Genetics: the scientific study of heredity

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Edmund Carter
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1 GENETICS 1

2 Mendel 1884) 2

3 Mendel Mendel was an Austrian monk who was in charge of the mo His work with pea plants has led to him being considered the Fath Genetics: the scientific study of heredity 3

4 Purple and White Flowers of Pea Plants 4

5 5

6 Peas Look Like? copyright cmassengale 6

7 Site of Gregor 7

8 Mendel s 2 Conclusions 1. Biological inheritance is determined by factors that are passed - factors = GENES determine traits - Each of the traits Mendel studied was controlled by one EX: GENE = seed color ; 2 contrasting forms - 2 contrasting forms: ALLELES ALLELE #1: yellow ALLELE #2: green

9 Mendel s 2 Conclusions Principle of Dominance: some alleles are dominant and othe - Inherit 2 dominant alleles: dominant allele will show - Inherit 2 recessive alleles: recessive allele will - Inherit 1 dominant and 1 recessive allele, the (HETEROZYGOUS)

10 erminology Homologous pair of chromosomes Chromosomes that have the same s Carry the same genes that control Individuals inherit one member of 10

11 11

12 erminology Trait A characteristic that can be passe Gene A section of DNA that has the i 12

13 erminology Allele Different forms of a gene (P) or ( Individuals inherit one allele from 13

14 erminology Alleles Allele for purple flowers (P) Gene for flower-color Allele for white flowers (p) 14

15 of Dominance Some alleles are dominant (P) and 15

16 erminology Dominant allele An allele that is fully expressed in th 16

17 erminology Recessive allele An allele that is only expressed (show 17

18 erminology Homozygous A pair of identical alleles for a tr Homozygous dominant PP - Two Homozygous recessive pp - Two 18

19 erminology Heterozygous Having two different alleles for a One dominant and one recessive a Dominant trait 19

20 erminology Phenotype The physical and physiological traits o Genotype The genetic make-up or combination 20

21 How Mendel's pea plants helped us understand genetics - Hortensia Jiménez Díaz - Y copyright cmassengale 21

22 f Segregation During the formation of gametes, c 22

23 enetic Crosses Monohybrid cross A cross involving a single trait be e.g. flower color 23

24 Square copyright cmassengale 24

25 notype in Flowers Genotype of alleles: P = purple flower p = white flower Possible combinations are: Genotypes PP Pp pp Homo. Dominant Hetero Homo. Recessive Phenotypes PURPLE PURPLE WHITE 25

26 nt Experiments Genotype: ¼ PP 2/4 Pp ¼ pp Phenotype: ¾ Purple ¼ white 26

27 copyright cmassengale 27

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29 29

30 w of Segregation 30

31 pplying the Law of Segregation 31

32 pendent Assortment Alleles for different traits segreg Mendel illustrated this law using a 32

33 enetic Crosses Dihybrid cross A cross involving two traits e.g. flower color & plant height Number of gametes 2 n (n = # of heterozygotes) copyright cmassengale 33

34 tion: or the following allele arrangements? Remember: 2 n (n = # of heterozygotes) 1. RrYy copyright cmassengale 34

35 wer: 1. RrYy: 2 n = 2 2 = 4 gametes RY Ry ry ry 35

36 brid Cross Traits: Seed shape & Seed color Alleles: R round r wrinkled Y yellow y green RrYy x RrYy y ry ry RY Ry ry ry ete combinations 36

37 id Cross R Y R Y R y ry ry R y ry ry 37

38 38 id Cross RRY Y RRY y RrY Y RrY y RRY y RRy y RrY y Rry y RrY Y RrY y rry Y rry y RrY y Rry y rry y rry y Round/Yellow: 9 Round/green: 3 wrinkled/yellow: 3 wrinkled/green: 1 9:3:3:1 phenotype ratio R Y R y ry ry R Y R y ry ry Sperm gs

39 id Cross Round/Yellow: 9 Round/green: 3 wrinkled/yellow: 3 wrinkled/green: 1 9:3:3:1 39

40 Mendel s laws LAW PARENT CROSS OFFSPRING DOMINANCE TT x tt tall x short 4/4 Tt tall SEGREGATION Tt x Tt tall x tall 3/4 tall 1/4 short INDEPENDENT ASSORTMENT RrGg x RrGg round & green x round & green 9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods copyright cmassengale 40

41 e Dominance 41

42 Dominance One allele is not completely dominant over t Example: snapdragon flowers Red (RR) x White (WW) RR = Red flower (homo dominant) WW = White flower (homo recessive) R W W R 42

43 Dominance W W R R W R W Genotype ratio 4/4 RW Heterozygous R R W R W Phenotype ratio 4/4 Pink 43

44 Dominance 44

45 inance The two alleles are completely dominant and 45

46 inance Examples: The A and B allele for blood types are cod In cattle the allele for red hair is codomina 46

47 e Problem Example: male Red bull (RR) C W C W x female white cow C R C R C W C R C W C R C R C W C R C W Phenotype ratio 4/4 Roan Genotype ratio 4/4 C R C W 47

48 inance copyright cmassengale 48

49 inance 49

50 Alleles When genes have more than two alleles The individual inherits only two of the a Example: There are three alleles for bl I A or A I B or B ii or O 50

51 Allele I A I B i Carbohydrate none (a) The three alleles for the ABO blood groups and their associated carbohydrates A B Red blood cell Genotype appearance Phenotype (blood type) I A I A or I A i A I B I B or I B i B I A I B AB ii (b) Blood group genotypes and phenotypes O

52 e Alleles The three alleles result in four possibl Phenotypes Genotypes 1. Type A = I A I A (AA) or I A i (AO) 2. Type B = I B I B (BB) or I B i (BO) 3. Type AB = I A I B (AB) 4. Type O = ii (OO) A and B dominant over O A and B are codominant 52

53 ce Problem Example: homozygous male Type B (BB) x A A B A B A B A B copyright cmassengale B A B Phenotype ratio 4/4 AB Genotype ratio 4/4 AB Heterozygous Codominant 53

54 c Traits Traits that are controlled by more than on Examples: At least three genes are involved In humans skin color, eye color, height and 54

55 genic Inheritance Fraction of progeny AaBbCc AaBbCc aabbcc Aabbcc AaBbcc AaBbCc AABbCc AABBCc AABBCC copyright cmassengale 55

Exploring Mendelian Genetics. Dihybrid crosses. Dihybrid crosses

Exploring Mendelian Genetics. Dihybrid crosses. Dihybrid crosses Objective 8: Predict the results of dihybrid genetic crosses by using Punnett squares Exploring Mendelian Genetics 11.3 Dihybrid cross--a cross that involves two pairs of contrasting traits. A cross between