Chromosomes in eukaryotes

‫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
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
© 2007 Paul Billiet ODWS
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
‫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
Euchromatin = can be transcriptionally active
Nuclear envelope and lamina
N. lamina
Nuclear lamina
Lamins are filamentous proteins in the
intermediate filament family
Lamin phosphorylation in
prophase disassembles
the nuclear lamina &
allows for nuc. envel.
Nuclear pore
• nuclear localization
signals (nuclear
import signals)
• nuclear export
• highly regulated
‫کروموزوم ها‬
‫• کروموزوم‪ :‬جسم رنگی که ازکروماتین تشکیل شده‬
‫• کروماتین‪ :‬متشکل از ‪ DNA‬و پروتئین و ‪RNA‬‬
‫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
‫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
Identifying chromosomes
Chromosomes can be identified by:
• Their size
• Their shape (the position of the
• Banding patterns produced by
specific stains (Giemsa)
Chromosomes are analysed by
organising them into a KARYOTYPE
© 2007 Paul Billiet ODWS
‫• هیستون ها‬
‫• ‪H1,H2A,H2B,H3,H4‬‬
‫• اسیدآمینه بازی لیزین‬
‫هسته هیستونی‬
‫• ‪H2A,H2B,H3,H4‬‬
Multiple coiling model
‫• هتروکروماتین‬
‫• یوکروماتین‬
‫• هتروکروماتین تشکیالتی ‪constitutive‬‬
‫• هتروکروماتین اختیاری ‪facultative‬‬
9.3.1 Chromosome structure
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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