GENETICS

1. GENETICS CHP. 5

2. GREGOR MENDEL1822-1884 • KNOWN AS THE FATHER OF GENETICS • EDUCATED IN MATH AND SCIENCE • WANTED TO BE A TEACHER BUT FAILED THE EXAM

3. MORE ABOUT MENDEL • HE WAS A MONK • IN THE MONASTERY HE WAS IN CHARGE OF THE GARDEN • HERE IS WHERE HE STARTED HIS WORK IN GENETICS

4. MENDEL’S EXPERIMENTS • HE USED PEA PLANTS • HE COULD CONTROL FERTILIZATION • WORK WITH ONE TRAIT AT A TIME • EASY TO GROW

5. MORE ON HIS EXPERIMENTS • HE BELIEVED THAT TRAITS WERE DETERMINED BY INDIVIDUAL UNITS • WE CALL THESE UNITS ALLELES • OFFSPRING GET ONE ALLELE FOR EACH TRAIT FROM EACH PARENT • FROM HIS EXPERIMENTS WITH PEAS HE DISCOVERED THE LAWS OF GENETICS

6. LAWS OF GENETICS • LAW OF DOMINANCE STATES THAT WHEN AN INDIVIDUAL IS HYBRID FOR A TRAIT, ONLY ONE ALLELE WILL EXPRESS ITSELF. THE ALLELE THAT EXPRESSES ITSELF IS CALLED DOMINANT. THE TRAIT THAT DOESNOT EXPRESS ITSELF IS CALLED RECESSIVE.

7. LAWS OF GENETICS CONT. • LAW OF SEGREGATION • LAW OF INDEPENDENT ASSORTMENT

8. ALLELE DIFFERENT FORMS OF ONE TRAIT DOMINANT ALLELE ALLELE THAT IS EXPRESSED IN OFFSPRING REPRESENTED BY A CAPITAL LETTER RECESSIVE ALLELE ALLELE THAT IS NOT EXPRESSED IN THE OFFSPRING REPRESENTED BY A LOWER CASE LETTER GENETICS TERMS

9. PUREBRED AN OFFSPRING THAT HAS THE SAME TWO ALLELES FOR A TRAIT BOTH ALLELES ARE DOMINANT OR RECESSIVE EXAMPLE AA OR aa HYBRID AN OFFSPRING THAT HAS TWO DIFFERENT ALLELES FOR A TRAIT ONE ALLELE IS DOMINANT ONE IS RECESSIVE EXAMPLE Aa MORE GENETICS TERMS

10. PUNNETT SQUARES • IT IS USED TO SHOW ALL THE WAYS THAT ALLELES CAN COMBINE

11. HOW TO MAKE AND USE PUNNETT SQUARES • SELECT A TRAIT TO BE STUDIED • LIST THE ALLELES FOR THE FEMALE ON THE TOP OF THE SQUARE • LIST THE ALLELES FOR THE MALE ALONG THE SIDE OF THE SQUARE • IF YOU DON’T KNOW, THE 1ST ONE LISTED IN THE PROBLEM GOES ACROSS THE TOP • THE 2ND ONE LISTED GOES ALONG THE SIDE • FILL IN EACH SQUARE WITH ONE MALE ALLELE AND ONE FEMALE ALLELE

12. GENOTYPE IT IS THE ALLELE COMBINATION THAT IS INHERITED IT IS THE LETTERS EX. AA, aa, Aa PHENOTYPE PHYSICAL APPEARANCE OF OFFSPRING DETERMINED BY DOMINANT ALLELE HOMOZYGOUS THIS MEANS THE SAME AS PUREBRED EX. AA, aa HETEROZYGOUS THIS MEANS THE SAME AS HYBRID EX. Aa TERMS FOR PUNNETT SQUARES

13. EXAMPLE PUNNETT SQUARE • Bird #1 has orange feathers • Its genotype is AA

14. EXAMPLE PUNNETT SQUARE • Bird #2 has blue feathers • Its genotype is aa

15. EXAMPLE PUNNETT SQUARE • This Punnett Square shows how we can combine the alleles for feather color of Bird #1 and Bird #2 • What are the possible outcomes for feather color? • What will happen in the F2 generation?

16. SEX-LINKED TRAITS • FEMALES HAVE XX AND MALES HAVE XY • Sex-linked traits, therefore, are traits determined by genes found on the X chromosome. If such a gene has a recessive allele it is much more likely to be expressed in males than females because they only have one copy of this gene • EXAMPLES HEMOPHILIA, COLOR-BLINDNESS

17. MUTATIONS • THESE ARE ANY PERMANENT CHANGES IN AN ALLELE • THEY CAN BE CAUSED • NATURALLY BY ALLELES NOT MATCHING UP CORRECTLY • X-RAYS, RADIOACTIVITY, CHEMICALS, DRUGS • THEY CAN BE HARMFUL OR HELPFUL • THEY CAUSE VARIATIONS WITHIN A POPULATION

18. Genetics Since Mendel • Incomplete dominance • this occurs when neither trait wants to dominate • The resulting phenotype is a combination of both but it is not BLENDING • incomplete dominance –Video • Polygenic inheritance • when a trait is controlled by more than one gene • Ex. Hair color, eye color • Multiple alleles • when a trait has more than one allele • Ex. Blood type in humans A, B, AB, O

19. More on Genetics Since Mendel • PEDIGREES • a tool used by scientists to track a trait through a family • Males are represented by squares and females by circles • Lines between a circle and square mean a marriage • Shaded in circles or squares mean that the person has the trait/disease • Half-shaded circles represent a carrier • A carrier has the trait/disease, but it is not showing because the dominant trait is the normal trait