Chapter 14 Human Genetics How can a change

Chapter 14 Human Genetics How can a change in the DNA of a human cause disease? How are these disorders diagnosed and treated?

Human Chromosomes Karyotype = chromosomes arranged in pairs & organized by size ●Humans have 46 chromosomes ● 2 of these are sex chromosomes XX = female XY = male ●The other 44 chromosomes are known as autosomes

Chromosomes are paired according to their size and banding patterns. These are HOMOLOGOUS PAIRS. Humans have 23 pairs normally.

Down Syndrome - an extra chromosome #21 (trisomy) Symptoms Cognitive impairment (low IQ) Heart defects Small stature Upward slant to eyes Vision impairment Deep straight crease on palm. Short life expectancy (40 -50 years)

World Down Syndrome Day is March 21 st. (3/21) Why that date? In 2018, supporters of WDS wore mismatched socks. What was the symbolism of that gesture?

Down Syndrome is caused by NONDISJUNCTION Failure of chromosomes to separate in meiosis – results in an egg (sperm) with too many or too few ●Down Syndrome (trisomy 21) ●Patau Syndrome (trisomy 13) ●Klinefelter Syndrome (XXY) ●Turner Syndrome (XO) ●Supermale (XYY)

Trisomy – 3 chromosomes Monosomy – 1 chromosome

Edward Syndrome - caused by an extra chromosome 18 (trisomy 18) Median life expectancy is 4 days. However, about 5 -10% survive beyond one year Source: https: //ghr. nlm. nih. gov/conditio n/trisomy-18

Patau Syndrome - caused by an extra chromosome 13 (trisomy 13) Severe deformities, most don’t survive but a few hours after birth.

I 2 What do you see? What does it mean?

At the age of 40, the incidence of Down Syndrome is 1 in 100. Source: http: //www. family-forecast. com/2017/07/10/why-was-35 chosen-for-advanced-maternal-age/ Women can be screened during pregnancy. A blood test during the first trimester measures abnormal levels of hormones and plasma proteins. This could indicate Down Syndrome or other problems. Other tests can be used to detect abnormalities. If the fetus is diagnosed with an abnormality, what options does the mother have? Opinion: Would you choose to have the prenatal tests done? Why or why not?

1. A picture of a person's chromosomes is called a ________. 2. In this pictures, chromosomes are arranged in pairs according to their ______. 3. Humans have ______ pairs of chromosomes. 4. The last set of chromosomes is the _____ chromosomes. 5. Males have what sex chromosomes? ______

6. A person who has an extra chromosome #21 has what disorder? _____ 7. If a person has XXY for sex chromosomes, he has what disorder? _________ 8. As a woman gets ______, her risk for having a child with down syndrome increases. 9. A human has 2 sex chromosomes, the other 44 chromosomes are called _______. 10. When chromosomes fail to separate during meiosis, ______ has occurred.

Complete this sentence. When a baby is born with an extra chromosome….

Human Genetic Traits Single Allele 1. PTC taster 2. Attached earlobes 3. Widow’s peak 4. Short big toe Polygenic 5. Skin Color 6. Eye Color 7. Height

Return to Punnett Squares! Quick Review of Terms Dominant Recessive Heterozygous Homozygous Codominant Bb x Bb

How is human inheritance studied? Biologists use pedigree charts which trace a trait within a family over several generations. Males are SQUARE Females are CIRCLES Shading represents a recessive (expressed) trait) If the trait being studied is attached earlobes (ee) than you can determine the genotypes of every member of the family.

The trait being studied is PTC tasting. The inability to taste the substance is recessive. Determine the genotypes of each member of this family. TT, Tt, or tt (nontaster)

Many traits are strongly influenced by environmental factors (ex: height, weight, personality) Nature vs Nurture question: How much of our traits are coded in DNA, and how much have been shaped by our upbringing?

Human Genome Chromosome 17 Our complete set of genetic info , includes thousands of genes Recall that a GENE is a segment of DNA that codes for a trait. These segments are located on chromosomes. A MAP of the chromosome helps us located and eventually treat genetic disorders. BRCA is associated with a higher risk of breast cancer

BLOOD TYPES Genes controlling blood types were 1 st genes to be identified ABO & Rh blood groups ( + and - )

ABO Blood Group = Multiple Allele Trait ●Controlled by 3 alleles: A, B, O ●A and B are codominant ●O is recessive to both A and B ●The blood type is the phenotype Type O negative is the universal donor - this blood can go to anyone because it will not trigger an immune reaction.

Genotype Blood Type AA, AO Type A BB, BO Type B AB codominant Type AB (universal recipient) OO recessive Type O (universal donor)

Blood Types Practice Mom has type A blood (genotype AO), dad has type AB blood. What blood types are possible among their children? Mom has type B blood (genotype BO), dad has type O blood. What blood types are possible among their children?

Human Genetic Disorders Phenylketonuria (PKU) - causes phenylalanine to build up in blood - Phe build up causes brain damage - Disorder is treated with a highly restrictive diet. - All newborns are screened for PKU - Recessive

Human Genetic Disorders Tay Sachs Disease (recessive) Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows and muscles used for movement weaken. Affected infants lose motor skills such as turning over, sitting, and crawling. Most will die within a few years.

Human Genetic Disorders Albinism (recessive) - lack of pigment, skin appears very pale

Other animals can be albino too. . Some animals are not albino, but they have reduced pigmentation. White lions that were bred for circuses are actually LEUCISTIC.

Cystic Fibrosis -This disease causes an inability of cells to clear mucus due to a problem with the cell membrane. - This results in mucus build-up, difficulty breathing, and infections

Dominant Traits Dd = disorder dd = normal Achondroplasia (dwarfism) Huntington’s disease Polydactyly How can two dwarfs have a normal child?

Sickle-Cell Disease codominant (AA, Aa, aa ) heterozygous is resistant to malaria Show the cross between two people who are carriers for sickle cell anemia. Aa x Aa

Match the disorder to the description: 1. Requires a very restrictive diet. 2. Mucus builds up in the lungs. 3. Loss of motor skills 4. Reduced skin pigment 5. Extra fingers or toes 6. Short stature (dwarfism) 7. Irregular shaped blood cells A. Polydactyly B. Tay-Sachs C. Sickle Cell Anemia D. Cystic Fibrosis E. Albinism F. PKU G. Achondroplasia

Synthesis: Compare the chromosomal disorder Down Syndrome to PKU, which is an autosomal recessive disorder. Consider: ● How each is inherited ● How each is diagnosed ● Life outcomes for each Work together to come up with a short paragraph answering the question. Refer back to your notes.