1. Inheritance of Traits Biology 2

2. How Genetics Work Genetics is the study of how traits are passed for parents to offspring We learned about chromosomes: –They are found in the nucleus –They are made of DNA –Humans have 46 chromosomes, but only 23 in the sex cells

3. How Genetics Work More about chromosomes: –All chromosomes contain genes –Genes are small sections that determine specific traits –Traits could be eye color, hair color, skin color, etc –In the body cells, the chromosomes are pair – so there are 23 pairs or 46 total –In the sex cells, the chromosomes are single – so there are only 23 total

4. Chromosomes

5. How Genetics Work

6. Traits are passed from parents to offspring Genotype vs. Phenotype –Genotype is the genetic make of the organism –Phenotype is what the organism looks like How can an offspring have characteristics that neither parent have? Because not all genes are expressed – some are “carried” by the parents and expressed in the offspring

7. How Genetics Work Dominant Traits –Genes that keep other genes from showing –An organism with two dominant genes is homozygous dominant & the trait is expressed –An organism with one dominant trait and one recessive trait is heterozygous & the trait is still expressed Recessive Traits –Genes that do not show when dominant traits are present –The only way for these traits to be expressed is when 2 recessive genes are present –This is called homozygous recessive

8. Punnett Squares Punnett Squares are used to predict the phenotype based off the genotype Uppercase letters will be used for all dominant genes are lowercase letters will be used for all recessive genes Remember: each gene has a pair and the pair is either going to be homozygous or heterozygous

9. Punnett Squares Setting up Punnett Squares – Step 1: draw a box with 4 squares

10. Punnett Squares Step 2 – on the top and side of the box write the parents’ genotype F f ff

11. Punnett Squares Step 3 – match up the top and side in each box inside the square F f ff Ff ff

12. Punnett Square Step 4 – Analyze the results Let’s say the “F” stands for freckles The father has a genotype Ff – What is his phenotype? The mother has a genotype ff – what is her phenotype? The possible combinations of the offspring are Ff or ff – what could their phenotypes be?

13. Punnett Squares

14. Punnett Squares were developed by Gregor Mendel He is said to be the father of genetics He noticed that pea plants had a variety of features and when he crossed them he got different results He developed the concept of dominant and recessive genes

15. Human Genetics There are a total of 46 chromosomes in each human body cell 23 pairs – 23 from the mother and 23 from the father 1 pair determines the sex of the offspring – these are called sex chromosomes The other 22 pairs are called autosomes

16. Human Genetics

17. Determining sex using Punnett squares:

18. Human Genetics Blood type is also determined by genetics OO is recessive A & B are dominant Combinations: AO, AA, BO, BB, AB, OO

19. Genetic Disorders What happens when something goes wrong in the genes? A genetic disorder can occur Some disorders are minor and can easily be lived with; however, others are fatal

20. Genetic Disorders http://www.noah-health.org/en/genetic/ http://www.noah-health.org/en/genetic/ Disorders of the Sex Chromosomes: –Hemophilia: blood disorder where the blood won’t clot –XXX syndrome: many don’t have signs or symptoms, but some can include delayed puberty, infertility, mental retardation (extreme cases) – occurs only in females –XXY syndrome: learning disablities, lower IQ’s – occurs only in boys

21. Genetic Disorders http://www.noah-health.org/en/genetic/ http://www.noah-health.org/en/genetic/ Disorders of the Sex Chromosomes: –Turner’s Syndrome: girls born without the other X chromosome – without treatment girls will not grow to full height or reach puberty

22. Genetic Disorders http://www.noah-health.org/en/genetic/ http://www.noah-health.org/en/genetic/ Other Disorders: –AlbinismAlbinism –Color-blindnessColor-blindness –Cystic FibrosisCystic Fibrosis –Down SyndromeDown Syndrome –Fragile X SyndromeFragile X Syndrome –Huntington’s DiseaseHuntington’s Disease –Klinefelter SyndromeKlinefelter Syndrome