Human GeneticsHuman GeneticsHuman Genetics

I. Mutations= changes in DNAI. Mutations= changes in DNAa. a. Germ CellGerm Cell Mutations– Mutations–

occurs during meiosis; occurs during meiosis; takes place in sex cellstakes place in sex cells

b. b. Somatic Mutations -Somatic Mutations -

take place in the body cellstake place in the body cells

c.c. Mutations increase the Mutations increase the amount of variation among amount of variation among offspring.offspring.

II. Gene MutationII. Gene Mutation=Changes in Nucleotides of DNA=Changes in Nucleotides of DNA

a. Point Mutationsa. Point Mutations (2 types) (2 types)

1.1.Base –pair substitutes:Base –pair substitutes:

may have no effect, may have no effect,

change amino acid; change amino acid;

or change to stop codonor change to stop codon

2.Frameshift Mutations• Base-pair insertion

or deletion• Result is a

nonfunctional protein

• Alters the reading frame of mRNA triplets

III. Chromosome MutationsIII. Chromosome MutationsA.A. DeletionDeletion: removal of a chromosomal segment: removal of a chromosomal segmentB.B. DuplicationDuplication: repeats a chromosomal segment: repeats a chromosomal segmentC.C. InversionInversion: segment reversal in a chromosome: segment reversal in a chromosomeD.D. TranslocationTranslocation: movement of a chromosomal segment to : movement of a chromosomal segment to

another non-homologous chromosomeanother non-homologous chromosome

IV. Causes of MutationsIV. Causes of MutationsA. ChanceA. Chance

B. Mutagen = environmental factor damages DNAB. Mutagen = environmental factor damages DNA

Ex. UV light (sun; skin cancer), cigarette tar, Ex. UV light (sun; skin cancer), cigarette tar, asbestos, virus, radiationasbestos, virus, radiation

V. KaryotypesV. Karyotypes

A.A. Shows chromosomes Shows chromosomes paired by size, shape, paired by size, shape, and appearance in and appearance in metaphase.metaphase.

B.B. Cells are treated, Cells are treated, photographed, sorted photographed, sorted and arranged by and arranged by homologous pairs.homologous pairs.

C.C. Chorionic villi sampling, Chorionic villi sampling, and amniocentesis can and amniocentesis can be used to diagnose be used to diagnose chromosomal chromosomal abnormalities.abnormalities.

VI. Changing Chromosome NumberVI. Changing Chromosome NumberA.A. NondisjunctionNondisjunction = =

failure of chromosomes failure of chromosomes to separate during to separate during Prophase I of Prophase I of meiosis;addition or loss meiosis;addition or loss of a chromosomeof a chromosome

B. MonosomyB. Monosomy occurs occurs when only one of a pair when only one of a pair is present (45)is present (45)

C. TrisomyC. Trisomy occurs when occurs when three of a particular three of a particular type of chromosome is type of chromosome is present (47)present (47)

D. D. Nondisjunction AbnormalitiesNondisjunction Abnormalities1.1. Many trisomies and nearly all monosomies are Many trisomies and nearly all monosomies are

fatal.fatal.2.2. XYY males (Jacob syndrome)- tall, acne, not XYY males (Jacob syndrome)- tall, acne, not

overly aggressiveoverly aggressive3.3. XO females (Turner syndrome)- short, webbed XO females (Turner syndrome)- short, webbed

neck, no puberty.neck, no puberty.

Turner syndrome affects approximately 1 out of every 2,500 female live births worldwide. It embraces a broad spectrum of features, from major heart defects to minor cosmetic issues. Some individuals with Turner syndrome may have only a few features, while others may have many. Almost all people with Turner syndrome have short stature and loss of ovarian function, but the severity of these problems varies considerably amongst individuals.

E.E. Trisomy = Extra chromosomes (47)Trisomy = Extra chromosomes (47)1.1. Klinefelter SyndromeKlinefelter Syndrome = XXY; male, some retardation, = XXY; male, some retardation,

low fertility (rare cases (48,XXXY) or low fertility (rare cases (48,XXXY) or (49,XXXXY)(49,XXXXY)

2.2. Triple X FemaleTriple X Female (XXX) – no physical abnormalities (XXX) – no physical abnormalities3.3. Fragile X SyndromeFragile X Syndrome – X chromosome broken; males; – X chromosome broken; males;

hyperactive or autistic, delayed speechhyperactive or autistic, delayed speech4.4. Down SyndromeDown Syndrome = extra 21st chromosome; mental = extra 21st chromosome; mental

retardation, fold of skin above eyes, weak musclesretardation, fold of skin above eyes, weak muscles

VII. Sex DeterminationVII. Sex DeterminationA.A. A. Thomas Hunt MorganA. Thomas Hunt Morgan

1.1. Experiments with Experiments with DrosophilaDrosophila (fruit fly) (fruit fly)

2.2. Sex Chromosomes Sex Chromosomes Determine GenderDetermine Gender

B.B. B. Autosomes are non-sex B. Autosomes are non-sex chromosomeschromosomes

C.C. (22 pairs)(22 pairs)D.D. C. Sex chromosomes C. Sex chromosomes

differ between males and differ between males and females.females.

