Chapter 9: DNA and Its Role in Heredity

Question 1

What criteria needed to be demonstrated before people could accept that DNA was the genetic material? (Circumstantial evidence)

Answer 1

present in the cell nucleus and in condensed chromosomes
doubled during S phase of cell cycle
was twice as abundant in diploid as haploid cell
showed the same patterns of transmission as the genetic info it was supposed to carry

Question 2

Miescher

Answer 2

took bandages isolated nucleus, a solution came out that he called nuclein
said eh I bet this is genetic material

Question 3

bacteriophage

Answer 3

viruses that infect bacteria

Question 4

transformation experiments

Answer 4

bacteria strain A + strain B DNA —–> bacteria strain B

Question 5

transgenic

Answer 5

artificially modified organism

Question 6

Chargaff’s rule

Answer 6

A nd T

C and G

Question 7

Nucleotide

Answer 7

deoxyribose in DNA, sugar in general

phosphate group

Question 8

Purines

Answer 8

A and G

double ring

Question 9

Pyrimidine

Answer 9

C and T

single ring

Question 10

helical

Answer 10

spiral shape
like spring
DNA
Franklin’s Crystallography results

Question 11

antiparallel

Answer 11

strands run in opposite directions

Question 12

What defines DNA structure?

Answer 12

double stranded helix of unifrom diameter
right handed
antiparallel
outer edges of nitrogenous bases exposed in major and minor grooves, which exist because the helices fromed by backbones are not evenly spaced
the surfaces of A-T and G-C base pairs are chemically distinct
the binding of proteins to specific base pair sequences is the key to DNA-protein interactions

Question 13

True or false: all regions of all DNA are right handed

Answer 13

false

Z-DNA= left handed regions

Question 14

What functions is the double stranded helix essential to?

Answer 14

storage of genetic info (tons of nucelotides allow for lots of storage)
Precise replication during the cell division cycle (complementary base pairing)
susceptibility to mutations
expression of the coded information as phenotypes [not obvious in the structure]

Question 15

Semiconservative replication

Answer 15

each strand of the parental DNA acts a template for a new strand, which is added by base pairing

Question 16

What are the two general steps for DNA replication?

Answer 16

double helix unwound to separate the two template strands and get them ready for base pairing
new nucleotides form complementary base pairs with the templates and then linked by phosdiester bongs
template read in 3’ to 5’

Question 17

Deoxyribonucleoside triphosphosphates (dNTPs) deoxyribocucleotides

Answer 17

each carry three phosphate groups
during synthesis they release the outer two in an exothermic reaction, giving the nergy for phosphodiester bond formation
between the third phosphate and the 3’ sugar position

Question 18

DNA polymerase

Answer 18

catalyzes the addition of nucleotides as the new DNA chain grows

Question 19

origin of replication

Answer 19

ori

pre-replication complex, with DNA polymerase, binds to it

Question 20

replication forks

Answer 20

once the pre-replication complex is binded to the DNA, where replication happens
opens up in one direction

Question 21

What does DNA replication begin with?

Answer 21

primer

Question 22

primer

Answer 22

starter strand that DNA polymerase can hook on to
generally short strand of RNA
degraded at the end

Question 23

Primase

Answer 23

enzyme that adds primer

one nucleotide at a time

Question 24

Leading strand

Answer 24

one of the newly synthesized strands

can dontinuously grow at 3’ end

Question 25

Lagging strand

Answer 25

one of the newly synthesized strands can't grow continuously because it orients away from the fork short backward stretches

Question 26

Okazaki fragment

Answer 26

short stretches of new DNA on the lagging strand

Question 27

True or false: each Okazaki fragment needs a new primer

Answer 27

true

Question 28

Processive

Answer 28

DNA polymerase is this | it catalyzes many sequential polymerization reaacitons each time it binds to a DNA molecule

Question 29

DNA ligase

Answer 29

connects the okazaki fragments

Question 30

True or false: chromosomes become a little shorter with each cell division

Answer 30

true

Question 31

Telomeres

Answer 31

repetitive sequences at the end of each strand prevents chromosomes form joining together TTAGGG repeats bind proteins to them #aglets

Question 32

Telomerase

Answer 32

enzyme | catalyses the addition of lost telomeric seuences in continually dividing cells

Question 33

What happens when the chromsome ends become too short and their protective role is lost?

Answer 33

apoptosis and cell death | contains an RNA sequence that acts as a tenokate for the DNA sequence

Question 34

What are the two major repair mechanisms?

Answer 34

Proofreading- right after DNA polymerase inserts a new nucleotide when it recognizes the mistake, it removes the wrong base and tries again Mismatch repair- after DNA has been replicated another set of proteins checks it out if there is an error, a section of the DNA will be removed and replaced

Question 35

Polymerase chain reaction

Answer 35

allows researchers to mak emultiple copies of short DNA sequences amplification uses a sample of double stranded DNA template some short primers dNTPs DNA polymerase salts ans buffers

Question 36

True or false: mutations are changes in the nucleotide sequence of DNA that are passed form one cell or organism to another

Answer 36

True

Question 37

Somatic Mutations

Answer 37

occur in somatic (body) cells passed on to daughter cells ex. patch of skin with sane mutation NOT PASSED ON TO OFFSPRING (unless you are a plant and you follow 0 rules)

Question 38

Germline mutations

Answer 38

occur in cells of the germ line give rise to new gametes a gamete with mutation passes it on to new organism

Question 39

Silent mutations

Answer 39

do not affect gene function either not expressed or have no effect most mutations in large genomes are silent

Question 40

Loss-of-function mutations

Answer 40

rither loss of expression of a gene or in the production of a nonfunctional protein or RNA some prevent transctiption or cause it to happen too soon sometimes, the protein doesn't work generally recessive inheritance

Question 41

Gain-of-function mutation

Answer 41

protein with altered function usually dominant common in cancer

Question 42

Conditional Mutations

Answer 42

cause phenotypes only under certain restrictive conditions wild-type expressed under permissive conditions many temp sensitive

Question 43

Point mutation

Answer 43

gain, loss, or substituion of a single nucleotide | if in a gene, results in a new allele, which may result in a new phenotype

Question 44

Chromosomal Mutations

Answer 44

extensive changes in chromsome structure | change position or orientation of DNA segment without removing genetic info or cause a segment to be duplicated or lost

Question 45

Mutagens

Answer 45

environmental substances that cause mutations such as radiation or chemicals cause point mutations

Question 46

Deletions

Answer 46

a type of chromosomal mutation removal of part of the genetic material ex. DNA molecules breaks at two points, the two ends rejoin and the middle is gone

Question 47

Duplications

Answer 47

a type of chromosomal mutation ex. homologues break at different positions and then reconnect at wronf partners one would lack a section (deletion) another would have two (duplication)

Question 48

Inversions

Answer 48

can also result from breaking and rejoining | a segment may be removed but then flipped so it runs in the opposite direction

Question 49

Translocations

Answer 49

segments of the chromosome break off and become joined to different chromosome may involve reciprocal exchanges often lead to duplications and deletions

Question 50

Spontaneous Mutations

Answer 50

permanent changes in the genetic material that occur without outside influence

Question 51

what can cause spontaneous mutations to occur?

Answer 51

DNA polymerase makes a mistake (some are not caught) Four nucleotide bases of DNA have alternate structure that affect base paring- each nucleotide can exist in two different forms(tautomers), one common one rare can pair wrongly Bases in DNA may change because of spontaneous chemical reactions- deamination converte amino to a keto to change C to U usually repaired Meiosis isn't perfect- nondisjunction and aneuploidy Gene sequences can be disrupted- random chromsome breakage/rejoining

Question 52

Induced Mutations

Answer 52

some agent from outside the cell (mutagen) causes a permanent change in the DNA sequence

Question 53

What causes induced mutations?

Answer 53

``` chemicals alter nucleotide bases some chemicals add groups radiation damages the genetic material can produce highly reactive chemicals can break down the sugar-phosphate backbone ```

Question 54

True or false: mutations tend to occur in certain places

Answer 54

true

Question 55

True or falsee: mutagens can only be artificial

Answer 55

false, they can also be natural

Question 56

Benefits of mutations

Answer 56

raw material of evolution

Question 57

Costs of Mutations

Answer 57

can be harmful if result in loss of function of genes or other things that are needed for survival