DNA

Question 1

DNA & Uses

Answer 1

Can be obtained from a variety of somatic
cells because each body cell has the entire
DNA blueprint within them

Can be used in:
- Forensics (identification)
- Determining genealogy (relatedness)
- Vaccine development (targeted medicine)

Question 2

Structure of DNA

• Double helix
• Backbone of DNA

Answer 2

Consists of a double helix that is omposed of nucleotides
- Nucleotides come in 2 equal pairs
Backbone of DNA : a nitrogenous base, a phosphate group, and a deoxyribose (sugar)

Sugar and phosphate groups form the backbone of the helix (or the spiral shape of DNA)
Nitrogenous bases stick out from backbone and bond to complementary bases from another helix

Question 3

Base Pairs of DNA

Answer 3

Base pairs form between 1 purine (adenine, guanine) and 1 pyrimidine (thymine, cytosine)

Pair 1 : adenine + thymine
Pair 2 : guanine + cytosine

Question 4

DNA Packaging
- DNA is wrapped around H –> N
- Short lengths connect…
Nucleosomes –> Chromatin fiber –> Chromosomes

Answer 4

DNA is wrapped around histone (proteins) to form nucleosomes
-Short lengths of DNA connect nucleosomes and they stack to form chromatin fiber and then are further coiled to form chromosome
Nucleosomes –> Chromatin fiber –> Chromosomes

Question 5

DNA Replication
(Where do it occur? & What is split?)
- Acts as template
- Used to reconstruct
- 2 new DNA are formed

Answer 5

Occurs during synthesis of Interphase

Strands of DNA are split
- Each portion of DNA acts as
template
- Complementary nature of
base pairs and the template
are used to reconstruct the
missing portion
- 2 new DNA strands are formed and are exact copies of original

Question 6

DNA Replication Process

Helicase
DNA Polymerase
DNA Ligase

Answer 6

Helicase (enzyme) splits helix making a replication fork (Y-shape)

DNA polymerase (enzyme) continuously adds base pairs to the leading strand)
- It alsoadds base pairs in sections (known as Okazaki fragments) to the other strand from the opposite direction known as the lagging strand)

DNA ligase binds fragments

Question 7

Telomeres (What is it?)

Answer 7

Telomeres are the ends of chromosomes
- They can’t add base pairs to the end of the lagging strand, so it becomes shorter with each DNA replication
- The shortening of chromosomes is associated with aging

Question 8

Telomerase (What does it help with? and Where are they found?)

• Elongate
• Found in G.S. & C. cells
• Not active in…

Answer 8

Telomerase, are a type of enzyme, that can help to elongate the lagging strand to complete itslength
- They are found in germ (sex) cells, stem cells, and cancer cells
- They are not active in adult somatic (body) cells

Question 9

DNA Repair

• Mismatch repair
• Nucleotide excision
• Mistakes that don’t get corrected…

Answer 9

Sometimes incorrect base pairs get added during replication
- Mismatch repair system : repair mechanisms by checking th errors and fixing it by removing the incorrect, mis-paired base and replacing it
- Nucleotide excision stsyem : repair mechanisms similarly by removing a few base pairs and replacing them

Mistakes that don’t get corrected can
result in mutations (permanent
changes to DNA)