Chromosomes in eukaryotes

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‫به نام پروردگار‬
‫زیست شناس ی سلولی و مولکولی‬
‫هسته سلول‬
‫اطالعات ژنومی‬
‫• پروکاریوت‪ :‬فاقد هسته حقیقی‬
‫• یوکاریوت‪ :‬واجد هسته حقیقی‬
‫• ویروسها‪،‬ویروئیدها‪:‬؟‬
Chromosomes in eukaryotes and
prokaryotes are different
PROKARYOTES
EUKARYOTES
single chromosome plus plasmids
many chromosomes
circular chromosome
linear chromosomes
made only of DNA
made of chromatin, a
nucleoprotein (DNA coiled
around histone proteins)
found in cytoplasm
found in a nucleus
copies its chromosome and divides copies chromosomes, then the
immediately afterwards
cell grows, then goes through
mitosis to organise
chromosomes in two equal
groups
© 2007 Paul Billiet ODWS
Chromosomes
in eukaryotes
• Found in the nucleus
• Condensed and visible during cell division
• At the beginning of mitosis they can be seen to consist of
two threads (sister chromatids) joined by a centromere
• The sister chromatids are identical copies
• During mitosis the sister chromatids separate and are
placed into two nuclei
© 2007 Paul Billiet ODWS
Image believed to be in the Public Domain
‫ساختمان‬
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‫دو غشا‪ :‬پوشش هسته‬
‫فضای بین دو غشا‪ :‬فضای پیش هسته‬
‫پروتئینهای غشا‬
‫فضای درون هسته‪ :‬نوکلئوپالسم‬
‫– هستک‬
‫– کروموزومها‬
Nucleus: structure and function
Heterochromatin =
too compacted,
transcriptionally inactive
nuclear envelope
Nucleolus
Euchromatin = can be transcriptionally active
Nucleoplasm
Nuclear envelope and lamina
cytoplasm
N. lamina
Nuclear
pore
heterochromatin
Nuclear lamina
Lamins are filamentous proteins in the
intermediate filament family
Lamin phosphorylation in
prophase disassembles
the nuclear lamina &
allows for nuc. envel.
Breakdown
Nuclear pore
• nuclear localization
signals (nuclear
import signals)
• nuclear export
signals
• highly regulated
‫کروموزوم ها‬
‫• کروموزوم‪ :‬جسم رنگی که ازکروماتین تشکیل شده‬
‫• کروماتین‪ :‬متشکل از ‪ DNA‬و پروتئین و ‪RNA‬‬
‫تعداد‬
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‫به اندازه ارگانیسم ارتباطی ندارد‬
‫نوعی آسکاریس ‪ 2‬عدد کروموزوم دارد‬
‫انسان ‪ 46‬عدد‬
‫برخی پروتوزوآ ‪ 300‬عدد‬
‫ممکن است موجودات مختلف تعداد یکسانی داشته باشند‬
‫سیب زمینی‪-‬نخل‪-‬شامپانزه ‪ 48‬عدد‬
‫اندازه و شکل‬
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‫اندازه و شکل در خالل تقسیم متفاوت است‬
‫اکثرا دوبازو‬
‫سانترومر(کینتوزوم)‪ :‬محل اتصال دوک میتوزی‬
‫در متافاز دوسری بازو دارند‬
A pair of homologous chromosomes (number 1) as seen
at metaphase
Locus (position of a gene or
DNA marker)
Allele (alternative form of a
gene/marker)
Identifying chromosomes
Chromosomes can be identified by:
• Their size
• Their shape (the position of the
centromere)
• Banding patterns produced by
specific stains (Giemsa)
Chromosomes are analysed by
organising them into a KARYOTYPE
© 2007 Paul Billiet ODWS
© Biologyreference.com
‫نوکلئوزوم‬
‫• هیستون ها‬
‫• ‪H1,H2A,H2B,H3,H4‬‬
‫• اسیدآمینه بازی لیزین‬
‫هسته هیستونی‬
‫• ‪H2A,H2B,H3,H4‬‬
‫سولنوئید‬
Multiple coiling model
‫کروماتین‬
‫• هتروکروماتین‬
‫• یوکروماتین‬
‫• هتروکروماتین تشکیالتی ‪constitutive‬‬
‫• هتروکروماتین اختیاری ‪facultative‬‬
9.3.1 Chromosome structure
NOR
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A 1-3 Large metacentric
1,2 or submetacentric
B 4,5 Large submetacentric,
all similar
C 6-12, X Medium sized,
submetacentric - difficult
D 13-15 medium-sized
acrocentric plus satellites
E 16-18 short metacentric
16 or submetacentric 17,18
F 19-20 Short metacentrics
G 21,22,Y Short acrocentrics
with satellites. Y no satellites.
‫موفق باشین•‬
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