genetics punnett squares and mendel. copyright pearson prentice hall genes and dominance mendel’s...
Post on 17-Dec-2015
249 Views
Preview:
TRANSCRIPT
S
GeneticsPunnett Squares and Mendel
Copyright Pearson Prentice Hall
Genes and DominanceMendel’s F1 Crosses on Pea Plants
Copyright Pearson Prentice Hall
Genes and DominanceMendel’s Seven F1 Crosses on Pea PlantsMendel’s F1 Crosses on Pea Plants
Copyright Pearson Prentice Hall
Genes and Dominance
What is the principle of dominance?
Copyright Pearson Prentice Hall
Genes and Dominance
The principle of dominance states that some alleles are dominant and others are recessive.
Copyright Pearson Prentice Hall
Mendel's F2 Generation
P GenerationF1 Generation
Tall Tall Tall Tall Tall TallShort Short
F2 Generation
Segregation
Copyright Pearson Prentice Hall
Segregation
The reappearance of the trait controlled by the recessive allele indicated that at some point the allele for shortness had been separated, or segregated, from the allele for tallness.
Copyright Pearson Prentice Hall
Segregation Alleles separate during gamete formation.
Copyright Pearson Prentice Hall
Punnett Squares
How do geneticists use Punnett squares?
Copyright Pearson Prentice Hall
A capital letter represents the dominant allele for tall.
A lowercase letter represents the recessive allele for short.
In this example,
T = tall
t = short
Punnett Squares
Copyright Pearson Prentice Hall
Punnett Squares
Possible gene combinations for the F2 offspring appear in the four boxes.
Copyright Pearson Prentice Hall
Punnett Squares
Organisms that have two identical alleles for a particular trait are said to be homozygous.
Organisms that have two different alleles for the same trait are heterozygous.
Homozygous organisms are true-breeding for a particular trait.
Heterozygous organisms are hybrid for a particular trait.
Copyright Pearson Prentice Hall
Punnett Squares
All of the tall plants have the same phenotype, or physical characteristics. (What it LOOKS like)
The tall plants do not have the same genotype, or genetic makeup.(The alleles that make up the characteristics)
Copyright Pearson Prentice Hall
Punnett Squares
The plants have different genotypes (TT and Tt), but they have the same phenotype (tall).
TTHomozygous
TtHeterozygous
Copyright Pearson Prentice Hall
Probability and
Segregation
Probability and Segregation
One fourth (1/4) of the F2 plants have two alleles for tallness (TT).
2/4 or 1/2 have one allele for tall (T), and one for short (t).
One fourth (1/4) of the F2 have two alleles for short (tt).
top related