Nature Of Dna/rna - Genetics

Front 1

Describe DNA structure.

Back 1

Polymer made up of similar monomers, linked by covalent bonds.

Made up of nucleoside monophosphate units.

Nucleoside units linked by Phosphodiester Linkages.

Adjacent DNA strands form hydrogen bonds, double helical structure.

Front 2

What are bases derived from? How does each base differ from the original structure?

Back 2

Purine/Pyramidine

Adenine/Guanine: Purine (2 rings)

Adenine: +NH2;

Guanine: +NH2, + C=O;

Cytosine/Thymine: Pyramidine (1 ring)

Cytosine: +NH2, + C=O;

Thymine: +CH3, + x2 C=O;

Front 3

Define a nucleoside.

Back 3

Base + Sugar

Front 4

Define a nucleotide.

Back 4

Base + Sugar + Phosphate Group.

Front 5

What does each nucleotide monomer consist of?

Back 5

5-carbon sugar (Deoxyribose)

Basic group attached to 1' carbon

Phosphate Residue attached to 5' carbon

Lacks OH group at 2' carbon

Increases stability: DNA > RNA

Front 6

Draw the structure of a nucleotide, including structure of phosphate group and sugar.

Back 6

Phosphate: PO32- --- O --- (5' C) Ribose Sugar (1' C) --- Nitrogenous Base

Front 7

Which bases pair up in DNA?

Back 7

Adenine + Thymine, Guanine + Cytosine

Front 8

How are nucleotides connected?

Back 8

Phosphodiester bonds between P=O on phosphate group (5' C) and OH group (3' C)

Front 9

What is meant by DNA having a sense of direction?

Back 9

One end of DNA will have an unlinked 5' end (Phosphate group) and the other will have an unlinked 3' end (Hydroxyl group)

5' -ACG......GTG- 3'

Front 10

Describe base composition between cells in the same organisms and between organisms.

Back 10

Tissues within the same species have same base composition.

Exact base composition differs between species.

A/T & G/C ratios tend toward 1.00

Front 11

Is DNA's helical structure right-handed or left-handed?

Back 11

Right-handed

Front 12

How is DNA represented in terms of sense of direction?

Back 12

5' ------------- 3'

3' ------------- 5'

Front 13

What degree of rotation exists between each base pair?

Back 13

36

Front 14

What contributes to DNA's structural stability?

Back 14

Van der Waals forces between bases on same strand.

Hydrogen bonds between bases on opposite strands.

Front 15

How many hydrogen bonds form between A/T and C/G?

Back 15

A/T: 2 hydrogen bonds

G/C: 3 hydrogen bonds

Front 16

Describe how major/minor grooves arise.

Back 16

Sugar-phosphate backbone not equally spaced along helical axis;

C-1' not directly opposite each other, but always equally spaced.

This causes regions where DNA strands close and far from each other

Front 17

Why are major grooves important in DNA metabolism?

Back 17

Alpha-helices can insert into the major grooves.

Side chains on these helices can interact with bases in the grooves.

Therefore Proteins that interact with DNA base sequence tend to have alpha-helices.

Front 18

What is the temperature range DNA will denature at, and what factors is it dependent on?

Back 18

65-80 Degrees Celsius

Since GC pairings form x3 hydrogen bonds, large numbers results in a stronger structure and so a greater temperature needed to overcome it.

Front 19

Describe the dimensions of DNA.

Back 19

Diameter: 2nm

Adjacent base pair distance: 0.34nm

Helical structure repeat: 3.4nm

Base pair rotation: 36 degrees

Human Genome size: 3 x 10^9 bp

Front 20

How is a Octameric Nucleosome Core?

Back 20

Complex consisting of 4 Histone Protein Dimers.

Front 21

Describe how DNA condenses into a chromosome.

Back 21

Double helix wraps twice around Nucleosomes;

Form 'Beads on a string' - 10nm Fibre

Beads condense - 30nm Fibre

Fibre loops on itself - 300nm Fibre

Eventually forms 700nm Chromatid

Chromatid replicates: 1400nm Chromosome

Front 22

Describe Epigenetic Processes.

Back 22

Modify DNA/histone proteins.

C residues in CpG methylated

Histones undergo acetylation/methylation.

Can influcence whether DNA is active/inactive

DNA sequence unchanged (e.g. no bases removed etc.)

Front 23

What role do Epigenetic Processes serve?

Back 23

Regulate gene expression

Any modifcations can be passed on to subsequent generations.

Front 24

Describe Genetic Blueprint.

Back 24

Split into genes;

Each gene encodes a protein/RNA molecule.

Vary wildly between organisms.

Front 25

What % of Eukaryotic DNA is coding DNA?

Back 25

3%

Front 26

What % of DNA is involved in gene expression in some way?

Back 26

~20%