Chromosomes and Human Genetics

1. Chromosomes and Human Genetics Ch. 11

2. Sex Chromosomes determine whether offspring will be male or female. XX- female XY-male Which sex determines the sex of the baby if mom and dad each give one? Sex determination Autosomes- non-sex chromosomes (traits) Wild-type allele- genes most common form. Mutant allele- less common form. Types of Chromosomes

3. A genome is the base sequence of all the DNA in an organism. A karyotype is a photograph of all of an organisms chromosomes that are froze and stained during metaphase. There are 23 different genes that are donated from each parent to make you..46. The Genome

4. Can be used to find certain chromosomal abnormalities such as down syndrome. Karyotypes

5. Genes that are located on the same chromosome, which are inherited together. Ie. Fruit fly’s red eyes and miniature wings inherited together. Those closer together, more likely to be inherited together. It is the chromosomes that assort independently, not the genes. Linked Genes

6. Researchers have made gene maps that show what traits(alleles) are on what chromosomes and where. I have a chart to show you. The farther apart the 2 genes are located, the more likely they are to be separated by a crossover. (Cross over more frequently) Genetic Mapping

7. Pedigrees are used to show how a trait and the genes that control it are inherited within a family. Let’s work a couple and let me explain how they work. Predictions and People

9. Tay Sachs Disease- people are not able to metabolize a particular lipid, it accumulates in the brain and results in blindness and brain damage. 1/3600 people 1/30 carriers Die by age 5 Cystic fibrosis results in an excessive secretion of mucus that accumulates in the digestive tract and lungs. 1/2500 newborns, 1/25 carriers (Caucasian) ½ live to age of 31 Recessive Disorders

10. Overview of Genetic Disorders • How many have you heard of?

11. Albinism don’t have skin pigment. PKU (Phenylketonuria)- accumulation of phenylalanine in tissues; lack of normal skin pigment, mental retardation. Sickle Cell Anemia- blood cells sickle shaped and can’t travel through blood vessels well. 1/10 Africans are carriers Co-dominant disorder More Recessive

12. In many cases, a person who has inherited a dominant disorder dies before they can pass it on to offspring. 1/500 people 4,400 known dominant disorders Huntington disease results in the deterioration of the nervous system. Homozygous dominant-Fatal Hh- live to be 40 Dominant Disorders

13. Acondroplasia- dwarfism Homozygous dominant-Lethal Aa- dwarf Marfan’s- can’t make connective tissue- TALL Abraham Lincoln Polydactlyty- extra fingers and toes 98% of people are recessive More Dominant Disorders

14. Incomplete Dominance is when two different alleles for the same trait combine. R=red, r=white Rr= Pink Codominance is when both alleles express themselves fully. Blood type. A, B or AB Difficult Predictions

15. Human Genes and Chromosomes • Only 2% of DNA in your chromosomes function as genes, those that are transcribed into RNA. • The average human genes consists of about 3,000 base pairs. • Chromosomes 21 and 22 are the smallest human autosomes.

16. 1.29a The action of genes, patterns of inheritance, and the reproduction of cells and organisms account for the continuity of life. 1.29b What are ways that inherited characteristics can be observed at the molecular and whole-organism levels, in structure, chemistry, and behavior?

17. Morgan studied Drosophila and found sex linked genes for eye color. Human sex-linked traits. Color Blindness is X-linked recessive. XcXc, XcY Hemophilia- blood doesn’t clot. Duchenne MD Why would males be more likely to have these disorders? Sex-Linked Traits

18. A random change in the sequence of nucleotides in DNA is a mutation. Chromosomal mutations- involve whole chromosomes. Gene mutations- result from changes in a single gene. 4 types of mutations: Deletion Duplication Translocation inversion 1.23a Inserting, deleting, or substituting DNA sequences can alter a gene.

19. When a chromosome breaks and a piece of it is lost. Chromosomal Deletion

20. When a part of the chromosome breaks off and is incorporated into its homologous chromosome. Duplication A B C o D E F A B B C o D E F

21. Occurs when part of a chromosome breaks off and attaches to a different, nonhomologous chromosome. Translocation

22. Occurs when part of a chromosome breaks off, turns around, and reattaches in the reverse order. Inversion

23. X-Chromosome Inactivation • Barr Bodies are formed in females because one X is all that is needed in some cells and the other is switched off randomly and forms a dense region in the nucleus. • Cats • You can tell if male or female by spots because genes that controls spots is located on X chromosome. Males will have one color of spot and females will have 2 colors. Why?

24. Nondisjuntion is the failure of chromosomes to separate correctly during mitosis or meiosis. Monosomy- the zygote has only one copy of a particular chromosome. Trisomy- the zygote has 3 copies a chromosome. Most of the times it is disruptive and kills the embryo, but if it survives there can be developmental difficulties. Nondisjunction

26. Monosomy Turners Syndrome Affects only girls Infertility Minimal physical abnormalities Trisomy Trisomy 18 (Edwards Syndrome) Trisomy 13 (Patau Syndrome) XXY (Kleinfelters) XYY XXX (Triplo X) Examples

27. Sex limited traits are only expressed in the presence of sex hormones and are only observed in one sex or the other. Autosomal Different colored plumage in male and female animals. Can you think of any? Sex Limited Traits

28. Sex Influenced traits are expressed in both sexes, but they are expressed differently. Male Pattern Baldness Sex Influenced Traits

29. 1.27 Humans, along with every other species has a unique DNA sequence. Everyone has a similar cell chemistry and anatomy, but are still different.

30. Human Genome Review • Click on the following link, choose your textbook and review the material and take self-test for Ch. 14. • Ch. 14 Review