Genetics: Chapter 6

Front 1

What was the phosphorus-rich, weakly-acidic material in which Friedrich Miescher extracted from the nuclei of a white blood cell? What did he call it?

Back 1

DNA; "nuclein"

Front 2

What are the three characteristics of DNA?

Back 2

deoxyribose sugar, found in nuclei, weakly acidic

Front 3

What does DNA contain?

Back 3

a ribose sugar that lacks a hydroxyl group
phosphate PO4 (acidic)
four kinds of nitrogenous bases

Front 4

What are the purines?

Back 4

adenine and guanine (AG)

Front 5

What are the pyrimidines?

Back 5

cytosine, uracil, thymine (CUT)

Front 6

What is the building block of nucleic acids?

Back 6

nucleotide

Front 7

What is a nucleotide made of?

Back 7

sugar + phosphate base + base

Front 8

The chain of alternating phosphate and sugar is known as a ___________ or the _____________ of DNA.

Back 8

polymer; backbone

Front 9

What are the characteristics of the smooth (S) strain?

Back 9

synthesizes a polysaccharide capsule that surrounds pairs of cells

capsule helps to evade (avoid) host's immune system

contains virulence (ability to cause disease)

Front 10

What are the characteristics of the rough (R) strain?

Back 10

unable to make capsular polysaccharide (lacks an enzyme)

arise spontaneously as mutants of S

fail to cause infection (non-virulent)

Front 11

What is the ability of a substance to change the genetic characteristics of an organism?

Back 11

transformation

Front 12

What resulted from mixing the R strain with heat-killed S strain? (Frederick Griffith experiment)

Back 12

The R strain transformed into S strain (virulent strain). The transformation was permanent and likely genetic. All future generations of the bacteria were S strain.

Front 13

What is the active agent of transformation?

Back 13

DNA

Front 14

What did Oswald Avery's laboratory discover?

Back 14

They could achieve transformation without using any animals, simply by growing R-form bacteria in medium in the presence of components from dead S forms.

Front 15

In the Avery experiment, enzymes that degraded RNA, proteins, or polysaccharides had no effect on the transforming principle, but an enzyme that degraded _________ completely destroyed its activity.

Back 15

DNA

Front 16

What is a bacteriophage?

Back 16

"bacteria eater" - virus for which the natural host is a bacterial cell

Front 17

List the steps of the life cycle of a bacteriophage. (Hershey-Chase experiment)

Back 17

1) Phage attaches to bacterium (host).

2) Phage injects its genes into host cell.

3) Phage DNA replicates; new phage proteins are made.

4) Phage particles assemble.

5) Cell bursts, releasing new phage.

Front 18

In Hershey-Chase experiment, two separate cultures of were infected with T2 bacteria. One culture contained medium with radioactive _______________ and the other ________________.

Back 18

phosphate (32P) and sulfur (35S)

Front 19

Where did most of the radioactive 32P go? (Hershey-Chase experiment)

Back 19

32P is in DNA --> went to pellet

Front 20

Where did most of the radioactive 35S go? (Hershey-Chase experiment)

Back 20

35S is in protein --> remained in supernatant

Front 21

What was the result of centrifugation of the Hershey-Chase experiment?

Back 21

heavier bacterial cells migrated to the bottom (32P)

lighter protein coats stayed in the supernatant (35S)

Front 22

The three domains of life (archaea, bacteria, eukaryote) use DNA to store genetic information. On the other hand, viruses use _________ or __________.

Back 22

DNA or RNA

Front 23

What does Chargraff's Rule state?

Back 23

In all DNA there is:

the same amount of adenine (A) and thymine (T)

the same amount of guanine (G) and cytosine (C)

Front 24

Why must DNA have a regular structure?

Back 24

because DNA fibers create a regular x-ray diffraction pattern

Front 25

Nucleotides in a DNA chain are linked together by _______________________.

Back 25

phosphodiester bonds

Front 26

Describe the DNA structure.

Back 26

double helix

sugar-phosphate backbone on outside and pairs of bases in the middle

Front 27

Bases are attached to backbones running in which direction?

Back 27

opposite; antiparallel

Front 28

An A on one strand can form two hydrogen bonds with a ______ on the other side. This is an example of ________________________.

Back 28

T; complementary base pairing

Front 29

The two free ends of DNA are different. Describe the 5' (five prime) end of the DNA helix.

Back 29

phosphate bound to the fifth carbon atom of the sugar ring

Front 30

The two free ends of DNA are different. Describe the 3' (three prime) end of the DNA helix.

Back 30

has a "free" third carbon (hydroxyl-group bound)

Front 31

Which form of DNA spirals to the right?

Back 31

B-form DNA; suggested by Watson and Crick; smooth backbone

Front 32

Which form of DNA spirals to the left?

Back 32

Z-form DNA; backbone takes a zigzag shape

Front 33

Where may Z-form DNA exist?

Back 33

in vivo (living organisms)

Front 34

Which form of DNA is found most in nature?

Back 34

B-form DNA (right-handed DNA)

Front 35

How is genetic information read?

Back 35

Proteins read genetic information from unwound DNA chains.

Front 36

Which form of replication consists of one strand of each new double helix being conserved from the parent molecule and the other being newly synthesized? (one old strand, one new strand)

Back 36

semiconservative replication; Watson and Crick model

Front 37

Which form of replication consists of the parental double helix remaining intact; both strands of one daughter helix are newly synthesized? (two old strands, two new strands)

Back 37

conservative replication

Front 38

Which form of replication consists of both strands of both double helixes containing both original and newly synthesized material at completion? (strands mixed with old and new particles)

Back 38

dispersive replication

Front 39

The Meselson-Stahl experiment confirmed semiconservative replication by growing E. coli cells in heavy isotope ________ medium instead of normal _________.

