Gene Mapping and Allele Combinations: Chromosomal Trait Identification Guide

2. Gene Labeling Gene Addresses are similar to your home address Approximate address, not exact

3. Turn to last page of gene labeling notes • We will learn how to identify where genes are located on chromosomes. • Recall…genes are sections of DNA that are transcribed/translated into a protein that is expressed as a trait. • The first gene we will map is on chromosome 1 ~ Rh factor

4. Mapping the Location of Rh factor/protein • Address: 1 p 3 • 1: stands for chromosome #1 • The arrow is the centromere • P: top half • 3: third dark band from centromere

5. Location of Rh factor/protein Rh factor • Draw a horizontal line through both chromosomes to map the location. (Anywhere in the 3rd band) • Label the line “Rh factor”

6. Try to map the gene for Eye shape on chromosome #3 • Check with a neighbor to see if you are correct!!!

7. Did you get it??? • Remember… anywhere in the 3rd band is okay Eye Shape

8. You are now ready to map and label the remaining genes • Recall…polygenic traits are located on several different chromosomes. • This means that you will have 4 chromosomes labeled “Eye Color Pigment,” 4 chromosomes labeled “Growth hormone tallness,” and 3 chromosomes labeled “ Hair color”

9. Map and Label the Remaining Genes on your paper • This means that you only need to map the locations for genes located on chromosomes 9, 15, 19 and 23 (both the male and female) • Please note that some chromosomes may have more than one gene located on it

10. What about those polygenic traits?? • Recall that when more than one chromosome contributes to the trait, it is considered polygenic • Polygenic traits have several allele combinations resulting in a wide range of phenotypes • Let’s look at eye color located on chromosomes 15 & 19

11. Eye color pigment • Brown eye genes are on chromosome 19. Brown is dominant to blue and green. BB, Bb, or bb • Green eye color is located on chromosome 15. Green is dominant to blue, but recessive to brown. GG, Gg, gg • Let’s combine these alleles and identify the resulting phenotypes

12. Eye color pigment • Brown - BB gg, BB Gg, BB GG, Bb gg, Bb Gg, Bb GG • Green - bb GG, bb Gg • Blue - bb gg

13. You try it!!!! • What eye color would result from BbGG?? • Brown • What about bbGg? • Green

14. Hair color works the same way • Genes for hair color are located on chromosomes 15, 18, 19 & 21 • This means there are 8 alleles that contribute to the trait. • The more dominant H alleles, the darker the hair. • To be platinum blonde, an individual must inherit all 8 recessive alleles!!!

15. Hair color genes • Look at chromosome #21 on your gene labeling notes • Notice all the possible combinations for hair color! • Look around the classroom. This is why there are so many variations in hair color ~ it’s POLYgenic!!!

16. Go ahead and create genotypes for eye & hair color on your genetic history WS • Remember, you need 2 alleles for each chromosome number • Fill in the corresponding phenotype

17. Growth hormone - tallness • The gene for growth hormone is found on chromosome 17, and the gene for growth hormone receptor is found on chromosome 5. • Differences in these genes can result in higher or lower levels of growth hormone production, or stronger or weaker responses to the presence of growth hormone, all of which can result in height variation.

18. Human height works a little differently • Genes for height are located on chromosomes 13,14, 16 & 17 • This means there are 8 alleles that contribute to the trait

19. Human height works a little differently • If a male inherits all recessive alleles, his genotype would be tttttttt his height would be 5’4” • This is called the base height • For each dominate allele he inherits, 2” are added to his base height

20. Human height works a little differently • EX: TT tttttt What would his height be? You guessed it…. 5’8” The 2 dominant alleles added 4” to his height

21. Let’s see how female height is different • If a female inherits all recessive alleles, her genotype would be tttttttt her height would be 5’0” • For each dominate allele she inherits, 2” are added to his base height

22. Human height works a little differently • EX: TT TTtttt What would her height be? You guessed it…. 5’8” The 4 dominant alleles added 8” to her height

23. Go ahead and create genotypes for height on your genetic history WS • Remember, you need 2 alleles for each chromosome number • Fill in the corresponding phenotype

24. You are ready to map the genotypes from your genetic history onto your karyotype When you draw the line, one allele should appear on one chromosome and the other allele on the other chromosome…remember, alleles segregate during gamete formation in meiosis Your Karyotype should similar to this:

25. Example Female Karyotype

26. Choose 2 colors, one light & one dark • In each chromosome pair, randomly color one chromosome the light color (this one came from your mom) and the other, the dark color (this one came from your dad). When you are done, your karyotype should look similar to this…

27. During meiosis, chromosomes segregate • This means there’s a 50/50 chance that a chromosome will end up in the gamete. • For each pair of chromosomes, flip a coin to determine which chromosome will be passed on to baby. Repeat for ALL chromosomes. • Heads –circle light color & Tails – circle dark color

28. Cut out the chromosome that was determined by the flip of the coin to be inherited by your baby. Make sure the color and allele are clearly visible after you have cut out the chromosome. • Glue the chromosomes onto baby’s karyotype. Make sure the pair of chromosomes labeled as Pair 1 is glued down in the 1st space, etc. for ALLchromosomes.

29. Build-A-Baby Workshop • Write your baby’s genotypes and phenotypes on the Baby’s Genetic History WS and answer the questions. • Papers must be stapled in the following order: • Baby’s Genetic History WS • Baby’s Karyotype • Baby’s Probabilities • Mom & Dad’s Genetic History WS (2 pgs) • Baby’s Picture – in color