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BIO168 Molecular Genetics
Chromatin, chromosomes and genomes
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Created by
Malini Bhattacharya
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Cards (27)
What is the diameter of an average human nucleus?
10 µm
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How long is the DNA in each cell?
About
2 m
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What are the two types of chromatin and their characteristics?
Euchromatin
: More
open
, allows
gene transcription
Heterochromatin: Tightly
packaged
, less
accessible
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Why is DNA packaged within the nucleus?
To
fit
,
organize
, and
protect
it
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What is the structure of the nucleosome?
Composed of DNA wrapped around
histones
Forms the basic unit of
chromatin
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What is the size of the fiber formed by nucleosomes?
11 nm
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Describe the Zig-zag model of the 30 nm fiber.
Nucleosomes
form a
tetra-nucleosome
Stacked like coins
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What is the alternative model to the Zig-zag model of chromatin fibers?
Solenoid Model
Six
nucleosomes
per twist of coil
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What is the size of the chromonema formed from the 30 nm fiber?
120 nm
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What are the functions of DNA packaging?
Fits within the
nucleus
Allows unpacking for
transcription
and repair
Protects DNA from
mutagens
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What are telomeres and centromeres primarily composed of?
Heterochromatin
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What is the significance of protecting DNA through packaging?
It prevents attacks from
mutagens
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How does euchromatin differ from heterochromatin in terms of gene transcription?
Euchromatin
allows transcription;
heterochromatin
does not
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If a cell's DNA is
uncoiled
, what risks does it face?
It can be attacked by
mutagens
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What is the total number of base pairs in the human genome?
3,200,000,000 base pairs
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What is the smallest genome size recorded and in which organism?
160,000
bp
in
Carsonella ruddii
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Which organism has the largest animal genome?
Australian lungfish
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Is genome size linked to organism complexity?
No
, genome size is
not
linked to complexity
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What are the sex chromosome configurations in humans and birds?
Humans: XX (females),
XY
(males)
Birds:
ZZ
(males),
ZW
(females)
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How do turtles determine sex?
Through environmental cues like
temperature
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What is the term for organisms with two identical sex chromosomes?
Homogametic
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What is the term for organisms with two different sex chromosomes?
Heterogametic
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What are the main differences between prokaryotic and eukaryotic genomes?
Prokaryotic: Circular, compact, common
operons
Eukaryotic: Linear, mostly introns, large genes
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What types of genomes can viruses have?
DNA
or
RNA
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How do viruses replicate?
They need host machinery to replicate
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What are prions?
Misfolded
proteins
that infect tissues
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What disease is associated with prions?
Creutzfeldt-Jakob disease
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