CHAPTER I INTRODUCTION A. Background Heredity is the passing of traits to offspring (from its parent or ancestors). This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause a species to evolve. The study of heredity in biology is called genetics, which includes the field of epigenetics. The ancients had a variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers to ripen; Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the time of conception, and Aristotle thought that male and female semen mixed at conception. Aeschylus, in 458 BC, proposed the male as the parent, with the female as a "nurse for the young life sown within her". Various hereditary mechanisms were envisaged without being properly tested or quantified. These included blending inheritance and the inheritance of acquired traits. Nevertheless, people were able to develop domestic breeds of animals as well as crops through artificial selection. The inheritance of acquired traits also formed a part of early Lamarckian ideas on evolution. In the 9th century AD, the Afro-Arab writer Al-Jahiz considered the effects of the environment on the likelihood of an animal to survive, and first described the struggle for existence. His ideas on the struggle for existence in the Book of Animals have been summarized as follows: "Animals engage in a struggle for existence; for resources, to avoid being eaten and to breed. Environmental factors influence organisms to develop new characteristics to ensure survival, thus transforming into new species. Animals that survive to breed can pass on their successful characteristics to offspring." From this view we.ve experiment about the B. Purpose

After doing this experiment we could prove the ratio number of genotype and phenotype from Law of Mendel and based on characteristic of human heredity C. Benefit The benefit of this experiment are made the student understood and know about characteristic of human heredity and could know about the Law of Mendel

CHAPTER II PREVIEW OF LITERATURE

An Austrian monk named Gregor Johann Mendel, towards the end of the 19th century made the crossing a series of experiments on peas (Pisum sativum). From the experiments done during these years, Mendel discovered the principles of inheritance, which later became the main basis for the development of genetics as a branch of science. Thanks to this work, Mendel recognized as the father of genetics. Mendel chose peas as experiment materials, primarily because these plants have a few pairs of very prominent trait differences, such as flower color is easy to distinguish between the purple and white. In addition, the peas can be pulverized plant itself, and with the help of humans, can also pulverized cross. This is caused by the existence of perfect flowers, the flowers which have male genitals and female. Another consideration is that peas have a life cycle is relatively short, and easy to cultivate and maintain. Mendel was also lucky, because by chance he used peas are diploid plants (having two sets of chromosomes). If he uses poliploid organisms, so he will not get a simple cross and easy to analyze. (Alimuddin, 2003). In one experiment plants Mendel crossed tall peas with a short. The selected plants are pure strains of plants, the plants that when pulverized itself will not result in different plants with. In this high plant will remain high yield crops. Similarly short plants will always result in shorter plants. With pure strains of high-crossed with a pure strain of short, Mendel, all getting higher plants. Furthermore, higher plants are allowed to cross pulverized itself. Shows the ratio of the offspring turned out (comparison) tall plants to short plants of 3: 1. In the scheme, Mendel's experiments can be seen in Figure 2.1 as follows.

P:

High

x

Short DD dd

Gamete

D

d

F1 :

High Dd

Pulverized itself (Dd x Dd) F2 : Gametes Gametes D DD (high) D Dd (high) High (D-) : short (dd) = 3 : 1 Dd (short) dd (short) D d

DD : Dd : dd = 1 : 2 : 1

Figure 2.1. Monohybrid crossing diagram for the high qualities of plants

Tall and short individuals are used in the early crosses are said to be elders (parental), abbreviated P. Results are the descendants heredity (filial) generation of the first, abbreviated to F1.Higher plants in P generation is denoted by DD, dd is a short plant. Meanwhile, tall plants obtained at F1 generation is represented by Dd. Monohybrid crosses on the diagram above, it appears that to produce the F1 Dd individuals, then both the DD and dd to form a gamete generation P (sex cells). Individual D DD form gametes, individuals were forming gametes dd d. Thus, Dd in

