Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry > DNA Lecture 6 > Flashcards

DNA Lecture 6 Flashcards

1
Q

All the DNA that encodes the primary sequence of some final gene product (polypeptide or RNA with a structural or catalytic function)

A

Gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

A single large DNA molecule and its associated proteins, containing many genes. It stores and transmits genetic information

A

Chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Although viral DNA molecules are small, the DNA molecules are much longer than the cells or viral packages in which they are found and vary greatly in size

A

Viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

These contain much more DNA than viruses, they can have single double-stranded circular DNA molecules, and small circular molecules of DNA free in the cytosol called plasmids

A

Bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

These cells have even more DNA than prokaryotic cells, with DNA arranged into chromosomes. The amount of DNA per chromosome and the number of chromosomes is species dependent

A

Eukaryotic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Human cells have ____ times more DNA than an E. coli cell

The human body has a total DNA length of

A

700

2x10^11 km
more than 2x the circumference of the Earth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

These cell types also have organelles, mitochondria, and chloroplasts than contain DNA.

In animal cells, mitochondrial DNA (mtDNA) is a

A

Eukaryotic cells

Circular Duplex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Genes and regulatory sequences make up almost all of the DNA in

A

Prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Many ______ genes have a notable structural feature:

Their nucleotide sequences contain one or more intervening sequences of DNA that don’t code for the amino acid sequence of the polypeptide product

A

Eukaryotic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Non-translated DNA segments in eukaryotic genes are called intervening sequences, aka ____, and the coding segments are called ___

A

Introns

Exons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Cellular DNA is compact and highly organized, the folding into cells of DNA needs to pack it and permit access to the info in DNA.

This important property of DNA means the coiling of a coil, like a telephone cord coiling on itself

A

Supercoilng

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

DNA is coiled in the form of a

Addition coiling about the axis produces ____, it relieves that structural strain

A

Double helix

Supercoiling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When the is no net bending of the DNA axis onto itself, DNA is in

A

Relaxed State

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Replication and transcription of DNA affect and are affected by ____

Both processes require, and helical intertwining complicates this.

A

supercoiling

Strand Separation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Does supercoiling occur in all cellular DNA?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The study of the properties of an object which don’t change under continuous deformations

A

Topology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

In DNA, this term means conformational changes due to thermal motion or interaction with proteins or other molecules

A

Continuous Deformation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

This means a DNA strand breakage

A

Discontinuous Deformations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Many naturally occurring DNA molecules, particularly bacteria but also DNA found in chloroplasts and mitochondria, are

A

Circular (no 5’ or 3’ end)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

A circular DNA structure can be created by forming ____ bonds between the 5’ phosphate of one end and the 3’ OH of the other end of each strand of a linear DNA molecule

A

Phosphodiester

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Plasmids and small viral DNAs are small circular DNAs. When they have no strand breaks, they are referred to as

A

Closed-Circular DNAs

22
Q

Closed circular DNA that closely conforms to the B-DNA structure, 10.5 bp/turn, are said to be

Or, in their natural form, they are

A

relaxed

Supercoiled

23
Q

DNA structure is strained, in a manner regulated by the cell, to induce

The strain is usually the result of _____ the DNA double helix in a closed circle.

A

supercoiling

Underwinding

24
Q

In isolated closed, circular DNA, the strain is accommodated by supercoiling rather than strand separation because less energy is required to supercoil than to break

A

Hydrogen bonds

25
Q

In vivo, underwinding DNA makes it easier to separate strands, and gives access to the information they contain

Every cell actively underwinds DNA with ____ processes. The resulting strain represents

A

Enzymatic

Stored Energy

26
Q

A topological property of double DNA, that doesn’t vary with deformations as long as the two strands remain intacts

It is defined as the number of times one closed, circular DNA strand is wound about another

A

Linking Number

27
Q

DNA underwinding is defined by

A

Topological linking number

28
Q

These type of properties are changed only by breaking and rejoining of backbone of one or both DNA strands

