Chapter 11

Question 1

right-handed twist

Answer 1

forms double helix of DNA; can be over- or underwound

Question 2

overwound helix

Answer 2

forms a positive supercoil

Question 3

underwound helix

Answer 3

forms a negative supercoil (form of all circular bacterial chromosomes)

Question 4

negative supercoiling functions

Answer 4

• facilitates functions that require DNA strand separation such as transcription and translation
• aids in compaction of chromosomes which helps with transmission
• necessary for binding of DNAa to origin of replication

Question 5

characteristics of prokaryotic chromosomes

Answer 5

• circular
• have single origin of replication
• occupies region of cytoplasm called nucleoid

Question 6

characteristics of eukaryotic chromosomes

Answer 6

• contain telomeres
• contained within the nuclear envelope
• compacted using histones
• linear
• have multiple origins of replication

Question 7

histone proteins

Answer 7

small proteins which DNA binds and winds around, and compacts DNA with the nucleus

Question 8

nucleosomes

Answer 8

formed by a complex of 8 histones

diameter of 11nm or 110A

Question 9

levels of DNA packaging

Answer 9

double helix (20 A)

1. histone proteins
2. nucleosomes (110 A)
3. tight helical fiber or salemoid structure (300 A)
4. supercoil (2400 A)
5. Chromosome (40,000 A)

Question 10

metacentric

Answer 10

centromere found near middle

Question 11

submetacentric

Answer 11

centromere found near top

Question 12

acrocentric

Answer 12

centromere found at top but still have 4 arms

Question 13

telocentric

Answer 13

centromere found at very top, only 2 bottom arms are present

Question 14

euchromatin

Answer 14

• state of DNA organization
• loosely packed
• accessible to transcription machinery
• found in prokaryotes
• major state of most genes

Question 15

heterochromatin

Answer 15

• state of DNA organization
• tightly packed
• inaccessible to transcription machinery
• major state of inactive X chromosome