Plant Genetics - Genetic Material

Question 1

Characteristics of Genetic Material

Answer 1

1. Contains all necessary info
2. Replicates accurately
3. Capable of change

Question 2

Genetic Materials consist of….

Answer 2

DNA - in all living organisms and some viruses
RNA - only in certain viruses

Question 3

Chemical Composition of DNA and RNA

Answer 3

1. Macromolecule (large)
2. Polymeric (many similar smaller molecules or monomers) monomers=nucleotide

Question 4

What are the “building blocks” of DNA?

Answer 4

Nucleotides

Question 5

What are the 3 parts of nucleotides?

Answer 5

1. Pentose (5-carbon) Sugar
2. Nitrogenous Base (nitrogen containing)
3. Phosphate group (PO4)

Question 6

What is the difference between a DNA and RNA Pentose sugar?

Answer 6

RNA-Ribose (OH)
DNA-Deoxyribose (H)

Question 7

What Nitrogenous Bases are present in DNA?

Answer 7

Adenine
Guanine
Thymine
Cytosine

Question 8

What Nitrogenous Bases are present in RNA?

Answer 8

Adenine
Guanine
Uracil
Cytosine

Question 9

What are purines?

Answer 9

Nitrogenous Bases that are…
Nine-membered
Double-ringed
2 Types: Adenine and Guanine

Question 10

What are Pyrimidines?

Answer 10

Nitrogenous Bases that are…
Six-membered
Single-ringed
3 Types: Cytosine, Thymine (DNA), Uracil (RNA)

Question 11

What makes up a Nucleoside?

Answer 11

1.Sugar
2. Base
3. Purines

Question 12

What makes up a Nucleotides?

Answer 12

1. Sugar
2. Base
3. Phosphate group

Question 13

What is a polynucleotide?

Answer 13

A chain of nucleotides
5’-3’ polarity

Question 14

What are Chargaff’s Rules?

Answer 14

1. A/T=1 or G/C=1
2. (A+T)/(G+C) Varies
3. (A+G)/(C+T)=1

Question 15

What 3 pieces of Info is the Watson-Crick model

Answer 15

1. DNA molecule is a polynucleotide chain
2. Chargaff’s Rule: Amount of A = Amount of T
   and Amount of G = Amount of A
3. Atomic structure is helical with 2 distinct regularities along the axis of 0.34 nm and 3.4 nm

Question 16

What are the main features of Watson-Crick Model?

Answer 16

1. 2 polynucleotide chains wound around each other in a right-handed double-helix
2. 2 strands are oriented in opposite directions (antiparallel) 5’ to 3’(——>) and 3’ to 5’ (<——)
3. Sugar-phosphate backbones on outside, bases oriented toward the central axis
4. Bases of opposite strands are bonded together by (weak) hydrogen bonds
5. Base pairs are 0.34 nm apart. A complete turn takes 3.4 nm with 10 base pairs per turn.
6. Grooves of unequal size between the sugar-phosphate backbones (allows protein contact with bases)

Question 17

Genome

Answer 17

Chromosomes that contain all the DNA an organism possesses

Question 18

C value

Answer 18

Amount of DNA in haploid genome of a species

Question 19

Supercoiling

Answer 19

DNA Twisted in space about its own axis
Looped Domains
-organization
-allows for 10-fold increase in compaction
-Associated with proteins

Question 20

Eukaryotic Chromosome

Answer 20

a linear, double-stranded DNA molecule running throughout its length
complex with proteins

Question 21

Chromatin

Answer 21

complex of DNA and chromosomal proteins

Question 22

What are the two types of chromosomal proteins?

Answer 22

1. Histone (most abundant, + charge, H1 H2A H2B H3 H4, highly conserved.
2. Non-histone (many types, - charge, differ in # and type and control structural roles and folding and packing)

Question 23

What are the levels of chromatin packing?

Answer 23

Nucleosomes connected by linker DNA “ beads on string”
Nucleosomes associate with each other
Formation of loop domains of DNA
Condensation of chromatins
Chromosome shape is formed

Question 24

What happens in the first level of packing DNA?

Answer 24

Nucleosomes connected by linker DNA “ beads on string”
Winding of DNA around histones = nucleosome
DNA wrapped 1 3/4x around an octomer of histone proteins
2 copies of each H2A, H2B, H3, H4
Histone H1, binds to DNA where it joins and leaves the octomer
Condenses DNAQ by 7 fold

Question 25

What happens in the second level of packing?

Answer 25

Chomatin fiber of packed nucleosomes associate with each other

Question 26

What happens in the thrid level of packing and what is it's significance?

Answer 26

Loop domains of DNA form, 10s-100k base pairs per loop, loops extend from the main chromosome axis Importance: Condensation and Regulation of gene expression

Question 27

Where is the degree of packing highly condensed?

Answer 27

During mitosis

Question 28

Where is the degree of packing the most dispersed?

Answer 28

During the S phase

Question 29

What are the two types of chromatin condensation?

Answer 29

1. Euchromatin (most common, normal condensation and de-condensation, highly transcribed regions) 2. Heterochromatin (remains highly condensed, transcriptionally inactive regions such as centromeres, telomeres, and other specific sites)