Chapter 1 Reading

Chapter 1 Reading

 
 

Discontinuous Variations

Variations which are very distinct in a population (such as albinism - total lack of melanin, made by defective tyrsinase) - either or

Polymorphism

Many common distinct variations in phenotypes

Continuous Variations

Unbroken range of varieties in a population's phenotype (such as height and weight)

Haplosufficient

When only a single allele is required for normal function (such as sickle-cell)

Null Allele

Alleles which fail to code for a functional protein (recessive?)

types of genetic mutations

nucleotide-pair substitution leads to amino acid substitution or premature stops

deletion and duplication

frameshift mutations is an alteration in the codon reading frame usually caused by a nucleotide deletion at sites where there is a short stretch of the same nucleotide sequence.

probing is a technique for detecting the presence of certain molecules. The probe will only bind with the specific macromolecule, and it is usually dyed fluorescent or made radioactive so the location can be recorded.

DNA probing relies on base complementation. DNA needs to be extracted and cut by restriction enzymes. Afterwards it is mixed with the probe in solution, this technique relies on the random motion of the genetic particles in the solution.

Southern Blot DNA is placed on a gel, and an electrical field (electrophoresis) is activated which makes the strands move at speeds inversely proportional to their size. The fragments are then placed on a porous membrane and heated to keep them in place, then in a solution filled with the probe.

Northern Blot probe technique for RNA. Western Blot probe technique for proteins using antibodies (probes - usually extracted from some animal, such as a rabbit) to bind to antigens (proteins being tested for).

Law of Segragation alternative traits (factors) that come together for one offspring, may be separated in the gametes

Independent Assortment differences for one trait are inherited independently of differences in another trait

Height in the pea plant is continuous

Norm of Reaction – The wide range of phenotype which can occur for each genotype by environmental influences.

Developmental Noise – Random environmental factors that might affect phenotype despite a fixed phenotype, and environment. This can be

Negative feedback processes limit the range of variations from environmental influences

Three levels of development - First is embryonic stages that are common to a wide variety of species in which genes alone account for the morphology (without environment)

Second level accounts for similarites shared between different species which may come from genes alone.

Third level is between the same species, and accounts for morphological, behavioral, and physiological differences affected by genes alone.

 
 

CHAPTER 2

 
 

autosomal inheritance variation based on a single gene on regular chromosomes

sex linked variation on single gene on the sex determining chromosomes

cytoplasmic variations are from differences in the genes of a cytoplasmic organelle

 
 

pure line were setup to make sure that any observed variations were a result of his deliberate manipulations, which is in effect a control experiement. In addition, he made reciprocal crosses, meaning each cross was done with both combinations of male/female and female/male, which produced the same result. This tells us that both male & female gametes carried genes for the chracters he was crossing. After his original cross produced all purple flowers, he selfed those, and got some progeny who were white, which led him to conclude that the white allele was present in the purple flower, but unexpressed. This is when he coined the terms dominant and recessive.

 
 

From the pure line, one phenotype would disappear from the F1 but then return for the F2 in the ration of 1:4

anthocyanin is the end-product of a biochemical pathway which gives pea-plants their purple color (psium savitum)