GENETICS THE SCIENCE OF HEREDITY. HEREDITY AND MENDEL GENETICS 1. TRAIT:2. HEREDITY:

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1 GENETICS THE SCIENCE OF HEREDITY

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3 HEREDITY AND MENDEL GENETICS 1. TRAIT:2. HEREDITY:

4 homologous 3 & 4. GENE and LOCUS

5 5. ALLELES: The different forms of a gene for a particular trait. Example: A, a

6 6. DOMINANT ALLELE: The form of a gene that is expressed and prevents the expression of the other form. They are shown with capital letters like A, B, C etc.

7 7.RECESSIVE ALLELE: The form of a gene that is expressed only when paired with a gene coding for the same trait. They are shown with lowercase letters like,a, b, c etc.

8 8.HOMOZYGOUS (PURE BREED): 9.HETEROZYGOUS (HYBRID): When both alleles are same. Example: BB, bb When the alleles are different. Example: Bb

9 10. PHENOTYPE: 11. GENOTYPE: Example: Tall pea plant Examples: Heterozygous tall pea plant or Homozygous tall pea plant

10 12. PARENTAL GENERATION(P): 14. SECOND FILIAL GENERATION (F 2 ): 13. FIRST FILIAL GENERATION (F 1 ): Example: tall stem X dwarf stem (selfing of the F 1 generation)

11 15. MONOHYBRID CROSS:

12 16. DIHYBRID CROSS: Ex: round, yellow seeded X wrinkled, green seeded

13 17.TEST CROSS: Test cross is used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous. Example: Phenotype tall X dwarf Genotype T? tt (TT or Tt) 1. %100tall 2. %50 tall %50 dwarf

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15 18. PUNNET SQUARE

16 19. PEDIGREE CHART: ı ıı ııı IDENTICAL TWINS FRATERNAL TWINS Example: ALBINIZM

17 19. PROBABILITY: A.The Rule of Independent Events: Previous events do not affect the probability of later occurrences of the same event. Ex. Probability of having a head or tail in a toss is ½

18 B. The Product Rule: The probability of independent events occurring together is equal to the product of the probabilities of these events occurring separately. Ex. Probability of having one head and one tail is ½ x ½ = ¼

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20 Each baby has a 50:50 chance of being either a male or a female. It doesn't matter how many other brothers or sisters are already in the family. Each baby is a separate entity and its sex is not influenced by the sexes of earlier children. What are the chances that a baby will be born a male or female?

21 Olasılık ve Genetik 1.Prensip: Şansa bağlı bir olayın bir defa denemesinden elde edilen sonuçlar, aynı olayın daha sonraki deneme sonuçlarını etkilemez. 10 defa attığımız paranın 10 defa da tura gelmesi halinde 11. defa tura gelme şansı yine 1/2 dir. Genotipi Aa olan bir bireyin gametleri 1/2 A ve 1/2 a’dır.

22 Olasılık ve Genetik 2. Prensip: İki bağımsız olayın birlikte olma şansı onların ayrı ayrı olma şanslarının çarpımına eşittir. İki tavla zarını birlikte attığımızda bunlardan birinin 4 gelme şansı 1/6 dır. Diğer zar içinde aynıdır.Aynı anda 4 gelme olasılığı 1/36 dır. **Bir ailenin doğacak 3 çocuğundan ikisinin erkek birinin kız olma olasılığı (a= kız, b= erkek) (a+b) 3 = a 3 + 3 a 2 b+ 3 b 2 a + b 3 3b 2 a = 3 (1/2) 2 ( 1/2) = 3/8

23 How meiosis produces genetic variation??? 1. Without meiosis, chromosome numbers would continually increase 2. Meiosis ensures daughter cells receive one of each kind of gene; precisely halves the chromosome number 3. Independent assortment provides 2n possible combinations of chromosomes in daughter cells 4. In humans with 23 haploid chromosomes, 2n = 223 = 8,388,608 possible combinations. 5. Variation is added by crossing-over; if only one crossover occurs within each bivalent, 423 or 70,368,744,000,000 combinations are possible 6. Fertilization also contributes to genetic variation; (223)2 = 70,368,744,000,000 possible combinations without crossing- over 7. With fertilization and crossing-over, (423)2 = 4,951,760,200,000,000,000,000,000,000 combinations are possible