Transcript g sex
Topic: Genetics Aim: How do we use pedigree charts to follow a trait through generations of a family? Do Now: next slide HW: Genetic Engineering Reading notes due tomorrow! T = tall t = short Cross two heterozygous plants. Tt x Tt T t T T T Tt t Tt tt T t T T T Tt t Tt tt Phenotype %: 75% tall 25% short Genotype %: 25% homozygous dominant 50% heterozygous 25% homozygous recessive Humans have 46 chromosomes in EVERY somatic cell in the body. Out the 46 chromosomes, 2 of them are sex chromosomes that determine gender. The other 44 chromosomes are called autosomes. 1. Identify the sex chromosomes found in males. • XY 2. Identify the sex chromosomes found in females. • XX • X chromosome is 3. Study larger than the Y Figure 8 on p.138. How do chromosome the X and Y chromosome differ in shape. How is the sex of an individual determined? • Eggs = X • Sperm = X or Y Female chromosomes Male chromosomes The X chromosome carries a couple of thousand genes but few, if any, of these have anything to do directly with sex determination. The X chromosome likely contains genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body. The Y chromosome likely contains genes that provide instructions for making proteins. The genes on this chromosome tend to be involved in male sex determination and development. Sex is determined by the SRY gene, which is responsible for the development of a fetus into a male. Other genes on the Y chromosome are important for male fertility. • To follow a trait 4. Explain through generations what a pedigree chart of a family is used for. 5. Identify how each of the following is represented in a pedigree chart. a. Male Square b. Female Circle c. A male with the trait Completely filled square d. A female with the trait Completely filled circle e. A carrier Half colored circle or square f. A normal male (does not have the trait) Empty square a. A normal female (does not have the trait) Empty cirlce 9. What does the horizontal line between the male and female represent? They have children with each other 10. What do the vertical lines represent? Offspring 11. How many offspring did the first generation have? 4 12. How many offspring from the first generation were born with the trait? None 13. One of the females in the 2nd generation had children with a male with the trait. a. How many children were born with the trait? 2 b. What is the genotype of the children with the trait? homozygous recessive 14. What is the mom’s genotype? heterozygous 6. How many offspring did the 1st generation have? 3 7. How many offspring from the 1st generation were born with the trait? 1 8. Individual 3 had children with individual 4. a. How many children did 3 and 4 have? 2 b. Which child was born with the trait? male c. What were the genotypes of individuals 3 and 4? heterozygous 9. What is the genotype of individual 2? Tt 10. If individual 2 had children with a normal female (without the trait), can they have children with the trait? No Let’s Review: 1. What are “regular” chromosomes called? 2. Explain the difference between sex chromosomes in a male and sex chromosomes in a female. 3. Put the following terms in order from smallest to largest: chromosomes, nucleus, DNA, genes 4. Put the following terms in order from largest number to smallest number: chromosomes, nucleus, DNA, genes http://www.brainpop.com/science/cellularlifeandgenetics/heredity/ 1 3 5 4 14 2 15 6 16 17 7 18 19 8 9 10 22 20 21 1. Identify the genotypes of 1 and 2. 2. How many offspring did 1 and 2 have? 3. Identify the genotype of 3. 11 12 13 25 23 24 1. Identify the genotype of the father. RR 2. Identify the genotype of the mother. rr G = green g = yellow Cross a pure green plant with a hybrid plant. GG X Gg G G G GG GG g Gg Gg G G G GG GG g Gg Gg Phenotype percentages: 100% green Genotype percentages: 50% heterozygous 50% homozygous dominant