[lecture 7] DNA (I)

Question 1

what is DNA

Answer 1

• genetic material present in all organisms
• carries a set of instructions that cells to manufacture the building blocks of life (proteins)
• DNA can be replicated

de-oxy-ribo-nucleic acid

Question 2

4 bases of DNA

Answer 2

adenine, guanine, thymine, cystine

A -(2) T
G -(3) C

Question 3

name the purines

Answer 3

adenine and guanine

Question 4

name the pyramidines

Answer 4

thymine and cystine

Question 5

how do nucleotides link together

Answer 5

phosphodiester bond

3’ carbon on one nucleotide and 5’ carbon on the next

Question 6

structure of DNA

Answer 6

• double helix (2 polynucleotide bond)
• ribose sugar, phosphate, nitrogenous base
• hydrogen bonds between nitrogenous bases
• antiparallel
• complimentary base pairing
• 1 complete turn of DNA in 10 base pairs
• diameter= 2 nm (1 purine + 1 pyramidine)

Question 7

what is a gene

Answer 7

basic physical unit of inheritance
and contains the information that
determines a particular trait

a gene is a sequence of nucleotide
bases in a DNA molecule-
codes for the production of a
specific sequence of amino acids,
that in turn make up a specific
protein

Question 8

eukaryotic DNA facts

Answer 8

1. stored in chromosomes: 23 pairs (46 total)
2. 22 autosomes, 1 sex chromosome

Question 9

how does 2 m DNA fit in a cell?

Answer 9

• proteins called histones package DNA in a DNA-protein complex called chromatin
  1. basic unit of chromatin- nucleosome
  2. nucleosomes join together and twist to make a shorter, thicker 30 nm (diameter) fibre
  3. 300 nm loops
  4. 300 nm loops compressed and folded to 250 nm wide fibre
  5. tightly coiled into a chromatid of a chromosome