The Human Genome Human Heredity January 6 th7

The Human Genome & Human Heredity January 6 th/7 th, 2008

Human Chromosomes 46 total (23 from mom and 23 from dad)

Key Terms Sex Chromosomes – two of the 46 total chromosomes. Determine whether a baby will be a boy or a girl. • If a baby gets an X from its mom and a Y from its dad, it will be a boy. • If a baby gets an X from its mom and an X from its dad, it will be a girl. Autosomal Chromosomes – the remaining 44 chromosomes. Where most of your inherited traits come from.

Different Types Of Inheritance Sex Linked Inheritance- applies specifically to genes located on the X chromosome. • Females – because they have two X chromosomes – are more likely to be carries and not show defective trait. This is because they would need the mutated gene on both chromosomes. • Males – because they only have one X chromosome – are more likely to express the disease. This is because there are really no genes on the Y chromosome to cover the effects of the abnormal X chromosome.

Sex Linked Inheritance- ex. Color blindness. Male (XY) are more likely to be affected and show the trait because they only have one X chromosome. Males can pass gene only to daughters. Why?

Practice 1. How is color blindness transmitted?

Different Types Of Inheritance Sex Linked Inheritancew

Are You Color Blind? 25. Everyone should see this. 29. People who are RED/GREEN color blind will not see anything.

Are You Color Blind? 45. People who are color blind will not see anything. 56. Even people who are color blind should see this.

Some Autosomal Disorders in Humans Type of Disorder Major Symptoms Disorders caused by Albinism Lack of pigment in skin, hair, and eyes. recessive alleles Cystic fibrosis Excess mucus in lungs, digestive tract, liver; increased susceptibility to infections. Galactosemia Accumulation of galactose (a sugar) in tissues; mental retardation; eye and liver damage. Phenylketomuria (PKU) Accumulation of phenlalanine in tissues; lack of normal skin pigment; mental retardation. Tay-Sachs disease Lipid accumulation in brain cells; mental deficiency; blindness; death in early childhood Disorders caused by Achondroplasia Dwarfism (one form) dominant alleles Huntington disease Mental deterioration and uncontrollable movements; symptoms usually appear in middle age Hypercholesterolemia Excess cholesterol in blood; heart disease Sickle cell disease Misshapen, or sickled, read blood cells; damage to many tissues Disorders caused by codominant alleles

Practice: Human Inherited Disorders Autosomal Dominant and Autosomal Recessive Traits 1. In autosomal recessively inherited disorders, do heterozygotes (also called “carriers”) show the genetic disorder? Why or why not? 2. In a recessive disorder, what is the probability of an offspring having the disorder when two carriers mate? Prove it. 3. What are two examples of recessive inherited disorders? Briefly explain the symptoms of each of the disorders. 4. Why are males more likely to have a recessive disorder than females? 5. What are the chances two carriers of Huntington’s disease will pass the trait to their offspring? Prove it.

Nondisjunction Normally Chromosome pairs are pulled to opposite ends during Anaphase I and II. Nondisjunction is when chromosomes do not properly separate. Gametes with the wrong number of chromosomes usually do not survive.

A few exceptions… • Down’s syndrome-Trisomy 21 (47 chromosomes) • Turner syndrome X 0 (45 chromosomes) • Klinefelter; s syndrome – XXX (47 chromosomes)

Activity: Looking at Karyotypes Questions to answer: 1. Circle the sex chromosomes. 2. Male or Female? _____ 3. Normal or Abnormal? _____ 4. If abnormal, circle the abnormality and tell what disease is present.

Activity: Looking at Karyotypes Questions to answer: 1. Circle the sex chromosomes. 2. Male or Female? _____ 3. Normal or Abnormal? _____ 4. If abnormal, circle the abnormality and tell what disease is present.

Activity: Looking at Karyotypes Questions to answer: 1. Circle the sex chromosomes. 2. Male or Female? _____ 3. Normal or Abnormal? _____ 4. If abnormal, circle the abnormality and tell what disease is present.

Activity: Looking at Karyotypes Questions to answer: 1. Circle the sex chromosomes. 2. Male or Female? _____ 3. Normal or Abnormal? _____ 4. If abnormal, circle the abnormality and tell what disease is present.

Home Work: Genetic Practice 1. In fruit flies, normal wings (W) are dominant to dumpy wings (w). Two normalwinged flies were mated and produced 298 normal-winged and 100 dumpy-winged flies. What were the parents’ genotypes? 2. Hemophilia is an X-linked trait. A normal male person has children with a normal female who carries the hemophilia allele. What is the probability their offspring will have hemophilia? What is the probability their daughters will have hemophilia? What is the probability their sons will have hemophilia? 3. Color-blindness is an X-linked trait. A male who is colorblind mates with a normal female. What is the probability their offspring will have color-blindness? What is the probability their daughters will have color-blindness? What is the probability their sons will have color-blindness? 4. In fruit-flies, white eyes are a recessive X-linked trait. If a male mates with a female and the offspring came up as follows, what were the parents’ genotypes? Male, White-Eyed Male, Red-Eyed Female, White-Eyed 98 102 99 101

Pedigrees January 8 th/9 th, 2008

Human Traits Pedigree – a chart that shows the relationships within a family. A square represents a male. A horizontal line connecting a male and a female represents a marriage. A shaded circle or square indicates that a person expresses the trait. A circle represents a female. A vertical line and a bracket connect the parents to their children. A circle or square that is not shaded indicates that a person does not express the trait.

In humans, dimples (D) is dominant to no dimples (d). Complete the pedigree below. For each individual, list the possible genotypes and the phenotype of each. dd Dd no dimples Dd Dd DD dimples Dd DD dd Dd DD dimples no dimples dd Dd no dimples

Problem Solving: Using a Pedigree Introduction: Imagine that you are a genetic counselor. The pedigree shown illustrates the inheritance of albinism – a condition in which a person’s skin, hair, and eyes lack normal coloring – in three generations of a family. A couple from the family has come to you for advice about how the trait is inherited. Your task is to determine whether the allele for albinism is dominant or recessive. Question to be answered: 1. Based on your analysis of the pedigree, is albinism caused by a dominant or recessive allele and how do you know?

Procedure: Inside each circle or square on the pedigree below, label each person with his or her phenotype: normal pigmented skin (NP) or albino (A). Then, inside each circle or square, write down each individual’s possible genotype. Albino Male Female Normal pigmented skin

Extra Credit • Office Hour Work – Blood Types

Blood Groups Multiple Alleles. More than just two forms of a gene. Much more realistic but much more complicated. Ex. Blood types 3 alleles IA, IB, i

Sample Blood type crosses. Directions: Cross the requested parents on the following pages. For each cross, list genotypes and genotype ratios; phenotypes, and phenotype ratios. Type A mom with a Type O Dad. Genotypes Genotype Ratios Phenotypes Phenotype Ratios

Type AB mom with a Type B Dad. Genotypes Genotype Ratios Phenotypes Phenotype Ratios

Type B mom with a Type A Dad. Genotypes Genotype Ratios Phenotypes Phenotype Ratios