F1 individuals is the result of the merger of the two gametes. Similarly, when the other individual is doing pollination Dd themselves to produce F2, then each will form the first gametes. Gametes produced by individuals Dd there are two kinds, namely D and d. Furthermore, the combination of these gametes obtained individuals with a ratio of F2 generation DD: Dd: dd = 1: 2: 1. If DD and dd are grouped into one (for both individuals representing high), then the ratio becomes D-: dd = 3: 1. From the diagram it also can be seen that the inheritance of a trait is determined by the inheritance of a particular material, which in this example is represented by D or d. Mendel called this material as inherited genetic (hereditary), which in the next stage until now called genes. (Anonim1, 2009). There are several terms that need to know to explain the principles of inheritance. As already mentioned above, P is the individual elders, F1 is the first generation offspring, and F2 is the second-generation offspring. Furthermore, gene D is said to be a dominant gene or allele, is d gene is recessive gene or allele. Alleles are alternative forms of a gene located on the locus (place) some. Dominant gene is said to D d gene, because gene expression will cover the D d gene expression if they are together in one individual (Dd). Thus, the dominant genes are genes whose expression covering alelnya expression. In contrast, recessive genes are genes whose expression is covered by alelnya expression. Individuals named individuals heterozygous Dd, and DD is dd individuals each individual is called homozygous dominant and homozygous recessive. The properties that can be directly observed in these individuals, ie, tall or short, is called the phenotype. Thus, the phenotype is a direct gene expression can be observed as a trait in an individual. Meanwhile, the underlying genetic makeup the appearance of a trait called genotypes. In the example above, the high phenotype (D-) can be produced from the genotype DD or Dd, are short phenotype (dd) only generated from the genotype dd. It appears that the individual is homozygous recessive, the symbol for the same phenotype to genotype symbols. (Anonim2. 2009)

Legal segregation , Before performing a cross, each individual produces gametes that contain half of the gene content of individual genes. For example, individuals will form gametes DD D, and individuals will form gametes dd d. In individual Dd, which produce gametes gametes D and d, will be seen that the gene D and gene d would be separated (disegregasi) to the gametes that formed it. This principle became known as the law of Mendel's laws of segregation or I Law of segregation: At the last time the formation of gametes, each pair of genes will disegregasi into each gamete is formed Independent Electoral Law , Crosses which concerns only one kind of inheritance patterns of such properties by the abovementioned Mendel called monohybrid crosses. Mendel did monohybrid crosses to the other six kinds of properties, namely flower color (purple-white), cotyledon color (green-yellow), seed color (green-yellow), the form of pods (flat-grooved), the surface of seeds (finely-wrinkled) , and the location of interest (axial-terminal) (Eisenmesser EZ. 2005). In addition monohybrid crosses, Mendel also made crosses dihybrid, which crosses involving two different kinds of patterns perwarisan instantaneous nature. One of them is the intersection of pure soy-smooth yellow seed with a pure strainwrinkled green seeds. Soybean plants resulted in F1 generation of all-smooth yellow seeds. When the F1 plants are allowed pulverized itself, then obtained four kinds of individual F2 generation, each of yellow seed-smooth, yellow-wrinkled, greensmooth, and green-wrinkled with the ratio 9: 3: 3: 1. If the gene that causes yellow seeds and green, respectively, are the genes G and g, are the genes that cause the smooth and wrinkled seeds, respectively, are genes and gene w W, then crosses dihybrid terdsebut scheme can be described as the following diagram. (Parson. 1994 ) If the gene that causes yellow seeds and green, respectively, are the genes G and g, are the genes that cause the smooth and wrinkled seeds, respectively, are genes and gene w W, then crosses dihybrid terdsebut scheme can be described as the following diagram.

