lecture 23

Question 1

What is the structure of DNA?

Answer 1

Two DNA strands with sugar-phosphate backbone and base (ATCG) in the middle

Question 2

How are two stands of DNA held together?

Answer 2

Two strands held by hydrogen bonds (2 vs 3) forming double helix

Question 3

Is DNA negative or positive, why?

Answer 3

Negative charge on phosphate (hence nucleic acid)

Question 4

How many base pairs i the human genome?

Answer 4

3x10^9 bp

Question 5

True/False: Gene has defined sequence and size

Answer 5

true

Question 6

What are the Key concepts that led to the discovery of DNA’s 3D structure

Answer 6

Chargaff’s rule
Sugar phosphate backbone positioned outside and nucleotide facing inside
Signature diffraction pattern
suggesting double helix structure.

Question 7

What is chargaffs rule?

Answer 7

In any species the number of A and T bases are equal, and the number of G and C bases are equal.

Question 8

What did the Signature diffraction pattern suggest?

Answer 8

double helix structure

Question 9

How is the turn in DNA structured?

Answer 9

every 10 bp

Question 10

What are the purines?

Answer 10

A and G

Question 11

What are the pyrimidines?

Answer 11

T and C

Question 12

How many bonds do A and T form?

Answer 12

2 hydrogen bonds

Question 13

How many bonds do C and G form?

Answer 13

3 hydrogen bonds

Question 14

What did Dr. Marie Maynard Daly do?

Answer 14

first african american to receive a Ph.D from Columbia University and the first African American women to receive a chemistry Ph.D in the United States

Question 15

What did Dr. Marie Maynard Daly research?

Answer 15

fractionation & preservation of nuclear components and discovery of important lysine amino acids in histone proteins

Question 16

DNA is organized into _____.

Answer 16

chromosomes

Question 17

What is Chromatin made up of?

Answer 17

DNA and histone (protein)

Question 18

DNA is a polymer of ____.

Answer 18

nucelotides

Question 19

Chromosomes are condensed ___.

Answer 19

chromatin

Question 20

What are telomeres?

Answer 20

a region of repetitive DNA sequences at the end of a chromosome.

Question 21

What does DNA replication ensure?

Answer 21

the continuity of cell characteristics with each division

Question 22

DNA replication is ____. (energy)

Answer 22

semiconservative

Question 23

What is the origin of DNA replicatipn?

Answer 23

at nucleotide-rich (AATATA) DNA sequence
replication occurs in both directions

Question 24

What enzyme participates in DNA replication?

Answer 24

DNA polymerase (and many others)

Question 25

What does DNA polymerase do in DNA replication?

Answer 25

adds nucleotide to 3’ end and extends the chain from 5’ to 3’

Question 26

What is the function of helicase?

Answer 26

unwinds parental double helix at replication forks

Question 27

What does single-strand binding protein do?

Answer 27

binds to and stabilizes single-stranded DNA until it is used as a template

Question 28

What does topoisomerase do?

Answer 28

relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands

Question 29

What does primase do?

Answer 29

synthesizes an RNA primer at 5' end of leading strand and at 5' end of each Okazaki fragment of lagging strand

Question 30

What does DNA pol III do?

Answer 30

using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand

Question 31

What does DNA pol I do?

Answer 31

removes RNA nucleotides of primer from 5' end and replaces them with DNA nucleotides

Question 32

What does DNA ligase do?

Answer 32

joins Okazaki fragments of lagging strand; on leading strand, joins 2' end of DNA that replaces primer to rest of leading strand DNA

Question 33

How is the leading strand synthesized?

Answer 33

-DNA pol I replaces RNA sequence (also called as primer) with DNA nucleotides. Adds nucleotides to 3’ end (like DNA polymerase III) -DNA ligase forms bonds between two DNA fragments.

Question 34

How is the lagging strand formed?

Answer 34

-DNA pol I replaces RNA primer with DNA nucleotides (for each Okazaki fragment). -DNA ligase forms bonds between DNA fragments. -Joins Okazaki fragments to form a lagging strand

Question 35

What is a pyrimidine dimer?

Answer 35

a kink caused by UV light in DNA, thymine dimer forms