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Mendel’s experiment.pptx

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Sitamarhi Institute of Technology
Sitamarhi Institute of Technology

Gregor Mendel conducted experiments breeding pea plants to discover the basic principles of heredity. He found that organisms have discrete factors (now known as genes) that determine traits, which exist in two versions (alleles). During reproduction, parents contribute one of each allele to offspring randomly. Mendel also discovered that traits are inherited independently and that dominant alleles mask recessive alleles when both are present. His work formed the basis of classical genetics and established the laws of segregation and independent assortment.

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Mendel’s experiment • Gregor Mendel discovered the basic principle of heredity by breeding pea plant in carefully planned experiment. • Mendel chose to work with peas because there are many varieties, short life span and large number of offspring from each mating. • A heritable feature that varies among individuals, such as flower color, is called a character. • Each variant for a character, such as purple or white color for flowers, is called a trait. • Mendel chose to track only those characters that occurred in two distinct, alternative forms. • He also made sure that he started his experiments with varieties that were true breeding.
Mendel’s experiment.pptx
Mendel’s conclusion • Organisms have discrete factors that determine its features (these ‘factors’ are now recognized as genes). • organisms possess two versions of each factor (these ‘versions’ are now recognized as alleles). • Each gamete contains only one version of each factor (sex cells are now recognized to be haploid). • Parents contribute equally to the inheritance of offspring as a result of the fusion between randomly selected egg and sperm. • For each factor, one version is dominant over another and will be completely expressed if present.
Mendel’s laws • Law of segregation: states that genes have alternative forms, or alleles which are separated during gamete formation so that each gamete carries only one allele for each gene. • Law of Independent assortment: states that the pair of alleles for a given gene segregates into gametes independently of the pair of alleles for any other gene. This law does not hold true for genes located on the same chromosome. • Principle of Dominance: states that expression of the dominant allele masks the phenotypic effect of the recessive allele. Not all genes show a complete dominance some show co-dominance or incomplete dominance.
Concept of recessiveness and dominance • Recessive alleles only show their effect if the individual has two copies of the allele (also known as being homozygous). For example, the allele for blue eyes is recessive, therefore to have blue eyes you need to have two copies of the 'blue eye' allele. • Dominant alleles show their effect even if the individual only has one copy of the allele (also known as being heterozygous). For example, the allele for brown eyes is dominant, therefore you only need one copy of the 'brown eye' allele to have brown eyes (although, with two copies you will still have brown eyes).
Example
Comparison of Recessive and Dominant Allele
Gene mapping • Gene mapping is the process of establishing the locations of genes on the chromosomes. Early gene maps used linkage analysis. The closer two genes are to each other on the chromosome, the more likely it is that they will be inherited together. By following inheritance patterns, the relative positions of genes can be determined. More recently, scientists have used recombinant DNA (rDNA) techniques to establish the actual physical locations of genes on the chromosomes.
Types of gene mapping
Uses of Gene mapping 1. Identify genes responsible for diseases. • Heritable diseases • Cancer 2. Identify genes responsible for traits. • Plants and Animals • Disease resistance • Meat or milk production

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Mendel’s experiment.pptx

  • 1. Mendel’s experiment • Gregor Mendel discovered the basic principle of heredity by breeding pea plant in carefully planned experiment. • Mendel chose to work with peas because there are many varieties, short life span and large number of offspring from each mating. • A heritable feature that varies among individuals, such as flower color, is called a character. • Each variant for a character, such as purple or white color for flowers, is called a trait. • Mendel chose to track only those characters that occurred in two distinct, alternative forms. • He also made sure that he started his experiments with varieties that were true breeding.
  • 3. Mendel’s conclusion • Organisms have discrete factors that determine its features (these ‘factors’ are now recognized as genes). • organisms possess two versions of each factor (these ‘versions’ are now recognized as alleles). • Each gamete contains only one version of each factor (sex cells are now recognized to be haploid). • Parents contribute equally to the inheritance of offspring as a result of the fusion between randomly selected egg and sperm. • For each factor, one version is dominant over another and will be completely expressed if present.
  • 4. Mendel’s laws • Law of segregation: states that genes have alternative forms, or alleles which are separated during gamete formation so that each gamete carries only one allele for each gene. • Law of Independent assortment: states that the pair of alleles for a given gene segregates into gametes independently of the pair of alleles for any other gene. This law does not hold true for genes located on the same chromosome. • Principle of Dominance: states that expression of the dominant allele masks the phenotypic effect of the recessive allele. Not all genes show a complete dominance some show co-dominance or incomplete dominance.
  • 5. Concept of recessiveness and dominance • Recessive alleles only show their effect if the individual has two copies of the allele (also known as being homozygous). For example, the allele for blue eyes is recessive, therefore to have blue eyes you need to have two copies of the 'blue eye' allele. • Dominant alleles show their effect even if the individual only has one copy of the allele (also known as being heterozygous). For example, the allele for brown eyes is dominant, therefore you only need one copy of the 'brown eye' allele to have brown eyes (although, with two copies you will still have brown eyes).
  • 7. Comparison of Recessive and Dominant Allele
  • 8. Gene mapping • Gene mapping is the process of establishing the locations of genes on the chromosomes. Early gene maps used linkage analysis. The closer two genes are to each other on the chromosome, the more likely it is that they will be inherited together. By following inheritance patterns, the relative positions of genes can be determined. More recently, scientists have used recombinant DNA (rDNA) techniques to establish the actual physical locations of genes on the chromosomes.
  • 9. Types of gene mapping
  • 10. Uses of Gene mapping 1. Identify genes responsible for diseases. • Heritable diseases • Cancer 2. Identify genes responsible for traits. • Plants and Animals • Disease resistance • Meat or milk production