P:

Yellow, soft GGWW

x

Green, Wrinkled ggww gw

Gametes

GW

F1 :

Yellow, soft GgWw Pulverized itself (GgWw x GgWw )

F2 : Gam etes Gametes GW Gw gW gw

GW

GGWW (Yellow,Sof t)

GGWw (Yellow,Soft)

GgWW (Yellow,Soft)

GgWw (Yellow,Sof t)

Gw

GGWw (Yellow,Sof t)

GGww (Yellow, Wrinkled) GgWw (Yellow, Soft)

GgWw (Yellow, Wrinkled) ggWW (Green, Soft)

Ggww (Yellow, Wrinkled) ggWw (Green, Soft)

gW

GgWW (Yellow,Sof t)

Gw

GgWw (Yellow Soft)

Ggww (Yellow, Wrinkled)

ggWw (Green, Soft)

ggww (Green, Wrinkled)

Figure 2.2. Dihybrid cross diagram for the nature of color and form beans Dihybrid cross from the diagram above can be seen that a ratio of F2 phenotypes 9: 3: 3: 1 as a result of the segregation of genes G and W are independent. Thus, gametes are formed may contain a combination of dominant genes with a dominant gene (GW), dominant gene with a recessive gene (Gw and gW), and the recessive gene with a recessive gene (gw). This is what became known as free elections law (the law of independent assortment), or the law of Mendel II. Segregation of a gene pair does not depend on the segregation of other gene pairs, so that in the gametes formed will be a combination of selection genes freely.

Diagram of a combination of gametes and gametes in the F2 generation produces individuals as in Figure 2.2 is called the Punnett diagram. There are other

ways that can be used to determine the combination of gametes in the F2 generation individuals, using a fork child diagrams (fork line). This method is based on mathematical calculations that the cross is a dihybrid cross monohybrid twice (Yatim, Wildan. 1974).

CHAPTER III EXPERIMENTS METHOD A. Place and Date The experiment was done at: Day and Date : Wednesday , December 16th 2009 Time Place : 13.15 14.50 pm : Laboratory of Biology, Mathematic and Science Faculty, Makassar State University at 2nd east floor part. B. Tools and Materials 1. Loupe

2. List of Phenotypes

A. Work Procedure 1. Look into the phenotype of each heredity characteristic that there is of list phenotype in our self. If couldnt deal please get help to friend in your group . Then, note the result to table form 2. If they have phenotype was dominant, so give the sign (-) for the second gene.3. Note and observe the characteristic of friends for the other group and

calculate its presentation

LIST OF PHENOTYPE FOR THE HUMAN HEREDITY THAT IT CONTROL BY 1 GENE WITH 2 ALLEL AND EACH ONE CREATED A CLEAR PHENOTYPE 1. Dimple of chin was dominant (D) and not was recessive (dd) 2. Tip of the auricle of ear as be free was dominant (E) and not was recessive (ee) 3. Thumb of left hand at up of right hand was dominant (F) and not was recessive (ff) 4. The knuckle bone of the little finger that most tip goes askew on it was dominant (B) and not was recessive (bb) 5. Hair at forehead stick out was dominant (W) and not was recessive (ww) 6. Hair at the finger (on second joints) was dominant (M) and not was recessive (mm) 7. Dimple was dominant (P) and not was recessive (pp) 8. Can rolled his/her tongue be along was dominant (L) and not was recessive (ll) 9. People that have incisor of on and be gap (G) and not was recessive (gg) 10. Can rolled his/her tongue be enter was dominant (A) and no was recessive (aa)

\

CHAPTER IV OBSERVATION RESULT A. Observation Result1. Personal Data

N o 1 2 3

The characteristic of heredity Dimple of chin was dominant (D) and not was recessive (dd) Tip of the auricle of ear as be free was dominant (E) and not was recessive (ee)

Geotipe Dd Ee

Thumb of left hand at up of right hand was Ff dominant (F) and not was recessive (ff)

4

The knuckle bone of the little finger that most

Bb

tip goes askew on it was dominant (B) and not was recessive (bb) 5 6 Hair at forehead stick out was dominant (W) and not was recessive (ww) Ww

Hair at the finger (on second joints) was Mm dominant (M) and not was recessive (mm)

7 8 9

Dimple was dominant (P) and not was recessive (pp) Can rolled his/her tongue be along was dominant (L) and not was recessive (ll)

Pp Ll

1. People that have incisor of on and be gap Gg (G) and not was recessive (gg)

A. Analysis of Data I. Analysis of Group Data 1. Dimple of Chin a) Dominant =Sum dominantsum of practican100 % =04100 %=0% b) Recessive =Sum dominantsum of practican100 % =44100 %=100 %

