1. Heredity and Genetics

2. Heredity 1. Is it possible for two parents with blue eyes to have a brown eyed child? 2. Is it possible for two parents with brown eyes to have a blue-eyed child? Discuss this with your group. Come to a decision and be prepared to explain the reasoning behind your answers.

3. Warm-up What have we learned so far about each of the following: DNA Genes Chromosomes

4. Chromosomes have genetic information and are passed to offspring Dividing onion cells chromosomes

5. Chromosomes have genetic information and are passed to offspring Human chromosomes stained with a special chemical and viewed under a high-powered microscope

6. What exactly are chromosomes? How do chromosomes contain genetic information?

7. Chromosome structure- DNA Chromosomes = long pieces of DNA

8. Chromosome structure- genes Human chromosome # 7 Contains about 1,800 genes Contains over 150 million nucleotides Link to view genes and DNA sequence Parts of chromosomes are called genes Genes help determine your characteristics –what are some example characteristics?

9. Trait – a characteristic of an organism ◦ Example: flower color Gene – part of a chromosome that helps determine a specific trait ◦ Example: flower color gene Allele – a form of a gene ◦ Example:  One allele is the “blue” form of the gene  One allele is the “red” form of the gene

10. Chromosomes come in pairs Cut out from picture and match each in pairs

11. How many chromosomes? Humans = 23 chromosome pairs, or 46 total. We think we have about 40,000 genes. Pea flower = 7 chromosome pairs (14 total) Fruit fly = 4 chromosome pairs (8 total) 13,601 genes identified so far! Potato = 24 pairs (total 48) Horse = 32 pairs (total 64)

12. Chromosomes come in pairs You get one copy of a chromosome from one parent and one copy of a chromosome from the other parent. This pair of chromosomes is called a “homologous pair” because they have the same genes on them - Flower chromosome 3 (from computer simulation) From Dad From Mom flower color gene

13. Chromosomes come in pairs IMPORTANT: homologous pairs have the same genes, but they are NOT IDENTICAL ◦ Alleles can be different From Dad From Mom flower color gene “Blue” allele of flower color gene “Red” allele of flower color gene

14. The combination of alleles determines the observed characteristics RED allele Chromosome combination Allele combination Observed characteristic RED allele RED allele BLUE allele BLUE allele BLUE allele red, red red, blue (or blue, red) blue, blue RED BLUE

15. Dominant and recessive alleles Only one red allele is needed for the flower to look red. Scientists call this a DOMINANT allele Two blue alleles are needed for the flower to look blue. Scientists call this a RECESSIVE allele

16. Symbols used for alleles The traditional symbols used for alleles are big and small letters The letter chosen usually refers to the dominant allele Example:R = Red allele r = Blue allele

17. The combination of alleles determines the observed characteristics RED allele Chromosome combination Allele combination Observed characteristic RED allele RED allele BLUE allele BLUE allele BLUE allele red, red red, blue (or blue, red) blue, blue RED BLUE

18. The combination of alleles determines the observed characteristics R Chromosome combination Allele combination Observed characteristic RR Rr rr RED BLUE RRrrr

19. Phenotype – the observed (or measurable) trait of an organism that relates to one gene Genotype – the two alleles that an organism has for a trait Example: Trait = “flower color” Phenotype = “RED” or “BLUE” Genotype =“RR” or “Rr” or “rr”

20. The combination of alleles determines the observed characteristics R Chromosome combination Allele combination Observed characteristic RR Rr rr RED BLUE RRrrr

21. The combination of alleles determines the observed characteristics R Chromosome combination GENOTYPE PHENOTYPE RR Rr rr RED BLUE RRrrr

22. Homozygous – the two alleles are the same RR and rr are homozygous genotypes Heterozygous – the two alleles are different Rr is a heterozygous genotype