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Essential Cell Biology > Chapter 5 -> DNA and Chromosomes > Flashcards

Chapter 5 -> DNA and Chromosomes Flashcards

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1
Q

What year was the structure of DNA discovered and who are the two main people credited with the finding?

A

1953, James Watson and Francis Crick

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2
Q

Describe the typical molecule of DNA and how it is held together etc.

A

Two long polynucleotide chains, each composed of four types of nucleotide subunits, held together by hydrogen bonds between the base portions of the nucleotides and the backbone being held together via covalent bonds

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3
Q

Who are the four main people that were involved in the discovery of DNA?

A

James Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins

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4
Q

Which three people were awarded the Nobel prize for the discovery of DNA

A

Maurice Wilkins, James Watson, and Francis Crick

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5
Q

The brief story of how DNA was discovered

A

Crick and Watson worked together, hypothesizing and building many models while Franklin and Wilkins worked together using x-ray crystallography. Watson and Crick become aware of Franklin’s data and use that to solve the structure

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6
Q

How many bases are there?

A

4- Adenine, Thymine, Guanine, and Cytosine

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7
Q

What type of bond holds together the nucleotide subunits within a DNA strand?

A

Phosphodiester Bonds that link the 5’ end of one sugar to the 3’ end of another

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8
Q

How many strands of nucleotides are in DNA?

A

2 Strands

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9
Q

Guanine and Cytosine make how many hydrogen bonds between them?

A

3 Hydrogen Bonds

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10
Q

Adenine and Thymine make how many hydrogen bonds between them?

A

2 Hydrogen Bonds

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11
Q

Structure of Eukaryotic Chromosomes
- Each human cell has ____meters of DNA
- Double-stranded DNA molecules are therefore packaged into _________
- Task of packaging DNA is done by specialized ________

A
  • 2
  • Chromosomes
  • Proteins
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12
Q

Bacteria Cells typically carry their genes on a single ______ (what shape) DNA molecule

A

Circular

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13
Q

Chromatin Definition

A

Complex of DNA and proteins that folds and packages the DNA

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14
Q

Human cells each contain ____ copies of every chromosome, one from the mom and the other from the dad

What is the name for theses chromosomes?

A

2

Homologous Chromosomes

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15
Q

What is the only non homologous chromosome pair in humans?

A

X and Y

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16
Q

How many base pairs are in the human genome?

A

3.2 Billion Base Pairs AKA nucleotides

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17
Q

What is a karyotype?

A

Ordered display of full set of 46 human chromosomes (think of the colorful chromosome image)

18
Q

What is the most important function of chromosomes?
AKA what do they carry?

A

To carry genes

19
Q

What is a gene?

A

Segment of DNA that contains the instructions for making proteins or RNA molecule

20
Q

What is a genome?

A

The entire genetic information that is carried by an organism

21
Q

How many genes are in a human?

A

Dr R- 20,000
Textbook- 24,000

22
Q

What is Junk DNA AKA non-coding DNA

A

DNA that does not carry information (excess interspersed DNA)
Usefulness to cell has not yet been demonstrated

23
Q

The more complex an organism is, the larger its genome- what are the faults in this claim?

A

Human genome can be 200x larger than yeast BUT 30x smaller than some plants

24
Q

How DNA is apportioned to chromosomes differs- give an example

A

46 chromosomes in humans while there are 100 chromosomes in a species of carp

25
Q

What is the cell cycle?

A

DNA molecule that has replicated and whose replicated copies have separated and partitioned equally into two daughter cells

26
Q

What occurs during interphase in the cell cycle

A

Big Picture: Chromosomes are duplicated
Details- chromosomes are extended as long thin threads of DNA and cannot be easily distinguished (dubbed interphase chromosomes), two specialized DNA sequences-> Replication origin (where duplication of DNA begins) and Formation of Telomeres sequence at the ends of chromosomes helps to protect the chromosome

As cell cycle proceeds, DNA coils up and adopts a more compact structure, beginning the formation of mitotic chromosomes

27
Q

During what phase in the cell cycle does chromosomal duplication take place?

A

Interphase

28
Q

What do telomeres do for DNA?

A

Mark ends of chromosome and serve as a protective cap

29
Q

What occurs during M phase in the cell cycle?

A

DNA coils up until it is highly condensed to the point where mitotic chromosomes are formed, and chromosomes are distributed to 2 daughter cells via the centromere allowing the mitotic spindles to attach to each duplicated chromosome to segregate the chromosomes
CHROMOSOMES ARE EASILY VIEWED HERE

30
Q

What is the centromere?

A

DNA sequence that allowed duplicated chromosomes to be apportioned to each daughter cell

31
Q

Where are interphase chromosomes found in the nucleus

A

They occupy specific regions such as the nuclear envelope or nuclear lamina of the nucleus so that they do not become entangled

32
Q

What two categories are the proteins that bind to DNA to form chromosomes divided into?

A

Histones (responsible for formation of nucleosome- first level of DNA packing) and Non Histones

33
Q

During what phase in the cell cycle does chromatin look like a string of DNA beads?
What are the beads on the string?

A

Interphase

Nucleosomes- the basic units of chromatin structure

34
Q

After mitosis- where the chromosomes are tightly packed, what happens?

A

They unfold into a more extended form

35
Q

Is all DNA packed equally tight in the interphase phase?

A

NO- regions that contain genes that are being expressed and more extended

36
Q

What is Heterochromatin?

A

Most highly condensed form of interphase chromatin - most DNA here does not contain genes
It is mostly concentrated around centromere and telomeres

37
Q

How does heterochromatin deactivate an X chromosome when there are two X’s present?

A

One of the two X chromosomes in each nucleus becomes highly condensed and the inactivated state of that X chromosome is inherited in all of the descendants of those cells

38
Q

What is the first level of DNA packing?

A

The formation of nucleosomes which in the interphase stage look like beads on a string

39
Q

What happens to nucleosomes after the first level of packing?

A

They are further packed to generate more compact structure

40
Q

What is a nucleosome?

A

DNA wound around a core of histone proteins

41
Q

What does the Chromatin Remodeling Complex do?

A

It is a protein machine that changes the structure of nucleosomes

42
Q

5 Sections of Packaging DNA

A

Short region of DNA double helix-> Beads on a string form of Chromatin-> Chromatin fiber of packed nucleosomes-> Chromatin Fiber that is folded into loops-> Entire Mitotic Chromosome

Essential Cell Biology (19 decks)

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