Genetics

What is genetics? Genetics has to do with how offspring resemble or differ from their parents. Offspring have traits that may differ or resemble those of their parents.

Traits are characteristics that are inherited, such as ____________________________________ eye color, size, fur color, length of claws.

Heredity is the passing on of traits (characteristics) from parents to offspring. Genetics is the study of heredity in organisms.

Gregor Mendel ( ) is the father of genetics. Mendel experimented with pea plants and showed how traits are inherited.

TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort Mendel’s Pea Plants What traits did Mendel work with? Traits are characteristics that are inherited.

A genes is a section of DNA on a chromosome that determines a trait. gene for brown hair gene Traits are controlled by genes. Genes are passed from parent to offspring. Section of DNA A chromosome

Example: trait -- hair color There are alternative forms of a gene. black, brown, blonde, red

blonde brown red Alleles are the different forms of a gene. Some possible alleles below are:

TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort Mendel’s Pea Plants trait: flower color the two alleles are: _________________ purple & white

TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort Mendel’s Pea Plants trait: pea shape the two alleles are: _________________ round & wrinkled

Each trait is controlled by two alleles, one from each parent. These alleles are located on homologous chromosomes. homologous chromosomes allele for brown hairallele for blonde hair maternalpaternal

Alleles may be dominate or recessive. Letters are used to represent alleles. TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort

Dominant alleles are always expressed(visible) they cover-up the recessive allele. They are represented by capital letters. TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort P Y R G T

Recessive alleles are often not expressed because they are covered-up by the dominant allele. They are represented by lower case letters of the dominant allele. TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort p g y r t P R G T Y

Organisms can have two dominant alleles. --- Pea shape: _____ Organisms can have one dominant allele and one recessive allele --- pea : _____ Organisms can have two recessive alleles --- Pea shape: _____ RR rr Rr

An organism is homozygous for a trait if the two alleles of a particular gene are the same. ____ ____ ____ ____ ____ PPppYY yyRR rrGGggTTtt TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort P Y R G T p y r g t

An organism is heterozygous for a trait if the two alleles of a particular gene are different. ____ ____ ____ ____ ____ Pp Yy Rr Gg Tt TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort P Y R G T p y r g t

Is the organism homozygous or heterozygous? XXss Bbbb nnMmddEe HHKKQq Rr ee FfjjYy

Two organisms may express the same trait, for example purple flower color, but have different alleles. Purple flower: ____ _______________________________ Purple flower: ____ _______________________________ – two purple alleles --- purebred PP one purple allele and one white allele Pp purple white Purple is dominant so it covers up the white hybrid

TRAITSDOMINANTRECESSIVE Flower colorpurplewhite Pea coloryellowgreen Pea shaperoundwrinkled Pod colorgreenyellow Plant heighttallshort Mendel’s Pea Plants Tt

The set of alleles that an organism has for a trait is called the genotype. What are the genotypes for? Homozygous tall ___ Heterozygous tall ___ Homozygous short ___ genogenes genotype = genes TT Tt tt

The physical appearance of a trait is called the phenotype. What are the phenotypes for? TT__________ Tt __________ tt __________ phph phenotype = physical appearance tall short

Unless you have an identical twin, you have a unique genome that determines all of your traits. A genome is all of an organism’s genetic material. The human genome consists of 3 billion nucleotide pairs.

1.Trait: Eye color dominant trait : brown eyes recessive trait: green eyes What letter is used to represent the dominant allele? ______ What letter is used to represent the recessive allele? ______ What is the genotype of a homozygous dominant individual? ______ phenotype? ________________ What is the genotype of a homozygous recessive individual? _______ phenotype? ________________ What is the genotype of a heterozygous individual? _______ phenotype? ________________

1.Trait: Fur color dominant trait : black fur recessive trait: white fur What letter is used to represent the dominant allele? ______ What letter is used to represent the recessive allele? ______ What is the genotype of a homozygous dominant individual? ______ phenotype? ________________ What is the genotype of a homozygous recessive individual? _______ phenotype? ________________ What is the genotype of a heterozygous individual? _______ phenotype? ________________

1.Trait: Freckles dominant trait : having freckles recessive trait: no freckles What letter is used to represent the dominant allele? ______ What letter is used to represent the recessive allele? ______ What is the genotype of a homozygous dominant individual? ______ phenotype? ________________ What is the genotype of a homozygous recessive individual? _______ phenotype? ________________ What is the genotype of a heterozygous individual? _______ phenotype? ________________