GeneticsGenetics

Study of heredityStudy of heredity

Heredity is the study of how offspring get Heredity is the study of how offspring get their traits from their parents.their traits from their parents.

Traits are physical characteristics:Traits are physical characteristics:Height, hair color, flower colorHeight, hair color, flower color

Where do traits come from?Where do traits come from?

Traits are controlled by genes.Traits are controlled by genes.

Genes are found on chromosomesGenes are found on chromosomes

Chromosomes are wound up DNAChromosomes are wound up DNA

ChromosomesChromosomes

Humans have 46 chromosomesHumans have 46 chromosomes

They are organized into 23 pairsThey are organized into 23 pairs

Chromosomes and GenesChromosomes and Genes

Every chromosome contains thousands of Every chromosome contains thousands of genesgenesEach gene has 2 partsEach gene has 2 partsThese parts are called allelesThese parts are called allelesOne allele comes One allele comes from each parentfrom each parent

AllelesAlleles

There are two kinds of allelesThere are two kinds of allelesDominant and recessiveDominant and recessive

Dominant alleles are more powerfulDominant alleles are more powerfulThey can hide recessive alleles when paired They can hide recessive alleles when paired together.together.

DOMINANT ALLELES ARE SHOWN DOMINANT ALLELES ARE SHOWN WITH CAPITAL LETTERSWITH CAPITAL LETTERSrecessive alleles are shown with lower recessive alleles are shown with lower case letterscase letters

Alleles and TraitsAlleles and Traits

The combination of alleles an organism The combination of alleles an organism has determines what it will look like.has determines what it will look like.

2 capital alleles (QQ) will show the dominant trait2 capital alleles (QQ) will show the dominant trait

2 lower case alleles (qq) will show the recessive 2 lower case alleles (qq) will show the recessive traittrait

1 dominant and 1 recessive allele (Qq) 1 dominant and 1 recessive allele (Qq) combination will show the dominant traitcombination will show the dominant trait

How does this work?How does this work?

Each parent give the offspring 1 allele.Each parent give the offspring 1 allele.

Qq

However…However…

Each parent has 2 possible alleles to give.Each parent has 2 possible alleles to give.But only one will be given to their offspringBut only one will be given to their offspring

Q

Q

q

q

Parents and OffspringParents and Offspring

The alleles the parents can give the The alleles the parents can give the offspring determine what the offspring will offspring determine what the offspring will be.be.

Offspring possibilitiesOffspring possibilities

The alleles given by the parents will The alleles given by the parents will determine what the offspring has.determine what the offspring has.

Q q+ =Qq

Defining allele combinationsDefining allele combinations

If the alleles given to the offspring by the If the alleles given to the offspring by the parents are the different it is called parents are the different it is called heterozygous or hybrid.heterozygous or hybrid.

Q q+ =

q Q+=

Qq

Qq

Defining allele combinationsDefining allele combinations

If the alleles given to the offspring by the If the alleles given to the offspring by the parents are the same it is called parents are the same it is called homozygous or purebred.homozygous or purebred.

Q Q+ =

q q+=

QQ

qq

Types of Homozygous/purebred Types of Homozygous/purebred combinationscombinations

If the 2 alleles given by the parents are If the 2 alleles given by the parents are dominant alleles it’s called homozygous dominant alleles it’s called homozygous dominant or a dominant purebred.dominant or a dominant purebred.

Q Q+ =QQ

Types of Homozygous/purebred Types of Homozygous/purebred combinationscombinations

If the 2 alleles given by the parents are If the 2 alleles given by the parents are recessive alleles it’s called homozygous recessive alleles it’s called homozygous recessive or a recessive purebred.recessive or a recessive purebred.

qqq q+ =

Genes and physical appearanceGenes and physical appearance

The genetic code found on the The genetic code found on the chromosomes is referred to as the chromosomes is referred to as the genotype. genotype.

QQ, Qq, qqQQ, Qq, qq

The physical trait that results is referred to The physical trait that results is referred to as the phenotype.as the phenotype.

Predicting the possible offspringPredicting the possible offspring

The tool geneticists use to predict the The tool geneticists use to predict the possible offspring is called a Punnett possible offspring is called a Punnett SquareSquare

Reading a Punnett SquareReading a Punnett Square

A Punnett square show the probability that A Punnett square show the probability that parents will have certain offspring.parents will have certain offspring.

Phenotypes:

•75% chance the offspring will be tall

•25% chance the offspring will be short

Genotypes:

•25% chance the offspring will be homozygous dominant/dominant purebred

•25%chance the offspring will be homozygous recessive/recessive purebred

•50% chance the offspring will be heterozygous/hybrid