1. Tip of the auricle of ears as be free a) Dominant =Sum dominantsum of practican100 % =14100%=25 % b) Recessive =Sum dominantsum of practican100 % =34100 %=75 %

1. Thumb of left hand at up of right hand

a) Dominant =Sum dominantsum of practican100 % =34100 %=75 % b) Recessive =Sum dominantsum of practican100 % =14100 %=25 %

1. The knuckle bone of the little finger that most tip goes askew on it a. Dominant =Sum dominantsum of practican100 % =44100%=100 % b. Recessive =Sum dominantsum of practican100 % =04100 %=0 %

1. Hair at forehead stick out a. Dominant =Sum dominantsum of practican100 % =04100%=0% b. Recessive =Sum dominantsum of practican100 % =44100 %=100%

1. Hair at the finger (on second joints) a. Dominant =Sum dominantsum of practican100 % =44100%=100 % b. Recessive =Sum dominantsum of practican100 % =04100 %=0 %

1. Dimple a. Dominant =Sum dominantsum of practican100 % =14100%=25% b. Recessive =Sum dominantsum of practican100 % =34100 %=75 %

1. Can rolled his/her tongue be along a. Dominant =Sum dominantsum of practican100 % =34100%=75% b. Recessive =Sum dominantsum of practican100 % =14100 %=25 %

1. People that have incisor of on and be gap a. Dominant =Sum dominantsum of practican100 % =44100%=100 %

b. Recessive =Sum dominantsum of practican100 % =04100 %=0 %

I. Analysis of class Data 1. Dimple of Chin a. Dominant =Sum dominantsum of practican100 % =032100%=0 % b. Recessive =Sum dominantsum of practican100 % =3232100 %=100 %

1. Tip of the auricle of ears as be free a) Dominant =Sum dominantsum of practican100 % =832100%=25% b) Recessive =Sum dominantsum of practican100 % =2432100 %=75 %

1. Thumb of left hand at up of right hand a) Dominant =Sum dominantsum of practican100 % =1632100%=50 % b) Recessive =Sum dominantsum of practican100 % =1632100 %=50 %

1. The knuckle bone of the little finger that most tip goes askew on it a. Dominant =Sum dominantsum of practican100 % =1923100%=59.4 % b. Recessive =Sum dominantsum of practican100 % =1423100 %=43.75 %

1. Hair at forehead stick out a. Dominant =Sum dominantsum of practican100 % =732100%=21.875 % b. Recessive =Sum dominantsum of practican100 % =2532100 %=78.125 %

1. Hair at the finger (on second joints) a. Dominant =Sum dominantsum of practican100 % =3232100%=100%

b. Recessive =Sum dominantsum of practican100 % =032100 %=0%

1. Dimple a. Dominant =Sum dominantsum of practican100 % =532100%=15.625% b. Recessive =Sum dominantsum of practican100 % =2732100 %=84.75%

1. Can rolled his/her tongue be along a. Dominant =Sum dominantsum of practican100 % =1632100%=50% b. Recessive =Sum dominantsum of practican100 % =1632100 %=50 %

1. People that have incisor of on and be gap c. Dominant =Sum dominantsum of practican100 % =2132100%=65.625 % d. Recessive =Sum dominantsum of practican100 % =1132100 %=34.4 %

A. Pembahasan 1. Analisis Data Group a) Lesung dagu sifat dominan (D) dan resesif (d), frekuensi untuk sifat lesung dagu, anggota grup IV semuanya bersifat resesif dengan persentase 100%.b) Ujung daun telinga menggantung bebas sifat dominan (E) dan resesif(e),

frekuensi untuk sifat ini berdasarkan hasil pengamatan, untuk sifat dominan (E) dengan jumlah frekuensi sebanyak 1 orang dengan

