genetics

ByDaisie S. Nubla

Assistant professor Ide la salle araneta university

Biological Science

Animal and Plant Cell

GENETICS

Ancient Greek γενετικός genetikos means genesis or origin discipline of biology science of genes, heredity and variation in living organisms deals with the molecular structure and function of genes with pattern of inheritance from parent to offspring gene distribution and variation in change in population

GENETICS

can be applied to the study of any living system from viruses and bacteria through plants (crops) and humans (Medical Genetics) living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding modern science of Genetics, which seeks to understand the process of inheritance only began with the work of Gregor Mendel.

GENETICS

GREGOR MENDEL

July 22, 1822 – January 6, 1884 Austrian Monk During his child hood, worked as a gardener and studied beekeeping studied at University of Olomouc Upon recommendation of his physics teacher Friedrich Franz he entered the Augustinian Abbey of St. Thomas in Brno in 1843 He took the name Gregor upon entering monastic life

GREGOR JOHANN MENDEL

He was ordained into priesthood in August 1847 In 1849, he was assigned as a teacher to a secondary school in the city of Znaim He took the licensure exam for teachers but he was failed During middle part of his life, he did groundbreaking into the theory of heredity Using pea pod plants, he studied the seven characteristics of it.


By tracing these characteristics, Mendel discovered 3 basic laws which governed the passage of a trait from one member of a species to another member of the same species 1st Law states that the sex cells of a plant may contain two different traits but not both of those traits


2nd Law stated that the characteristics are inherited independently from another (the basis of recessive and dominant gene composition) 3rd Law stated that each inherited characteristic is inherited by two hereditary factors (known more recently as genes. One from each parents, which decides whether a gene is recessive or a dominant.


If a seed gene is recessive, it will not show up within a plant, however the dominant trait will. His work later became the basis for the study of modern genetics, and are still recognized and used today’ His work led to the discovery of particulate inheritance, dominant and recessive traits, genotype and phenotype, concept of heterozygous and homozygous


Hybridization is matting and crossing of two true-breeding varieties P generation(parental) is the true – breeding parents F1 generation (first filial generation) is a

hybrid offspring F2 generation ( second filial

genentation) produced if allowing F1 hybrid to self-pollinate

MENDEL’S EXPERIMENTAL QUANTITATIVE APPROACH

allele pairs separate during gamete formation and randomly unite at fertilization.

two purpose of this are

developed pure lines

counted the results and kept the statistical notes

LAW OF SEGREGATION

a population that breeds true for a particular trait [ this was an important innovation because any non-pure (segregating) generation would and did confuse the results of genetic experiments]

PURE LINE

Results from Mendel's Experiments

Parental Cross F1 Phenotype

F2 Phenotypic Ratio F2 Ratio

Round x Wrinkled Seed Round

5474 Round:1850 Wrinkled 2.96:1

Yellow x Green Seeds Yellow

6022 Yellow:2001 Green 3.01:1

Red x White Flowers

Red 705 Red:224 White 3.15:1

Tall x Dwarf Plants

Tall l787 Tall:227 Dwarf 2.84:1

Results from Mendel's Experiments

literally means, “the form that it shown” the outward, physical appearance of a particular trait Mendel’s pea plants exhibited the following phenotypes

round or wrinkled seed yellow or green seed red or white flower tall or dwarf plant

PHENOTYPE

Pea color

Pea shape

The allele that expresses itself at

the expense of an alternate allele,

the phenotype that is expressed in

the from the cross of two pure lines

DOMINANT

An allele whose expression is suppressed in the presence of a dominant allele, the phenotype that disappears in the F1

generation from the cross of two pure lines and reappears in the F2

generation

RECESSIVE

1. The hereditary determinants are of a particulate nature. These determinants are called genes

2. Each parent has a gene pair in each cell for each trait studied. The F1 from a cross of two pure lines contains one allele for the dominant phenotype and one from the recessive phenotype. These two allele comprise the gene pair

MENDEL’S CONCLUSION

3. One member of the gene pair segregates into a gamete, thus each gamete only carries one member of the gene pair.

4. Gametes unite at random and irrespective of the other gene pairs involved.

MENDEL’S CONCLUSION

Allele one alternative form of a given allelic pair, tall and dark are the allele for the height of pea plant; more than two alleles can exist for any specific gene, but only two of them will be found in any individualAllelic pair the combination of two alleles which comprise the gene pair.

MENDELIAN GENETICS DEFINITION

Homozygous an individual which contains only one allele at the allelic pair, for example DD is a homozygous dominant; while dd is homozygous recessive, pure lines are homozygous for the gene of interest.


