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Words to know… Heredity - the passing of traits from parent to offspring. Genetics - the study of heredity. Trait- a specific characteristic Gene- chemical.

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Presentation on theme: "Words to know… Heredity - the passing of traits from parent to offspring. Genetics - the study of heredity. Trait- a specific characteristic Gene- chemical."— Presentation transcript:

1 Words to know… Heredity - the passing of traits from parent to offspring. Genetics - the study of heredity. Trait- a specific characteristic Gene- chemical factor that determines a trait Allele- A segment of a gene Hybrid- the offspring crosses between parents with different traits

2 Gregor Mendel Father of Genetics He lived in a monastery; He was a teacher and took care of the garden Mendels knowledge helped us understand heredity. He studied the pea plant most of all.

3 Mendel's Process Mendel took a true-breeding (or pure) plants that always produce offspring with the same trait when they self-pollinate and cross pollinated it with a true breeding plant with a different trait. The P generation is the true-breeding generation or the parent generation.

4 Pollination Self pollination occurs when pollen is transferred from the anthers (male) of one flower to the stigma (female) of the same flower. Cross-pollination occurs between two plants.

5 The F1 generation is the offspring of the P generation. Mendel called the plants in the second generation the second F2

6 Mendel established three principles (or Laws) from his research 1.The Principle of Dominance and Recessiveness - one trait is masked or covered up by another trait 2.Principle of Segregation - the two factors (alleles) for a trait separate during gamete formation 3.Principle of Independent Assortment - factors of a trait separate independently of one another during gamete formation; another way to look at this is, whether a flower is purple has nothing to do with the length of the plants stems - each trait is independently inherited

7 Mendels Laws copyright cmassengale7

8 Results of Monohybrid Crosses Inheritable factors or genes are responsible for all heritable characteristics Inheritable factors or genes are responsible for all heritable characteristics Phenotype is based on Genotype Phenotype is based on Genotype Each trait is based on two genes, one from the mother and the other from the father Each trait is based on two genes, one from the mother and the other from the father True-breeding individuals are homozygous ( both alleles) are the same True-breeding individuals are homozygous ( both alleles) are the same copyright cmassengale8

9 Law of Dominance copyright cmassengale9 In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. All the offspring will be heterozygous and express only the dominant trait. RR x rr yields all Rr (round seeds)

10 Law of Dominance copyright cmassengale10

11 Law of Segregation During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. copyright cmassengale11

12 copyright cmassengale12 Applying the Law of Segregation

13 Law of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another. Alleles for different traits are distributed to sex cells (& offspring) independently of one another. This law can be illustrated using dihybrid crosses. This law can be illustrated using dihybrid crosses. copyright cmassengale13

14 Dominant - stronger & mask other genes; the trait that shows up more frequently – represented by a capital letter Recessive- weaker the trait that shows up less frequently – represented by a lower case letter

15 A chromosome is made up of DNA. A gene is a segment of DNA on a chromosome that controls a particular hereditary trait. Each of two or more alternative forms of a gene is called an allele. Mendels factors are now called an allele.

16 copyright cmassengale16 Mendel stated that physical traits are inherited as particles Mendel stated that physical traits are inherited as particles Mendel did not know that the particles were actually Chromosomes & DNA Mendel did not know that the particles were actually Chromosomes & DNA Particulate Inheritance

17 Probability is the likelihood that a specific even will occur. It is the mathematical chance that something will occur.

18 Punnett Square Used to help solve genetics problems copyright cmassengale18

19 Types of Genetic Crosses Monohybrid cross - cross involving a single trait e.g. flower color Monohybrid cross - cross involving a single trait e.g. flower color Dihybrid cross - cross involving two traits e.g. flower color & plant height Dihybrid cross - cross involving two traits e.g. flower color & plant height copyright cmassengale19

20 More Terminology Genotype - gene combination for a trait (e.g. RR, Rr, rr) Genotype - gene combination for a trait (e.g. RR, Rr, rr) Phenotype - the physical feature resulting from a genotype (e.g. red, white) Phenotype - the physical feature resulting from a genotype (e.g. red, white) copyright cmassengale20

21 Genotypes Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure Heterozygous genotype - gene combination of one dominant & one recessive allele (e.g. Rr); also called hybrid Heterozygous genotype - gene combination of one dominant & one recessive allele (e.g. Rr); also called hybrid copyright cmassengale21

22 ?????? What is the phenotype of a heterozygous flower? What is the genotype of a heterozygous flower? What is the genotype of a homozygous dominant?

23 Dihybrid Cross copyright cmassengale23RYRyrYry RYRy rY ry

24 Dihybrid Cross copyright cmassengale24 RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RYRyrYryRY Ry rY ry

25 Test Cross A mating between an individual of unknown genotype and a homozygous recessive individual. A mating between an individual of unknown genotype and a homozygous recessive individual. copyright cmassengale25

26 Its not all that easy! Multiple alleles- trait that is determined by more than two alleles (ex. Human blood types) Polygenic traits- trait influenced by several genes; genes may be on same chromosome or on different one (ex. Human eye color, weight, skin tone)

27 Incomplete dominance The phenotype is in between that of the parents. It is like a mixture (pink flower) Example: Snap Dragon

28 Codominance Both alleles are expressed. With Codominance you can see two dominant alleles.

29 Codominance Two alleles are expressed (multiple alleles) in heterozygous individuals. Two alleles are expressed (multiple alleles) in heterozygous individuals. Example: blood type Example: blood type 1.type A= I A I A or I A i 1.type A= I A I A or I A i 2.type B= I B I B or I B i 2.type B= I B I B or I B i 3.type AB= I A I B 3.type AB= I A I B 4.type O= ii 4.type O= ii copyright cmassengale29

30 Codominance Problem Example:homozygous male Type B (I B I B ) x heterozygous female Type A (I A i) copyright cmassengale30 IAIBIAIB IBiIBi IAIBIAIB IBiIBi 1/2 = I A I B 1/2 = I B i IBIB IAIA i IBIB

31 Another Codominance Problem copyright cmassengale31 Example:Example: male Type O (ii) x female type AB (I A I B ) IAiIAiIBiIBi IAiIAiIBiIBi 1/2 = I A i 1/2 = I B i i IAIA IBIB i

32 Codominance Question: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? Question: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? boy - type O (ii) X girl - type AB (I A I B ) boy - type O (ii) X girl - type AB (I A I B ) copyright cmassengale32

33 Thomas Hunt Morgan Discovered that females have XX chromosomes and males have XY by studying a fruit fly. Sex Chromosomes determine the sex of an organism. He discovered that the gene for eye color in fruit flies is a sex linked trait carried on the Y chromosome

34 Sex-linked Traits Traits (genes) located on the sex chromosomes Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y Sex chromosomes are X and Y XX genotype for females XX genotype for females XY genotype for males XY genotype for males Many sex-linked traits carried on X chromosome Many sex-linked traits carried on X chromosome The genes interact with other genes scattered throughout the genome The genes interact with other genes scattered throughout the genome copyright cmassengale34

35 Blood Type AntigenAntibodyCan donate toCan receive from A B AB O

36 Karyotype of Kleinfelters and Turners

37 Pedigree

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