Human Genetic Traits

Human Genetic Traits

Homunculus How is heredity passed on?: Spermist vs Ovists Spermist conception of a human sperm it contained a mini-me! Mendelian

Genetics Gregor Mendel Mendels Three Principles Dominance Segregation (1822-1884) Independent Assortment The foundation of classical genetics

(Even though he didnt know about genes!) Dominance Traits of both parents inherited, but one shows over the other Traits are not blended Dominance Mechanism Two alleles are carried for each trait In true-breeding individuals (pure breed), both alleles are the same

Hybrids, on the other hand, have one of each kind of allele One trait is dominant, the other trait is recessive Segregation Each gamete (egg or sperm) will carry half the traits of one parent and half the traits for the other parent 23n

23n Independent Assortment Two different parental characteristics will be inherited independently of one another during gamete formation - Dad could have an allele for brown hair AND blonde these alleles end up being assorted in sperm independently

Example: eye, hair or skin color Human Genome Project U.S. govt. project coordinated by the Department of Energy and the National Institutes of Health, launched in 1986 by Charles DeLisi. Definition: GENOME the whole hereditary information of an organism that is encoded in the DNA Project Goal: to identify the approximate 100,000+ genes in the human DNA - determine the sequences of the 3 billion bases that

make up human DNA - store this information in databases - develop tools for data analysis - address the ethical, legal, and social issues that arise from genome research Modeled Organisms whose genes we have sequenced Bacteria (E. coli, influenza, several others) Yeast (Saccharomyces cerevisiae)

Plant (Arabidopsis thaliana) Fruit fly (Drosophila melanogaster) Mouse (Mus musculus) Importance of genetics Understanding hereditary diseases and to develop new treatments Donor matches Paternity Forensics Evolution

Migration Genetic Testing Would you want to know? Ethical concerns Cost Insurance companies Autosomes & Sex Chromosomes Difference between Meiosis and Mitosis

Meiosis I Interphase Prophase I Metaphase I Anaphase I

Telephase I Crossing Over of Nonsister Chromatids between Homologous Chromosomes Meiosis II Prophase II Metaphase II

Anaphase II Telephase II X X-bearing sperm X Egg

XX Female Y Y-bearing sperm X Egg XY

Male Sex Determination Maleness derived from Y chromosome - Dad

determines! Female reproductive structures degenerate Genes of the Sex Chromosome X chromosome Has over 1500 genes Most genes on X dont have

corresponding alleles on the Y chromosome Y chromosome Has about 200 genes Some genes are unique only to the Y Sex Chromosomal Disorders Turner Syndrome X only one sex chromosome Short, thick neck and stature Do not undergo puberty, or menstruate,

No breast development Kleinfelter Syndrome XXY Testis and prostate underdeveloped No facial hair

Breast development Long arms and legs: big hands and feet Can be mentally retarded XXY XO Genetic Testing Gel electrophoresis

Polymerase Chain Reaction PCR way of copying specific DNA fragments from small sample DNA material "molecular photocopying" Its fast, inexpensive and simple

Genetic Definitions Genes- genetic material on a chromosome that codes for a specific trait

Genotype- the genetic makeup of the organism Phenotype- the expressed trait Allele- an alternative form of a gene Dominance Mechanism Two alleles are carried for each trait In true-breeding individuals, both alleles are the same (homozygous). Hybrids, on the other hand, have one

of each kind of allele (heterozygous). One trait is dominant, the other trait is recessive Genetic Information Genes are traits Eye color Ear lobe connectedness Genes produce proteins Enzymes are proteins

Homologous Chromosomes gene: gene: location location allele: allele: specific specific trait trait Allele Example

Gene = eye color Alleles brown blue green lavender Allele Examples appearance B

B eye color: homozygous Allele Examples appearance B b

eye color: heterozygous, brown dominant over blue Genotype vs Phenotype genotype homozygous (dominant) B

B heterozygous B b homozygous (recessive)

b b phenotype appearance appearance Punnett Square

If male & female are heterozygous for eye color B b B B b

B b B B B

b b b female X B

male b b brown: blue: 3/4 offspring 1/4 offspring

PKU Each parent carries one gene for PKU. P p P p

P P P P p p

P p p p X P p

Possible genotypes: 1PP 2Pp 1pp Possible phenotypes:no PKU PKU Compare this to what would have happened if one parent was homozygous for sickle cell.




all offspring are carriers of sickle cell trait Where Does Genetic Diversity Come From? Mutations (any change in the DNA sequence)

Chromosomal Aberrations/Mutations Genetic Recombination (e.g., from sexual reproduction) Sickle Cell Mutation NORMAL Hb CTG ACT CCT GAG GAG AAG TCT Leu Thr Pro Glu Glu Lys Ser SICKLE CELL

CTG ACT CCT GAG GTG AAG TCT Leu Thr Pro Glu Val Lys Ser mutation Autosomes and Sex Chromosomes Red-Green Color Blindness Sex-linked trait XC

Y Normal male XC X XC Xc

Normal female recessive gene Possible outcomes: Xc XC Y


Xc Xc Y XCXC XCXc XCY Normal Normal Normal female Female male (carrier)

XcY Color-blind male allele allele EE ee

unconnected unconnected earlobe earlobe connected connected earlobe earlobe P gametes F1

gene gene EE x ee E unconnected e Ee

connected F1 Ee x Ee gametes 1/2 E 1/2 e 1/2 E 1/2 e

Punnett Square F2 E e E

EE Ee e Ee ee

1 EE 2 Ee 1 ee Genotypes Phenotypes Experiment Experiment to to determine determine dominant

dominant vs. vs. recessive recessive Genetic Sleuthing My eye color phenotype is brown. What is my genotype? Complexities

Multiple genes for one trait Example: eye color Blended traits (incomplete dominance) Influence of the environment (UV, smoking,

alcoholism) Complexities Co-dominance-neither allele is recessive and the phenotypes of both alleles are expressed.

Blood types- AB (not O); sickle cell anemia heterochromia Disorders Downs Syndrome (chrom 21) Alzheimers (chrom 1, 10, 14, 19, 21) Huntingtons (chrom 4) Tongue Roller

R = Tongue Roller r = Unable to Roll Tongue Widows Peak W = Widows Peak w = Lack of Widows Peak Free Ear Lobe Attached Ear Lobe

E = Free Ear Lobe e = Attached Ear Lobe Hitchhikers Thumb Hi = Straight Thumb hi = Hitchhikers Thumb Bent Little Finger

Bf = Bent Little Finger bf = Straight Little Finger Mid-digital Hair M = Mid-Digital Hair m = Absence of Mid-Digital Hair Dimples D = Dimples

d = Absence of Dimples Short Hallux Ha = Short Hallux ha = Long Hallux Short Index Finger Ss = Short Index Finger S1 = Long Index Finger

*Sex-Influenced Trait Blaze B = blaze b = no blaze

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