Presentation is loading. Please wait.

Presentation is loading. Please wait.


Similar presentations

Presentation on theme: "GENETICS Ch. 11."— Presentation transcript:


2 Gregor Mendel Genetics is the study of heredity.
Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breeding garden peas.

3 2. Mendel cross-pollinated pea plants
He cut away the male parts of one flower, then dusted it with pollen from another

4 3. What did Mendel conclude?
He concluded that factors are passed from one generation to the next.

5 4. The Principle of Dominance
Paternal Maternal eye color locus b = blue eyes eye color locus B = brown eyes 4. The Principle of Dominance The Principle of Dominance – some alleles are dominant and other are recessive. Alleles 1. Alternative forms of genes. 2. Units that determine heritable traits.

6 5. Dominant and Recessive alleles
Dominant alleles – upper-case a. homozygous dominant (BB – Brown eyes) Recessive alleles – lower case a. homozygous recessive (bb – blue eyes) b. Heterozygous (Bb – Brown eyes)

7 Phenotype vs. Genotype Outward appearance Physical characteristics
Examples: 1.Brown eyes eyes Arrangement of genes that produces the phenotype Example: 1. TT, Tt 2. tt

8 6. Segregation Alleles separate during meiosis

9 7. Recessive traits show up about 1/4th of the time.
Because there is only a 25% chance that two recessive alleles will be paired together.

10 9. Punnett square A Punnett square is used to show the possible combinations of gametes. Monohybrid Cross

11 Monohybrid Cross Example: Cross between two heterozygotes for brown eyes (Bb) BB = brown eyes Bb = brown eyes bb = blue eyes B b Bb x Bb male gametes female gametes

12 Monohybrid Cross B b Bb x Bb 1/4 = BB - brown eyed
1/4 = bb - blue eyed 1:2:1 genotype 3:1 phenotype BB Bb bb

13 Dihybrid Cross

14 Dihybrid Cross RY Ry rY ry RY Ry rY ry

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

16 Dihybrid Cross Example: cross between round and yellow heterozygous pea seeds. R = round r = wrinkled Y = yellow y = green RrYy x RrYy RY Ry rY ry x RY Ry rY ry possible gametes produced

17 10. Independent Assortment
This means all gametes will be different! B b sperm haploid (n) meiosis II Chromosomes separate independently of eachother B F B b meiosis I Bb Ff b f Bb diploid (2n) Bb Ff B f Bb Ff B F

18 Independent Assortment
Genes for different traits can segretate independently during the formation of gametes without influencing eachother Question: How many gametes will be produced for the following allele arrangements? Remember: 2n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq

19 Answer: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry
2. AaBbCCDd: 2n = 23 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes

20 11. Incomplete Dominance One allele is not completely dominant over another r R All Rr = pink (heterozygous pink) produces the F1 generation Rr


22 11. Codominance Both alleles are expressed
Example: blood 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii Black cow + white cow = spotted cow

23 12. Which shows more genetic variation. (more combos?)
Male CC with female Cc Male cc with female Cc C c C c

24 Genetic Engineering

25 Gene Therapy

26 Is cloning a possibility?
Is it right to use cloning to create an entirely new human being? Is it ethical to create an embryonic copy of John Doe to supply cells to keep John alive? Does a multicellular ball of tissue -- an embryo -- have the same rights and status as a human being?

27 How does Mendel’s principles apply to organisms
The basic principals can be applied to humans as well as any other living organism.

28 And now it’s time for…. Spongebob Genetics!!!!!

Download ppt "GENETICS Ch. 11."

Similar presentations

Ads by Google