molecular biology 1

Question 1

what is the difference between deoxyribose and ribose

Answer 1

deoxyribose is missing an oxygen hydroxy group on carbon 2

Question 2

how are the sugars joined together

Answer 2

sugars are joined together via a 5’-3’ phosphodiesterase bond which are strong covalent bonds

Question 2

how are the sugars joined together

Answer 2

sugars are joined together via a 5’-3’ phosphodiesterase bond which are strong covalent bonds

Question 3

nucleoside

Answer 3

base and 5 carbon sugar

Question 4

nucleotide

Answer 4

nucleoside and phosphate group

Question 5

purines

Answer 5

adenine and guanine

Question 6

pyrimidines

Answer 6

cytosine, thymine, uracil

Question 7

describe the DNA structure

Answer 7

• antiparallel double helix
• phosphate sugar backbone
• base pairs on the inside are held together with hydrogen bonds.

Question 8

primary structure of DNA?

Answer 8

sequence of nucleotides

Question 9

secondary structure of DNA?

Answer 9

spatial arrangement of the nucleotide chains

Question 10

how are base pairs held together

Answer 10

hydrogen bonds

Question 11

A-T

Answer 11

2 hydrogen bonds

Question 12

G-C

Answer 12

3 hydrogen bonds

Question 13

chromatin =

Answer 13

histone + DNA

Question 14

genetics

Answer 14

the tern used t describe inheritance of changes in base sequences

Question 15

why does the double helix normally exist in the B-helix form

Answer 15

because there are major and minor grooves formed by the structure

Question 16

what is the polarity of DNA?

Answer 16

this is the direction that DNA will run, the way which they are lined together, give DNA polarity.

Question 17

how can chromosomes be distinguished between each other

Answer 17

size and G banding

Question 18

what is a karyotype and what technique is used to find it

Answer 18

• a karyotype is a full set of chromosomes
• G banding

Question 19

what reaction is chromosomes pulled apart

Answer 19

condensation

Question 20

what forms the phosphate sugar backbone?

Answer 20

the joining of the sugars via a phosphate

Question 21

what is the charge of the phosphate sugar backbone

Answer 21

negative

Question 22

biggest and smaller chromosome?

Answer 22

1- biggest
21- shortest

Question 23

how does fluorescent marking work for identifying chromosomes?

Answer 23

• complementary probes of DNA can be made that will match the DNA being analysed
• these probes have fluorescent markers on them
• When the DNA strands are separated, they naturally want to be in a double helix so they bind to the fluorescent probe which allows for the image of chromosomes to be made.

Question 24

what are the 2 parts of the chromosome

Answer 24

telomere and centromere

Question 25

what does the centromere allow

Answer 25

it allows for separation of DNA to opposite ends during mitosis

Question 26

what is a nucleosome consist of

Answer 26

147 base pairs of DNA double helix wrapped around a histone core (DNA wrapped around histones)

Question 27

what allows histone and DNA to bind

Answer 27

the fact that the histone is positively charged and the DNA is negatively charged

Question 28

what does histone H1 do?

Answer 28

it provides a unique role in anchoring the DNA to the histone and telling it to keep folding in the right direction, this helps the nucleosome to become more condensed.

Question 29

how is the chromosome made

Answer 29

the nucleosome continues condensing.

Question 30

how are proteins condensed in the cell cycle?

Answer 30

enzymes called condensins allow the proteins to adopt a very tight structure

Question 31

why do chromosomes need to be remodelled and how is it done

Answer 31

• chromosomes need to be remodelled to allow protein access in order to use the genetic info.
• done using a remodelling complex and requires energy

Question 32

what is epigenetic modification and what are examples

Answer 32

changes in gene expression that do not cause changes in the DNA sequence.
methylation, acetylation, phosphorylation

Question 33

acetylation

Answer 33

this removes the positive charge from the histone which decreases the binding of the positively charged DNA, causing relaxation of the structure.

Question 34

what % of our genome codes for proteins?

Answer 34

approx 1.5% with the rest being junk proteins

Question 35

why are repetitions in DNA important in forensics?

Answer 35

as consecutive repeats at different locations will be different for different people
this sample can be used in gel electrophoresis to identify the matching repeats.

Question 36

what is myotonia

Answer 36

this is the inability to relax muscles at will

Question 37

what causes myotonic dystrophy

Answer 37

this is caused by a trinucletide repeat that occurs many times in a row at a particular location.
for most people a trinucleotide repeat is not going to cause any problems, but id the repeat is very large this can lead to muscular dystrophy.

Question 38

structure of mitochondrial DNA

Answer 38

17000 base pairs long
circular
2-10 copies in mitochondrion with several mitochondria per cell.

Question 39

why can mitochondria be good for forensics

Answer 39

because there are more copies and their smaller culcular structure makes them more stable allowing it to be purified while DNA can’t.

Question 40

where are mitochondria dna inherited and what is this implication on disease?

Answer 40

• inherited from mother
• this means if there is a defect in the mitochondria it will only come from the mother.
  (it is also useful to see lineage)

Question 41

what are the 2 types of repeat in DNA

Answer 41

• interspersed repeats
• tandem repeats

Question 42

what is an example of interspersed repeats?

Answer 42

SINE and LINE which are often derived from retroviruses

Question 43

what is an example of TANDEM repeats

Answer 43

satellites, mini satellites and micro satellites