Plant Genetics - Genetic Material Flashcards
Characteristics of Genetic Material
- Contains all necessary info
- Replicates accurately
- Capable of change
Genetic Materials consist of….
DNA - in all living organisms and some viruses
RNA - only in certain viruses
Chemical Composition of DNA and RNA
- Macromolecule (large)
- Polymeric (many similar smaller molecules or monomers) monomers=nucleotide
What are the “building blocks” of DNA?
Nucleotides
What are the 3 parts of nucleotides?
- Pentose (5-carbon) Sugar
- Nitrogenous Base (nitrogen containing)
- Phosphate group (PO4)
What is the difference between a DNA and RNA Pentose sugar?
RNA-Ribose (OH)
DNA-Deoxyribose (H)
What Nitrogenous Bases are present in DNA?
Adenine
Guanine
Thymine
Cytosine
What Nitrogenous Bases are present in RNA?
Adenine
Guanine
Uracil
Cytosine
What are purines?
Nitrogenous Bases that are…
Nine-membered
Double-ringed
2 Types: Adenine and Guanine
What are Pyrimidines?
Nitrogenous Bases that are…
Six-membered
Single-ringed
3 Types: Cytosine, Thymine (DNA), Uracil (RNA)
What makes up a Nucleoside?
1.Sugar
2. Base
3. Purines
What makes up a Nucleotides?
- Sugar
- Base
- Phosphate group
What is a polynucleotide?
A chain of nucleotides
5’-3’ polarity
What are Chargaff’s Rules?
- A/T=1 or G/C=1
- (A+T)/(G+C) Varies
- (A+G)/(C+T)=1
What 3 pieces of Info is the Watson-Crick model
- DNA molecule is a polynucleotide chain
- Chargaff’s Rule: Amount of A = Amount of T
and Amount of G = Amount of A - Atomic structure is helical with 2 distinct regularities along the axis of 0.34 nm and 3.4 nm
What are the main features of Watson-Crick Model?
- 2 polynucleotide chains wound around each other in a right-handed double-helix
- 2 strands are oriented in opposite directions (antiparallel) 5’ to 3’(——>) and 3’ to 5’ (<——)
- Sugar-phosphate backbones on outside, bases oriented toward the central axis
- Bases of opposite strands are bonded together by (weak) hydrogen bonds
- Base pairs are 0.34 nm apart. A complete turn takes 3.4 nm with 10 base pairs per turn.
- Grooves of unequal size between the sugar-phosphate backbones (allows protein contact with bases)
Genome
Chromosomes that contain all the DNA an organism possesses
C value
Amount of DNA in haploid genome of a species
Supercoiling
DNA Twisted in space about its own axis
Looped Domains
-organization
-allows for 10-fold increase in compaction
-Associated with proteins
Eukaryotic Chromosome
a linear, double-stranded DNA molecule running throughout its length
complex with proteins
Chromatin
complex of DNA and chromosomal proteins
What are the two types of chromosomal proteins?
- Histone (most abundant, + charge, H1 H2A H2B H3 H4, highly conserved.
- Non-histone (many types, - charge, differ in # and type and control structural roles and folding and packing)
What are the levels of chromatin packing?
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
What happens in the first level of packing DNA?
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
What happens in the second level of packing?
Chomatin fiber of packed nucleosomes associate with each other
What happens in the thrid level of packing and what is it’s significance?
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
Where is the degree of packing highly condensed?
During mitosis
Where is the degree of packing the most dispersed?
During the S phase
What are the two types of chromatin condensation?
- Euchromatin (most common, normal condensation and de-condensation, highly transcribed regions)
- Heterochromatin (remains highly condensed, transcriptionally inactive regions such as centromeres, telomeres, and other specific sites)