Bellwork : Which fact interests you the most and why?

Bellwork: Which fact interests you the most and why?

Genetics Mendelian Genetics & Patterns of Inheritance

Biology And Society: Testing Before Birth • Genetic testing • Allows expectant parents to test for possibilities in their unborn child. • Includes amniocentesis and CVS. • Has risks associated with it.

The Role of Environment • Many human characteristics result from a combination of heredity and environment.

The Chromosomal Basis of Inheritance • The chromosome theory of inheritance states that • Genes are located at specific positions on chromosomes. • The behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns.

Figure 9.23

Linked Genes • Linked genes • Are located close together on a chromosome. • May be inherited together. • Sex chromosomes • Influence the inheritance of certain traits. • Due to linkage

Gregor Mendel1822-1884 The father of genetics

Gregor Mendel • He was an Austrianmonk. He is important because carried out the first important studies of heredity. He studied plants because plants have male & female parts so that they can reproduce sexually. • Was the first person to analyze patterns of inheritance. • Deduced the fundamental principles of genetics

Peas In an Abbey Garden • Mendel studied garden peas because • These plants are easily manipulated. • These plants can self-fertilize.

Peas In an Abbey Garden • Mendel carried out some cross-fertilization. • He also created true-breeding varieties of plants. • Mendel then crossed two different true-breeding varieties.

Peas In an Abbey Garden • Mendel performed many experiments. • He tracked several characteristics in pea plants from which he formulated several hypotheses.

Heredity • The passing on of characteristics from parents to children (offspring).

Genetics • The branch of biology that studies heredity.

Traits Inherited characteristics Often represented by single letters. Examples Tall plant = T Short plant = t Purple flowers = F White flowers = f

Allele The different forms of a gene for the same trait. For example if we look at a particular plant’s flower color we have two possibilities F (for purple flowers) and f (for white flowers). One allele comes from the female parent, one comes from the male parent.

Homozygous • Two alleles of the same trait are the same • Example: TT or tt

Heterozygous • Two different alleles for the same trait • Example Tt

Dominant • The allele that is always displayed in a mixed (heterozygous Tt) cross. • Represented by anupper case letter ex: T Tongue curling is a dominant trait.

Recessive • A gene that is only displayed if both alleles are the same. • Represented by a lower case letter ex: t The bent finger is dominant and the straight finger is recessive.

Question • Is “W” dominant or recessive? • Is “w” dominant or recessive?

Genetic Alleles and Homologous Chromosomes Homologous chromosomes Have genes at specific loci. Have alleles of a gene at the same locus.

Phenotype • What the organism looks like. • Memory trick: PH in “phenotype” is like the PH in “photo” • Example: red, white, furry, bald.

Genotype • The genetic constitution of the organism. In other words the genes of that organism. • Memory trick: GEN in “genotype” is like the GEN in “gene” • Example: RR, rr, Rr

Question • In a heterozygous cross of short plants and tall plants how would you represent the trait with letters?

Question • In a heterozygous flower if the dominant trait’s genotype was for a purple phenotype and the recessive trait’s genotype was for a yellow phenotype. What would the flower’s phenotype be?

P Generation The parental generation These are true breeding plants. They will always produce the same traits. They are homozygous for a trait YY or yy

F1 Generation The first generation. These result after a cross from two parents of the P generation with different traits. Heterozygous Yy The F1 generation are often referred to as hybrids as they will have mixed genotypes but the same phenotype.

F2 Generation These are the offspring of a cross between the heterozygous F1 generation Yy X Yy These offspring will havemixed genotypes andphenotypes.

Bellwork 11/18/10 - Week 15 Monohybrid Cross – 1 trait Example: hair color B (blue hair) dominant b (white hair) recessive Make A Punnett Square  Genotype Mother = BB What is the mother’s phenotype? Father = bb What is the father’s phenotype?

Question • How do you set up a Punnett square for this cross?

Make a Punnett I (colors used in genotypes to help you to see where each one goes in the box) Mother BB (take one B and put it over each box) B = blue hair b = white hair B B Father bb b b Fill in the genotypes for each offspring

Make a Punnett I (colors used in genotypes to help you to see where each one goes in the box) Mother BB (take one B and put it over each box) B = blue hair b = white hair B B Father bb bB bB b b bB bB What is the phenotype for each offspring?

Make a Punnett I (colors used in genotypes to help you to see where each one goes in the box) Mother BB (take one B and put it over each box) B = blue hair b = white hair B B Father bb bB bB b Blue Hair Blue Hair b bB bB Blue Hair Blue Hair

Question • How many white haired offspring are there? • How many blue haired offspring are there?

Answer • 0 • 4 or 4/4

Answer • Both parents are Bb • They both have blue hair

Mendel’s First Law This law states that allele pairs separate or segregate during the formation of eggs and sperm (gamete formation), and randomly come back together (unite) at fertilization. The Law of Segregation

Mendel’s Second Law Different traits are inherited separately (independently) of each other. The Law Of Independent Assortment

Mendel’s Third Law If a homozygous dominant parent (TT) is crossed with a homozygous recessive parent (tt) the offspring will ALWAYS be Tt, displaying the dominant phenotype. The Law Of Dominance

Question • So how do we predict the probability of offspring types between two parents? Think about how we predict a coin flip: • With a coin flip. 1 in 2 that it will be heads.

Punnett Square Used to show all possible combinations.

Question There are two parents who are both heterozygous for hair color, where blue was B and white was b • What is the genotype for each parent? • What is the phenotype for each parent?

Make a Punnett II (colors used in genotypes to help you to see where each one goes in the box) Mother Bb(take one B and put it over each box) B = blue hair b = white hair b B Father Bb b B Fill in the genotypes for each offspring What is the phenotype for each offspring?

Question How many white haired offspring are there? How many blue haired offspring are there?

Dihybrid Cross • Used for two traits Example: R (round) dominant Y (yellow) dominant r (wrinkled) recessive y (green) recessive Genotype Mother = RyrY What is the mother’s phenotype? Father = RyrY What is the father’s phenotype?

Dihybrid Cross Used for two traits Example: R (round) dominant Y (yellow) dominant r (wrinkled) recessive y (green) recessive Genotype Mother = RYry What is the mother’s phenotype? Father = RYry What is the father’s phenotype?

Bellwork : Which fact interests you the most and why?