persentase

25% dan untuk sifat resesif sebanyak 3 orang dengan

persentase 75%. c) Ibu jari tangan kiri diatas ibujari tangan kanan adalah sifat dominan (F) dan sifat resesif (f). Untuk sifat Dominan pada grup yaitu 75% dan untuk sifat resesifnya 25%. d) Ujung ibu jari kelingking menyerong kedalam adalah sifat dominan (B), resesif (b). Untuk sifat dominan yang di miliki kelompok ini semuanya bersifat dominan dengan persentase 100%. e) Rambut dahi menjorok merupakan sifat dominan (W), sifat resesif (w) semuanya bersifat resesif dengan persentase sebesar 100%. f) Rambut pada ruas jari merupakan sifat dominan (M), sifat resesif (m). Semuanya bersifat dominan dengan persentase sebesar 100% g) Lesung pipi merupakan sifat dominan (P), sifat resesif (p). Untuk sifat dominan memiliki persentase sebesar 25 % dan Untuk sifat resesif memiliki persentase sebesar 75%. h) Menggulung lidah memanjang merupakan sifat dominan (L) dan resesif (l). Untuk sifat dominan memiliki persentase sebesar 75% dan untuk sifat resesif memiliki persentase sebesar 25 % i) Gigi seri atas bercelah merupakan sifat dominan. Untuk sifat dominan semuanya bersifat dominan dengan persentase sebesar 100 % 1. Analisis Data Semua grup a) Adanya lesung dagu merupakan sifat dominan (D) dan resesif (d). Untuk data ini semua sample bersifat resesi (d) dengan persentase sebesar 100% b) Memiliki ujung telinga menggantung bebas merupakan sifat dominan (E) dan resesif (e). Untuk sifat dominan memiliki persentase sebesar 25% dan sifat resesif memiliki persentase sebesar 75%.

c) Pada ibu jari tangan kiri diatas ibu jari tangan kanan merupakan sifat

dominan. Untuk sifat dominan dan resesif pada data ini memiliki hasil yang sama dengan persentase sebesar 50%. d) Pada ruas jari kelingking paling ujung menyerong kedalam. Untuk sifat dominan pada data ini memiliki persentase sebesar 59.4% dan memiliki sifat resesif sebesar 43.75%. e) Untuk rambut ruas yang menjorok merupakan sifat dominan (W), sifat resesif (w). Untuk sifat dominan pada data ini memiliki persentase sebesar 21,875% dan memiliki sifat resesif sebesar 78,125%. f) Untuk rambut yang tumbuh pada ruas jari merupakan sifat dominan (M) dan resesif (m). Untuk sifat dominan pada data ini memiliki persentase sebesar 100%. Semuanya kelompok bersifat dominan. g) Mempunyai lesung pipi yang merupakan sifat dominan (P) dan resesif (p). Untuk sifat dominan pada data ini memiliki persentase sebesar 15,625 dan resesif memiliki persentase sebesar 84.75%. h) Dapat menggulung lidah dan memanjang merupakan bersifat dominan (L), resesif(l). Untuk sifat dominan pada data ini memiliki persentase sebesar yang sama dengan sfat resesif sebesar 50%.c. Untuk gigi seri atas bercelah bersifat dominan (G) dan resesif (g). Untuk

sifat dominan pada data ini memiliki persentase sebesar 65.625 % dan resesif memiliki persentase sebesar 34.4 %

CHAPTER V CNCLUSION AND SUGGESTION

A. Conclusion

The conclusions that can be taken after this observation are:1. Every organism, change by factor descendant (gene) 2. According to Law of Mendel that from cross dominant will cover that

recessive alel if the second there is a may same3. Every organism have characteristic of heredity, which the characteristic of

heredity arrange by geneA. Suggestion

for the next practican, must make a good work with the other group so, the practicum will be better and with this way the practicum could be finished quickly

BIBLIOGRAPHY

Alimuddin. 2003. Genarl Biology. Makassar: Jurusan Biologi FMIPA UNM Anonim1. 2009. Hereditys. file:www. ///http:/heredity/.htm. Accessed on December 20th 2009 Anonim2. 2009. Segregation of Mendel..www. wikipedia.com. Accesed on December 20th 2009 Eisenmesser EZ. 2005. Gregor Mendels experiment.Jakarta: Erlangga Parson.1994. Biology of university. Jakarta: Pustaka Setia Yatim, Wildan. 1974. Biology of University. Bandung: Tarsito

Heredity is the passing of traits to offspring (from its parent or ancestors). This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause a species to evolve. The study of heredity in biology is called genetics, which includes the field of epigenetics.

