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Cell Biology > DNA > Flashcards

DNA Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the structure of DNA?

A

Double helix

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2
Q

How many base pairs are there for every complete turn of the DNA helix?

A

10

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3
Q

How are nucleotides in DNA held together?

A

By the sugar phosphate backbone

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4
Q

What type of bond forms between individual nucleotides on the sugar phosphate backbone?

A

Covalent bonds between 5’ phosphate and 3’ -OH of deoxyribose

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5
Q

What type of bond forms between complementary base pairs?

A

Hydrogen

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6
Q

In what direction do the two strands of DNA run?

A

Antiparallel

  • 5’ to 3’ on one strand
  • 3’ to 5’ on the other strand
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7
Q

What is a nucleoside?

A

Pentose sugar and a nitrogenous base

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8
Q

What is a nucleotide?

A

Pentose sugar, nitrogenous base and a phosphate group

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9
Q

What are the three functions of DNA?

A

Gene expression
Replication
Store genetic information

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10
Q

Describe the process by which a gene is expressed.

A
  1. Promoter regions on DNA establish the gene to be expressed (RNA polymerase II)
  2. Transcription - RNA polymerase moves along the template strand synthesising an mRNA molecule containing the code for the gene to be expressed
  3. Translation - mRNA is used as a template to assemble a sequence of amino acids which further folds to produce a protein
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11
Q

Describe the process of DNA replication.

A
  1. Complementary strands are fully separated
  2. Each strand acts as a template
  3. Free bases form hydrogen bonds with the exposed strand
    - semi conservative replication
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12
Q

What is a chromosome?

A

A string of DNA combined with proteins

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13
Q

Are humans haploid or diploid?

A

Diploid

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14
Q

How many chromosomes do humans have?

A

46

  • 22 pairs of autosomes
  • 1 pair of sex chromosomes
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15
Q

What is the structure of a chromosome?

A 
Telomere
P arm
Centromere
Q arm 
Telomere
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16
Q

Where is the telomere found and what is its function?

A

Found at either end of the chromosome

Protects the chromosome and the genetic information carries

17
Q

How are telomeres affected during DNA replication and why?

A

Short pieces of the telomere are lost

This ensures no genetic information is lost during DNA replication

18
Q

What is the function of the centromere?

A

Holds metaphase chromosomes together

Attaches to mitotic spindle during cell division

19
Q

How are bands numbered on chromosomes?

A

From the centre out

20
Q

What type of dyes are used to stain chromosomes?

A

Fluorescent

21
Q

Describe the process by which DNA is transformed into a chromosome.

A
  1. DNA coils around a histone to form a nucelosome
  2. H1 protein binds to the outside of the nucelosome to form a chromatosome
  3. Chromatosomes fold to produce 30nm fibre
  4. 30nm fibre forms loops 300nm in length
  5. Loops are compressed and folded to produce 250nm wide fibre
  6. Tight coiling of 250nm wide fibre produces chromatids
  7. Chromatids are joined by centrosomes to form chromosomes
22
Q

What is a nucleosome?

A

DNA coiled around a histone octamer

23
Q

What is an octamer?

A

2 molecules of each of 4 different histones = H2A, H2B, H3 and H4

24
Q

How many times does DNA wrap around a histone octamer?

A

1.65

25
Q

How are nucleosomes separated?

A

By sections on linker DNA that are up to 80 nucleotides long

26
Q

What binds to linker DNA?

A

Other proteins; regulatory, structural

27
Q

What helps fold fibre and attach nuclesomes to each other?

A

Interactions between the 4 core histone proteins

28
Q

How long is the fibre formed when nucleosomes start to fold?

A

30nm

29
Q

Roughly, how long are the loops of nucleosome fibre?

A

300nm

30
Q

How wide is the fibre produced when loops of nucleosome fibre are compressed?

A

250nm

31
Q

What is required for the compressing and folding of nucleosome fibre?

A

ATP

Cell Biology (11 decks)

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