The linking number for a closed, circular DNA is always

A

Topological

An integer

29
Q

If two DNA strands are interwound in a right handed helix, the linking number is

Conversely, if the strands are interwound in a left handed helix, the linking number is

In DNA, linking numbers are typically

A

Positive

Negative

Positive

30
Q

Consider a closed circular DNA with 2100 bp

In the relaxed state, there are 10.5 bp/turn

LK is _____ If two turns are removed by underwinding the molecule, the linking number becomes _____

and the (delta)lk =

A

200

198

-2

31
Q

If there is a nick (break) in a DNA strand, Lk is

A

Undefined

32
Q

Specific linking difference can also be called

A

Superhelical Density

33
Q

Superhelical density ( σ)can by calculated as the number of turns removed to the number of turns present in relaxed DNA

A

σ = ∆Lk/Lko

34
Q

In the previous example ∆Lk=-2 and Lko = 200, what is the superhelical density

A

σ = -2/200 = 0.01 = 1%

1 percent of helical turns present have been removed

35
Q

The degree of unwinding in cellular DNA is..

A

5 to 7% or σ =0.05 to 0.07

36
Q

The negative sign in supercoiling means the DNA is

The positive sign means that it is

A

Underwound

Overwound

37
Q

The linking number can be changed + or - _____ by breaking one DNA strand, rotating the ends 360 degrees about the unbroken strand and rejoining the broken ends

A

+ or - one

38
Q

Two forms of circular DNA that differ only in a topological property such as a linking number

A

Topoisomers

39
Q

Linking number (the number of times the two strands are linked together) can be broken down into two structural components, what are they?

A

Write (Wr) and Twise (Tw)

40
Q

A measure of the of the coiling of the helix axis (supercoiling)

Determines the local twisting or spatial relationship of neighboring base pairs

A

Writhe

Twise

41
Q

In terms of writhe and twist, linking number is equal to

A

Lk= Tw + Wr

42
Q

Do Tw and Wr have to be integers?

A

No

43
Q

In the example in the figure, the B form of DNA is bent into a circle. Since there are 105 bp and 10.5 bp/turn, what is the twist?

The ends are sealed together without twisting to give a relaxed circle, so T=

W=

L=

This is a ___ circle

A

10

T=10

W=0

L=10

Relaxed

44
Q

In another example, the DNA is underwound by one turn and then the ends are joined together to form a circle (L used to be 10)

What is T?

What is W?

What is L?

How many bp/turn?

This is a ___ circle

A

T=9

W=0

L=9

105/9 = 11.67

Strained

45
Q

In another example, the DNA molecule (L=10) supercoils rather than absorbing the strain with a change in twist. The one twist of the coil is right-handed, so it is defined as

W=

T=

L=

What type of structure is this?

A

Negative Supercoil

W=-1

T= 1-

L=9

Tertiary Structure

46
Q

Most naturally occurring supercoiled DNA molecules are left or right handed?

W will be ____ if the DNA is overwound such that the supercoil will be lefthanded

A

Right handed (-W)

Positive

47
Q

In addition to supercoiling and strand separation, the underwinding of DNA also helps promote a number of structural changes in the molecule

For example, underwinding a DNA helix keeps the required strand separation need to form the ___ structure described in the last lecture

Also, underwinding a right -handed DNA helix facilitates formation of short stretches of left handed DNA in regions where base sequence favors ____

A

Cruciform

Z form

48
Q

Enzymes that increase or decrease the extent of DNA underwinding. They change the linking number.

They play an important role in replication and DNA packing

A

Topisomerases

49
Q

This topoisomerase breaks on of the two DNA strands, the change in Lk is ±1

A

Type I topisomerase

50
Q

This topoisomerase breaks both DNA strands, and the change in LK is ±2

A

Type II topoisomerase

51
Q

The effects of the topoisomerase enzymes can be demonstrated by

More supercoiled structure are compact, so they move farther down the gel

A

Agarose Gel electrophresis

Biochemistry (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions