GENETICS PRELIMS

Hippocrates

Male seed is thicker or more solid while the female is more fluid.

Aristotle

The vital heat fluid; Semen was regarded as highly purified blood.

Semen

The vital heat fluid

Semen

Was regarded as highly purified blood.

Pythagoras

Vapors were from various organs unite to form individuals.

Vapors

Where various organs unite to form individuals.

Jan Swammerdam

He theorized that sex cells contain a complete miniatures of an adult, perfect in every form called a homunculus.

Homunculus

Theorized by Swammerdam, sex cells contain a complete miniatures of an adult, perfect in every form.

William Harvey

An organism is derived from substances present in the egg that differentiate into adult structure during embryonic development.

Casper Wolff

Disapproved the Theory of Preformation. Offered experimental evidence that no preformed embryo existed in the egg of the chicken.

Pierre Louis Maupertuis

Proposed that minute particles, one from each body, united in sexual reproduction to form a new individual.

Charles Darwin

Noted that each part of the body produced minute particles “gemmules” or “pangenes” which were contained in the blood of the entire body but eventually concentrated in the reproductive organs.

The Theory of Pangenesis

The body produced minute particles “gemmules” or “pangenes” which were contained in the blood of the entire body but eventually concentrated in the reproductive organs.

Blending

An individual represents of both parents and acquired characters would be inherited too.

August Weismann

Disapproved the Theory if Pangenesis. His experiment was the 22nd generation of mice where the tails of the parents were cut. Need to prove The absence of tails to offspring.

Gregor Mendel

Father of Modern Genetics, Has four postulates.

Friedrich Miescher

Identified DNA as an acidic substance found in cell nuclei.

Nuclein

First term for DNA

William Bateson

Coined the word “genetics”

Wilhelm Johanssen

First experiments on quantitative traits in broad beans.

Herman Nilsson-Ehle

First experiments on quantitative traits in wheat.

Thomas Morgan

Conducted the experiments on Drosophila (fruit flies). Genes are carried on chromosomes and the mechanical basis for heredity.

Eugenics Movement

Popular, fueling racist sentiment and leading to involuntary sterilization laws.

1910-1930

Eugenics Movement year

Karl Landsteiner

ABO Blood Types

Genetic Recombination (1931)

Caused by a physical exchange of chromosomal pieces.

Harriet Creighton and Barbara Mcclintock

Genetic Recombination is cased by a physical exchange of chromosomal pieces as shown in corn.

Beadle and Tatum (1941)

One gene encodes one protein.

Erwin Chargaff (1950)

In DNA, there are equal amounts of A and T, and equal amounts of C and G. However, the A+T to C+G ratio can differ between organisms.

Alfred Hershey and Martha Chase (1952)

DNA is the molecules that mediates heredity, as shown in bacteriophage labeling experiments.

Watson and Crick (1953)

DNA is in the shape of a double helix with antiparallel nucleotide chains and specific base paring.

Meselson and Stahl (1958)

DNA replication is semi-conservative, as shown using equilibrium density gradient centrifugation.

Hamilton Smith (1970)

The first restriction enzyme is purified.

Cohen and Boyer (1972-1973)

Recombinant DNA is first constructed.

Fred Sanger (1977)

DNA sequencing technology is developed.

XY Sex Determination

• Females are homogametic (XX), producing X-carrying eggs.

• Males are heterogametic (XY), producing X- and Y-carrying sperm.

SRY Gene

The presence of the Y chromosomes that determines maleness, which triggers male development.

Drosophila melanogaster

Common fruit fly

XO Sex Determination

• Females are XX

• Males have a single X chromosome (XO)

• The absence of a second sex chromosome in males determines maleness.

ZW Sex Determination

• Females are heterogametic (ZW) and determine the sex of the offspring.

• Males are homogametic (ZZ)

Haplo-diploid Sex Determination

• Females develop from fertilized diploid eggs (2n).

• Males develop from unfertilized haploid eggs (n).

Parthenogenesis

A natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization.

X-Linked Inheritance

• Males (XY) express all X-linked traits because they have only one X chromosome.

• Females (XX) can be homozygous or heterozygous for X-linked traits.

Y-Linked Inheritance

• Only males inherit Y-linked traits.

• Traits are passed directly from father to son.

• The Y chromosome carries relatively few genes, many of which are involved in male-specific development.

Genes

Inherited characteristics are under the control of particulate factors.

Genes

Transmitted from one generation to another by vehicles called chromosomes.

Chromosomes

Vehicles that transmit genes from one generation to another.

Crosses (Mating)

Affected by chance deviation and evaluated using statistical analysis.

Human Traits

Initially studied using pedigrees.

Gregor Johann Mendel

Performed first set of hybridization experiments with garden pea.

1865

Mendel first reported the results of simple genetic crosses between strains of garden peas.

Mendel’s Experimental Approach

Chose an organism that was easy to grow and hybridize artificially. Easy to cross-breed during experiments.

Phenotype

Physical appearance of a trait in an individual.

Genotype

Genetic makeup of an individual whether it is diploid or haploid.

Allele

Alternative forms of a single gene.

Homozygous

When both alleles are the same.

Heterozygous

When the alleles are different.

Character

Heritable feature

Trait

Variant of a character

Parental Generation

P

First Filial Generation

F1

Second Filial Generation

F2

Monohybrid Cross

Only involves one pair of contrasting traits.

Reginald C. Punnet

Developed the Punnet Square in 1967

Male Parent

X-axis / Horizontal column

Female Parent

Y-axis / Vertical Column

Unit Factors in Pairs

Genetic characters are controlled by unit factors that exists in pairs in individual organisms.

Concept of Dominance and 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, the recessive one.

Segregation

During the formation of gametes, the paired unit factor separate or segregate randomly so that each gamete receives one or the other.

Test Cross

An organism expressing a dominant phenotype but unknown genotype. Crossed with homozygous recessive individulal.

Dihybrid Cross

Uses two characters that are under study.

Independent Assortment

During gamete formation, segregating unit factors assort independently of each other.

Trihybrid Cross

Apply to three pairs of contrasting traits. Also referred to as three-factor cross.

Human Pedigrees

The pattern of inheritance of a specific type of phenotype can be studied even in humans.

Transmission/Classical Genetics

Deals with the heredity and variation.

• Planned Experimental/Cross Breeding

• Pedigree Analysis

Planned Experimental Breeding

Mendel’s Experiments

• Garden pea is ideal for genetic study

• Chose true-breeding/pure breeding which is between homozygous garden peas for his experiments.

• Worked with single-character crosses (Monohybrid cross)

Pisum sativum

Garden Pea

Monohybrid Cross

Single-character Crosses

Sample Pedigree

1st Generation (Grandparents)

2nd Generation (Parents, Aunts, and Uncles)

3rd Generation (Children)

Cytogenetics

Study the genes in the cell particularly in the chromosome.

Provide the chromosomal basis of sex determination.

Explain the distribution of boys and girls in the family.

Karyotyping

Karyogram

Molecular Genetics

Investigate in detail the nature of genetic material, it’s structure, mode of replication, and how it acts to produce the phenotye.

DNA

Genetic Material

Population Genetics

Genetic structure of a population.

Pattern of genetic variation in populations.

Changes in genetic structure through time.

Applied Genetics

Practical applications of Genetics

• Animal husbandry and plant breeding

• Epidemiological Genetics

• Eugenics

• Medicolegal Genetics

• Genetic Counseling

• Genetic Engineering

• Recombinant DNA Technique and Gene Cloning

Animal Husbandry and Plant Breeding

To produce high yielding varieties of food crops like disease-resistant plants and varieties of cows and pigs.

Epidemiological Genetics

For better therapy, management and prevention of recurrence of inherited disease.

Eugenics

Choice of partners for marriage and have an estimate of the likelihood of appearance of desirable trait.

Medicolegal Genetics

To solve legal problems like dispute in paternity and exchange of babies in the hospital nursery.

Genetic Counseling

For deciding abortion and planning responsible parenthood through amniocentesis.

Genetic Engineering

Repair of defective genes.

The process of manually adding new DNA to an organism.

GMO Transgenic Organisms

Plants with resistance to some insects.

Plants that can tolerate herbicides.

Crops with modifies oil content.

Recombinant DNA Techniques and Gene Cloning

DNA fragments are cut out of their normal position in the chromosome using restriction enzymes and then inserted into other chromosomes or DNA molecules using enzymes.

Amelogenesis imperfecta

This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage.

Cause: Mutation in the AMELX, ENAM, and MMP20 genes.

Treatment: Crowning

Genetikos

Genitive/Generative

Genesis

Origin

Genea

Genes/Race or Generation

Gen

To produce, to become, or to grow into something

Genetics

It is the study of genes and how they are transmitted from parents to offspring.

Species Characteristics

Similarities - Individuals of the same species may have characteristics common to all of them (denote common origin)