Introduction to Introduction to GeneticsGenetics

Ms. LazzaroMs. Lazzaro

HeredityHeredity►passing characteristics from parent passing characteristics from parent

to offspring (children)to offspring (children)

►Fertilization-male and female Fertilization-male and female gametes combine to form new gametes combine to form new offspring offspring

►Pollination – (in plants) pollen Pollination – (in plants) pollen grains fertilize female gametegrains fertilize female gamete

GeneticsGenetics

►study of hereditystudy of heredity

Gregor MendelGregor Mendel

► in charge of monastery garden, in charge of monastery garden, ► Father of geneticsFather of genetics► studied characteristics of peas and how studied characteristics of peas and how

characteristics are passed on characteristics are passed on ► Normally peas self –pollinate = males Normally peas self –pollinate = males

fertilize female’s egg of same flowerfertilize female’s egg of same flower► He would cause cross-polination = offspring He would cause cross-polination = offspring

(seeds) of 2 different parents(seeds) of 2 different parents► Studied 7 characteristics – study a few or Studied 7 characteristics – study a few or

else too manyelse too many

Mendel’s FindingsMendel’s Findings►Due to his observations, Mendel decided Due to his observations, Mendel decided

that there must be two factors controlling that there must be two factors controlling each trait. He concluded that there was a each trait. He concluded that there was a dominantdominant (A) and a (A) and a recessiverecessive (a) form of (a) form of each trait and that presence of the each trait and that presence of the dominant form masked the recessive form. dominant form masked the recessive form. Each of these forms is now called an Each of these forms is now called an alleleallele..

►Mendel’s Mendel’s law of segregationlaw of segregation says that a says that a pair of factors is separated or segregated pair of factors is separated or segregated during the formation of gametes (meiosis).during the formation of gametes (meiosis).

►Mendel’s Mendel’s law of independent assortmentlaw of independent assortment says that factors for different traits are says that factors for different traits are distributed to gametes independently from distributed to gametes independently from one another.one another.

TraitTrait

►CharacteristicCharacteristic►example: eye color or hair color or example: eye color or hair color or

heightheight

GenesGenes

►Factors or piece of DNA that Factors or piece of DNA that determines a characteristic determines a characteristic

►for example a piece of DNA codes for a for example a piece of DNA codes for a protein or product which determines protein or product which determines these characteristicsthese characteristics

AllelesAlleles

►different forms or versions of a genedifferent forms or versions of a gene►Example: blue, brown, green eye colorExample: blue, brown, green eye color►Example: Gene: height; alleles = tall Example: Gene: height; alleles = tall

short; short; ►Organisms have 2 alleles for each gene Organisms have 2 alleles for each gene

(1 on each chromosome) (1 on each chromosome)►Gametes have 1 allele because haploid Gametes have 1 allele because haploid ►Let Y = yellow and y = green since Let Y = yellow and y = green since

same gene & (only 2 alleles) lets use the same gene & (only 2 alleles) lets use the same letter same letter

DominantDominant►seen even if other versions are present ex: Yy seen even if other versions are present ex: Yy

and YY both appear yellow no blendingand YY both appear yellow no blending►designated with a capital letterdesignated with a capital letter►usually more common but not alwaysusually more common but not always

►NOT seen if other versions are presentNOT seen if other versions are present►Only if homozygous recessive yyOnly if homozygous recessive yy► designated with a lower case letterdesignated with a lower case letter

Recessive

GeneotypeGeneotype

►Genetic make-upGenetic make-up►the alleles you havethe alleles you have►HomozygousHomozygous = have the same alleles = have the same alleles

for a particular gene example: YY or for a particular gene example: YY or yyyy

►Heterozygous Heterozygous = have different = have different alleles for a particular gene alleles for a particular gene example: Yyexample: Yy

PheneotypePheneotype

►Physical appearancePhysical appearance►characteristics we see characteristics we see ► If YY or Yy = appears yellow (so phenotype = yellow)If YY or Yy = appears yellow (so phenotype = yellow)► If yy = greenIf yy = green► Why is Yy yellow not green?Why is Yy yellow not green?