Chapter 3 Flashcards
transmission genetics
field of genetics concerned with heredity and the mechanisms by which genes are transferred from parent to offspring
The seven pea plant traits
Height, seed color, seed shape, pod color, pod shape, flower color, position of flowers
selfing
in plant genetics, the fertilization of a plant’s ovules by pollen produced by the same plant (self-fertilization)
P1
parental generation
F1
first filial generation
F2
second filial generation
reciprocal crosses
a pair of crosses in which the genotype of the female in one is present as the genotype of the male in the other
particulate unit factors
the factors that serve as the basic units of heredity and are passed unchanged from generation to generation, determining various traits expressed by each individual plant
Mendel’s First Three Postulates
- UNIT FACTORS IN PAIRS
- DOMINANCE/RECESSIVENESS
- SEGREGATION
UNIT FACTORS IN PAIRS
a specific unit factor exists for each trait
each diploid individual receives one factor from each parent.
DOMINANCE/RECESSIVENESS
When two unlike unit factors responsible for a single character are present in a single individual, one unit factor is dominant to the other, which is said to be recessive.
the trait expressed in the generation is controlled by the dominant unit factor.
The trait not expressed is controlled by the recessive unit factor.
SEGREGATION
During the formation of gametes, the paired unit factors separate, or segregate, randomly so that each gamete receives one or the other with equal likelihood.
phenotype
the overt appearance of a genetically controlled trait
genes
the fundamental physical unit of heredity, whose exist can be confirmed by allelic variants and which occupy a specific chromosomal locus
alleles
one of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects
genotype
The allelic or genetic constitution of an organism; often, the allelic composition of one or a limited number of genes under investigation.
homozygote
An individual with identical alleles for a gene or genes of interest. These individuals will produce identical gametes (with respect to the gene or genes in question) and will therefore breed true.
heterozygote
An individual with different alleles at one or more loci. Such individuals will produce unlike gametes and therefore will not breed true
testcross
A cross between an individual whose genotype at one or more loci may be unknown and an individual who is homozygous recessive for the gene or genes in question
dihybrid cross
A genetic cross involving two characters in which the parents possess different forms of each character (e.g., yellow, wrinkled peas).
Mendel’s Fourth Postulate:
Independent Assortment
a genetic principle that describes how different genes separate independently during the development of reproductive cells
product law
In statistics, the law holding that the probability of two independent events occurring simultaneously is equal to the product of their independent probabilities.
trihybrid cross
three-factor cross
chromosomal theory of inheritance
The idea put forward independently by Walter Sutton and Theodor Boveri that chromosomes are the carriers of genes and the basis for the Mendelian mechanisms of segregation and independent assortment.
diploid
(2n) The condition when cells contain homologous pairs of each chromosome, one derived from the paternal parent and one from the maternal parent.
haploid
(n) The number of homologous chromosome pairs characteristic of an organism or species.
sum law
The law that holds that the probability of one of two mutually exclusive outcomes occurring, where that outcome can be achieved by two or more events, is equal to the sum of their individual probabilities.
mutant type starch-branching enzyme (SBEI)
wrinkled genes for wrinkled pea
too many type of sugar (sucrose - not starch) that brings in water causing pea to burst
Tay–Sachs disease (TSD)
a devastating recessive disorder involving unalterable destruction of the central nervous system. Infants with TSD are unaffected at birth and appear to develop normally until they are about 6 months old.
blindness, deafness, mental retardation, paralyzation by age 5
results from the loss of activity of a single enzyme hexosaminidase A (Hex-A)
recessive mutations
a change in a gene that only causes a health condition when both copies of the gene are mutated
The Particle Theory of Inheritance
which states that hereditary traits act like particles, units, or factors as they are passed from generation to generation
Law of Segregation
which states that his hereditary factors do not blend but remain distinct during breeding—thus, disproving the blending theory
Law of Independent Assortment
which states that character traits are not connected but are inherited independent of one another. This law was soon to be modified
