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INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

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INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12. Quick review…. Genetics is the field of biology devoted to understanding how characteristics are transmitted form parents to offspring. Generations: P Tall x Short F1 Tall (tall is dominant) F2 3 Tall : 1 short. - PowerPoint PPT Presentation

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Page 1: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

INHERITANCE PATTERNS AND HUMAN GENETICS

Chapter 12

Page 2: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Quick review…

Genetics is the field of biology devoted to understanding how characteristics are transmitted form parents to offspring.

Page 3: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

• The DOMINANT factor/gene masks the effect of the other factor in the F1 generation. – Use CAPS ex. T for tall

• The RECESSIVE factor/gene’s effect can only be seen in the P generation or F2 generation when the DOMINANT gene is absent. – Use lower case ex. t for short

Generations:P Tall x ShortF1 Tall (tall is dominant)F2 3 Tall : 1 short

Page 4: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

MENDEL’S 2 LAWS:

#1 LAW OF SEGREGATION:• A pair of factors is

segregated, or separated, during the formation of gametes.

• Factors for different characteristics are distributed to gametes independently.

#2 LAW OF INDEPENDENT ASSORTMENT:

Page 5: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

GENOTYPE is the genetic makeup of the organism.TT = homozygous dominantTt = heterozygoustt = homozygous recessive

PHENOTYPE is the physical appearance of that organism.Ex. Tall or short

MENDELIAN INHERITANCE- DOMINANCE…. 2 phenotypes only.

If someone has the dominant phenotype but you aren’t sure of Their genotype… use a pedigree (humans) or do a test cross.

Page 6: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Other Patterns of Inheritance:1. Incomplete Dominance- blending seen in heterozygote (ex.

pink flowers, brown hair)2. Codominance- both dominant and recessive phenotypes

seen in heterozygote. (ex. type AB blood, roan horse fur color)3. Polygenic- more than 1 gene determines the phenotype. (Ex.

Eye color, Hair color aabbcc)4. Multiple alleles- more than just 2 alleles (Ex. Blood type = A allele, B allele, O allele is recessive.)

Page 7: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

EX. Polygenic Inheritance- when the trait is controlled by multiple genes so

many phenotypes are possible.

AaBbCc x AaBbCc

Huge variety in possible Phenotypes of the offspring

- skin, hair, eye color- foot size- nose length- height

Page 8: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Multiple alleles- trait controlled by three or more alleles.

-Ex. ABO blood groups:

- TYPE A - TYPE B

- TYPE AB Shows Codominance!

- TYPE O

Page 9: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

The process of using phenotypes to deduce

genotypesWhen someone has the DOMINANT phenotype you are uncertain of their genotype.

TT or Tt

When someone has the recessive phenotype you can be sure of their genotype.

tt

Page 10: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

DIRECTIONS:

• For each of the following single gene/ Mendelian traits, write your phenotype on the line.

• Write as much of your genotype as you can be certain. - both alleles if RECESSIVE (rr)- one allele if DOMINANT (R __)

• Repeat the process by studying two blood relatives (parents work the best)

• Use a pedigree.

Page 11: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

1. HAIR TYPEvery curly or straightTT, Tt tt

Page 12: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

2. Hair ColorDark or LightDD, Dd dd

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3. Hair LineContinuous or Widow’s PeakWW, Ww ww

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4. Iris ColorPigmented or BlueEE, Ee ee

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5. Lens of EyeAstigmatism or NormalAA, Aa aa

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6. Nose ShapeRoman (convex) or ConcaveNN, Nn nn

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7. Ear LobeFree/Long or AttachedLL, Ll ll

Page 18: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

8. P.T.C. TasterTaster or NontasterRR, Rr rr

Page 19: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

9. Tongue CurlingCan curl or Can not curlCC, Cc cc

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10. Point of chinDimpled or NO dimpleII, Ii ii

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11. Number of FingersPolydactylism or Normal #PP, Pp pp