The ancients had a variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers to ripen; Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the time of conception, and Aristotle thought that male and female semen mixed at conception. Aeschylus, in 458 BC, proposed the male as the parent, with the female as a "nurse for the young life sown within her". Various hereditary mechanisms were envisaged without being properly tested or quantified. These included blending inheritance and the inheritance of acquired traits. Nevertheless, people were able to develop domestic breeds of animals as well as crops through artificial selection. The inheritance of acquired traits also formed a part of early Lamarckian ideas on evolution. In the 9th century AD, the Afro-Arab writer Al-Jahiz considered the effects of the environment on the likelihood of an animal to survive, and first described the struggle for existence.[1][2] His ideas on the struggle for existence in the Book of Animals have been summarized as follows: "Animals engage in a struggle for existence; for resources, to avoid being eaten and to breed. Environmental factors influence organisms to develop new characteristics to ensure survival, thus transforming into new species. Animals that survive to breed can pass on their successful characteristics to offspring."[3] In 1000 AD, the Arab physician, Abu al-Qasim al-Zahrawi (known as Albucasis in the West), wrote the first clear description of haemophilia, a hereditary genetic disorder, in his Al-Tasrif. In this work, he wrote of an Andalusian family whose males died of bleeding after minor injuries.[4] During the 1700s, Dutch microscopist Antoine van Leeuwenhoek (16321723) discovered "animalcules" in the sperm of humans and other animals. Some scientists speculated they saw a "little man" (homunculus) inside each sperm. These scientists formed a school of thought known as the "spermists". They contended the only contributions of the female to the next generation were the womb in which the homunculus grew, and prenatal influences of the womb. An opposing school of thought, the ovists, believed that the future human was in the egg, and that sperm merely stimulated the growth of the egg. Ovists thought women carried eggs containing boy and girl children, and that the gender of the offspring was determined well before conception. Pangenesis was an idea that males and females formed "pangenes" in every organ. These pangenes subsequently moved through their blood to the genitals and then to the children. The concept originated with the ancient Greeks, and influenced biology until as recently as a century ago. The terms "blood relative", "full-blooded", and "royal blood" are relics of pangenesis. Francis Galton, Charles Darwin's cousin, experimentally tested and disproved pangenesis during the 1870's. [edit] Types of heredity

This section may require cleanup to meet Wikipedia's quality standards. Please improve this section if you can. (August 2009) Dominant and recessive An allele is said to be dominant if it is always expressed in the appearance of an organism(phenotype). For example, in peas the allele for green pods, G, is dominant to that for yellow pods, g. Since the allele for green pods is dominant, pea plants with the pair of alleles GG (homozygote) or Gg (heterozygote) will have green pods. The allele for yellow pods is recessive. The effects of this allele are only seen when it is present on both chromosomes, gg (homozygote). [by: Qurat-ul-ain Basit. Lahore, Pakistan] The description of a mode of biological inheritance consists of three main categories: 1. Number of involved loci

Monogenetic (also called "simple") one locus Oligogenetic few loci Polygenetic many loci

2. Involved chromosomes

Autosomal loci are not situated on a sex chromosome Gonosomal loci are situated on a sex chromosome

X-chromosomal loci are situated on the X chromosome (the more common case) Y-chromosomal loci are situated on the Y chromosome

Mitochondrial loci are situated on the mitochondrial DNA

3. Correlation genotypephenotype

Dominant Intermediate (also called "codominant") Recessive

These three categories are part of every exact description of a mode of inheritance in the above order. Additionally, more specifications may be added as follows: 4. Coincidental and environmental interactions

