Gregor Mendels Peas Gregor Mendels Peas Genetics is

Gregor Mendel’s Peas • Gregor Mendel’s Peas – Genetics is the scientific study of heredity. • Gregor Mendel was an Austrian monk. • Mendel studied garden peas

Gregor Mendel’s Peas –Mendel knew that – the male part of each flower produces pollen, (containing sperm). – the female part of the flower produces egg cells. – Together they make a new plant

Gregor Mendel’s Peas • Pea flowers are self-pollinating. (Pollen can fertilize the flower it was made on) • Self-pollination results in the offspring getting all its DNA from 1 organism.

Gregor Mendel’s Peas • Mendel used True-Breeding Pea plants – Plants that were homozygous for a trait • To prevent Self pollination- Mendel removed either the male or the female parts from each flower.

Gregor Mendel’s Peas • Mendel took a brush and crosspollinated the flowers by hand! • Mendel was able to produce seeds that had two different parents.

Genes and Dominance • Genes and Dominance – A trait is a specific characteristic that varies from one individual to another.

Genes and Dominance • Each original pair of plants is the P (parental) generation. • The offspring are called the F 1, or “first filial, ” generation. • The offspring of crosses between parents with different traits are called hybrids. • The F 1 hybrid plants all had the character of only one of the parents.

Genes and Dominance • Mendel studied seven pea plant traits, each with two contrasting characters. • He crossed plants with each of the seven contrasting characters and studied their offspring.

Genes and Dominance Mendel’s F 1 Crosses on Pea Plants

Genes and Dominance Mendel’s Seven F 1 Crosses on Pea Plants Mendel’s F 1 Crosses on Pea Plants

Genes and Dominance • Mendel's first conclusion was that biological inheritance is determined by factors that are passed from one generation to the next. • We call these factors GENES

Genes and Dominance • Mendel luckily chose traits controlled by a single gene with different forms. • The different forms of a gene are called alleles(ah-le-eels).

GENOTYPE vs PHENOTYPE • GENOTYPE – are the actual DNA coded genes or instructions that make you. • PHENOTYPE – The express or what the genotype looks like in the physical world. For short – What you look like.

Genes and Dominance – The principle of dominance states that some alleles are dominant and others are recessive.

Genes and Dominance • Dominant alleles – Only need one for this form to show in the phenotype Possible Genotype – (DD or Dr) • Recessive – Need two alleles for this one to show in the phenotype Possible Genotype– (rr)

Segregation • Segregation – Mendel crossed the F 1 generation with itself to produce the F 2 (second filial) generation. – The traits controlled by recessive alleles reappeared in one fourth of the F 2 plants.

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.

Segregation • During the formation of GAMETES (sex cells) – Alleles are separated (segregated) into different resulting daughter cells.

Segregation • Alleles separate during gamete formation.

Using a Punnett Square

What is a PUNNETT SQUARE? • A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine • A way to show phenotype & genotype • A chart that shows all the possible combinations of alleles that can result when genes are crossed

What is a PUNNETT SQUARE? • Letters stand for dominant and recessive alleles • An uppercase letter stands for a dominant allele • Lowercase letters stand for recessive alleles

Using a PUNNETT SQUARE To set up a Punnett square, draw a large square, and then divide it into 4 equal sections (also squares). It should look something like this:

Using a PUNNETT SQUARE Now you need two parents to mate, ones with a known genotype For example, a red flower (genotype Rr) and a white flower (genotype rr). Rr x rr

Using a PUNNETT SQUARE Place one of the parents on top, and one on the left. You should get a something similar to this:

Using a PUNNETT SQUARE Finally, take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this:

Using a PUNNETT SQUARE • The two-letter combinations are the possible genotypes of offspring • They are: Rr, rr, and rr genotypes • From this it is possible to determine the probability (chance) that a flower will have a red phenotype (2/4 or 50%) or a white phenotype (2/4 or 50%)