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General Biology 210 > Chapter 16: The Molecular Basis of Inheritance > Flashcards

Chapter 16: The Molecular Basis of Inheritance Flashcards

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1
Q

What are the evidences that support DNA as the genetic material?

A
  1. DNA can transform bacteria
  2. Viral DNA can program cells.
  3. DNA composition varies among species.
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2
Q

What are two chemical components of chromosomes?

A

DNA and protein.

The role of DNA in heredity was first discovered while studying bacteria and viruses that infect them.

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3
Q

Transformation

A

Change in genotype and phenotype due to assimilation of external DNA by a cell.

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4
Q

What is evidence that DNA can program cells?

A

Viruses infect DNA

Bacteriophages/phages are enclosed by a protective protein coat.

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5
Q

To produce more viruses, what must be done?

A

Viruses must infect a cell and take over the cells metabolic machinery.
ex) E coli can reprogram host cells to produce viruses.

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6
Q

What is some additional evidence that DNA is the genetic material?

A

DNA is a polymer of nucleotides consisting of a nitrogenous base, deoxyribose, and a phosphate group. The base can be Adenine, Thymine, Guanine, or Cytosol.

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7
Q

Ratios of nucleotide basis

A
  1. a number of adenines equals the number of thymine (30.3%)

2. a number of guanines equals the number of cytosines (19.9%)

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8
Q

What is Chargaffs rules?

A
  1. Base compositions varies between species

2. Within species, number of A and T bases are equal and number of G and C are equal.

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9
Q

How does DNA structure support its function?

A
  1. Helix shape allows room for all of the genetic information (10 nucleotides per turn)
  2. Double helix suggests basic mechanism of DNA replication
  3. width suggested that DNA molecule was made up of two strands. (double helix)
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10
Q

Who are Maurice Wilkins and Rosalind Franklin?

A

They used the x-ray cystallography to study molecule structure of DNA.

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11
Q

What did the x-ray images do?

A
  • enabled Watson to see DNA is helical.
  • the width of the helix and the spacing of the nitrogenous bases.
  • width suggested that DNA molecule was made up of two strands. (double helix)
  • purine pairs w/ pyrimidine (A-T) (G-C)
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12
Q

Where does the DNA structure begin?

A
  • Replication of DNA beings at the origins replication
  • Proteins that start DNA replication recognize the origin on DNA and attach to the DNA, separating the two strands and opening up the replication “bubble.”
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13
Q

What happens inside of the bubble?

A
  • Replication of DNA proceeds in both directions until the entire molecule is copied.
  • Multiple replication bubbles form and eventually fuse, speeding up the copying of a very long DNA.
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14
Q

Replication Fork

A

At each end, a Y-shaped region is where the parental strands of DNA unwind.

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15
Q

Helicases

A

Enzymes that untwist the double helix, at the replication forks separating two parental strands and making them available as template strands.

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16
Q

Single strand binding

A

This happens after parental strands separate.

- Bind to the unpaired DNA strands, keeping them from re-pairing.

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17
Q

What does untwisting of the double helix cause?

A

Causes tighter twisting/strain ahead of replication fork.

- Topoisomerase helps relieve this strain by breaking, swelling, and rejoining DNA strands.

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18
Q

Can enzymes that synthesize DNA initiate the synthesis of polynucleotides?

A

No, the can only add nucleotides to the end of an already existing that is base paired w/ the template strand.

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19
Q

Initial nucleotide chain

A

is produced during DNA synthesis is actually a short strength of RNA, not DNA.

20
Q

What is a primer?

A
  1. a primer is a short RNA chain that is synthesized by the enzyme primase.
  2. It connects to the DNA template strand before complementary DNA
21
Q

DNA polymerase

A
  • they make synthesis of new DNA go faster
  • In eukaryotes there are about 11 different kinds
  • Use a primer and DNA template strands to signify where the DNA nucleotides must line up
22
Q

Origin of replication

A
  • Initiator of DNA replication

- on the DNA this origin is always found on at a specific sequence of nucleotides

23
Q

How do cells prevent shortening of DNA caused by the end-replication problem?

