7.1 DNA Structure Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Describe the structure of DNA including the antiparallel strands, 3’ - 5’ linkages and hydrogen bonding between purines and pyrimidines

A
  • The carbon atoms in deoxyribose are numbered, with the nitrogenous bases attached to C1and the phosphate group attached to C5
    • Nucleotides are joined by a covalent phosphodiester bonds between the C5phosphate group and the C3hydroxyl group
    • The chain is constructed 5’ - 3’, as new nucleotides bond to the exposed C3 hydroxyl group
    • The nitrogenous bases interact via hydrogen bonding (complementary base pairing)
    • In order for the bases to associate one strand must run antiparallel to the other (3’ - 5’)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

State the number of hydrogen bonds between A and T

A

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

State the number of hydrogen bonds between G and C

A

3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline the structure of nucleosomes

A
  • The DNA of eukaryotes associates with proteins called histones
    • DNA is wound around an octamer of histones (8 histones)
    • The octamer and DNA combination is secured to a H1 histone, forming a nucleosome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Outline the function of nucleosomes

A

Nucleosomes serve two main functions
• They protect DNA from damage
• They allow long lengths of DNA to be packaged (supercoiled) for mobility during mitosis/meiosis
• When supercoiled, DNA is not accessible for transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define exon

A

The part of the gene which codes for a protein (expressed sequence)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define intron

A

A non coding sequence of DNA within a gene which is cut out by enzymes when RNA is made into mature mRNA (interrupting sequence)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Outline the features of exons (unique or single copy genes)

A
  • Smaller proportion of genome
    • Occur once in the genome
    • Long base sequences
    • Usually genes
    • May be translated
    • Low rate of mutation
    • Very similar between individuals
    • Not used for DNA profiling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Outline the features of introns (repetitive sequences)

A
  • Larger proportion of genome
    • Occur many times in the genome
    • Short base sequences
    • Not genes
    • Never translated
    • Higher rate of mutation
    • Varies greatly between individuals
    • Used for DNA profiling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Distinguish between eukaryotic and prokaryotic DNA with regards to introns

A

Eukaryotic DNA contains introns but prokaryotic DNA does not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly