1. DNA and chromosome structure

Question 1

Types of nucleic acids

Answer 1

• DNA
• RNA

Question 2

Building blocks of nucleic acids

Answer 2

1. Phosphate Group
2. Nitrogenous Base
3. Sugar

Question 3

Two kinds of sugar are:

Answer 3

1. Ribose (in RNA)
2. 2-Deoxyribose (in DNA)

Question 4

Difference between Ribose and 2-Deoxyribose:

Answer 4

• OH Group is present on 2’ Carbon of Ribose.
• No Oxygen present on 2’ Carbon of 2-Deoxyribose.

Question 5

Two kinds of Nitrogenous Base:

Answer 5

1. Purines
2. Pyrimidines

Question 6

Purines are:

Answer 6

• Adenine (A) and Guanine (G)
• AGGIES
• Purine ring = two rings

Question 7

Pyrimidines are:

Answer 7

• Cytosine (C), Uracil (U), Thymine (T)
• CUT
• Pyrimidine Ring = one ring

Question 8

Nucleic Acid Building Block

Phosphate Group components:

Answer 8

1. One Phosphate
2. 4 Oxygens: One double bonded O. One single bonded O. Two single bonded O-.

Question 9

Nucleosides are:

Answer 9

• Sugar + Nitrogenous Base
• Nucleoside + Phosphate Group = Nucleotide

Question 10

Nucleic Acids

What are Nucleic Acids:

Answer 10

String of nucleotides bound by PHOSPHODIESTER BONDS

Question 11

Nucleic Acids

Phosphodiester Bonds:

Answer 11

Bonds from 3’ to 5’ end.
* 5’ CH2 - Phosphate group end.
* 3’ C - OH end.

Question 12

Nucleic Acids

What happens when phosphodiester bonds are formed:

Diagram on Slide 14

Answer 12

1. 5’ Phosphate group end binds to 3’ OH group.
2. OH on phosphate group + 3’ OH + Condensation reaction = Phosphodiester bond.
3. A phosphodiester linkage connects the 5’-phosphate group and the 3’-OH group of adjoining nucleotides. H2O byproduct.

Slide 14

Question 13

Triphosphate Nucleotides are:

Diagram on Slide 15

Answer 13

Precursors to growing chain of nucleic acids.
* 5’ end always gets added to 3’ end in a growing chain.
* Energy is released when 5’ phosphate end is added.

Slide 15

Question 14

Nucleic Acid Structure

Primary Structure of Nucleic Acids:

Answer 14

Sequence of nucleotides bound by phosphodiester bonds
* 5’ to 3’ orientation

Question 15

Nucleic Acid Structure

Secondary Structure of Nucleic Acids:

Answer 15

Determined by interactions between Nitrogenous Bases
* Hydrogen bonds between bases of complementary strands
* G-C = Three bonds
* A-T = Two Bonds

Question 16

3 Types of Ribonucleic Acid (RNA)

Answer 16

1. Messenger RNA (mRNA)
2. Transfer RNA (tRNA)
3. Ribosomal RNA (rRNA)

Question 17

mRNA:

Answer 17

• FORMED during GENE TRANSCRIPTION in NUCLEUS
• Template for protein synthesis
• mRNA is link between DNA information and protein production

Question 17

DNA information is found where?

Answer 17

In the genome, NUCLEUS

Question 18

Protein Production is where?

Answer 18

The Cytoplasm

Question 19

tRNA purpose:

Answer 19

• TRANSLATES nucleotide sequence into protein sequence
• Match codons with amino acids.

Question 20

tRNA Structure:

Answer 20

1. Anticodon attaches to corresponding codon.
2. Anticodon SEQUENCE reads 5’-3’. Same for codon sequence.
3. Has an amino acid on 3’-OH group

Question 21

Ribosomes formed by:

Answer 21

1. Proteins (~35%)
2. RNA (65%)

Question 22

Ribosomes have two subunits:

Answer 22

1. Large subunit (50S)
2. Small subunit (30S)

Question 22

DNA Primary Structure:

Answer 22

1. Double stranded
2. Antiparallel chains/strands
3. Two strands held together through hydrogen bonding between nitrogenous base pairs. (A and T = 2 Bonds) (C and G = 3 Bonds).
4. The two strands are called complementary.

Question 23

What would be easier to break?
* The interaction between nucleotides in the same strand
* The interaction between complementary nucleotides in opposite strands

Answer 23

The interaction between complementary nucleotides in opposite strands.

Question 24

Two strands of DNA can be separated if necessary. Why?

Answer 24

Allows DNA to be:
1. Replicated
2. Transcribed
Both processes require partial separation of the two strands.

Question 25

Why is it harder to break a strand of DNA?

Answer 25

1. Protects the sequence of nucleotides from being altered.
2. Protects genetic information contained in sequence.

Question 26

DNA Secondary Structure:

Answer 26

1. Two chains coiled around central axis. Double Helix.
2. Nitrogenous bases lie perpendicular to axis. STACKED on one another.
3. Each turn = 10 BP per chain.
4. Minor and Major grooves.

Question 27

Chromatin

Histones:

Answer 27

• DNA Packaging through formation of NUCLEOSOMES
• A set of proteins
• FIVE TYPES: H1, H2A, H2B, H3, H4

Question 28

Why do you think Histones are rich in positively charged residues like lysine?

Answer 28

The positive charges allow them to closely associate with the negatively charged DNA through electrostatic interactions.
* The negatively charged DNA is wrapped around positively charged histone.

Question 29

Nucleosomes:

Answer 29

• A section of DNA that is wrapped around a core of proteins (HISTONES).
• Formed when the negatively charged DNA surrounds the histone octamers

Question 30

Nucleosomes = Octomers

Answer 30

Histone octamer is the eight-protein complex found at the center of a nucleosome core particle
* a nucleosome is an octamer because it is composed of eight histone proteins

Question 31

Heterochromatin

Answer 31

1. Very COMPACT and DENSE DNA
2. Mostly formed by: Regions of genome with NO GENES or Genes that are PERMANENTLY REPRESSED
3. Most of Y Chromosome is in here.
4. Centromeres and Telomeres DO NOT have genes on theme. Made of Heterochromatin.

Question 32

Euchromatin

Answer 32

1. Chromatin is MORE RELAXED
2. Allows genes to be TURNED ON AND OFF

Question 33

What would happened if a gene that is being expressed Is relocated to Heterochromatin
* It would stop being expressed and it could not be turned on
* It would stop but it could still be turned on
* Nothing, It would continue being expressed

Answer 33

It would stop being expressed and it could not be turned on.