Intro to DNA

Question 1

Difference between DNA and RNA

Answer 1

DNA is double stranded
Requires DNA polymerase 
Thymine
Histone 
Stable 
Within nucleus 

Euchromatin - less coiled (white) - beads on a string
Heterochromatin - more coiled - not expressed - solenoid

Question 2

Solenoid

Answer 2

30nm length

Question 3

Nucleoside

Answer 3

Base and sugar

Question 4

Pyrimidine

Answer 4

Thymine and cytosine

Question 5

Nucleotide bonds

Answer 5

Phosphodiester bond

Question 6

Secondary structure of DNA

Answer 6

Hydrogen bonds

Question 7

DNA Strands

Answer 7

Complimentary

Antiparallel

Question 8

Meiosis vs mitosis

Answer 8

Mitosis is cell division for somatic cells
1 cycle
Produce 2 diploid cells (identical)
Cell replacement
Prometaphase - spindle fibres attach to kineticore which is attached to the centromere
No crossing over
No random assortment

Question 9

Meiosis

Answer 9

4 haploid cells
2 rounds

Prophase 1 - crossing over as chiasmata (bivalent)
Metaphase 1 - homologous chromosome align at metaphase plate forming a tetrad - random assortment
Anaphase 1- disjunction
Telophase 1 - 23 chromosomes in each cell

Question 10

Endogenous mutations

Answer 10

Free radicals
Transposable elements
Replication errors

Question 11

Bulky adduct

Answer 11

Bulky chemicals added on

Question 12

Intercalating agents

Answer 12

Chemicals that from between bases which interfere with translation and transcription

Question 13

Interstrand cross links

Answer 13

Physically link the 2 DNA strands interfering with DNA replication

Question 14

Apurinic site

Answer 14

Complementary base lost

Question 15

Deamination

Answer 15

C — U

Question 16

DNA exonuclease

Answer 16

Reverse polymerase

3 prime to 5 prime

Question 17

Backwards slippage

Answer 17

New strand loops out
New strand is one nucleotide longer
Insertion
Slows down

Huntington’s
Fragile X
Spinocerabellar ataxia

Question 18

Forward slippage

Answer 18

Template strand loops out
New strand is one nucleotide shorter
Deletion
Replication speeds up

Question 19

DNA damage too high

Answer 19

apoptosis
Cell cycle transition stoppped
Senescence - permanent cell cycle arrest

Question 20

Base eviction repair

Answer 20

Uracil detected where it shouldn’t be

Removed so nucleotide is baseless
Baseless nucleotide removed
Hole filled with complementary correct nucleotide - DNA polymerase
Ligase seals DNA

Question 21

Nucleotide excision repair

Answer 21

Pyrimidine dimers detected 
Surround DNA opened to form a bubble 
Enzyme cuts out damaged region 
DNA polymerase replaces the DNA lost
Ligase seals

Question 22

Non homologous ends joining

Answer 22

Bind broken ends together using ligase

May clause mutation as DNA needs to be cut for DNA ligase to work

Ends protected

Question 23

Homologous directed repair

Answer 23

Use sister chromatids or homologous chromosome

Perfect repair

Damaged chromatid invades sister chromatid
Cut region make a copy

Regions - Holliday junctions