Chapter 1: The Genetic Revolution Flashcards
Blending theory of inheritance
The belief that inheritance worked like the mixing of fluids
The long-term expectation of blending inheritance:
Over many generations of intermating among individuals all members of the population will come to express the same average value of a trait.
Why is the expectation of blending inheritance wrong and provide an example:
There are people with a range of heights, from short to tall, and we have not all narrowed in on a single average height despite the many generations that humans have dwelled on Earth.
What did Mendel propose? (2)
- Each individual pea plant has two copies of the gene that controls flower color in each of the cells of the plant body (somatic cells). However, when the plant forms sex cells, or gametes (eggs and sperm), only one copy of the gene enters into these reproductive cells (see Figure 1-3). Then, when egg and sperm unite to start a new individual, once again there will be two copies of the flower color gene in each cell of the plant
- The gene for flower color comes in two gene variants, or alleles—one that conditions purple flowers and one that conditions white flowers. He proposed that the purple allele of the flower color gene is dominant to the white allele such that a plant with one purple allele and one white allele would have purple flowers. Only plants with two white alleles would have white flowers
Mendel’s 2 conclusion (2)
(1) that genes behaved like particles that do not blend together
(2) that one allele is dominant to the other, enabled him to explain the lack of blending in the first-generation hybrids and the re-appearance of white-flowered plants in the second-generation hybrids with a 3:1 ratio of purple to white flowered plants.
Thomas H. Morgan (2)
- Demonstrated that Mendel’s genes are located on chromosomes
- He proved the chromosome theory of inheritance
Ronald Fisher (3)
- Resolved how Mendelian genes explained the inheritance of continuously variable traits such as height in people
- Fisher’s core idea was that continuous traits are each controlled by multiple Mendelian genes
- Fisher’s insight is known as the multifactorial hypothesis.
The multifactorial hypothesis
Continuously variable traits are each controlled by multiple Mendelian genes.
Edward Tatum and George Beadle+ the experiment (3)
- Proposed that genes encode enzymes
- Using bread mold (Neurospora crassa) as their experimental organism, they demonstrated that genes encode the enzymes that perform metabolic functions within cells
- one-gene–one-enzyme hypothesis
What are genes made of?
Genes are made of deoxyribonucleic acid (DNA)
James Watson and Francis Crick
Determined that the molecular structure of DNA was in the form of a double helix—two strands of DNA wound side-by-side in a spiral.
Structural of DNA (4)
- Structure of the double helix is like a twisted ladder
- The sides of the ladder are made of sugar and phosphate groups
- The rungs of the ladder are made of four bases: adenine (A), thymine (T), guanine (G), and Cytosine (C)
- The bases face the center, and each base is hydrogen bonded to the base facing it in the opposite strand.
Specific organization of the bases + bonding (2):
- Adenine in one strand is always paired with thymine in the other by a double hydrogen bond, whereas guanine is always paired with cytosine by a triple hydrogen bond.
- The bonding specificity is based on the complementary shapes and charges of the bases.
ACTG makes how many amino acid in total?
20!
mRNA
A messenger molecule made of ribonucleic acid (RNA) that carries information in the DNA in the nucleus to the cytoplasm where proteins are synthesized.
Mutation is——–, ——–
mutation is recessive, loss of function
this is showing….Mutation is…..,….
mutation is recessive, loss of function
showing incomplete dominance
