Mendelian GeneticsGregor Mendel

Father of modern genetics

Objectives• I can compare and contrast mitosis & meiosis.• I can properly use the genetic vocabulary

presented.• I can differentiate and gather data from the

genetic tools of karyotypes, Punnett squares genetic tools of karyotypes, Punnett squares and pedigrees.

• I can describe and apply Mendel’s Laws.• I can set up and utilize Punnett squares.• I can describe different patterns of inheritance.

Cell Division Review• mitosis produces

two daughter cells genetically identical to the original parent cell (diploid)cell (diploid)

• meiosis produces four daughter cells with exactly half the genetic material of the original parent cell. (haploid)

Gametogenesis-meiosisCreation of the gametes.

• Male meiosis generally results in the production of four sperm that are capable of producing offspring.offspring.

• Female meiosis generally results in the production of ONE viable oocyte plus 3 polar bodies.

• allele: different forms of a gene found in the gene pool – ie: A , B & O alleles for human blood type.

• phenotype: the physical trait in an organism – ie: hitchhiker’s thumb

• genotype: the actual genes of an organism – ie: homozygous recessive (aa)

• dominant allele: if present, determines the phenotype of trait -ie: roll tongue

• recessive allele: No dominant allele present, trait will be expressed – ie: no tongue roll.

• homozygous: the two alleles are the same • homozygous: the two alleles are the same (dominant – AA or recessive - aa).

• heterozygous: the two alleles are different (one big, one small - Aa)

• autosomal trait: a gene located on one of the autosomes (any chromosome that is not a sex chromosome).

• sex-linked trait: a gene located on one of the sex chromosomes (either the X (X-linked) or Y (Y-linked) chromosome).

A karyotype is a picture of an individuals chromosomes

Chromosome numbers are arranged by size.

Pictures are taken when the cell is in metaphase

Karyotype of normal human male & female. 46 chromosomes (23 pair)

Sex chromosomes are the last pair

•DNA make up your chromosomes.•Chromosomes are where your genes are stored.•Genes determine your traits (proteins).your traits (proteins).

•You inherit 1 allele from eachparent for each trait. (total of 2)•Traits have dominant forms and recessive forms.•Your alleles will determine your genotype and phenotype.

Mendel’s Lawsworked with pea plants to make observations.

• Law of Segregation - The two forms of a gene (now known as alleles) present in each organism segregate into different cells during gamete formation.

• Law of Independent Assortment - The (two) • Law of Independent Assortment - The (two) alleles of the many different genes present in any given (diploid) organism segregate/assort from one another in a random fashion.

• Law of Dominance - alleles can be dominant or recessive. The dominant allele, if present, will always determine the trait.

Laws of Segregation & Independent assortment

Law of Dominance

Tools for GeneticsKaryotype

Pedigrees show how a single heritable trait runs through generations.

Pedigree

Punnett Squares

Punnett Squares

The outside of a Punnett Square represents the possible gametes that pa parent can give based on the law of segregation.

gametes

gametes

gametes

The inside of the Punnett Square represents the possible offspring if those two gametes fertilized each other. In this example, all of the offspring would be yellowbecause they each have a dominant allelle.

AaAa

Aa Aa

Punnett Square Practice!!

Cross a male who is heterozygous for tongue rolling (Tt) with a female that is homozygous recessive (tt)

T t

t recessive (tt)t

t

Genotypic ratio:______________TT : Tt : tt

Phenotypic ratio: ______________Rolling ; no rolling

Punnett Square Practice!!

Cross 2 parents who are heterozygous for freckles (Ff)

F f

FF

f

Genotypic ratio:______________FF : Ff : ff

Phenotypic ratio: ______________Freckles ; no freckles

Patterns of Human Inheritance• Dominance – If dominant allele is present, it is

expressed. • Incomplete dominance - Neither allele fully

expressed in heterozygote -Aa; looks like a mixture of both (red & white = pink)mixture of both (red & white = pink)

• Co-dominance – both alleles equally expressed in heterozygote -Aa (AB blood type)

• Sex-linked – traits on the sex chromosomes• Polygenic – many genes control ONE trait

(height)

Pedigrees