More Beginning Genetics Review Go Over Zork Worksheet Notes: Mendel the Monk took a Pea… 5 th Period: recount your traits

3 Gregor Mendel ( ) Responsible for the Laws governing Inheritance of Traits copyright cmassengale

4 Gregor Johann Mendel  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century copyright cmassengale

5 Gregor Johann Mendel  Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants  He found that the plants' offspring retained traits of the parents  Called the “Father of Genetics" copyright cmassengale

6 Genetics Vocabulary  Trait - any characteristic that can be passed from parent to offspring  Heredity - passing of traits from parent to offspring  Genetics - study of heredity copyright cmassengale

A pea plant that always produced seeds that grew into short plants A pea plant that always produced seeds that grew into tall plants This cross always produced tall pea plants The offspring were ¾ tall and ¼ short When you crossed two of these plants

Mendel’s Ideas Something in the pollen and egg of the pea plant determines (decides) the height of the plant – we call this a gene. The gene for pea plant height can be one of two types: Tall or short. We call these alleles. Alleles are the forms that a gene can take. (some traits can have more than 2 alleles.) One of the traits always shows up if its allele is present. This is the dominant allele. A trait that is masked if the dominant allele is present is called the recessive allele.

Because plants use sexual reproduction… Each gene has two copies in each plant Where do these two copies come from? – One from the pollen (male) – One from the egg (female) So a tall plant can be TT or Tt (Humans also get one copy of a gene from each parent.)

Genes have “grammar rules” Dominant = shown as a capital letter. – (Tall plants = dominant = T) Recessive = shown as lower case (but use the same letter as the dominant allele) – (Short plants = recessive = t)

Many human traits are caused by the same simple genetic patterns as Mendel’s Peas Eye color for example Brown eyes are dominant = B Blue eyes are recessive = b A person with blue eyes = bb A person with brown eyes could be Bb or BB Note: there are actually two genes for eye color and 4 possible alleles – more on that later.

MORE vocabulary: If a person has two of the same genes like BB or bb they are called HOMOZYGOUS (homo = same) Two dominant (BB) = HOMOZYGOUS DOMINANT Two recessive (bb) = HOMOZYGOUS RECESSIVE If a person has one dominant and one recessive, (Bb) they are called HETEROZYGOUS (hetero = different)

How to Keep Track of Alleles… Use a Punnett Square What could be the possible phenotypes of the offspring if we cross – a pea plant that is heterozygous for seed pod color with one that is homozygous dominant? Possible pollen and egg Pod color Green is dominant (G) Yellow is recessive (g) Homozygous Dominant = GG (has green seed pods) Heterozygous = Gg (also has green seed pods) G G G g GG G G G g G g ALL OFFSPRING HAVE? GREEN SEED PODS

What if we crossed Possible pollen and egg Heterozygous = Gg (has green seed pods) Heterozygous = Gg (also has green seed pods) G g G g GG G g G g g g

Possible pollen and egg Homozygous recessive = gg (has yellow seed pods) Heterozygous = Gg (also has green seed pods) g g G g Gg G g g g g g