Lecture 2 Mechanisms of Mendelian genetics Flashcards
Albinism
a genetic defect; occurs when melanocytes cannot make enough melanin to color hair, skin and eyes. There is no cure for this disorder
Tyrosinase
enzyme that TYR gene produces; required for synthesis of melanin pigment
Role of Melanin
-protection of DNA in skin cells against UV radiation (sunlight)\
-In the eye, melanin is needed for proper eyesight
Green Revolution (genes in agriculture)
increased agricultural production worldwide
-high yielding crops
-resistance to disease/pests
-facilitate harvest
ex of gmo (corn, soy, cotton, papaya, rice, rapseed, potatoes, tomatoes, dairy products, peas)
The 3 divisions of genetics
● Transmission Genetics
● Molecular Genetics
● Population Genetics
Transmission Genetics
● The oldest field of genetics
● Explores the inheritance patterns of traits
● How traits are passed from one generation to the next
● The conceptual framework was provided by Gregor Mendel in the
1860s
○ Genetic determinants pass from parent to offspring as discrete
units
■ These are now termed genes
● The basic experimental
approach is the genetic cross
○ Two selected individuals are mated
○ The traits in question are analyzed over several generations
○ Analysis is often quantitative in nature
Molecular Genetics
Focuses on a Biochemical Understanding of the Hereditary Material
● Most modern field of genetics
● molecular features of DNA underlie gene expression
● Gene organization and function
● Detailed analysis of DNA, RNA and proteins
Population Genetics
Concerned With Genetic Variation and Its Role in Evolution
● Genetic variation of populations and
● How variation is related to the environment
● Develop mathematical theories to explain the prevalence of certain alleles
within populations
Model Organisms
● Model genetic organisms are organisms with characteristics that
make them useful for genetic analysis
● Six have been the most intensively studied genetically
● Some Characteristics
○ Short generation time
○ Production of numerous progeny
○ The ability to be reared in a laboratory environment
Centromere
attachment point for spindle microtubules
Telomeres
Tpis of a linear chromosome
Origins of replication
Where the DNA synthesis begins
Meiosis
The production of haploid gametes
- Four cells are produced from each original cell.
- Chromosome number in each new cell is reduced by
half. The new cells are haploid. - Newly formed cells from meiosis are genetically
different from one another and from the parental cell. - Meiosis in animals
– Spermatogenesis: male gamete production
– Oogenesis: female gamete production
Fertilization
The fusion of haploid gametes
Genetic variation
Consequences of meiosis
Mendel’s Experiments; two types of crosses
● Monohybrid Crosses
● Dihybrid crosses
Law of Segregation
● Principle of Segregation
● Concept of Dominance
Cross between two parents that differ in a single characteristic.
1. one character is encoded by two genetic factors.
2. two genetic factors (alleles) separate when gametes are formed.
3. The concept of dominant and recessive traits.
4. Two alleles separate with equal probability into the gametes.
Each individual diploid organism possesses two alleles for any
particular characteristic.
Two alleles segregate when gametes are formed, and one allele
goes into each gamete.
Genetic Terminology
● An allele is a variant form of a gene
● Some genes have a variety of different forms, which are located at the
same position, or genetic locus, on a chromosome.
● Humans are called diploid organisms because they have two alleles
How to predict genetic crosses (punnet square)
Independent events
P(A and B) = P(A) x P(B)
go to slide 33 and 34
comparision between segragation and independent assortment
slide 37
