Intro to DNA/RNA I

Question 1

Who originally found DNA and what did he call it?

Answer 1

Friedrich Miescher in 1871. He called them nucleins

Question 2

What is the Griffith Experiment (1928)?

Answer 2

The first demonstration of transformation of a specific genetic trait from one organism to another.

Question 3

What did Avery, MacCarty & McLeod do in 1944?

Answer 3

They fractionated cell-free extraction of virulent pneumococcus and identified that DNA, not protein, caused transformation. First evidence that DNA carries genetic information.

Question 4

What did Hershey and Chase do in 1951?

Answer 4

Sometimes called the “Waring Blender” experiment. They watched a T2 bacteriophage infect the bacteria Escherichia coli. DNA “has some function” as genetic material.

Question 5

What kind of polarity does DNA have?

Answer 5

5’-3’

Question 6

How are deoxyribose or ribose linked?

Answer 6

Via phosphate groups The 3’-OH of one group is linked to the 5’-OH of the next by a phosphodiester bridge. This is the backbone of DNA

Question 7

Do bases project away from the backbone or toward the backbone?

Answer 7

Away from the backbone.

Question 8

Chargraff’s Rule

Answer 8

%G=%C, %A=%T i.e %purines=%pyrimidines ALWAYSSS!!!!

Question 9

What did Franklin and Wilkins do in 1953?

Answer 9

Showed that DNA gave a characteristic X-ray diffraction pattern.

Question 10

What was the pattern that was found of DNA?

Answer 10

Helical Comprised of two strands Has 2 periodicities along long axis (0.34nm and 3.4nm)

Question 11

What did Watson and Crick do in 1953?

Answer 11

Developed a 3D model of DNA that was not fully accepted until 1960.

Question 12

Are strands of DNA parallel or antiparallel?

Answer 12

Antiparallel that are said to be complementary to each other.

Question 13

What are some other conformations the DNA molecule can adopt?

Answer 13

B form (right handed helix - main) Z form (left hand form) Cruciform (more exotic)

Question 14

What can DNA triple helices possibly be used for?

Answer 14

A novel class of drugs designed to modify gene expression like oncogenes in cancer.

Question 15

What does DNA’s flexibility allow?

Answer 15

To be folded when being packed into the nucleus To wrap around proteins like histones

Question 16

What type of coiled state is DNA in while in a cell?

Answer 16

A negative supercoil (underwound)

Question 17

What two enzymes can modify supercoiling?

Answer 17

Topoisomerase I DNA Gyrase Helicases

Question 18

What does Topoisomerase do?

Answer 18

Relaxes supercoiled DNA which is energetically favorable

Question 19

What does DNA Gyrase do?

Answer 19

Converts relaxed DNA into negatively supercoiled DNA which requires ATP

Question 20

What four antibiotics inhibits Bacterial DNA gyros?

Answer 20

Novobiocin Nalidixic acid Ciproflaxacin

Question 21

What do helicases do?

Answer 21

Unwinds the two DNA strands which requires ATP to break hydrogen bonds

Question 22

What happens when DNA is heated then cooled?

Answer 22

When heated it goes through denaturation which separates the strand then when it cools down the strands go through annealing thus reforming bonds between complementary strands

Question 23

How many hydrogen bonds do GC and AT pairs contain?

Answer 23

GC = 3 bonds AT = 2 bonds The more GC content the higher the melting temperature of DNA

Question 24

What is hypochromism?

Answer 24

When DNA strands are allowed to anneal, base stacking reduces UV absorbance

Question 25

What is hyperchromism?

Answer 25

If helix is denatures, base stacking is destroyed resulting in UV absorbance going up

Question 26

Define a gene.

Answer 26

Portion of a chromosome that determines phenotype Changes in gene alter phenotype

Question 27

Who found the one gene-one enzyme hypothesis?

Answer 27

Garrod in 1909 when working on human alkaptonuria Genes work by controlling synthesis of specific enzymes

Question 28

What did Sumner do in 1926?

Answer 28

Showed that enzymes are proteins

Question 29

What did Beadle and Tatum do in 1941?

Answer 29

Working on mutants in mold Neurospora they found that each mutant lost one enzyme.

