1. Biology Unit Four D– Human Genetics and Pedigrees
Mrs. Pearson’s First Semester Biology
*For those watching by recording, watch for questions on the slides throughout
the presentation. me the answers to the questions within two days of the
lesson being presented in order to receive credit for watching the recording.

2. AND THE WINNER IS… Food Spoilage!!
Because I won’t know what foods I can use until I get there, I will do it in reverse and run the Costa Rica piece first and the Wisconsin piece second.
Because the amount of “critters” in Costa Rica, I will use a container with a thin fabric screen and will not leave it outside.

3. Let’s have a hand for… Caitlyn Abbott Kristen Barstow Sabrina Haug
Leeanna Heinrichs
Melissa Hunt
Christopher King
Kayla Morris
Chyenne Nechkash
Emily Patik
Courtney Pigeon
Dana Radtke
Stephanie Spatz

4. The Prize 50 extra credit points OR
100% on one lab not yet completed (be sure to tell me which one)
Mrs. P today with your choice!

5. KEY CONCEPT Genes can be mapped to specific locations on chromosomes.

6. Lesson Objectives
Discuss gene linkage and mapping
Discuss expression of sex-linked traits
Understand pedigrees and karyotypes

7. Gene linkage was explained through fruit flies.
Morgan found that linked traits are on the same chromosome
Wild type
Mutant

8. Chromosomes, not genes, assort independently during meiosis
Remember that meiosis is the making of sperm and egg cells
Remember that during meiosis the cell divides in such a way that only half of the genetic material will be passed on
So what does it mean when we say that the chromosomes assort independently?

9. Chromosomes, not genes, assort independently during meiosis
Maybe they will separate like this… 4 4 7 7

10. Chromosomes, not genes, assort independently during meiosis
BUT maybe they will separate like this… 4 4 7 7

11. Chromosomes, not genes, assort independently during meiosis
They are independent – don’t have to separate the same 4 4 7 7

12. Linked genes are not inherited together every time.
Chromosomes exchange homologous genes during meiosis – what do we call this process?

13. Linkage maps estimate distances between genes.
The closer together two genes are, the more likely they will be inherited together.
Cross-over frequencies are related to distances between genes.
Linkage maps show the relative locations of genes.

14. When crossing over happens here, genes A and B stay together.

15. But, when crossing over happens here, genes A and B get separated.
When genes are close to each other on the chromosome, it’s more likely that they will be inherited together. A A A A B B B B

16. Cross-over frequencies can be converted into map units.
gene A and gene B cross over 6.0 percent of the time
gene B and gene C cross over 12.5 percent of the time
gene A and gene C cross over 18.5 percent of the time
**Those watching by recording, include in your why genes A and B would be more likely to be linked than A and C.

17. KEY CONCEPT A combination of methods is used to study human genetics.

18. Human genetics follows the patterns seen in other organisms.
The basic principles of genetics are the same in all sexually reproducing organisms.
Inheritance of many human traits is complex.
Single-gene traits are important in understanding human genetics – why?
**Those watching by recording, include in your why single-gene traits are important in understanding human genetics.

19. Females can carry sex-linked genetic disorders.
Males (XY) express all of their sex linked genes – why?
Expression of the disorder depends on which parent carries the allele and the sex of the child – why? X Y

20. What chromosome will the mom give to the baby
What chromosome will the mom give to the baby? The X or the Y chromosome? Why?
She will always give the baby an X chromosome because that is all she has.
So… if mom is a carrier of a sex-linked disease, will her daughters have the disease?
Her daughters will only have the disease if they receive mom’s X chromosome that has the disease gene on it AND they receive an X chromosome from dad with the disease gene on it.
They might be a carrier.
They might not be a carrier
Will her sons have the disease? X Y

21. What chromosome will the mom give to the baby
What chromosome will the mom give to the baby? The X or the Y chromosome? Why?
Will her sons have the disease?
Her sons will only have the disease if they receive mom’s X chromosome that has the disease gene on it. X Y

22. What chromosome will the dad give to the baby
What chromosome will the dad give to the baby? The X or the Y chromosome?
The dad’s sons will receive the Y chromosome from their dad.
The dad’s daughters will receive the X chromosome from their dad.
If the dad has a sex-linked disease gene on his X chromosome, will his daughters have the disease?
They will ONLY have the disease if they also receive an X chromosome from their mom that ALSO has the disease gene on it.
If they do not have the disease, will the daughters be carriers?
Yes – they will for certain have the disease gene from the X chromosome from their dad. X Y

23. What chromosome will the dad give to the baby
What chromosome will the dad give to the baby? The X or the Y chromosome?
If the dad has a sex-linked disease on the Y chromosome, will his sons have the disease?
Yes – they can only receive the Y chromosome from their dad so they will have the disease. X Y

24. A pedigree is a chart for tracing genes in a family.
Phenotypes are used to infer genotypes on a pedigree – which phenotype would help the most in determining unknown genotypes?
Autosomal genes show different patterns on a pedigree than sex-linked genes.

25. If the phenotype is more common in males, the gene is likely sex-linked – why?

26. Several methods help map human chromosomes.
A karyotype is a picture of all chromosomes in a cell.
X Y
** Those watching by recording, include in your whether the person this karyotype came from was male or female.

27. Karyotypes can show changes in chromosomes.
deletion of part of a chromosome or loss of a chromosome
large changes in chromosomes
extra chromosomes or duplication of part of a chromosome

28. Review
Linkage maps estimate distances between genes
Human genetics follows the patterns seen in other organisms
Females can carry sex-linked genetic disorders
A pedigree is a chart for tracing genes in a family
If the phenotype is more common in males, the gene is likely sex-linked
A karyotype is a picture of all chromosomes in a cell

29. Questions?