Penetrance Complete

Incomplete (percentual number)

Expressivity Invariable Variable

Heritability (in polygenetic and sometimes also in oligogenetic modes of inheritance) Maternal or paternal imprinting phenomena (also see epigenetics)

5. Sex-linked interactions

Sex-linked inheritance (gonosomal loci) Sex-limited phenotype expression (e.g., cryptorchism) Inheritance through the maternal line (in case of mitochondrial DNA loci) Inheritance through the paternal line (in case of Y-chromosomal loci)

6. Locuslocus interactions

Epistasis with other loci (e.g., overdominance) Gene coupling with other loci (also see crossing over) Homozygotous lethal factors Semi-lethal factors

Determination and description of a mode of inheritance is primarily achieved through statistical analysis of pedigree data. In case the involved loci are known, methods of molecular genetics can also be employed. [edit] Charles Darwin: theory of evolution Main article: Charles Darwin See also: Evolution Charles Darwin proposed a theory of evolution in 1859 and one of its major problems was the lack of an underlying mechanism for heredity. Darwin believed in a mix of blending inheritance and the inheritance of acquired traits (pangenesis). Blending inheritance would lead to uniformity across populations in only a few generations and thus would remove variation from a population on which natural selection could act. This led to Darwin adopting some Lamarckian ideas in later editions of On the Origin of Species and his later biological works. Darwin's primary approach to heredity was to outline how it appeared to work (noticing that traits could be inherited which were not expressed explicitly in the parent at the time of

reproduction, that certain traits could be sex-linked, etc.) rather than suggesting mechanisms. Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity. Galton rejected the aspects of Darwin's pangenesis model which relied on acquired traits. The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice and found that their offspring continued to develop tails. [edit] Gregor Mendel: father of modern genetics Main article: Gregor Mendel See also: Modern evolutionary synthesis The idea of particulate inheritance of genes can be attributed to the Moravian[5] monk Gregor Mendel who published his work on pea plants in 1865. However, his work was not widely known and was rediscovered in 1901. It was initially assumed the Mendelian inheritance only accounted for large (qualitative) differences, such as those seen by Mendel in his pea plants and the idea of additive effect of (quantitative) genes was not realised until R.A. Fisher's (1918) paper on The Correlation Between Relatives on the Supposition of Mendelian Inheritance. [edit] Modern development of genetics and heredity Main articles: History of genetics and Modern evolutionary synthesis In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the modern evolutionary synthesis. The modern synthesis bridged the gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that:[6][7] 1. All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms and the observational evidence of naturalists. 2. Evolution is gradual: small genetic changes, recombination ordered by natural selection. Discontinuities amongst species (or other taxa) are explained as originating gradually through geographical separation and extinction (not saltation).3. Selection is overwhelmingly the main mechanism of change; even slight

advantages are important when continued. The object of selection is the phenotype in its surrounding environment. The role of genetic drift is equivocal; though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological genetics were obtained. 4. The primacy of population thinking: the genetic diversity carried in natural populations is a key factor in evolution. The strength of natural selection in the wild was greater than expected; the effect of ecological factors such as

niche occupation and the significance of barriers to gene flow are all important. 5. In palaeontology, the ability to explain historical observations by extrapolation from micro to macro-evolution is proposed. Historical contingency means explanations at different levels may exist. Gradualism does not mean constant rate of change. The idea that speciation occurs after populations are reproductively isolated has been much debated. In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the frequencies of alleles between one generation and another' were proposed rather later. The traditional view is that developmental biology ('evo-devo') played little part in the synthesis, but an account of Gavin de Beer's work by Stephen Jay Gould suggests he may be an exception.[8] Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no doubt, however, that the synthesis was a great landmark in evolutionary biology. It cleared up many confusions, and was directly responsible for stimulating a great deal of research in the post-World War II era. Trofim Lysenko however caused a backlash of what is now called Lysenkoism in the Soviet Union when he emphasised Lamarckian ideas on the inheritance of acquired traits. This movement affected agricultural research and led to food shortages in the 1960s and seriously affected the USSR.