Chapter 1 - Major Biological Functions of DNA

Question 1

Genetics

Answer 1

Study of genes and variation in cells, individuals and populations.

How does heredity happen?
Where does variation come from?

Question 2

Gene

Answer 2

functional unit of heredity and variation.

DNA sequence involved in making RNA and protein.

Question 3

Molecular Genetics

Answer 3

The study of structure and function of genes at the molecular level.

Question 4

Alleles

Answer 4

variant forms of a gene caused by differences in DNA sequences.

(variation in eye color/height)

Question 5

Genotype

Answer 5

genes inherited by an organism

Question 6

Phenotype

Answer 6

Visible traits

Body plan, behavior, illnesses/diseases

Question 7

Genome

Answer 7

entire DNA sequence (ACGT) of an organism.

Question 8

Gene Expression

Answer 8

“turning on” a gene to produce RNA and protein (coding gene).

Question 9

Coding RNA

Answer 9

makes protein (mRNA)

Question 10

Non-coding RNA

Answer 10

does not make protein (tRNA, ribosome RNA)

Question 11

Protein expression

Answer 11

the type and abundance of proteins in the cell.

Question 12

What determines the phenotype of the cell?

Answer 12

Proteins because they control every reaction in the cell.

Even though DNA is the information molecule that directs protein expression/

Question 13

Enzymes

Answer 13

catalyzes the synthesis and transformation of all biomolecules.

Question 14

Structural proteins

Answer 14

maintains the cell shape.

Question 15

Signalling proteins

Answer 15

hormones and receptors.

Question 16

How do alleles contribute to phenotypic variation?

Answer 16

Alleles of a gene have differences in DNA sequence that result in variation in protein expression and therefore, phenotype.

Question 17

Why sequence genomes?

Answer 17

To understand the types and abundance of RNA and protein result in a phenotype of an organism, we need to identify all the genes in the genome.

More complex = larger genome size but number of genes does not speak about complexity.

Question 18

Why is studying molecular genetics important?

Answer 18

Human health, Forensics (DNA Fingerprinting), Agriculture, Environment, Evolutionary biology

Question 19

Who established DNA as the hereditary molecule in 3 classical experiments? (Who studied how the transfer of genetic information happens?)

Answer 19

1. Griffith
2. Avery, MacLeod & McCarthy
3. Hershey & Chase

Question 20

Griffith Experiment

Answer 20

Transforming principle.

Streptococcus pneumonia was transformed from non-virulent to virulent.

Transformation was permanent and heritable.

1. Smooth Strain: virulent. Has a polysaccharide (sugar-based) coat that protected it from the immune system.
2. Rough Strain: non-virulent. (doesn’t cause sickness)

Question 21

Avery, Macleod & McCarthy

Answer 21

Identified what is the transforming principle: DNA, RNA or protein.

They separated cells by component. If the molecule is absent and transformation is gone, that is the transformation molecule.

Question 22

Hershey & Chase

Answer 22

Found evidence from bacteriophage.

Two radioactive isotopes were injected into the phages.

a) Sulfur: affects proteins.
b) Phosphorus: affects DNA.

1. One batch of phage was labeled with S, the other labeled with P.
2. Phages infected bacteria.
3. Cultures were centrifuged to separate bacteria from phages.
4. Radioactivity was measured.
   - Heavier material (bacteria) moved to bottom forming a lump called a pellet & Lighter materials (phage) remained near the top forming a layer called supernatant.
5. P was found in the pellet (inside bacteria) and S was found in the supernatant (outside bacteria).

Found the final evidence establishing DNA as the hereditary molecule even though proteins were more complex.

Question 23

Bacteriophage Reproduction

Answer 23

1. Lytic Cycle: virus hijacks cell to make viral proteins, the cell splits and releases the viral proteins.
2. Lysogeny: bacteriophage inserts itself into the bacteria chromosome.

Question 24

Lytic Cycle Steps

Answer 24

microphage docks onto bacteria, injects viral DNA, microphage is replicated, cell breaks open and mature phage released.

Question 25

Lysogeny

Answer 25

Recombination of bacteriophage and bacterial DNA to create mature phages.

Can switch to the lytic cycle.