Answer 30

Question 31

What is the physical template stand of a gene called?

Answer 31

The antisense strand

Question 32

What is the non-template strand of a gene called?

Answer 32

Sense or coding strand/sequence

Question 33

Does mRNA have the same sequence as the sense strand or the antisense strand?

Answer 33

The sense strand with the exception of using U instead of T

Question 34

Define Genome.

Answer 34

The total amount of DNA within a cell

Question 35

What are some examples of extrachromosomal DNA?

Answer 35

Bacterial plasmids Eukaryotic mitochondrial DNA

Question 36

Does genome size correlate with species complexity?

Answer 36

Nope it does not

Question 37

Describe bacterial chromosomes

Answer 37

Always double stranded (ds) DNA Single, circular chromosome

Question 38

Describe Extrachromosomal DNA (plasmids)

Answer 38

Non-essential Always ds DNA, circular arrangement Often carries genes for antibiotic resistance (R factors)

Question 39

What are Eukaryotic genomes comprised of?

Answer 39

1) Chromosomal DNA - always linear ds DNA 2) Mitochondrial DNA - always circular ds DNA

Question 40

Are the 22 pairs of autosomes numbered from largest to smallest or smallest to largest?

Answer 40

Largest to smallest

Question 41

What is a Karyotype?

Answer 41

Cytogenic techniques use stains to identify banding patterns. Chromosomes are arrested in metaphase when they are duplicated and maximally condensed.

Question 42

Classes of Short Interpersed Elements (SINES)

Answer 42

Satellite DNA - alpha satellites, mini satellies, Heterochromatin

Question 43

What is Chromatin?

Answer 43

DNA + proteins

Question 44

Why are proteins important in chromatin composition?

Answer 44

Critical for DNA compaction

Question 45

How many types of histones (proteins) are there and are they basic or acidic?

Answer 45

5 types: H1, H2A, H2B, H3, and H4 Very Basic (lots of lys and arg)

Question 46

What happens if the protein scaffold of chromatin is digested away?

Answer 46

DNA unwinds

Question 47

What is the primary structure of DNA compaction?

Answer 47

Nucleosomes

Question 48

How many bp's of DNA wrap around a histone octomer?

Answer 48

140bp

Question 49

What is a nucleosome?

Answer 49

DNA + a histone core

Question 50

What are nucleosomes connected by?

Answer 50

20-60 bp "linker" associated with histone H1

Question 51

What do nucleosomes look like?

Answer 51

Beads on a string

Question 52

Compaction overview

Answer 52

Chromatids\> Coil \> Rosette \> Loop \> Solenoid (30nm fiber) \> Nucleosome \> Double helix Start at double helix

Question 53

What is the primary structure of compaction?

Answer 53

Nucleosome

Question 54

What is the secondary structure of compaction?

Answer 54

Solenoids

Question 55

What is the tertiary structure of compaction?

Answer 55

Loop - primary form of chromatin found in interphase nucleus

Question 56

What are the 3 specialized regions of chromosomes?

Answer 56

Origins of replication (ori) Telomeres Centromeres

Question 57

What is the origin of replication?

Answer 57

Specific DNA sequence recognized by proteisn required for replication

Question 58

What are telomeres?

Answer 58

Regions at the end of chromosome with many repetitive sequences that are no replicated during S-phase

Question 59

How are the repetitive elements added to the end of replicated chromosomes?

Answer 59

By an enzyme called telomerase

Question 60

What are the functions of Telomeres?

Answer 60

Seal chromosome ends to prevent fusion Attach chromosome to nuclear envelope Facilitate replication

Question 61

What are centromeres?

Answer 61

Signle region of each chromosome that serves as an attachment point for proteins which link the chromosome to the mitotic spine.

Question 62

What is the specific attachment region of the centromere called?

Answer 62

Kinetochore

Question 63

How are centromeres classified?

Answer 63

By location Metacentric: center Submetacentric: slightly off center Acrocentric: near one end

Question 64

What are short arms of chromosomes called?

Answer 64

p

Question 65

What are long arms of chromosomes called?

Answer 65

q

Question 66

Which 5 chromosomes are condensed to form the nucleolus?

Answer 66

13, 14, 15, 21, 22