Chapter 2 Flashcards
Webster’s Definition of DNA
An essential of all living matter and a basic material in the chromosomes of the cell nucleus: it contains the genetic code and transmits the hereditary pattern
Purpose of DNA
- Make copies of itself so cells can divide and carry the same information
- Carry instructions on how to make proteins
What does DNA stand for?
Deoxyribonucleic acid
Where is DNA found?
Almost every cell of the body
DNA’s “Alphabet”
DNA is made up of four nucleotides, represented by 4 letters: A, T, G, C
What is the important of the letters in DNA?
The order of the letters is what makes everyone different
How similar is human DNA?
Over 99% of human DNA is the same from person-to-person
How is nuclear DNA inherited?
Half of the nuclear comes from the mother and half comes from the father
True or False: An individual’s DNA profile remains the same throughout life
True
True or False: Each person’s DNA is the same in every cell
True
What are nucleic acids composed of?
Long chains of repeating units called nucleotides
What are the three components of nucleotides?
- Sugar
- Nitrogen-containing heterocyclic base
- Phosphoric acid unit
What is the sugar in RNA?
Ribose
What is the sugar in DNA?
Deoxyribose
What is the difference between ribose and deoxyribose?
In ribose, there is an H attached to the 2’ position of the ring
In deoxyribose, it is an OH group
Nitrogenous bases
Form a bond with carbon 1 of the pentose ring
Purines
Double-ringed bases
Adenine and Guanine
Pyrimidines
Single-ring bases
Cytosine, Thymine (DNA only), and Uracil (RNA only)
What is the primary structure of DNA?
The sequence of bases in a strand of DNA
(e.g. AATTTGGCTTAA)
What is the secondary structure of DNA?
The double helix: each DNA molecule has two polypeptide chains wound around each other like a spiral structure
Ladder Analogy for Secondary Structure of DNA
The phosphate-sugar backbone represents the handrails
Pairs of bases linked together by hydrogen bonds represent the steps
What does DNA being anti-parallel mean?
The strands of the double helix are organized in opposite orientation, so that the 5’ end of one strand is aligned with 3’ end of the other strand
Chromatin
The complex of DNA and proteins in the nucleus of the interphase cell
Can individual chromosomes be distinguished in chromatin?
No
Nucleosomes
The basic subunit of chromatin
What are nucleosomes composed of?
200 base pairs and an octane of histone proteins
Histones
Conserved DNA-binding proteins of eukaryotes that form the nucleosome
Genes
Segments of DNA molecules that control the production of different proteins in an organism
How do genes vary?
Vary in terms of the number and sequence of base pairs they contain
What do genes consist of?
Exons and introns