GENETICS The study of how hereditary information is passed from parent to offspring.

KARYOTYPE A karyotype is a picture of the chromosome pairs. A karyotype is a picture of the chromosome pairs.

GENETIC DISORDERS

LIST OF GENETIC DISORDERS Sickle Cell Anemia Sickle Cell Anemia PKU PKU Hemophilia Hemophilia Down Syndrome Down Syndrome Tay Sachs Tay Sachs Fragile X Fragile X Color-blindness Color-blindness

PUNNETT SQUARES Cross Male and Female Cross Male and Female –(sex determination)

DOMINANT/RECESSIVE If a gene is dominant, it shows-it is more powerful. *T* If a gene is dominant, it shows-it is more powerful. *T* If a gene is recessive, it may show-it is weaker. *t* If a gene is recessive, it may show-it is weaker. *t*

GENOTYPE AND PHENOTYPE Genotype Genotype –What the genes (letters) say  Ex. TT or Tt or tt Phenotype Phenotype –How the genes appear (physically)  Ex. Tall or Short

GENETICS Gregor Mendel Gregor Mendel –“ father of genetics ” –Studied the inheritance of pea plants in the 1850 ’ s –Crossed (mated) pea plants with different traits and helped develop the 3 laws of genetics  1. Law of Dominance  2. Law of Segregation and Recombination  3. Law of Independent Assortment

LAW OF DOMINANCE Cross 2 pure/homozygous tall (TT) pea plants. Cross 2 pure/homozygous tall (TT) pea plants. –Ex. Cross 2 pure/homozygous short (tt) pea plants. Cross 2 pure/homozygous short (tt) pea plants. –Ex.

LAW OF DOMINANCE Cross two hybrid/heterozygous pea plants. Cross two hybrid/heterozygous pea plants. –Ex.

CO-DOMINANCE or INCOMPLETE DOMINANCE For some traits, there are TWO dominant alleles (genes). For some traits, there are TWO dominant alleles (genes). Two things can happen: Two things can happen: –1. Co-Dominance: Both alleles are expressed –2. Incomplete Dominance: Alleles blend together

CO-DOMINANCE Punnet Square Punnet Square

CO-DOMINANCE

INCOMPLETE DOMINANCE When neither allele dominates-the result is a new phenotype. When neither allele dominates-the result is a new phenotype. –Ex. 4 o ’ clock flower

INCOMPLETE DOMINANCE

MULTIPLE ALLELES Sometimes there are more than two possible alleles for a trait. Sometimes there are more than two possible alleles for a trait. –Ex. Blood types Rules for blood typing (three alleles). Rules for blood typing (three alleles). –1. Type A dominates Type O –2. Type B dominates Type O –3. Type O is recessive –4. Type A is CO-DOMINANT to Type B

BLOOD TYPES TypeGenotypePhenotype

BLOOD TYPE PUNNET SQUARE Cross a homozygous Type A mother with a homozygous Type O father. Cross a homozygous Type A mother with a homozygous Type O father. Cross a homozygous Type A mother with a heterozygous Type B father. Cross a homozygous Type A mother with a heterozygous Type B father.

BLOOD TYPE PUNNET SQUARE Cross two heterozygous Type A parents. Cross two heterozygous Type A parents.

BLOOD GENOTYPES Type A- I I Type A- I I Type B- I I Type B- I I Type O- i i Type O- i i Type AB- I I Type AB- I I

LAW OF SEGREGATION AND RECOMBINATION During meiosis, the two genes responsible for each trait separate from each other. During meiosis, the two genes responsible for each trait separate from each other. Each gamete contains only one gene for each trait. Each gamete contains only one gene for each trait. –Ex. Hybrid TallPure Short Tttt

SEGREGATION AND RECOMBINATION

LAW OF INDEPENDENT ASSORTMENT If 2 traits are crossed at the same time (dihybrid cross), each trait is inherited randomly. If 2 traits are crossed at the same time (dihybrid cross), each trait is inherited randomly.

SEX LINKED DISORDERS The X chromosomes carry some genes that the Y chromosomes do not. The X chromosomes carry some genes that the Y chromosomes do not. –Ex. Hemophilia (a recessive disorder)  h is the gene for hemophilia  H is the gene for non-hemophilia (normal)  Genotypes X YX YX XX X X X  Cross a normal male with a hemophiliac female.

SEX LINKED DISORDERS Cross a hemophiliac male with a carrier female. Cross a hemophiliac male with a carrier female. Cross a colorblind male with a normal female. Cross a colorblind male with a normal female.

GENE CHROMOSOME THEORY Each gene is found in a specific place on a chromosome (locus/loci). Each gene is found in a specific place on a chromosome (locus/loci).

LINKED GENES Some traits are found on the same chromosome and are usually inherited together. Some traits are found on the same chromosome and are usually inherited together. –Ex.  Red hair and _____________

PEDIGREE CHART Hemophiliac Story Hemophiliac Story

PEDIGREE CHART

MUTATIONS Some mutations can occur during meiosis. Some mutations can occur during meiosis. –Ex. Non-disjunction causes Down Syndrome Other mutations can be caused by environmental factors. Other mutations can be caused by environmental factors. –1) Chemicals such as asbestos, pesticides and industrial pollutants can cause genetic changes (mutation). –2) Radiation –3) Natural conditions may influence which genes are expressed. Ex. Cold temperatures change fur color.