DNA Organization

Question 1

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

Answer 1

Organization of DNA in most prokaryotes

Question 2

Back bone has been nicked.

-relaxes from supercoiling

Answer 2

Relaxed circular DNA

Question 3

Allows DNA to fit inside the cell

-Amount and type of supercoiling depends on the starting point

Answer 3

Supercoiled Circular DNA

Question 4

Formation from contortion of supercoiling and twisting.

Answer 4

2 supercoiled DNA forms

Question 5

Untwisting the DNA

-Compacting DNA

Answer 5

Negative supercoiling

Question 6

Twisting

• introducing more twisting causes DNA to contort.
• Compacting DNA

Answer 6

Positive supercoiling

Question 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

Answer 7

Topoisomerases

Question 8

2 DNA linked like a chain

Answer 8

Catenated DNA

Question 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

Answer 9

b. by supercoiling the DNA

Question 10

-Nucleus, mitochondria, choloroplasts

Answer 10

Organization of DNA in Eukaryotes

Question 11

Amount of haploid DNA in an organism in base pairs

Answer 11

C value

Question 12

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

Answer 12

C value paradox

Question 13

1n

Answer 13

haploid

Question 14

2n

Answer 14

diploid

Question 15

Complete set of chromosomes

Answer 15

karyotype

Question 16

Group that gives DNA its (-) charge

Answer 16

Phosphate

Question 17

DNA is positively or negatively charged?

Answer 17

Negatively

Question 18

DNA and associated protein in the nucleus

Answer 18

Chromatin

Question 19

Histones

Nonhistones

Answer 19

Proteins associated with DNA

Question 20

Help pack chromatin into the nucleus

• (+) charged because DNA is (-) charged
• consists of H1, H2A, H2B, H3, H4
• very highly conserved

Answer 20

Histones

Question 21

Various types:

• DNA replication
• DNA repair
• Transcription
• Recombination

Answer 21

Nonhistones

Question 22

DNA wound around a histone core

Answer 22

Nucleosomes

Question 23

DNA connecting two nucleosomes together

Answer 23

linker DNA

Question 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.

Answer 24

Eukaryotic DNA packing

Question 25

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

Answer 25

Dynamic Packing | Eukaryotic DNA packing

Question 26

Double helix wound around histones to form nucleosomes

Answer 26

10 nm fiber

Question 27

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

Answer 27

DNA packing

Question 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

Answer 28

Euchromatin

Question 29

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

Answer 29

Heterochromatin

Question 30

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

Answer 30

Constitutive Chromatin

Question 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

Answer 31

Facultatvie Chromatin

Question 32

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

Answer 32

Unique-sequence DNA

Question 33

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

Answer 33

Distribution of sequences

Question 34

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

Answer 34

Repetitive DNA

Question 35

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

Answer 35

Repetitive sequence DNA

Question 36

Distributed at irregular intervals on the genome | ex. transposable elements

Answer 36

Dispersed Repeated Sequences

Question 37

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

Answer 37

Tandemly Repeated DNA

Question 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

Answer 38

Satellite DNA

Question 39

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

Answer 39

Centromere

Question 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

Answer 40

Telomeres

Question 41

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

Answer 41

exonuclease