Mendel’s Discovery L.O: To be able to explain Mendel’s experiments and why he is called the father of genetics Starter: inheriting gender sheet

What does this picture show?

Boy or Girl? XY X XXXY GirlBoy “Allele”

Each chromosome may have a different version of a gene. Different versions of a gene, that code for different versions of a characteristic, are called alleles. The chromosomes in a matching pair contain the same type of genes that code for the same characteristics. Different versions of genes version for yellow petals version for red petals gene for petal colour gene for petal colour

Pairs of alleles – homozygous If the alleles in a matching pair are the same, they are called homozygous alleles. allele for yellow petals allele for yellow petals allele for red petals allele for red petals What colour are the flowers with these homozygous pairs of alleles? (Click twice on each bud to reveal the flower; click again to close them.)

Pairs of alleles – heterozygous If the alleles in a matching pair are different, they are called heterozygous alleles. Which characteristic is expressed if alleles are different? allele for yellow petals allele for red petals Some alleles are dominant to other forms of a gene and will always be expressed. Which is the dominant allele in this heterozygous pair? Which is the recessive allele in this heterozygous pair? (Click twice on the bud to reveal the flower; click again to close it.)

Modern Genetics Guten tag! My name is Gregor Mendel. I am the father of modern genetics because of the work I did on pea plants in 1865… Take two plants; one which is pure-bred for tallness and one pure-bred for shortness, and cross them: X Mendel’s experiment:

Modern Genetics All the plants produced were tall. Now cross two of these plants… 3 out of every 4 plants were tall, leading Mendel to hypothesise that “for every characteristic there must be two determiners”

Modern Genetics My Conclusions: Plant characteristics are determined by hereditary units One hereditary unit comes from each parent Hereditary units can be dominant or recessive, they never mix.

Modern Genetics Achtung! Unfortunately, nobody knew about chromosomes or genes when I published my findings so no one believed me until after my death, when more powerful microscopes were available.

Each chromosome may have a different version of a gene. Different versions of a gene, that code for different versions of a characteristic, are called alleles. The chromosomes in a matching pair contain the same type of genes that code for the same characteristics. Different versions of genes version for yellow petals version for red petals gene for petal colour gene for petal colour

Pairs of alleles – homozygous If the alleles in a matching pair are the same, they are called homozygous alleles. allele for yellow petals allele for yellow petals allele for red petals allele for red petals What colour are the flowers with these homozygous pairs of alleles? (Click twice on each bud to reveal the flower; click again to close them.)

Pairs of alleles – heterozygous If the alleles in a matching pair are different, they are called heterozygous alleles. Which characteristic is expressed if alleles are different? allele for yellow petals allele for red petals Some alleles are dominant to other forms of a gene and will always be expressed. Which is the dominant allele in this heterozygous pair? Which is the recessive allele in this heterozygous pair? (Click twice on the bud to reveal the flower; click again to close it.)

To Do:  Read through the information on Mendel and answer the questions

Key words Gamete Zygote Allele Dominant Recessive Homozygous Heterozygous This allele determines the development of a characteristic This is formed when an egg is fertilised by a sperm This allele will determine a characteristic only if there are no dominant ones This word refers to a pair of chromosomes being made of two different alleles of a gene An egg or a sperm are called this This word refers to a pair of chromosomes being made of two of the same alleles of a gene An alternative form of a gene