Ch 11 Chromosome Structure & Organelle DNA

Question 1

structure of DNA: nucleotide sequence

Answer 1

primary structure

Question 2

structure of DNA: double-stranded helix

Answer 2

secondary structure

Question 3

structure of DNA: higher-order folding that allows DNA to be packed in cell

Answer 3

tertiary structure

Question 4

tertiary structure that forms from strain on DNA helix by being overwound or underwound

Answer 4

supercoiling

Question 5

supercoiling occupies ____ space than relaxed dna

Answer 5

less

Question 6

strain placed on DNA by overrotation (adding two turns)

Answer 6

positive supercoiling

Question 7

strain placed on DNA by underrotation (removing two turns)

Answer 7

negative supercoiling

Question 8

what type if supercoiling is most DNA?

Answer 8

most DNA is negative supercoiling

Question 9

enzymes that add or remove rotations from DNA helix

Answer 9

topoisomerases

Question 10

function of supercoiling

Answer 10

packing of DNA within cell
helps with unwinding for replication & transcription

Question 11

describe bacterial chromosomes

Answer 11

single circular DNA molecule
nucleoid region
stabilized by proteins and supercoiled

Question 12

describe eukaryotic chromosomes

Answer 12

single long linear DNA molecule with lots of packing and folding (chromatin)

Question 13

complex of DNA + proteins

Answer 13

chromatin

Question 14

which type of chromatin:
undergoes the normal process of condensation & decondensation throughout the cell cycle
where transcription takes place
located on chromosome arms
crossing over is common

Answer 14

euchromatin

Question 15

which type of chromatin:
remains in highly condensed state throughout cell cycle
characterized by lack of transcription
absence of crossing over

Answer 15

heterochromatin

Question 16

permanent chromatin, located at centromeres & telomeres

Answer 16

constitutive heterochromatin

Question 17

chromatin that occurs during developmental stages

Answer 17

facultative heterochromatin

Question 18

?what chromatin is the Y chromosomes largely consisted of?

Answer 18

Y chromosome is largely constitutive chromatin

Question 19

small positively charged proteins that make up nucleosomes of chromatin

Answer 19

histones

Question 20

list the five major types of histones

Answer 20

H1, H2A, H2B, H3, H4

Question 21

why are histones positively charged?

Answer 21

high % of argine and lysine in histones give the net positive charge

Question 22

core particle of eight histones and 145-147 bp of DNA wrapped around ~ 2 times

Answer 22

nucleosome

Question 23

what histones make up the core of a nucleosome?

Answer 23

two H2A, two H2B, two H3, and two H4

Question 24

what’s the purpose of the histone tail?

Answer 24

each histone has a positively-charged tail that extends out from the nucleosome and interacts w/ negative phosphate groups in the backbone of DNA and neighboring nucleosomes

Question 25

job of the H1 histone

Answer 25

clamps DNA in place around nucleosome

Question 26

attachment site for kinetochore & spindle microtubules

Answer 26

centromere

Question 27

what type of chromatin is the centromere mostly composed of?

Answer 27

chromatin is mostly heterochromatin

Question 28

why do nucleosomes in centromeres have CENP-A in place of H3 histone?

Answer 28

CENP-A alters the nucleosome/chromatin structure, allowing kinetochore proteins to bind & spindle microtubules attach

Question 29

special protective structures at ends of chromosomes to prevent degradation

Answer 29

telomeres

Question 30

repeated units of series of adenine/thymine nucleotides, followed by several guanine nucleotides located towards end of chromosomes

Answer 30

telomeric sequences

Question 31

G-rich strand extending beyond complementary C-rich strand

Answer 31

G-rich overhand

Question 32

formation of t-loop and its purpose

Answer 32

G-rich overhand folds over and pairs with DNA to form t-loop, protects end of telomere from degradation

Question 33

lengthens telomeres to prevent chromosome shortening during replication

Answer 33

telomerase

Question 34

eukaryotic DNA sequence: found once/few times in genome, usually encodes proteins

Answer 34

unique-sequence DNA

Question 35

genes present in similar but not identical copies

Answer 35

gene families

Question 36

eukaryotic DNA sequence: 150-300 bp repeated thousands of times

Answer 36

moderately repetitive DNA

Question 37

repetitive DNA that appear one after another

Answer 37

tandem repeats

Question 38

repetitive DNA that is scattered throughout

Answer 38

interspersed repeats

Question 39

short repeats

Answer 39

SINEs (short interspersed elements)

Question 40

longer repeats of several thousand bp

Answer 40

LINEs (long interspersed elements)

Question 41

eukaryotic DNA sequence: <10 bp repeated in hundreds of thousands of copies, usually lots of tandem repeats and non-coding DNA

Answer 41

highly repetitive DNA

Question 42

describe the endosymbiotic theory

Answer 42

mitochondria & chloroplasts were once free-living bacteria that become internal inhabitants of early eukaryotes

Question 43

what are some evidence that supports the endosymbiotic theory?

Answer 43

-many protists are hosts to endosymbiotic bacteria
-mitochondria & chloroplasts similar in size to present day bacteria and have own DNA
-possess ribosomes similar to bacterial ribosomes
-***sequences in mtDNA & cpDNA closely relate to sequences of bacterial DNA

Question 44

describe uniparental inheritance of organelle-encoded traits

Answer 44

mtDNA usually inherited from female parent
cpDNA usually inherited from male parent

Question 45

occurrence of two distinct varieties of DNA within the cytoplasm of a single cell

Answer 45

heteroplasmy

Question 46

organelles segregate randomly in heteroplasmic cells during cell division

Answer 46

replicative segregation

Question 47

describe human mtDNA

Answer 47

two strands:
-Heavy strand has more quanine
-Light strand has more cytosine
-D Loop is where replication and transcription is initiated