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12. Little FingerBent or StraightFF, Ff ff

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13. Hypermobility of ThumbLoose Jointed or Not soHH, Hh hh

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14. Thumb ExtensionHitchhiker’s Thumb or Not H’H’, H’h’ h’h’

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15. Middigital HairPresent or AbsentMM, Mm mm

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16. Palmar MuscleNormal (2) or Long (3)UU, Uu uu

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17. AllergiesTendency Or No tendencyA’A’, A’a’ a’a’

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18. VeinsVaricose or NormalVV, Vv vv

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19. White Skin SpottingFreckles or No frecklesSS, Ss ss

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20. White Forelock

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LIST OF STRANGE MENDELIAN TRAITS• Ear wiggling• Misshapen toes or teeth• Inability to smell musk or skunk• Lack or teeth, eyebrows, nasal bones or thumbnails• Whorl in the eyebrow• Tone Deafness• Hairs that are triangular in cross-section or that have multiple

hues (colors)• Hairy knuckles, palms, soles, or elbows• Egg-shaped pupils• Magenta urine after eating beets• Sneezing fits in bright sunlight.

Page 33: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

DNA in chromosomes contain information to make proteins.

Geneticists use their knowledge of DNA and the way chromosomes behave to study how traits are inherited and expressed.

Page 34: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

The parent’s genotype can be agene pair of either:

- TT homozygous dominant- tt homozygous recessive- Tt heterozygous

The parent can make gametes (sperm or eggs), through the process of MEIOSIS, that have either one or the other of the gene pair in it.

Page 35: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

SEX DETERMINATIONMORGAN’s Fruit fly (Drosophila)breeding experiments ofthe 1900’s revealed theidentity of sex chromosomes.

In males they were differentXY; in females they were thesame XX.

The other chromosomes (22 in humans) are AUTOSOMES.

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The male determines the sex of the offspring…

<--The FEMALE XX can only make X gametes.

<--The MALE XY can make either X gametes or Y gametes.

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SEX LINKAGE traits caused by genes found on a

sex chromosome

X-LINKED GENES:Genes located on the X chromosome.• Women can be carriers.• Ex. gene for ALD (Lorenzo’s Oil)

Y-LINKED GENES:Genes located on the Y chromosome.Only males show these traits.Ex. SRY- triggers male development

of testis.

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Males exhibit X-linked traits more often than women because they only have ONE X chromosome.

• Females have two XBXb or sex linked genes.

• Females can be “carriers” of the bad gene yet not show the disease..

• Males only have one X or sex linked gene since they are XbY.

• Males have a higher chance of having the condition than if it were on an autosome.

• THERE IS NO HETEROZYGOUS for men.

Page 39: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

X-linked Examples:

• Eye color in Drosophila• Red-green colorblindness• Male Pattern Baldness• Hemophilia• Duchenne Muscular Dystrophy• ALD (adreno leuko dystrophy)

Page 40: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

What do you see in the circle?

Do your bruises look like this?

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If a carrier (woman) for hemophilia marries a normal man, what are the chances of having kids who are hemophiliacs? Who are not?

What if the man is a hemophiliac???????

Page 42: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

LINKAGE GROUPS

Genes located on the same chromosome are said to be linked.

Linked genes tend to be inherited together.

Examples: Hair color and intelligence are linked in humans. fur color and deafness in cats are linked.

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I’m kidding about intelligence and hair color being linked.

• But if they were linked…

• What would the phenotype(s) be of children of a dumb,blonde & smart,brunette

Page 44: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

smart,brunette

• If that smart,brunette had kids w/ a dumb,blonde

What kinds of kids could they have? What is the probability of each?

Page 45: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Parental Phenotypes:• Smart, brunette• Dumb, blondeRecombinant

Phenotypes:• Smart, blonde• Dumb, brunette

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Linked genes result in traits that tend to be inherited together…

If the intelligence and hair color genes were linked, we’d only see smart-brunettes and dumb-blondes. (HA HA)

So, since there are smart blondes- are these genes on separate chromosomes or on the same chromosome yet separated by crossing over?????

