DNA form and function Flashcards
What do proteins act as
4 points
- enzymes
- structural
- receptors
- messengers - hormones and cytokines
Most genes encode a
single protein
DNA (deoxyribonucleic acid) structure of DNA nucleotide
6 points
- Phosphate
- Sugar = deoxyribose
3. Base: adenine guanine cytosine thymine
- Carbons in sugar are named 1’, 2’, 3’, 4’ and 5’
- Base linked to the 1’ carbon
- Phosphate linked to the 5’ carbon
Pyrimidine nucleotides
3 points
- 6 membered rings
- dTMP (thymine)
- dCMP (cytosine)
Purine nucleotides
3 points
- 9 membered rings
- dAMP (adenine)
- dGMP (guanine)
DNA structure
bonds between
5’ and 3’ ends of nucleotides
The nucleotides in DNA are linked by
2 points
- phosphate bonds (phosphodiester bonds) between the sugars
- The 3’ carbon of one sugar linked to the 5’ carbon of the next nucleotide
Ends of DNA strand are called the
- 5’ and 3’ ends
- 5’ end: The 5’ carbon of the terminal nucleotide is free
- 3’ end: The 3’ carbon of the terminal nucleotide is free
who discovered structure f DNA in 1953
watson and crick
Franklin and wilkins
X-ray diffraction pattern indicating a helical structure
Base pairing
Hydrogen bonds
A to T 2
2 apples in tree
G to C 3
3 cars in garage
antiparallel strands
one in direction 5’ to 3’
other in direction 3’ to 5’
Base-pairing is specific:
Adenine Thymine (2 hydrogen bonds) Guanine Cytosine (3 hydrogen bonds)
Always Purine paired to Pyrimidine
Genotypic function
2 points
- information storage and replication.
- Genetic material must store genetic information and accurately transmit that information from parents to offspring, generation after generation.
Phenotypic function
2 points
- gene expression.
- Genetic material must control the development of the phenotype of the organism. i.e. the genetic material must dictate the growth and differentiation of the organism from the zygote to the mature adult.
Evolutionary function
2 points
- mutation.
- Genetic material must undergo changes so that organisms can adapt to modifications in the environment. Without such changes, evolution could not occur.
unity and diversity of life
DNA in all species shows
- molecular consistency (similar structure)
- variation (unique base sequences)
genomes
Bacteria
10 6 nucleotides; one circular chromosome
genomes
Yeast/fungi
10 7-10 8; linear chromosomes
genomes
Plants
10 8-10 11; linear chromosomes
genomes
mammals
3.4 x 10 9 nucleotides; 23 pairs of chromosomes
Each chromosome is made of
- Chromatin - a very long linear DNA molecule
2. proteins that maintain structure and regulate activity of the genes
Packaging DNA
3 points
- DNA double helix wrapped around a complex of histone proteins = forms a nucleosome
- Nucleosomes on the strand of DNA coil or fold to form a chromatin fibre
- The chromatin fibre forms looped domains which further fold to form the chromosome
packaging DNA
5 steps
DNA helix Nucleosomes Chromatin Looped chromatin Chromosome
