Chapter 14 Human Heredity

14.1 Human Chromosomes Genome: Full set of genetic information that an organism carries in its DNA. Karyotype: Shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size.

Sex chromosomes: Two of the 46 chromosomes in the human genome that determine the individuals sex. The two letters are X or Y. If you are female, which two chromosomes are you? XX If you are male, which two chromosomes are you? XY

What sex is this individual?

Autosomes: All the none sex chromosomes.

Sex-linked gene: Genes located on the sex chromosome. In humans most sex linked genes are located on the X chromosome because it is much bigger than the Y chromosome.

Colorblindness Colorblindness is inherited as sex linked X recessive traits. XB Xb XB Xb Xb Xb Y XB Y Xb Y

WHAT NUMBERS DO YOU SEE? Normal 15 Colorblind 17

WHAT NUMBERS DO YOU SEE?

WHAT NUMBERS DO YOU SEE? Normal 5 Colorblind 2

NOW WHAT NUMBER DO YOU SEE?

X Chromosome Inactivation Calico Cats Color gene on X chromosome In female cats, one x chromosome is “inactivated” as a Barr body. (not found in males) Male cats will have spots of only one color

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?

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.

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

Attached earlobe

Can determine genotypes!

14.2 Human Genetic Disorders Every affected person has an affected parent. About half of the offspring of an affected person are also affected (assuming only one parent is affected). The phenotype occurs equally in both sexes. Examples: Huntington’s Disease & Achondroplasia (dwarfism)

Disorders inherited as dominant traits

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.

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

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

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

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

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

14.3 Studying the Human Genome Scientists can use tools to cut, separate, and then replicate DNA base by base, scientists can now read the base sequences in DNA from any cell. Restriction enzymes: Highly specific substances that cut even the largest DNA molecule into precise pieces called restriction fragments.

After the DNA is cut, scientists can use gel electrophoresis to separate and analyze DNA. Procedure used to separate and analyze DNA fragments. DNA (- charge) is placed in small pocket with gel on the other end (+ charge) The - charged DNA will move to the + side.

Comparing DNA Who watches this show? What do these detectives want to find at a crime scene? DNA!

EcoRI Restriction Enzyme Identifies the sequence http://youtu.be/yYIZgS-L5Sc?t=4m24s

Who committed the crime?

Human Genome Project In 1990, DNA technology enabled scientists to completely sequence the human genome. Completed in 2003. 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.

Human Genome Project 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.

The Human Genome Project created new fields in biology. Bioinformatics: Application of mathematics and computer science to store, retrieve, and analyze biological data. Genomics: Study of whole organisms, including genes, and their functions.

The Human Genome Project pinpointed genes and associated particular sequences in those genes with numerous diseases and disorders. The Human Genome Project identifies many ethical, legal, and social issues surrounding its data. The 1000 Genomes Project, launched in 2008, will study genomes of 1000 people, to study the development and diseases.