If you do a test cross of your Heterozygote you can see if the genes Are linked (5:5:1:1) or not (1:1:1:1).

Page 47: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Chromosome maps can be created by conducting breeding experiments.

Linked genes that separate by crossing over X% of the time are X map units apart.

Compare 4 phenotype inheritance to 2 phenotype inheritance.

Genes can now be placed on a chromosome in some order.

Page 48: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

• Genes W and Z separate by crossing over 20% of the time.

• Genes W and X separate by crossing over 5% of the time, and

• genes Z and X are separated by crossing over 25% of the time.

• CONSTRUCT A CHROMOSOME MAP.• Z W X• I----20-------I--5--I

Page 49: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Mutations, Disease, & Human Mendelian Traits

1. Where they occur/ significance.2. Types: Chromosome or Gene3. Diseases & Inheritance Patterns.4. Using Phenotypes to deduce

Genotypes

Page 50: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

1. Germ cell mutation• occurs in the gametes• does not effect the organism• may be passed on to offspring if fertilized

2. Somatic mutation• occurs in the organism’s body cells & can affect the organism• ex. Skin cancer & leukemia• are not passed on to offspring

3. Lethal mutation• causes death (often before birth)• is not passed on if death occurs before reproduction

4. Beneficial mutation• result in phenotypes that are beneficial.• beneficial phenotypes lead to increased reproduction.

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Mutation: a change in the DNA sequence.A) chromosome mutations (affects many genes)B) gene mutations (one gene)

A) Chromosome mutations:Cross over errors:1. Deletion- loss of a piece due to breakage.2. Inversion- a piece is attached upside down.3. Translocation- a piece reattaches to a non-homologous

chromosome.Segregation Error:1. Nondisjunction- failure of homologous chromosomes to

separate during meiosis. ex. Down Syndrome = Trisomy 21 (egg usually has 2 of

#21)

Page 52: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

Chromosome Mutations

nondisjunction

Page 53: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

B) Gene mutations/ point mutations- are nucleotide differences.

1. Substitution- one nucleotide is switched for another.- ex. sickle cell anemia

2. Frame shift mutations- occur when nucleotides are added or removed either more or fewer than 3 nucleotides at a time. - addition- deletion

Page 54: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

GENE MUTATION: SUBSTITUTION ex. Sickle Cell Gene- Hemoglobin

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INHERITANCE OF GENETIC DISEASES follow different

Patterns of Inheritance

1. Single allele Dominant2. Single allele recessive3. X-linked 4. Sex influenced

Page 56: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

PEDIGREE ANALYSIS• Humans have about 100,000 genes.

• Most studies are of disease-causing genes.- easy to track through generations..

• A pedigree is a family record that shows how a trait is inherited over several generations.

Page 57: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

1. Single allele DOMINANT- need only one gene to have the disease.- huntington’s disease (1/10,000) Hh- dwarfism Dd- cataracts Cc- polydactyly Pp

PATTERN: effected individuals in every generation of both male and female sex.

Page 58: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

2. Single allele recessive- The individual needs two genes to have the disease.- Albinism aa- Cystic fibrosis (1/200 whites) cc- Phenylketonuria (1/1800) pp- Hereditary deafness dd- Sickle cell anemia (1/500 African-Americans) sc sc- Tay-Sachs disease (1/1600 European Jews) tt

Pattern: 2 healthy parents have effected child of either sex.

Page 59: INHERITANCE PATTERNS AND HUMAN GENETICS Chapter 12

3. X-Linked- women need two genes, men

need only one gene.- colorblindness XcXc XcY-hemophilia (1/7000) XhXh XhY-muscular dystrophy (1/10,000) XdXd XdY-Icthyosis simplex-ALD

Pattern: more common in males, Can kip generations.