Theme 1A

Question 1

What is heredity/inheritance and how have humans been studying it?

Answer 1

The transmission of traits from one generation to the next. Humans have been studying inheritance via artificial selection (artificially selecting desireable traits)

Question 2

What are traits?

Answer 2

Any characteristics of an individual that is heritable

Question 3

What are some false notions about inheritance that have since been changed over time?

Answer 3

• Species are constant
• New species arise when existing species interbreed (ex: minotaur)
• Parental traits blend
• Acquired characteristics are passed on to the next generation (if you lose a finger, your kid won’t have a finger)

Question 4

Who was Hartsoeker?

Answer 4

A man who believed in something called “preformation”. Basically sperm contained fully formed miniature humans that were nourished in the womb; all humans fully developed before birth but were just really tiny before

Question 5

What is a gene?

Answer 5

Functional unit of heredity and variation. A specific DNA sequence that codes for a specific mRNA and protein of a specific characteristic (to make phenotype)

Question 6

What is a genome?

Answer 6

All genetic information of an organism (entire DNA sequence)

Question 7

What are alleles?

Answer 7

Variants of a gene caused by differences in DNA sequences

Question 8

What is a genotype?

Answer 8

The specific genes inherited by an individual

Question 9

What is a phenotype?

Answer 9

Visible traits of an individual (has an environmental component!)

Question 10

What is gene expression?

Answer 10

“turning on” a gene; basically transcription and translation occuring to produce RNA and proteins. This is turning a genotype into a phenotype (follows the central dogma)

Question 11

What is protein expression?

Answer 11

The type and abundance of proteins in a cell, proteins ultimately determine the phenotype of the cell because they control every reaction in the cell (even if DNA is the information molecule that directs protein expression)

Question 12

What are enzymes?

Answer 12

Sometimes proteins. Catalyze the synthesis and transformation of biomolecules

Question 13

What are structural proteins?

Answer 13

Maintenance of the cells shape

Question 14

What are signalling proteins?

Answer 14

Hormones and receptors that play a big part in homeostasis

Question 15

What creates phenotypic variation?

Answer 15

• Different alleles: slight variation in gene sequence results in changes in amino acid sequence of proteins)
• Differential regulation of gene and protein expression (how much is expressed)

Question 16

What is the chromosomes theory of inheritance?

Answer 16

Individuals have 2 copies of each chromosome. Homologous chromosomes separate independantly during meiosis. Gametes have 1 copy of each chromosome and zygotes are a random combination of 2 gametes

Question 17

What are chromosomes composed of?

Answer 17

Both proteins and DNA. Proteins make up 50-60% and DNA makes up 40-50%

Question 18

Who is Griffith and what was his experiment?

Answer 18

Discovered genetic transformation that genetically altered pneumonia

Question 19

Describe Griffith’s experiment.

Answer 19

He injected a mouse with heat killed virulent bacteria, where nothing happened. Then he injected it with nonvirulent bacteria and the mouse died. This suggested that some molecules released when S cells died could genetically transform living R cells into S cells. This transformation is permanent and heritable.

Question 20

What is the difference between s cells and r cells?

Answer 20

• S “smooth” strain pneumonia cells is surrounded by a polysaccharide capsule which protects it from the immune system, it is also virulent (can cause disease)
• R “rough” strain pneumonia cells lack a polysaccharide capsule, cannot evade immune system so is therefore benign

Question 21

What did Avery, MacLeod, and McCarthy want to do in their experiment?

Answer 21

They wanted to know the chemical nature of the transforming principle (was it DNA, a protein, or RNA?).
- They wanted to eliminate each molecule in s cells and see whether or not the transformation of r cells into virulent s cells would still occur

Question 22

Describe Avery, MacLeod, and McCarthy’s experiment.

Answer 22

1. Kill S cells, lyse (explode) the cells, remove lipids and sugars so only DNA, RNA, and proteins are left. Add living R cells to each tube and look for living S cells
2. Test 1: add protease enzyme to break down protein (transformation still happened)
3. Test 2: add ribonuclease to break down RNA (transformation still happened)
4. Test 3: add DNAse enzyme to break down DNA (transformation did not occur)

Question 23

What is a bacteriophage?

Answer 23

Viruses that infect bacteria

Question 24

What did Hershey and Chase use for their experiment?

Answer 24

Bacteriophage and E.Coli host. Does the bacteriophage inject proteins or DNA into the host as its genetic material. DNA uses phosphorus in phosphodiester bonds, proteins use sulfur in amino acids

Question 25

What is the life cycle of a bacteriophage?

Answer 25

- Lytic infection: massive reproduction of virus resulting in host cell dying - After attachment, the virus genetic material is injected into the host and the phage coat remains outside - Viral DNA takes over the host, hundreds of copies are made, progeny virus bursts from the host

Question 26

How did Hershey and Chase finalize that DNA is the genetic material?

Answer 26

They had two populations of the virus: radioactive phosphorus (P32) in DNA and radioactive sulfur (S35) in proteins. Experiment 1: sulfur not found in host cells or progeny virus particles Experiment 2: phosphorus found in host cells and progeny virus particles