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Bio152 > U2L10 > Flashcards

U2L10 Flashcards

1
Q

State the nitrogenous bases of a DNA strand

A

Thymine, Guanine, Cytosine, Adenine
Uracil - only in RNA

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2
Q

What is attached to a deoxyribose sugar?

A

Phosphate group and Nitrogenous base

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3
Q

What backbone does a DNA strand have?

A

Sugar phosphate

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4
Q

What did Rosalind Franklin and Maurice Wilkins do?

A

Used X-ray crystallography to produce a picture of the DNA molecule

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5
Q

How did the Xray images help Watson?

A
  • Helped him conclude the DNA is helical
  • Helped him calculate the width of the helical and the space between nitrogenous bases
  • The photo suggested that DNA molecules formed a double helix
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6
Q

What are phosphate groups attached to?

A

5’ ends

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7
Q

What do covalent sugar phosphate bonds link?

A

Nucleotides of each strand

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8
Q

What holds nitrogenous bases together?

A

Hydrogen bonds

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9
Q

What did Watson and Crick do?

A

Build models of a double helix
Watson built a model where backbones were antiparallel (run in opposite directions)

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10
Q

What did Watson determine?

A

That adenine pairs with Thymine and guanine pairs with cytosine

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11
Q

Chargaff’s rule

A

A=T
G=C

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12
Q

Species A has 4 million GC pairs and 2 million AT pairs.
Species B has 4 million AT pairs and 2 million GC pairs.
Which do you think can live at higher temperature? Why?

A

Species A because GC forms 3 hydrogen bonds whereas AT forms 2 hydrogen bonds. It takes energy to break down more hydrogen bonds so species A will be more resistant to higher temperatures

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13
Q

List some of the proteins involved in the initiation of DNA replication

A

Topoisomerase, primase, helicase, single strand binding proteins

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14
Q

What does topoisomerase do?

A

Prevents DNA from getting tangled and relives pressure - unwinds DNA

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15
Q

How many types of DNA polymerase are there and what do they do?

A

2 types - DNA polymerase 2 and 3 - add correct nucleotides

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16
Q

How does antiparallel structure affect replication

A

DNA polymerase adds nucleotides only to the free 3’ end of a growing strand, therefore a new DNA strand can elongate only in 5’ to 3’

17
Q

Which way does a leading strand move?

A

Towards the replication fork

18
Q

How is the lagging strand elongated?

A

DNA polymerase must work in the direction away from the replication fork. The lagging strand is synthesized as series of segments called Okazaki fragments which are joined by DNA ligase

19
Q

What does helicase do?

A

Unwinds the parental double helix

20
Q

What happens if nucleotides are not placed in the right spot?

A

Repair enzymes correct errors in base pairing

21
Q

What happens in a nucleotide excision repair?

A

A nuclease cuts out and replaces damaged stretches of DNA

22
Q

What is the evolutionary significance of altered DNA nucleotides

A

changes in sequence have chances of being permanent and can be passed down to the next generation - these changes (mutations) are sources of genetic variation upon which natural selection operates

23
Q

What are telomeres?

A

Eukaryotic chromosomal DNA molecules have special nucleotide sequences at their ends called telomeres

24
Q

What does repeated rounds of replication produce?

A

Shorter DNA molecules with uneven ends

25
Q

What do telomeres postpone?

A

The erosion of genes near the ends of chromosomes - shortening of telomeres is connected to aging

26
Q

What does telomerase do?

A

Catalyzes lengthening of telomeres in germ cells

27
Q

How can the shortening of telomeres be a good thing?

A

Might protect cells from cancerous growth by limiting the number of cell divisions

28
Q

Describe DNA molecules in bacteria and eukaryotic

A

Bacterial chromosomes are double stranded - circular DNA molecules with small amounts of protein
In a bacterium - DNA is supercoiled and found in nucleoid
Eukaryotic chromosomes are linear DNA molecules with large amounts of protein

29
Q

What is chromatin?

A

Complex of DNA and protein found in nucleus of eukaryotic cells

30
Q

Inheritance of Tay Sachs disease

A

Autosomal recessive

31
Q

Inheritance of cystic fibrosis

A

Autosomal recessive

32
Q

Inheritance of sickle cell anemia

A

Autosomal recessive

33
Q

Inheritance of Achondroplasia

A

Autosomal dominant

34
Q

Inheritance of hemophilia

A

X linked recessive

35
Q

Inheritance of colour blindness

A

X linked recessive

Bio152 (19 decks)

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