Introduction + history

Question 1

Molecular Genetics

Answer 1

DNA is the primary carrier of genetic information in all organisms

The genome (DNA in the nucleus) is passed on in the form of chromosomes

Question 2

Organization of Chromosomes

Answer 2

Strands of DNA wrap tightly around a core group of eight stabilization proteins, known as histones

Negatively charged DNA and positively charged histones attract one another

The complex of eight histones enveloped by the coiled DNA is called a nucleosome

HISTONES ORGANIZE THE DNA

Question 3

chromosome organization (nucleosome construction)

Answer 3

• Nucleosomes are complexes of histones and strands of nucleotides
• Chromatin are coiled strands of nucleosomes
• Chromosomes are tightly coiled, condensed forms of chromatin

Question 4

Human Chromosomes

Answer 4

Humans have 46 chromosomes:
- 44 are somatic chromosomes
- 2 are sex chromosomes

• The somatic chromosomes have been numbered 1 to 22, according to size, with chromosome 1 being the largest
• Only a fraction of the human genome is known to code for specific proteins
• The current estimate is that 42, 000 genes exist
  More than 95% of the human genome is noncoding

Question 5

Variable Number
Tandem Repeats (VNTR)

Answer 5

Noncoding regions are filled with VNTRs

These are sequences of base pairs that repeat over and over again

Varies among individuals, in length, and positioning within the genome

Huntington’s disease is associated with a repetitive sequence within a gene

Question 6

Mendel and Meischer

Answer 6

Mendel and Meischer were discovering the fundamental basics of genetics separately

Mendel was crossbreeding peas and Meischer was discovering nuclein

Question 7

Griffith

Answer 7

Griffith accidentally discovered the transforming principle

Used pneumonia bacterium, S-strain (virulent) and R-strain (not virulent)

Injected mice with different strains and got different results

Question 8

Avery, McLeod, and McCarty

Answer 8

Avery, McLeod, and McCarty “confirmed” DNA transformation

Used Streptococcus bacterium, S-strain (virulent) and R-strain (not virulent)

Added enzymes to heat-killed S-strain that would destroy DNA, RNA, or protein

Injected mice with different strains; results clearly showed that DNA was the transforming substance

Question 9

Hershey and Chase

Answer 9

Hershey and Chase concluded DNA is the hereditary material

Used bacteriophage virus to infect bacteria

Added radioactive isotopes (sulfur to label proteins; phosphorus to label DNA)

E. coli cells were infected with radioactive bacteriophages; only radioactive DNA was detected in the E. coli

Question 10

Chargaff’s Rules

Answer 10

Many scientists discovered the nitrogenous bases

Chargaff discovered the ratio of purines and pyrimidines were equal

This was later termed, complementary base pairing

Question 11

Wilkins and Franklin

Answer 11

Franklin used X-ray crystallography to study the shape of DNA molecule

Bombarded compounds with X-rays

Franklin determined the shape of DNA was an “X” with a sugar-phosphate backbone facing the outside of the molecule, a double-helix, and rotated

Question 12

Watson and Crick

Answer 12

Watson and Crick never completed any experiments to determine the structure of DNA

Built the model of the double-helical DNA structure with sugar-phosphate backbones, nitrogenous bases, uniform diameter of the helix, and
anti-parallel strands