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AP Biology - Mrs. Unger 24-25 > Unit 5: DNA Structure and History > Flashcards

Unit 5: DNA Structure and History Flashcards

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1
Q

Define

Genome

A

All of a cell’s genetic information

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2
Q

Describe the

Human Genome

A

46 chromosomes in total (2 sets (2n) of 23 (n=3) chromosomes)
Around 3 billion nucleotides
Around 20-25,000 genes

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3
Q

Define

Chromosome

A

One DNA molecule + all associated proteins

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4
Q

Compare and contrast

Prokaryotic & Eukaryotic Chromosomes

A

Both: Contain DNA
Proks:
* Found in cytosol / nucleoid region
* Singular
* Circular (loops back on self)
* “Naked” – fewer proteins associated
Euks
* Found in nucleus
* Multiple chromosomes present
* Linear (has ends)
* Has many associated proteins

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5
Q

Define

Chromatin

A

All of the DNA and associated proteins in the cell; may be condensed or relaxed
Chromosome = 1 DNA
Chromatin = all of the chromosomes

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6
Q

List

What forms may chromosomes be in?

A

Heterochromatin or euchromatin

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7
Q

Describe

Heterochromatin

A

Highly condensed form of chromatin
Allows separation of individual chromosomes
Does not allow access for transcription

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8
Q

Describe

Euchromatin

A

“True” chromatin – loose / not tightly condensed
Allows access of enzymes for transcription
Would get tangled if trying to separate individual chromosomes

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9
Q

Why must DNA be packaged/coiled?

A

So it all fits into the nucleus
AND
so that it is organized to either be used in transcription or separated for cell division

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10
Q

Describe how DNA is packaged into tight chromosomes

A

Note: “Chromosome” can refer to individual DNA molecules within the chromatin OR can refer to the highly condensed, super-coiled structures

From smallest to largest:
DNA coils into nucleosomes
Nucleosomes bundle to make a 30 nm fiber
The 30 nm fiber loops
The loops coil to make chromosome

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11
Q

Define

Histone

A

Protein molecules that bind to DNA and allow it to coil

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12
Q

Define

Nucleosome

A

A “ball” of DNA wrapped twice around 8+1 histone proteins

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13
Q

Define

Karyotype

A

An image that shows all chromosomes in their condensed state, organized by size

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14
Q

Describe the work of

Thomas Hunt Morgan

A

Supported the chromosomal theory of inheritance and showed that genetic information existing in the chromosomes
Did not determine whether genetic info was in the DNA or protein

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15
Q

Describe the work of

Frederick Griffith

Hint: Bacteria and mice

A

Used bacteria that had two forms: pathogenic (illness-causing) or non-pathogenic (“safe”) and infected them into mice
Found that non-pathogenic live bacteria, if mixed with heat-killed pathogenic material, would still lead to a deadly strain that would kill the mice
Concluded that the bacteria could be transformed

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16
Q

Define

Transformation

(related to DNA)

A

A change in the genes and/or physical traits of an organism due to its cells taking up DNA from its environment

17
Q

Describe the work of

Hershey & Chase

Hint: radioactive sulfur and phosphorus

A

Used radioactive P and S (which can be detected) to grow bacteria-infecting viruses
The radioactive P would be incorporated into DNA but not proteins
The radioactive S would be incorporated into proteins but not DNA
They infected bacteria with each type of virus and found that the radioactive P entered the bacteria and the radioactive S did not
Concluded that DNA (but not proteins) were “injected” into bacteria when infected

18
Q

Describe the work of

Chargaff

A

Analyzed the types of nucleotides found in various organisms, and found that for all organisms, the amount of T equaled A, and C equaled G

19
Q

State

Chargaff’s Rule

A

In DNA, the amount of A=T and C=G

20
Q

Describe the work of

Rosalind Franklin

A

Used X-ray crystallography to determine the 3-D structure of DNA was likely a helical shape

21
Q

What is X-ray crystallography?

A

Method of crystallizing molecules and shooting Xrays at it
The angles of the X-rays bouncing of the molecules can be calculated to determine the shape of the individual molecules

22
Q

Describe the work of

James Watson & Francis Crick

A

Used models of nucleotides, information from Franklin, and information from Chargaff to model the correct structure of the DNA molecule

23
Q

List the parts of a nucleotide

A

Pentose (five carbon sugar)
Phosphate group (on the 5-carbon of the sugar)
Nitrogenous base (on the 1-carbon of the sugar)

24
Q

List the

Key elements of DNA’s structure

There’s five you should list

A

-Sugar and phosphates “face” outward
-Nitrogenous bases “face” inward
-Double stranded helix
-Antiparallel
-Nitrogenous bases have specific base pairings

25
Q

What pentose is in DNA?

A

Deoxyribose

26
Q

What nitrogenous bases are in DNA?

A

adenine (A)
thymine (T)
guanine (G)
cytosine (C)

27
Q

List / define the

Pyrimidines

A

One-ringed nitrogenous bases
Cytosine and Thymine

28
Q

List / define the

Purines

A

Two-ringed nitrogenous bases
Guanine and Adenine

29
Q

Define

Antiparallel

A

DNA strands run in opposite directions

30
Q

Describe / explain

5’ and 3’

A

5’ = the end of DNA where the phosphate on the 5-carbon is free / not bound to another nucleotide
3’ = the end of DNA where the hydroxyl group on the 3-carbon is free / not bound to another nucleotide

31
Q

This end is the…

A

5’ end

32
Q

This end is the…

A

3’ end

33
Q

How would this DNA strand be written?

A

5’-CGAT-3’

34
Q

How would you write the complementary strand of DNA?

A

5’-ATCG-3’

35
Q

State the Rule of Complementary Base Pairing

A

In DNA:
A always binds to T
C always binds to G

36
Q

Why does DNA have complementary base pairing?

Consider the structures of each nucleotide

A

A purine and pyrimidine must bind to maintain the diameter of DNA
A and T each have two polar regions for hydrogen bonding
C and G each have three polar regions for hydrogen bonding
This ensures that A always binds to T and C always binds to G

AP Biology - Mrs. Unger 24-25 (21 decks)

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