Back 39

heavy isotope = 15N
normal DNA = 14N

Front 40

In the Meselson-Stahl experiment, DNA was extracted from the cells of 14 N medium (normal DNA), 15 N medium (heavy isotope), and 15 N transferred to 14 N medium. What was the next step of this experiment?

Back 40

centrifugation - separating the mixture of solid and liquid by spinning it

Front 41

In the Meselson-Stahl experiment, after growing E. coli for several generations, it was found that the DNA of the cells in the medium containing 15N was _______________ than normal because..

Back 41

heavier

because of the 15N atoms in it

Front 42

The Meselson-Stahl experiment is consistent with ________________________ replication.

Back 42

semiconservative; because there is one new strand and one old strand

Front 43

What kind of replication does complementary base pairing produce?

Back 43

semi-conservative replication

Front 44

Explain the steps of semiconservative replication.

Back 44

double helix unwinds

stands separate

each strand acts as a template for new strand

complementary base pairing ensures that T signals addition of A on new strand, and G signals addition of C

two daughter helices produced after replication

Front 45

In which direction do DNA polymerases create strands?

Back 45

5' -> 3'

Front 46

Which enzymes are responsible for making DNA strands from nucleotides?

Back 46

DNA polymerases (also known as Kornberg enzyme)

Front 47

Describe the direction of DNA in one word.

Back 47

antiparellel

Front 48

Which enzymes are responsible for creating the 3' -> 5' strand of DNA?

Back 48

RNA polymerases

Front 49

In which direction is the leading strand produced?

Back 49

continuously in the 5' -> 3' direction following the moving replication fork

Front 50

In which direction is the lagging strand produced?

Back 50

discontinuously in the form of smaller fragments (Okazaki fragments)

Front 51

How is the initial free 3' end (Okazaki fragment) provided in the leading strand?

Back 51

by a short RNA primer

Front 52

How are primers made?

Back 52

by primase = RNA polymerase

Front 53

How is the shorter fragment of a lagging strand created?

Back 53

RNA primer

Front 54

Okazaki fragments are connected by a ______________________.

Back 54

DNA ligase = DNA glue

Front 55

Which enzyme is implicated in DNA repair, can digest DNA and RNA from 5' and 3' end, and digests RNA primers from the 5' end while simultaneously filling gaps?

Back 55

DNA polymerase I

Front 56

Which enzyme is responsible for the replication of damaged DNA?

Back 56

DNA polymerase II

Front 57

Which enzyme is the primary enzyme of DNA synthesis?

Back 57

DNA polymerase III

Front 58

DNA polymerases I, II, and III each have proofreading capabilities of _____________________________.

Back 58

3' -> 5' exonuclease activity

Front 59

In DNA synthesis, RNA primers are replaced with ______________.

Back 59

DNA bases

Front 60

In eukaryotic replication, which enzyme is responsible for extending the RNA primer with 20 nucleotides?

Back 60

polymerase a

Front 61

In eukaryotic replication, which enzyme is the main polymerase, displaces Okazaki fragments, and keeps synthesizing DNA?

Back 61

polymerase b

Front 62

Replication can be described as _______________ (direction).

Back 62

bidirectional

replication forks move in opposite directions

Front 63

What is the site in which DNA polymerase starts and concentrates?

Back 63

origin of replication

Front 64

Replication is bidirectional and takes place in the ______________________.

Back 64

replication bubble

Front 65

Eukaryotic chromosomes are ______________ than prokaryotic chromosomes.

Back 65

longer

Front 66

How many origins of replication do eukaryotic chromosomes have?

Back 66

several hundred

Front 67

Unwinding of chromosomes causes ________________.

Back 67

supercoiling

As one region (strand) of DNA is untwisted, the other strand becomes supercoiled.

Front 68

What relaxes the supercoiling of DNA and allows it to be accessible?

Back 68

topoisomerases by nicking, unwinding, and suturing the DNA

Front 69

What generates diversity?

Back 69

new mutations, new combinations of already existing alleles:

independent assortment of homologous chromosomes

crossing-over and recombination

Front 70

Complementary strands are redundant. Therefore, there are 2 copies of information if...

Back 70

there is an error or damage in DNA

Front 71

What does the term d-loop mean?

Back 71

d-loop = displaced DNA/displaced loop

Front 72

Chromosomes that carry a mix of alleles derived from different homologs are ______________.

Back 72

recombinants

Front 73

DNA molecules ___________ and ___________ during the process of recombination.

Back 73

break and rejoin

Front 74

The two strands of a DNA molecule do not break and rejoin at the same location on the double helix. The segment of the DNA molecule located between two breakpoints is called a _________________.

Back 74

heteroduplex (indicates strand breakage and invasion)

Front 75

During which phase of meiosis does double strand breakage occur?

Back 75

prophase

Front 76

Describe what occurs during resectioning.

Back 76

The 5' ends on each side of the break are degraded to produce two 3' single-stranded tails.

Front 77

During recombination, when the 5' end on the right side of the break is connected to the 3' end of the invading strand, the resulting X structures are called _______________________.

Back 77

Holliday junctions

Front 78

How many sister chromatids are on each chromosome?

Back 78

two

Front 79

Which enzyme cuts DNA within the strand?

Back 79

endonuclease

Front 80

During recombination, if two strands are not identical, what results?

Back 80

base pair mismatch in the heteroduplex

Front 81

Where are heteroduplexes formed?

Back 81

between two crossovers/Holliday junctions

Front 82

A small segment of information from one homologous chromosome transfers to the other. What is this called?

Back 82

gene conversion --> can give rise to an unequal yield of two different alleles (change in allele frequency)

Front 83

Mismatch leads to a _______ ratio.

Back 83

3:1