Lecture 1

Question 0

What was discovered in the late 19th century?

Answer 0

Hereditary information carried on chromosomes

Question 1

What is a gene?

Answer 1

The information-containing elements that determine the characteristics of a species

Question 2

When are chromosomes visible by light microscopy?

Answer 2

When the cell undergoes division

Question 3

What do chromosomes contain?

Answer 3

DNA and protein

Question 4

What are the building blocks of DNA?

Answer 4

Nucleic Acids

Question 5

What are nucleotides joined together by?

Answer 5

Phosphodiester linkage between 5’ and 3’ carbon atoms

Question 6

What do polynucleotides have?

Answer 6

Polarity, 5’ phosphoryl end, and 3’ hydroxyl end

Question 7

What is the structure of DNA?

Answer 7

2 long polynucleotide chains with 4 types of nucleotide subunits
Nucleotides are 5 carbon sugar and nitrogenous base covalently linked via glycosidic bond
Sugar is deoxyribose
Adenine, cytosine, guanine, and thymine bases
Double Helix - 1 turn/10bp
Antiparallel

Question 8

What are the purines in DNA?

Answer 8

Adenine and guanine

Question 9

What are the pyrimidines in DNA?

Answer 9

Cytosine and thymine

Question 10

What is a genome?

Answer 10

A complete set of information in an organism’s DNA

Question 11

True or False?

At replication, the entire genome must be duplicated and passed to the daughter cell.

Answer 11

True

Question 12

How many nucleotides does the human genome have?

Answer 12

3.2x10^9 nucleotides distributed over 24 different chromosomes

Question 13

What is a chromosome?

Answer 13

Single long linear DNA molecular associated with proteins that fold and pack it into compact structure.

Question 14

How many copies of each chromosome does the human cell have?

Answer 14

2 copies - maternal and paternal homologs-

Except germ cells and RBCs

Question 15

How many pairs of autosomes are the in the human cell?

Answer 15

22 pairs

Question 16

How many sex chromosomes does a human have?

Answer 16

2

Question 17

What information is found on chromosomes?

Answer 17

Genes
-encoding proteins and RNA molecules
Interspersed DNA that does not contain genes
-regulatory information , junk DNA

Question 18

How much of the average gene size comprise of coding region?

Answer 18

5%

Question 19

What is the percentage of DNA sequence in exons (protein coding sequences)?
Whole genome

Answer 19

1.5%

Question 20

What are functional sequences?

Answer 20

Sequences that are relatively conserved during evolution

Question 21

What are non-functional sequences?

Answer 21

Sequences that mutate randomly w/o consequence

Question 22

What are coding regions?

Answer 22

Exons that are typically 145 bp that are floating in a sea of large introns

Question 23

What is conserved synteny?

Answer 23

Large blocks of genes are conserved in the same order on the chromosome (compared to ancestors)

Question 24

What happens in interphase?

Answer 24

Chromosomes are replicated; they are decondensed and cant be easily distinguished

Question 25

What happens during mitosis?

Answer 25

Become highly condensed and separated into two daughter nuclei

Question 26

What are 3 important components of chromosomes?

Answer 26

DNA replication origin: where duplication of the DNA begins Centromere: allows one copy of each duplicated and condensed chromosome to be pulled into each daughter cell Telomeres: repetitive sequences at the end of a chromosome that enable the ends to be efficiently replicated

Question 27

What is chromatin?

Answer 27

Protein + nuclear DNA

Question 28

What is the most basic unit of chromosome packing?

Answer 28

nucleosome. Repeats after 200 nt

Question 29

How many histone proteins are in each individual nucleosomes core particle?

Answer 29

8 histones

Question 30

What are the 8 histones?

Answer 30

2 molecules each of H2A, H2B, H3, H4

Question 31

What is linker DNA?

Answer 31

Exposed DNA between nucleosome core particles | About 80 nt long

Question 32

What are histones?

Answer 32

Small proteins with common structural motif called histone fold.

Question 33

What bonds form between histones and DNA?

Answer 33

142 hydrogen bonds in each nucleosomes Hydrophobic interactions Salt linkages - lysine and arginine comprise more than 1/5 of histone residues, effectively neutralize negatively charged DNA backbone

Question 34

Are histones are conserved or non-conserved?

Answer 34

Highly conserved, most changes would e lethal

Question 35

True or False | Nucleosomes are static?

Answer 35

False, It is in a dynamic situation to allow for rapid localized access to DNA for gene expression. Nucleosomes are in a constant state of flux

Question 36

What allows for a further loosening of DNA/histone contact?

Answer 36

Chromatin remolding complexes. Related to Helicase and are ATP dependent Bind to both protein core and DNA

Question 37

What is the zig-zag model?

Answer 37

Theory how the nucleosome packs and becomes a dense fibrous.. Stacking that may be facilitated by histone tails and histone 1 is present in 1:1 ration with nucleosome cores

Question 38

What is the linker histone?

Answer 38

H1 Larger histone Less well conserved

Question 39

What is needed to pack DNA?

Answer 39

Incredible amount of condensing. Mitotic chromosomes are condensed 500 x more than in interphase

Question 40

What are the DNA binding proteins involved in forming chromosomes?

Answer 40

Histones and non histones

Question 41

What forms beads on a string?

Answer 41

Chromatin isolated directly from interphase nucleus that is partially unfolded

Question 42

What breaks down DNA by cutting between Nucleosomes and degrading the exposed DNA (linker protein)

Answer 42

Nucleases

Question 43

What is the nucleosome core particle?

Answer 43

Disk shaped particle that DNA wraps 1.7 x around

Question 44

What are the tails of histones subject to?

Answer 44

N terminal a.a tail that extends out from the core are subject to covalent modifications important for chromatin regulation

Question 45

What adds to various chromosome structures?

Answer 45

Specialized variant histones