Gregor Mendel Genetics

Embed Size (px)

DESCRIPTION

Gregor Mendel Genetics

Text of Gregor Mendel Genetics

Gregor Mendel

Gregor Mendel

When two heterozygousplants are crossedthe expected andobserved phenotypicratio will always be3:1

This was the same for all 7 of his tests

Gregor Mendel

Mendel concluded that the two alleles for each characteristic separate during gamete production.

This segregation of alleles corresponds to the distribution of homologous chromosomes to different gametes in meiosis

Known as the law of segregation

Gregor Mendel

Genotype of alleles:R = red flowerr = orange flower

All genes occur in pairs, so 2 alleles affect a characteristic

Possible combinations are:

Genotypes RR Rrrr

Phenotypes RED RED ORANGE

Practice

For each genotype: heterozygous (He) or homozygous (Ho)

Which of the genotypes would be purebred?

__________________________________________________

Which of the genotypes would be hybrid?

__________________________________________________

TT_____Bb______DD______Ff ______tt _____Dd_____ff ______Tt ______BB______dd_____

Ho

Ho

Ho

Ho

Ho

Ho

He

He

He

He

TT, ff, DD, BB, tt, dd

Dd, Bb, Tt, Ff

Practice

Determine the phenotype for each genotype

Yellow body color is dominant to blue

YY_______________ Yy _______________yy _______________

Square shape is dominant to round

SS________________Ss_______________ ss________________

Yellow

Yellow

Blue

Square

Square

Round

Practice

For each phenotype, give the possible genotypes

A tall head (T) is dominant to short (t)

Tall_______________Short_______________

Pink body color (P) is dominant to yellow (p)

Pink_______________Yellow______________

TT, Tt

tt

PP, Pp

pp

Genetic Crosses

Monohybrid cross: cross involving a single trait

Flower color, plant height

Dihybrid cross: cross involving two traits

Flower color & plant height

Punnett squares help determine the possible combinations of genotypes that can occur in the offspring.

It also shows the probability of each genotype occurring

Genetic Crosses

Genetic Crosses

Solving Punnett squares only takes a few steps:

Determine the genotypes of the parent organisms

Write down your cross

Draw your Punnett square

Split the letters of the genotype for each parent & put them outside the Punnett square

Determine the possible genotypes of the offspring by filling in the Punnett square

Summarize the results (both genotype and phenotype of the offspring)

Genetic Crosses

Sometimes the question already tells you, other times you need to understand the vocabulary. Read carefully!

Write down the genotypes of the parents

Ex: Tt x tt

Draw the Punnett square

Genetic Crosses

Split the letters of our cross Tt x tt

This split represents the process of meiosis

The vertical represents the male gamete

The horizontal represents the female gamete

Genetic Crosses

Each box represents a possible genotype of the offspring

Genetic Crosses

Summarize the results of the offspring; both genotype and phenotype

Genotype:

50% TT50% tt

Phenotype:

50% tall50% short

SpongeBob is heterozygous for his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities if they had children. (look at old questions!)

Cross: ___________ x ___________

Punnett Square

Genotypes:Genotypic ratio:

Phenotypes:Phenotypic ratio:

Practice

________________

ss

Ss

S

s

s

s

Ss

Ss

Ss

ss

Square, Round

Ss, ss

3:1

3:1

Patrick met Patti at a dance. They are both heterozygous for their pink body color, create a Punnett square to show the possibilities if they had children. (look at old questions!)

Cross: ___________ x ___________

Punnett Square

Genotypes:Genotypic ratio:

Phenotypes:Phenotypic ratio:

Practice

________________

Pp

Pp

P

p

P

p

PP

Pp

Pp

pp

Pink, yellow

PP, Pp, pp

1:2:1

3:1

Gregor Mendel

In one dihybrid cross, Mendel studied the inheritance of seed color and seed shape

The allele for yellow seeds (Y) is dominant to the allele for green seeds (y).

The allele for round seeds (R) is dominant to the allele for wrinkled seeds (r).

Gregor Mendel

He crossed true-breeding plants that has yellow, round seeds (YYRR) with true-breeding plant that had green, wrinkled seeds (yyrr)

One possibility is that the two characteristics are transmitted from parents to offspring as a package

The Y and R alleles and the y and r alleles stay together

Gregor Mendel

The Y and R alleles andthe y and r alleles staytogether

This was not consistentwith Mendels results

Gregor Mendel

An alternative hypothesis is that the two alleles segregate independently of each other

Known as the law of independent assortment

The presence of one specific allele for one trait has no impact in the presence of a specific allele for the second trait.

Gregor Mendel

In our example, the F1 offspring would still produce yellow, round seeds. (YyRr)

However, when the F1s produced gametes, genes would be packaged into gametes with all possible allelic combinations.

Four classes of gametes (YR, Yr, yR, and yr) would be produced in equal amounts.

Gregor Mendel