1. Chapter 12
Human Genetics

2. 12.1 The nucleus contains an information rich genome
DNA can store vast amount of information in a tiny space. In one chromosome there are 3 billion base pairs!

3. DNA packaging in a single cell
If you could straighten out all the DNA molecules in a cell’s 46 chromosomes and place them end to end, the DNA would stretch for 2 meters or 6 and a half feet!
Genome:
Complete set of an organism’s genetic material.
Histones:
Small protein balls

4. The genome can fit into the nucleus
DNA wraps around histones
DNA is wrapped into a tight helical fiber
Coil further into thick “supercoil”
Loops and compacts DNA in each chromosome

5. Human genome project
In 1990, DNA technology enabled scientists to completely sequence the human genome.
Government funded the Human Genome Project and a rough draft was completed in 2000.
Knowing the sequence of nucleotides helps us understand which regions of DNA is used for coding.
This can tell us the function of that polypeptide.

6. Why is this important to us?
Compare our human genome to other organisms.
Health and identifying genes can help diagnose, treat, or prevent diseases.
Ex. Cancer, allergies, diabetes.

7. 12.2 Accidents affecting chromosomes can cause disorders
Meiosis occurs repeatedly in a person’s lifetime as males produce sperm or females produce eggs. Usually this happens without error but an accident can cause serious problems.

8. What is trisomy 21? Trisomy 21:
Condition when an individual has three number 21 chromosomes, resulting in down syndrome.
Error happens in meiosis 1.

9. In most cases, human embryo with an abnormal number of chromosomes results in a miscarriage.
Risk of having a child with down’ s syndrome increases with the age of the mother:
Women under age 23—1 in 2,000 births
Women at age 30—1 in 1,300 births
Women at age 35—1 in 400 births
Women at age 40—1 in 90 births
Women at age 45—1 in 32 births
Women at age 50—1 in 8 births

10. Turner’s Syndrome
When female has an X and the other chromosome is missing. (X,0)
Rare, swollen hands and feet, dry eyes, infertile

11. Klinefelter’s Syndrome
Condition when males have an extra X chromosome. (XXY)
Less testosterone, weaker muscles, less facial hair

12. Non disjunction:
Errors in chromosome number are usually caused by homologous chromosomes or sister chromatids failing to separate during meiosis.

13. Damaged chromosomes
Change in chromosome structure may also cause disorders. If a chromosome breaks it can affect genes.
Types of changes…
Duplication:
Part of a chromosome is repeated.

14. Deletion:
Fragment of a chromosome is lost. Sever problems!
Inversion:
Reversing a fragment of the original strand.
Translocation:
Fragment of one chromosome attaches to a nonhomologous chromosome.

15. Jumping genes Transposons “jumping genes”:
Genetic element that moves from one location to another in a genome.
Barbara McClintock discovered that genes in corn cells could move around in a chromosome, which changed the corns color.

16. 12.3 Mendel’s principles apply to humans
Would you like to know the probability of your children having specific traits?
Eye color? Hair color? Deaf?
Would you like to know the probability of your children having a disability?

17. We can! Knowing each member of your family's genetics can help predict offspring!
Pedigree:
Family tree that records and traces the occurrence of a trait in a family.

18. pedigree Square = male Circle = female
Colored shapes = affected individuals
Horizontal lines = parents

19. Attached earlobe

20. Can determine genotypes!

21. Disorders inherited as recessive traits
Some allele combination can be fatal.
Most human genetic disorders are recessive.
Recessive disorders could be albinism, to Tay-Sachs disease.
Tay-Sachs leads to major
nerve damage.

23. Disorders recessive traits
What genotype does the parents have to be if a disorder is recessive?
They have to be heterozygous!
Carrier:
Individual who has one copy of
the allele for recessive disorder
but does not show trait.

24. Disorders inherited as dominant traits

25. Disorders inherited as dominant traits
Small number of human disorders are inherited as dominant traits.
Born with extra fingers and toes or achondroplasia.
Genotype for these disorders are heterozygous.
Having two copies of this allele is fatal.

26. Sex linked disorders
Sex-linked alleles are located on one sex chromosome but not on the other.
Example being colorblindness

28. Predicting and treating genetic disorders
Who would like to know what the odds are of your children having specific traits?
When two people are considering having children and have both family histories they can meet with a genetic counselor.
Genetic counselor:
Trained to collect and analyze data about inheritance patterns and explain results and their significance.

29. 12.4 Genetic changes contribute to cancer
Recall cancer is uncontrollable cell growth.
We have genes that help function our cell cycle.
Growth factors:
Produce proteins that initiate cell division.
Tumor-suppressor genes:
Produce proteins that stop cell division.

30. If several mutations happen in our growth genes it is called oncogene.
Cancer causing gene.
Cells with oncogene become over stimulated and divide more often.