Heterozygous an individual which contains one of each member of the gene pair, example the Dd.

Genotype the specific allelic combination for a certain gene or set of genes.


Backcross the cross of an F1 hybrid to

one of the homozygous parents; for pea plant height the cross would be Dd x DD or Dd x dd; most often though a backcross is a cross to a full recessive parent.

DIFFERENT TYPE OF CROSS IN GENETICS

Testcross the cross of any individual to a homozygous recessive parent, used to determine if individual is homozygous dominant or heterozygous.Monohybrid cross a cross between parents that differ at a single gene pair (usually AA x Aa)


Monohybrid the offspring of two parents that are homozygous for alternate alleles of a gene pair.

is good for describing the relationship between alleles. when an allele is homozygous it will show its phenotype it is the phenotype of the heterozygous which permit us to determine the relationship of the allele


Dominance the ability of one allele to express its phenotype at the expense of an alternate allele.

the major form of interaction between alleles generally the dominant allele will make a gene product that the recessive can not. therefore the dominant allele express itself whenever it is present


A handy diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic make up

PUNNETT SQUARE

Mendel derived this law by performing breeding experiments in which he followed only a single character.

He identified this law by following two characteristics at the same time. example 2 of the 7 characters Mendel’s studied is were seed color and seed shape

Each pair of alleles segregates independently of other pairs of alleles during gamete formation

LAW OF INDEPENDENT ASSORTMENT

seed color may be yellow (Y) or green (y) seed shape round (R) or wrinkled (r) example YYRR will have a parental cross with yyrr

F1 plants will be dihybrids

heterozygous YyRr phenotypic categories with a ratio of 9:3:3:1 9 yellow-round to 3 green-round to 3 yellow-wrinkled to one-green wrinkled

LAW OF INDEPENDENT ASSORTMENT

Occurs when the phenotype o the

heterozygote is completely indistinguishable

from that of the dominant homozygote

COMPLETE DOMINANCE

Occurs when phenotype of the heterozygous genotype is an intermediate of the phenotypes of the homozygous genotypes.

example the snap dragon flower color is either homozygous for red or white when the red homozygous flower is paired with the white one, the result is pink pink now is being called as this

INCOMPLETE DOMINANCE

Occurs when the contributions of both

alleles are visible in the phenotype

example is A and B alleles are

codominant in producing AB blood

group phenotype

in which A- and B- type antigens

are being made

CO - DOMINANCE

fatal, recessive genetic disorder in children that causes progressive destruction of the Central Nervous System Infants having this kind of disease are normal for the first few months relentless deterioration of mental and physical abilities becomes blind, deaf and unable to swallow

TAY SACHS DISEASE

Greek word that means ‘stopping’

A gene at one locus alters the

phenotypic expression of a gene at a

second locus

EPISTASIS

from a Greek word pleion have multiple phenotypic effects responsible for the multiple symptoms associated with certain hereditary diseases

cystic fibrosis sickle cell disease

PLEIOTROPY

Many Human Traits Follow Mendelian

Patterns of Inheritance

To analyze the results of matting that have already occurred collection of information about a family’s history for a particular trait and assembling this information into a family tree describing the interrelationship of parents and children across the generation

PEDIGREE ANALYSIS

one importance of this is to help us predict the future

a serious matter when the alles in question cause disabling or deadly hereditary diseases instead of innocuous human variation such as hairline or earlobe configuration

PEDIGREE ANALYSIS

Recessively Inherited Disorder

Most common lethal genetic disease in U.S. chloride transport of channels are defective or absent in the plasma membrane of a children result is abnormally high concentration of extracellular chloride which causes mucus that coats certain cells to become thicker and stickier Most children die before their 5th birthday

CYSTIC FIBROSIS

most common inherited disorder caused by substitution of single amino acid by the hemoglobin protein of red blood cells. multiple effect of a double dose of this is an example of pleiotropy no cure

SICKLE CELL DISEASE

forbidden love

consanguineous a disease causing recessive allele

more likely produce offspring homozygous for recessive traits

MATING OF CLOSE RELATIVES

Achondroplasia a form of dwarfism

heterozygous individuals have the dwarf phenotype

therefore all people who are not achondroplastic dwarf are homozygous for recessive allele

DOMINANTLY INHERITED DISORDERS

some genetic disorders can be detected at birth one common screening program is Phenylketonuria (PKU) phenylalanine and its by-product phenylpyruvate can accumulate to toxic levels in the blood causing mental retardation.

NEW BORN SCREENING

genetics

Documents

seed gene

gregor johann mendel

gene pair segregates

gene pairs

specific gene

work ofgregor mendel

round x

dwarf plant