More Patterns of Inheritance Autosomal inheritance – genes are located on the autosomes, same for both male and female Sex-linked inheritance – genes located on the sex chromosomes, different for male and female Sex-influenced traits – sex hormones create different phenotypes in males and females (Ex. Baldness) Multiple alleles – has more than 2 alleles for the same gene (Ex. blood types) Polygenic inheritance – coded for by many genes (skin color, hair color, height) 1

2 Sex-linked Traits Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y XX genotype for females XY genotype for males Many sex-linked traits carried on X chromosome

3 Sex-linked Traits Sex Chromosomes XX chromosome - femaleXy chromosome - male fruit fly eye color Example: Eye color in fruit flies

4 Sex-linked Trait Problem Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) X R Y x X r X r Remember: the Y chromosome in males does not carry traits. RR = red eyed Rr = red eyed rr = white eyed XY = male XX = female XRXR XrXr XrXr Y

5 Sex-linked Trait Solution: X R X r X r Y X R X r X r Y 50% red eyed female 50% white eyed male XRXR XrXr XrXr Y

Sex-linked Inheritance Color Blindness – recessive, on X chromosome Normal Vision is dominant Genotypes: X C X C – normal female, non carrier X C X c’ – normal female, carrier (may pass recessive allele on to sons and/or daughters) X c’ X c’ – colorblind female (will pass recessive allele to all children X C Y – normal male X c’ Y – colorblind male (will pass recessive allele to daughters only)

~Hemophilia – bleeder’s disease, recessive, linked to the X chromosome Protein Factor VIII or IX is missing but is necessary to clot blood Genotypes: X H X H – normal female, non carrier X H X h – normal female, carrier X h X h – hemophiliac female X H Y – normal male X h Y – hemophiliac male

Genetic Rarities & Abnormalities What can happen when meiosis goes awry…

I.Twins a)Identical – develop from the same fertilized egg (zygote), genetically identical, always same sex b)Fraternal – 2 sperm fertilize 2 different eggs, genetically different

Conjoined Twins Fusion OR fission in utero

Nondisjunction (Chromosomal mutation) – chromosomes do not separate during meiosis a)Sex Chromosomes i.Turner’s Syndrome – XO – 45 chromosomes, female, sterile ii.Kleinfelter’s syndrome – XXY – 47, XXXY – 48, or XXXXY – 49 chromosomes, male, sterile b)Autosomes i.Down’s syndrome (Trisomy 21) extra 21 st chromosome ii.Trisomy 8 and 13 – result in miscarriages

Karyotypes

Down’s Syndrome Trisomy 21 1 in 700 births Mental retardation Males are sterile but females are not

Klinefelter’s Syndrome XXY 1 in 1,000 Usually sterile because of low sperm count Tall, sparse body hair Suffer from gynecomastia- male breast tissue Testosterone treatments

Turner’s Syndrome XO genotype—Monosomy X 1 in 2,500 births Short, sterile 75% result in non-disjunction from the father

Other Diseases a)Sickle Cell Anemia – codominant, causes sickle cell shaped red cells in hemoglobin, common in people with African descent b)Tay-Sachs – metabolic disorder, deteriorates brain, death by age 4, recessive is lethal c)Cystic Fibrosis – thick mucus clogs, lungs, pancreas, liver. Death by age 20 without proper diet/medication

Sickle cell

Making a Pedigree A family tree traces a family name and various family members through successive generations. Through a family tree, you can identify the relationships among your cousins, aunts, uncles, grandparents, and great-grandparents.

29 Female Carriers

Pedigrees Illustrate Inheritance A pedigree is a graphic representation of genetic inheritance. It is a diagram made up of a set of symbols that identify males and females, individuals affected by the trait being studied, and family relationships.

Pedigrees Illustrate Inheritance Male Female Affected male Affected female Mating Parents Siblings Known heterozygotes for recessive allele Death

Pedigrees Illustrate Inheritance In a pedigree, a circle represents a female; a square represents a male. Highlighted circles and squares represent individuals showing the trait being studied. Circles and squares that are not highlighted designate individuals that do not show the trait. Female Male ? I II III IV Human Heredity

Pedigrees Illustrate Inheritance A half-shaded circle or square represents a carrier, a heterozygous individual. Human Heredity

Pedigrees Illustrate Inheritance A horizontal line connecting a circle and a square indicates that the individuals are parents, and a vertical line connects parents with their offspring. Each horizontal row of circles and squares in a pedigree designates a generation, with the most recent generation shown at the bottom. The generations are identified in sequence by Roman numerals, and each individual is given an Arabic number ? I II III IV Human Heredity

dd Dd DD Dd

DD Dd dd

Hemophilia pedigree beginning with Queen Victoria

How to know… Family history (mostly probabilities) Genetic testing (ex: spit test) Karyotyping Amniocentesis