A
  • Eurkaryotic chromosomal DNA molecules have at their ends nucleotide sequences called telomeres.
  • telomeres have repeated DNA sequences.
  • telomeres do not prevent the shortening of DNA molecules, but postpone the erosion of genes near ends of DNA molecules.
24
Q

Telomerase

A
  • Catalyzes the lengthening of telomeres in eurkaroytic germ cells, by restoring their original length and compensating for the shortening that occurs during DNA replication.
  • telomerase is not active in somatic cells
  • activity in germ cells result telomeres of maximum length in zygote
  • protect cells from cancerous growth
25
Q

What is a chromosome like in bacteria cells?

A
  • double-stranded, circular DNA molecule associated with a small amount of protein.
  • DNA is “supercoiled” and found in the nucleoid
26
Q

Chromosomes in a Eurkaryotic cell are like?

A
  • linear DNA molecules associated with a large amount of protein.
  • Chromatin, a complex of DNA and protein and is found in the nucleus.
  • Histones, are proteins that are responsible for the first level of DNA packing in chromatin.
27
Q

What is a nucelosome?

A

the basic unit of DNA packing, the “string” between the beads are called linker DNA

28
Q

How large is the coil/fold forming the chromatin?

A

30nm

29
Q

Looped domains

A

The 30-nm fiber, in turn forms loops.

30
Q

Most chromatin is loosely packed in the nucleus during interphase and condenses prior to mitosis, what does this show?

A

several of the same levels of higher order packing.

31
Q

Euchromatin

A

Loosely packed chromatin

32
Q

During interphase a few regions of chromatin are highly condensed to?

A

Centromeres and telomeres are condensed to heterochromatin, which is less compacted and makes it difficult for the cell to express genetic information coded in these regions.

33
Q

Semiconservative replication

A

The two strands of parental molecule separate, and each functions as a template for synthesis of a new, complementary strand.

34
Q

Antiparallel structure

A

they are oriented in opposite directions to each other

35
Q

Leading strand

A

Strand of DNA being replicated continuously. In DNA replication, the strand that is made in the 5’ to 3’ direction by continuous polymerization at the 3’ growing tip.

36
Q

Lagging strand

A

A lagging strand requires a slight delay before it is replicated, and it must be replicated discontinuously in small fragments.

37
Q

Okazaki Fragments

A

Fragments of the lagging strand

38
Q

DNA ligase

A

finishes the task, joining the sugar phosphate backbones of all the okazaki fragments.

39
Q

How do the leading and lagging strands differ?

A

The leading strand is synthesized in the same direction as the movement of the replication fork, whereas the lagging strand is synthesized in the opposite direction.

40
Q

If the result of the Hershey and Chase experiment had been that radioactive sulfur (35S) was found inside the cells instead of radioactive phosphorus (32P), what could have been concluded?

A

It would have been concluded that protein functions as the genetic material (this, of course, did not occur).

41
Q

Define and diagram “semiconservative” as it applies to DNA replication.

A

A newly replicated DNA has one strand that had been present in the original and one completely new strand. Concept

42
Q

What enzyme does a gamete-producing cell include that compensates for replication-associated shortening?

A

telomerase

43
Q

Which of the following is true of heterochromatin but not of euchromatin?

A

It remains tightly coiled at the G1 phase.

44
Q

Which of the following results from Griffith’s experiment is an example of transformation?

A

Mouse dies after being injected with a mixture of heat-killed S and living R cells

45
Q

Does the distribution of bases in sea urchin DNA and salmon DNA follow Chargaff’s rules?

A

Yes, because the %A approximately equals the %T and the %G approximately equals the %C in both species.

General Biology 210 (6 decks)

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