1.1. Human female is XXHuman female is XX2.2. Human male is XY. Human male is XY.

(#23)(#23)

D. Sex chromosomes carry genes for traits D. Sex chromosomes carry genes for traits unrelated to sex.unrelated to sex.

E. Single, recessive allele on X expressedE. Single, recessive allele on X expressed

F. Males express sex-linked alleles moreF. Males express sex-linked alleles more

G. Example of Sex Link TraitsG. Example of Sex Link Traits

Color BlindnessColor Blindness

Hemophilia – blood doesn’t clotHemophilia – blood doesn’t clot

x x = normalx x = normal x y = normalx y = normal

x x = normal x x = normal x y = x y = hemopheiliahemopheilia

XXhhXXhh = hemophilia = hemophilia

H h

H H

H

h

VIII. Human Genetics TraitsVIII. Human Genetics Traits

A. Single Allele TraitsA. Single Allele Traits1. Sickle Cell Anemia1. Sickle Cell Anemia

a. Sickle shaped red cells a. Sickle shaped red cells

b. Clump; block arteries, lack 0b. Clump; block arteries, lack 022, ,

pain, weakness, deathpain, weakness, death

c. AA= normal cellc. AA= normal cell

AA’= both kinds; protected from AA’= both kinds; protected from

malariamalaria

A’A’= sickle cellsA’A’= sickle cells

2. Huntington’s Disease2. Huntington’s Disease

a.a. Cause by one dominant alleleCause by one dominant allele

b.b. Brain cells degenerate; no muscle control; deathBrain cells degenerate; no muscle control; death

c.c. Occurs at 30 -40; passed to child 50% of timeOccurs at 30 -40; passed to child 50% of time

HhHh hhhh

HhHh hhhh

H h

h

h

3. Tays-Sacs, Cystic Fibrosis, Phenylketonuria,Dwarfism

Tays Sachs Disease is an inherited incurable disease of the central nervous system. Its symptoms first appear when a baby is about 6 months old. The baby stops smiling and

developing through the normal developmental stages. Blindness and paralysis follow within the next four years resulting in the child's death by the age of five years. Most babies die

within the first two years.

B. Polygenic TraitsB. Polygenic Traits= 2 or more genes control trait= 2 or more genes control trait1.Skin color - 4-7 genes with additive effect of amount 1.Skin color - 4-7 genes with additive effect of amount

of melaninof melanin

2. Eye Color – blue (light melanin), brown (lot of 2. Eye Color – blue (light melanin), brown (lot of melanin)melanin)

3. Height3. Height

C. Multiple Allele TraitsC. Multiple Allele Traits

= Trait with 3 or more alleles; only get 2= Trait with 3 or more alleles; only get 21. ABO Blood group system; types – A, B, AB, O1. ABO Blood group system; types – A, B, AB, O

2. AA =type A AO = type A 2. AA =type A AO = type A OO = type O OO = type O

BB= type B BO = type BBB= type B BO = type B AB= type AB AB= type AB*A,B codominant *A,B codominant *Both dominant to O*Both dominant to O

D. Sex Influenced TraitsD. Sex Influenced Traits

= not a sex chromosomes; influenced by sex hormones= not a sex chromosomes; influenced by sex hormones

1.1. B=Baldness; dominant in males and B=Baldness; dominant in males and recessive in femalesrecessive in females

2.2. BB=bald females and malesBB=bald females and males

3.3. BB” – female will not lose her hairBB” – female will not lose her hair

4.4. BB” – male will lose hairBB” – male will lose hair

IX. Studying HumansIX. Studying Humans

A. Population Sampling = A. Population Sampling = select a number to represent select a number to represent whole populationwhole population

B. Twin Studies – B. Twin Studies – environment vs. geneticsenvironment vs. genetics

C. Pedigree Studies –C. Pedigree Studies – family chart of traitsfamily chart of traits

D. D. DNA fingerprinting = study theDNA fingerprinting = study thepatterns of bands obtained patterns of bands obtained from electrophoresis from electrophoresis

1. Gel electrophoresis – 1. Gel electrophoresis – process to separate DNA process to separate DNA fragments by size of chargefragments by size of charge

IN: P 34IN: P 34Contrast 2 types of point mutations. Contrast 2 types of point mutations.

OUT: P34OUT: P34

Mutations occur at 2 levels. What are they?Mutations occur at 2 levels. What are they?

IN: P 36IN: P 36A new species has been discovered. A new species has been discovered. The organism has 18 chromosomes. The organism has 18 chromosomes. How many chromosomes would the How many chromosomes would the new species have if a monosomy new species have if a monosomy

occurred? …a trisomy?occurred? …a trisomy?OUT: P36OUT: P36

Hemophilia is a sex linked disease. Hemophilia is a sex linked disease. Cross a normal male with a female that Cross a normal male with a female that is a carrier of the disease. What percent is a carrier of the disease. What percent of the males will have hemophilia?of the males will have hemophilia?

IN: P 38IN: P 38What do you know about sickle cell What do you know about sickle cell

anemia?anemia?OUT:OUT:

Explain polygenic traits in your own Explain polygenic traits in your own words. How would an albino occur?words. How would an albino occur?