genetics the study of how hereditary information is passed from parent to offspring

GENETICSGENETICS

The study of how hereditary The study of how hereditary information is passed from information is passed from

parent to offspring.parent to offspring.

KARYOTYPEKARYOTYPE

A A karyotypekaryotype is a picture of the is a picture of the chromosome pairs.chromosome pairs.

GENETIC DISORDERSGENETIC DISORDERS

LIST OF GENETIC LIST OF GENETIC DISORDERSDISORDERS

Sickle Cell AnemiaSickle Cell Anemia PKUPKU HemophiliaHemophilia Down SyndromeDown Syndrome Tay SachsTay Sachs Fragile XFragile X Color-blindnessColor-blindness

PUNNETT SQUARESPUNNETT SQUARES

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

DOMINANT/RECESSIVEDOMINANT/RECESSIVE

If a gene is If a gene is dominantdominant, it shows-it is , it shows-it is more powerful. *T*more powerful. *T*

If a gene is If a gene is recessiverecessive, it may show-it , it may show-it is weaker. *t*is weaker. *t*

GENOTYPE AND PHENOTYPEGENOTYPE AND PHENOTYPE

GenotypeGenotype– What the genes (letters) sayWhat the genes (letters) say

Ex. TT or Tt or ttEx. TT or Tt or tt

PhenotypePhenotype– How the genes appear (physically)How the genes appear (physically)

Ex. Tall or ShortEx. Tall or Short

GENETICSGENETICS

Gregor MendelGregor Mendel– ““father of geneticsfather of genetics””– Studied the inheritance of pea plants in Studied the inheritance of pea plants in

the 1850the 1850’’ss– CrossedCrossed (mated) pea plants with (mated) pea plants with

different different traitstraits and helped develop the 3 and helped develop the 3 laws of geneticslaws of genetics 1. Law of Dominance1. Law of Dominance 2. Law of Segregation and Recombination2. Law of Segregation and Recombination 3. Law of Independent Assortment3. Law of Independent Assortment

LAW OF DOMINANCELAW OF DOMINANCE

Cross 2 Cross 2 pure/homozygouspure/homozygous tall (TT) tall (TT) pea plants.pea plants.– Ex.Ex.

Cross 2 Cross 2 pure/homozygouspure/homozygous short (tt) short (tt) pea plants.pea plants.– Ex.Ex.

LAW OF DOMINANCELAW OF DOMINANCE

Cross two Cross two hybrid/heterozygoushybrid/heterozygous pea pea plants.plants.– Ex.Ex.

CO-DOMINANCE or INCOMPLETE CO-DOMINANCE or INCOMPLETE DOMINANCEDOMINANCE

For some traits, there are TWO For some traits, there are TWO dominant dominant allelesalleles (genes). (genes).

Two things can happen:Two things can happen:– 1. Co-Dominance: Both alleles are 1. Co-Dominance: Both alleles are

expressedexpressed– 2. Incomplete Dominance: Alleles blend 2. Incomplete Dominance: Alleles blend

togethertogether

CO-DOMINANCECO-DOMINANCE

Punnet SquarePunnet Square

CO-DOMINANCECO-DOMINANCE

INCOMPLETE DOMINANCEINCOMPLETE DOMINANCE

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

INCOMPLETE DOMINANCEINCOMPLETE DOMINANCE

MULTIPLE ALLELESMULTIPLE ALLELES

Sometimes there are more than two Sometimes there are more than two possible alleles for a trait.possible alleles for a trait.– Ex. Blood typesEx. Blood types

Rules for blood typing (three alleles).Rules for blood typing (three alleles).– 1. Type A dominates Type O1. Type A dominates Type O– 2. Type B dominates Type O2. Type B dominates Type O– 3. Type O is recessive3. Type O is recessive– 4. Type A is CO-DOMINANT to Type B4. Type A is CO-DOMINANT to Type B

BLOOD TYPESBLOOD TYPES

TypeType GenotypeGenotype PhenotypePhenotype

BLOOD TYPE PUNNET BLOOD TYPE PUNNET SQUARESQUARE

Cross a homozygous Type A mother Cross a homozygous Type A mother with a homozygous Type O father.with a homozygous Type O father.

Cross a homozygous Type A mother Cross a homozygous Type A mother with a heterozygous Type B father.with a heterozygous Type B father.

BLOOD TYPE PUNNET BLOOD TYPE PUNNET SQUARESQUARE

Cross two heterozygous Type A Cross two heterozygous Type A parents.parents.

BLOOD GENOTYPESBLOOD GENOTYPES

Type A- I IType A- I I Type B- I IType B- I I Type O- i i Type O- i i Type AB- I IType AB- I I

LAW OF SEGREGATION AND LAW OF SEGREGATION AND RECOMBINATIONRECOMBINATION

During meiosis, the two genes During meiosis, the two genes responsible for each trait separate responsible for each trait separate from each other. from each other.

Each gamete contains only one gene Each gamete contains only one gene for each trait. for each trait. – Ex. Hybrid TallEx. Hybrid Tall Pure ShortPure Short

TtTt tttt

SEGREGATION AND SEGREGATION AND RECOMBINATIONRECOMBINATION

LAW OF INDEPENDENT LAW OF INDEPENDENT ASSORTMENTASSORTMENT

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

SEX LINKED DISORDERSSEX LINKED DISORDERS

The X chromosomes carry some genes The X chromosomes carry some genes that the Y chromosomes do not. that the Y chromosomes do not. – Ex. Hemophilia (a recessive disorder) Ex. Hemophilia (a recessive disorder)

h is the gene for hemophiliah is the gene for hemophilia H is the gene for non-hemophilia (normal)H is the gene for non-hemophilia (normal) GenotypesGenotypes

X YX Y X YX Y X XX X X XX X X X X X Cross a normal male with a hemophiliac female.Cross a normal male with a hemophiliac female.

SEX LINKED DISORDERSSEX LINKED DISORDERS

Cross a hemophiliac male with a Cross a hemophiliac male with a carrier female.carrier female.

Cross a colorblind male with a Cross a colorblind male with a normal female.normal female.

GENE CHROMOSOME GENE CHROMOSOME THEORYTHEORY

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

LINKED GENESLINKED GENES

Some traits are found on the same Some traits are found on the same chromosome and are usually chromosome and are usually inherited together.inherited together.– Ex. Ex.

Red hair and _____________Red hair and _____________

PEDIGREE CHARTPEDIGREE CHART

Hemophiliac StoryHemophiliac Story

PEDIGREE CHARTPEDIGREE CHART

MUTATIONSMUTATIONS

Some mutations can occur during meiosis.Some mutations can occur during meiosis.– Ex. Non-disjunction causes Down SyndromeEx. Non-disjunction causes Down Syndrome

Other mutations can be caused by Other mutations can be caused by environmental factors.environmental factors.– 1) Chemicals such as asbestos, pesticides and 1) Chemicals such as asbestos, pesticides and

industrial pollutants can cause genetic changes industrial pollutants can cause genetic changes (mutation).(mutation).

– 2) Radiation 2) Radiation – 3) Natural conditions may influence which genes 3) Natural conditions may influence which genes

are expressed. Ex. Cold temperatures change are expressed. Ex. Cold temperatures change fur color.fur color.