Molecula 1, Structure of DNA

Question 1

What polymer makes up DNA?

Answer 1

Nucleotide

Question 2

What are the three molecules that DNA?

Answer 2

• 2 deoxyribose sugar
• Base A?T?C?G
• Phosphate group

Question 3

How many individual phosphates does a nucleotide have? Can you name them using alpha beta and gamma

Answer 3

3
The closest to sugar alpha and furthest gamma

Question 4

Which bases are Pyrimidines?

Answer 4

Cytosine and Thymine

Question 5

Which bases are purines?

Answer 5

Adenine and guanine

Question 6

How many bonds does AT and CG have each?

Answer 6

• AT = 2 hydrogen bonds
• CG = 3 hydrogen bonds

Question 7

Which carbon numbers make the bonds in-between DNA nucleotides?

Answer 7

Carbon 3 of first nucleotide
Carbon 5 of Second nucleotide

Question 8

What is the advantage of hydrogen bonds within DNA?

Answer 8

· Complementary bases (A/G and C/T) held together by weak hydrogen bonds which is useful as it allows DNA strands to easily separate and join (DNA helicase and DNA polymerase)

Question 9

What does Chargaff’s rule state?

Answer 9

Chargaff’s rule states that the total number of purines and pyrimidines will be equal.

Question 10

What are the 3 types of DNA helix forms?

Answer 10

A-DNA
B-DNA
Z-DNA

Question 11

How does each form of DNA differ from each other? Also include when each is formed?

Answer 11

— A-DNA = (nw) narrow major groove, wide minor groove
Function= rare only forms when there is not enough water around- dehydrating conditions
— B-DNA = (wn) wide major groove narrow minor groove.
Most common type of DNA
— Z-DNA = (fn) Flat major groove, narrow minor groove

Question 12

What is INTERGENIC DNA?

Answer 12

DNA regions within coding GENES

Question 13

How is DNA lenght measured?

Answer 13

Measure in BASE PAIRS

Question 14

Two different gene, Gene A and Gene B are 10000 and 100 bp long, does this indicate that gene A has 100 times more genetic material than gene B? No, why not? Yes, why yes?

Answer 14

No because genes are discontinuous: containing EXONS and INTRONS
· Exons – contain the information required to make a protein
· Introns – information that is not needed to make protein

Question 15

What is the average length of an exons?

Answer 15

145 bp

Question 16

What is the average length of an intron?

Answer 16

Average mean length of an intron (useless) is 3365 bp

Question 17

Of the total RNA produced in the nucleus what percentage is coding? What is the rest of the RNA for?

Answer 17

Of the total RNA made in the nucleus 4% is coding-RNA, the rest 96% is non-coding RNA which is used in many other functions for example tRNA. Non-coding doesn’t indicate that is useless.

Question 18

What type of gene families are there within the DNA?

Answer 18

• Simple- gene families = these are genes that are identical within the DNA
• Complex gene families=
  Genes are not the same, but they have a similar DNA sequence
  code for similar protein
  Provides proteins with slightly different function which allows organismal complexity

Question 19

How do genes in multigene families arise?

Answer 19

Genes in a multigene family arise by gene duplication
Onw gene duplicates, which eventually leads to gene families

Question 20

How are complex genes families formed?

Answer 20

The duplicated genes start gradually changing by mutations; therefore, the members of the gene family have slightly different sequences.

Question 21

Why and HOW does time affect genes families?

Answer 21

· The greater the time has passed since duplication, the greater the differences in code between the pair of genes.

Question 22

How can you tell a recent duplication from an ANCIENT duplication?

Answer 22

Difference in DNA base sequence can be used to estimate how recently the duplication has occurred.

Recent duplication (slight difference) whereas Ancient duplication (significant difference)

Question 23

Define molecular clock

Answer 23

The molecular clock is a measure of the rate at which the sequence of a gene changes

Question 24

What can be molecular clock used for?

Answer 24

· We can use the molecular clock to work out an estimate of when a pair of genes were formed by duplication.
Remember the more recent the duplication the more similar the gene as mutation changes the sequences of duplicates over time.

Question 25

What are PSEUDOGENES?

Answer 25

Pseudogenes are genes that have mutated in such a way that they no longer make sense, so they do not code for protein anymore