Lect. 1 - DNA, Chromosome, and Genomes 1

Question 1

What are the building blocks of DNA?

Answer 1

Nucleic Acids; joined together by a phosphodiester linkage b/w 5’ and 3’ C

Question 2

5’ end

Answer 2

phosphoryl

Question 3

3’ end

Answer 3

hydroxyl

Question 4

Nucleotides

Answer 4

5C sugar and nitrogenous base covalently linked via glycosidic bond

Question 5

What is the sugar in DNA?

Answer 5

deoxyribose

Question 6

Length of a turn

Answer 6

10bp

Question 7

antiparallel

Answer 7

each strand’s sequence is complementary to partner

Question 8

Purines

Answer 8

adenine and guanine

Question 9

Pyrimidines

Answer 9

cytosine and thymine

Question 10

Adenine pairs w/?

Answer 10

Thymine (2 H bonds)

Question 11

Guanine pairs w/?

Answer 11

cytosine (3 H bonds)

Question 12

Genome

Answer 12

complete set of info in an organisms DNA

Question 13

What is DNA packaged into?

Answer 13

chromosomes

Question 14

How many chromosomes is DNA distributed over?

Answer 14

24

Question 15

DNA + protein =

Answer 15

chromatin

Question 16

Translocations

Answer 16

can occur during an abnormal recombination event; balanced ones maintain the correct amount of genetic material

Question 17

What info is found on chromosomes?

Answer 17

Genes (encoding proteins and RNA molecules)

Interspersed DNA that doesn’t contain genes (regulatory info and junk DNA)

Question 18

Interphase

Answer 18

chromosomes are replicated; they are decondensed and can’t be easily distinguished

Question 19

Mitosis

Answer 19

chromosomes become highly condensed and separated into 2 daughter nuclei

Question 20

What are the chromosome requirements?

Answer 20

A copy must be passed on to each daughter cell at division which requires replication, separation of copies and partitioning to daughter cells

Question 21

DNA replication origin

Answer 21

where duplication of DNA begins

Question 22

Centromere

Answer 22

Allows 1 copy of each duplicated and condensed chromosome to be pulled into each daughter cell when the cells divides. The kinetochore protein complex attaches to the centromere

Question 23

Telomeres

Answer 23

At the ends of a chromosome, contain repetitive sequences that enable the ends to be efficiently replicated

Question 24

How does the DNA fit?

Answer 24

mitotic chromosomes are condensed 500 times compared to interphase DNA; must allow rapid localized access to DNA for gene expression

Question 25

Nucleosomes

Answer 25

most basic unit of chromosome packing

Question 26

What is an individual nucleosome core particle consist of?

Answer 26

8 histone proteins; 2 molecules each of H2A, H2B, H3, H4 and 2x stranded DNA that is 147 nucleotide pairs long

Question 27

Linker DNA

Answer 27

can be few to 80nt; nucleosomes repeat every 200 nucleotide pairs or so

Question 28

Histones

Answer 28

small proteins w/ common structural motif called histone fold. disc shaped w/ DNA wrapped 1.7 turns

Question 29

N terminal aa tail on histone

Answer 29

extends out from core and is subject to covalent modifications important for chromatin regulation

Question 30

Interactions b/w DNA and histone

Answer 30

142 H bonds are formed b/w DNA and histone core in each nucleosome; hydrophobic interactions; salt linkages

Question 31

Salt linkages b/w DNA and histone

Answer 31

lysine and arginine (positive) comprise more than 1/5 of histone residues; effectively neutralize negatively charged DNA backbone

Question 32

Chromatin remodeling

Answer 32

allow further loosening of DNA/histone contact; proteins bind to both protein core and to DNA which changes the structure of nucleosome temporarily, making DNA less tightly bound

Question 33

Nucleosome packing

Answer 33

Forms a dense fibrous structure w/ diameter of 30 nm

Question 34

Histone tails

Answer 34

largely unstructured, suggesting that they are highly flexible; tails can form interaction w/ adjacent nucleosomes; they help condense chromatin

Question 35

Histone H1

Answer 35

linker histone; larger than others and less well conserved; contacts both DNA and protein; changes path of DNA as it exits the nucleosome