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Flashcards in DNA Organization Deck (41):
1

-Circular chromosomes
-Double stranded (dsDNA)
-May also contain plasmids
-Found in the nucleoid

Organization of DNA in most prokaryotes

2

Back bone has been nicked.
-relaxes from supercoiling

Relaxed circular DNA

3

Allows DNA to fit inside the cell
-Amount and type of supercoiling depends on the starting point

Supercoiled Circular DNA

4

Formation from contortion of supercoiling and twisting.

2 supercoiled DNA forms

5

Untwisting the DNA
-Compacting DNA

Negative supercoiling

6

Twisting
-introducing more twisting causes DNA to contort.
-Compacting DNA

Positive supercoiling

7

Amount and type of supercoiling controlled by:?
-highly conserved enzymes
-relieve twisting by two types:
I. Make a nick in one strand
II. Cuts both strands

Topoisomerases

8

2 DNA linked like a chain

Catenated DNA

9

How doe bacteria package their DNA?
a. using histones
b. by supercoiling the DNA
c. by acetylating the DNA
d. by methylating the DNA
e. all of the above

b. by supercoiling the DNA

10

-Nucleus, mitochondria, choloroplasts

Organization of DNA in Eukaryotes

11

Amount of haploid DNA in an organism in base pairs

C value

12

Increase in DNA doesn't always mean and increase in complexity of the organism.

C value paradox

13

1n

haploid

14

2n

diploid

15

Complete set of chromosomes

karyotype

16

Group that gives DNA its (-) charge

Phosphate

17

DNA is positively or negatively charged?

Negatively

18

DNA and associated protein in the nucleus

Chromatin

19

Histones
Nonhistones

Proteins associated with DNA

20

Help pack chromatin into the nucleus
-(+) charged because DNA is (-) charged
-consists of H1, H2A, H2B, H3, H4
-very highly conserved

Histones

21

Various types:
-DNA replication
-DNA repair
-Transcription
-Recombination

Nonhistones

22

DNA wound around a histone core

Nucleosomes

23

DNA connecting two nucleosomes together

linker DNA

24

1. Double helix is wound around histones to form nucleosomes
2. 10nm fiber is condensed and wound into 30 nm fiber
3. 30nm fiber is attached to protein scaffold.

Eukaryotic DNA packing

25

Can unpack and/or repack depending on gene transcription and other events
ex. during the cell cycle

Dynamic Packing
(Eukaryotic DNA packing)

26

Double helix wound around histones to form nucleosomes

10 nm fiber

27

Packing is less uniform during interphase (depends on the gene)
-dynamic upon gene expression
-organized to support proper gene expression

DNA packing

28

-Chromatin that exhibits normal condensation and decondensation during the cell cycle.
-genes are actively being transcribed and are thus loosely packed
-typically devoid of repetitive sequences

Euchromatin

29

Two types:
1. Constitutive Chromatin
2. Facultative Chromatin
-Packed tightly

Heterochromatin

30

-Type of heterochromatin
-present in all cell in the same location on every chromosome
ex. centromere

Constitutive Chromatin

31

-Type of heterochromatin
-can change during development
ex. Barr body on X chromosome
-DNA condenses or decondenses depending upon the status of the cell. (permanently silencing genes)
-Euchromatin-->Heterochromatin

Facultatvie Chromatin

32

Occurring once or only a few times in the genome
-ex. protein coding

Unique-sequence DNA

33

Two types:
1. Unique-sequence DNA
2. Repetitive DNA

Distribution of sequences

34

Can occur a few times up to a million times, depending on the sequence.
ex. telomeres and rRNA(ribosomal RNA)

Repetitive DNA

35

Two types:
1. Dispersed repeated sequences
2. Tandemly repeated DNA

Repetitive sequence DNA

36

Distributed at irregular intervals on the genome
ex. transposable elements

Dispersed Repeated Sequences

37

Sequence that repeats itself many times in a row
ex. telomeres, or genes

Tandemly Repeated DNA

38

-Highly repetitive DNA
- a fraction of a eukaryotic organism's DNA that differs in density from most of its DNA as determined by centrifugation, that consists of short repetitive nucleotide sequences, that does not undergo transcription, and that is often found in centromeric regions

Satellite DNA

39

-Consists of heterochromatin
-tandemly repeated sequences (specifically satellite DNA)
-form a constrictive region because of tight packing

Centromere

40

-Tandemly repeated DNA at the ends of linear chromosomes.
ex. TTAGGGTTAGGG...
-Protect from exonucleases
-Protect from DNA repair enzymes that form free ended DNA to other free ended DNA

Telomeres

41

-Defense mechanism against foreign DNA
-enzymes that chew up the chromosome

exonuclease