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genes&inheritance.pptx
- 1. Genes and Inheritance GCEStudy Buddy Biology
- 2. Chromosomes ●Genetic materials foundinside the nucleus of a cell ●Made up of DNA & protein ●Appear as very thin & thread-like structures called Chromatins ●Each cell in each type of organism has a definite number of chromosomes ●Each cell has Diploid Number of chromosomes: 1 set of Paternal Chromosomes + 1 set of Maternal Chromosomes
- 3. chromosom e gene controlling skin colour genecontrolling tongue rolling gene controlling eye colour gene controlling blood group ●A gene is a short length of DNA on a chromosome which is a unit determining an inherited character ●It consists of a chemical substance called deoxyribonucleic acid (DNA)
- 4. chromosom e gene controlling skin colour genecontrolling tongue rolling gene controlling eye colour gene controlling blood group ●DNA is responsible for telling the cell to make the right type of protein & control the metabolic activities of the cells
- 5. ●Chromosomes always existin pairs in the body (somatic) cells ●Each human somatic cell has 46 chromosomes ○23 pairs of homologous chromosomes Homologous Chromosomes
- 6. ●Members of homologous chromosomescarry the same genes (controlling the same character) in same loci ●But the genes on the members of homologous chromosomes may be of different forms (effects) ●Alleles allele for white skin colour allele for dark skin colour
- 7. ●Alternative forms ofgenes on the same position of the homologous chromosomes which control the same character but have different expressions Alleles
- 8. What would happenif gametes are formed by mitosis? Male (2n) Female (2n) Sperm (2n) Egg (2n) Zygote (4n) Sperm/Egg (4n) Zygote (8n) Mitosis Fertilization Mitosis Fertilization
- 9. Meiosis ●Producing cells withchromosome number half of the parent cell ●Two nuclear divisions ○Meiosis I and meiosis II ●Four haploid cells are produced
- 10. First Meiotic Division ●Chromosomesbecome visible ●Nuclear membrane disappears ●Homologous chromosomes pair up (not in mitosis) ●Crossing-over (not in mitosis) may occur between homologous chromosomes ●Homologous chromosomes line up in the middle of cell randomly ●The 2 members of each homologous chromosome separate from each other and move towards the opposite poles of the cell ●Nuclear membrane reforms
- 11. Second Meiotic Division ●Separationof chromatids of each chromosome ●4 daughter cells with half of the chromosome number of the parent cell are formed ●Occurrence of meiosis ○Plants: anthers and ovules ○Mammals: testes and ovaries
- 12. Comparison between Mitosis &Meiosis Mitosis Meiosis Number of division 1 2 No. of daughter cells produced 2 4 Type of cells produced Somatic (body) cells Gametes (sex cells) Chromosome number of daughter cells Same as parent cell (diploid) Half of parent cell (haploid) Pairing of homologous chromosomes No Yes Occurrence Growing tissues Reproductive tissues (gonads) Role For growth and replacement For gamete formation
- 13. Significance of meiosis ●Producehaploid gametes which, after fertilization, can restore normal diploid conditions ●Produce genetic variations
- 14. Sources of genetic variation ●Differentcombination of the genes of each gamete ●Random fusion of gametes during fertilization
- 15. Heredity: tendency ofan individual to resemble his parents Variation: the differences between individuals of the same species Genetics: the study of how characters are transferred or inherited from one generation to the next The pattern of inheritance and variation
- 16. Mendel’s Breeding Experiment Monohybrid Inheritance: ●Theinheritance of just one pair of contrasting characters ●Cross 2 pure breeding parents with contrasting characters
- 17. Mendel’s experiment ●A numberof different traits that can be studied ●Plant should be self fertilizing and have a flower structure that limits accidental contact. ●Offspring should be fully fertile
- 18. 7 characteristics studied 1.Seedshape 2.Seed colour 3.Flower colour
- 19. ●Pod shape ●Pod colour 7characteristics studied
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- 21.
- 22. Principle of segregation ●Monohybrid ●purebreeding ●self fertilization ●parental generation ●F1 generation
- 23. F2 generation ●P generation ○smoothx wrinkle ●F1 generation ○all smooth ●F2 generation ○smooth : wrinkle 3 : 1
- 24.
- 25. Dihybrid cross ●Defintion ofthe alleles ●Determination of the dominance ●construction of the Punnett’s square
- 26. Principle of Independent Assortment ●Recombinationof alleles into each small square ●Determination of Phenotype and Genotype ratios in the next generation ●Labeling the generations e.g. P,F1..
- 27. white purple x pure-breeding parents first filial (F1) generation secondfilial (F2) generation all purple 705 purple 224 white monohybrid ratio 3:1
- 28. Terms ●Genotype - thegenetic composition ●Phenotype - the external appearance ●Homozygous (pure-breeding) ○with the same alleles in the same character ●Heterozygous (hybrid) ○with different alleles ●Dominant gene (or character) ○which expresses its effect even in heterozygous condition ●Recessive gene (or character) ○which expresses its effect only in homozygous condition ●Pedigree ○it shows the inheritance of one or more characters in different generations ●Test cross ○cross the organism with dominant character to an organism with homozygous recessive character ○to test whether the organism with the dominant character is homozygous or heterozygous
- 29. Sex Determination ●in human:by sex chromosomes ○male : XY ○female : XX ●chromosomes other than sex chromosomes somatic chromosomes which control normal body characters ●22 pairs are identical in both sexes (human) ○autosomes ●The 23rd pair is different in male and female ○sex chromosomes
- 30. Twins ●identical twins ○one embryoseparates into two and each develops into a new individual ○they should have same characters and same sex ●non-identical twins ○formed from two different zygotes from two separate fertilizations ○they usually have different characters ○they may have different sexes
- 31. human height continuou s variation ●continuous variation ○witha continuous range of intermediate values ○eg. height, weight, intelligence quotient, heart beat No. of individuals Types of Variations
- 32. Types of Variations ●discontinuousvariation ○the character is clear-cut & not showing intermediates ○eg. tongue rolling, ear lobes and colour of corn albinis m
- 33. ●Meiosis ○homologous chromosomes separateindependently from each other and pass into a different gamete ( INDEPENDENT ASSORTMENT). As a result, a great variety of gametes are produced ●Random Fertilization ○since fertilization is a random process, there are many possible different combinations of genes in a zygote ●Mutation ○genetic make-up may suddenly change ○sometimes occur naturally ○rate may greatly increased if the organism is exposed to radiation, certain chemicals or neutron bombardment ○most mutation are harmful ●Environmental Factors ○cause variation in characters with continuous variation Causes of Variations
- 34. ●Deoxyribose Nucleic Acid ●Avery long, thin molecule made up of DNA nucleotides ●2 nucleotide strands in the form of double helix ●DNA together with proteins made up the chromosomes ●Chromosomes are mainly found inside the nucleus in human cells DN A
- 35. DNA is apolymer of DNA nucleotides Each nucleotide consists of ... Pentos e Phosphate Organic bases 4 types of bases : A T G C
- 36. DNA nucleotides condenseinto DNA molecule A G A T T C T C T T A A G A G C
- 37.
- 38. ATG GTT AAAATC CCC CTG GGT ATG GTG ATT Transcription & Translation AA 1 AA2 AA3 AA 4 AA 5 AA6 AA 7 AA8 AA 9 AA10 Polypeptide Proteins serve as ●enzymes ●Hormones ●Structural proteins Genetic information stored as triplet codes of bases in DNA