing at meiosis
87
amphidiploid
interspecific hybrid having a complete diploid chromosome set from each parent form
88
what is amphidiploid also called
allotetraploid (doubled diploid)
