Genetics & heredity Chapters 9.1 & 9.2

Remember… If it is in RED it goes in your notes If it is in BLACK it is important, so pay attention

Keep an eye out for HOOTIE!! If you see him RAISE YOUR HAND!! You will receive 5 ROCKS cards IF you are correct HINT: He won’t be this big :)

Mendel What did Mendel study? Pea plant genetics

He found that the plants had offspring. What does Purebred mean? Mendel He found that the plants had offspring. What does Purebred mean? Many generations have same traits without a change. EX. TT or tt

What does hybrid mean? There have been changes over the generations Mendel What does hybrid mean? There have been changes over the generations Ex. Tt or Pp or Bb

Alleles Alleles are the different forms of genes TYPES Dominant-ALWAYS SHOWS THROUGH. Labeled with a capital letter Recessive-HIDDEN traits. Labeled with a lower case letter.

Pp Dominant Allele Recessive Allele

What trait will show through in this T-Pink t-Blue What trait will show through in this example? TT Pink

What trait will show through in this T-Pink t-Blue What trait will show through in this example? Tt Pink

What trait will show through in this T-Pink t-Blue What trait will show through in this example? tt Blue

Is the purebred or Hybrid? T-Pink t-Blue Is the purebred or Hybrid? TT Pure

Is the purebred or Hybrid? T-Pink t-Blue Is the purebred or Hybrid? Hybrid Tt

Is the purebred or Hybrid? T-Pink t-Blue Is the purebred or Hybrid? tt Pure

Definitions Genotype- the genes of an organism for one specific trait Phenotype- the physical appearance of a trait in an organism

Heterozygous= two different alleles for a trait (Hybrid) HUGE TO KNOW!!!! Homozygous= two alleles that are the same for a trait (Pure) EX. TT, tt, BB or bb Heterozygous= two different alleles for a trait (Hybrid) EX. Tt, Bb

HINT::::: HETEROZYGOUS ALWAYS MEAN DOMINANT!!!!!!!!!!!!!

Practice We use two letters to represent the genotype. A capital letter represents the dominant form of a gene (allele) lowercase letter represents a recessive form of the gene (allele). Example below: P=dominant purple and p= recessive white The phenotype for this flower is violet while its genotype (if homozygous) is PP. The phenotype for this flower is white while its genotype is pp (to be white the flower must have two of the recessive copies of the allele).

Punnett Squares The Punnett square is the standard way of working out what the possible offspring of two parents will be. It is a helpful tool to show allelic combinations and predict offspring ratios.

Before we go further lets review how to set up a Punnett Square… We begin by constructing a grid of two perpendicular lines.

B B b For this example lets consider a genotype of BB crossed with bb. Next, put the genotype of one parent across the top and the other along the left side. For this example lets consider a genotype of BB crossed with bb. B B b Notice only one letter goes above each box It does not matter which parent’s genotype goes on either side.

Next, fill in the boxes by copying the column and row head-letters down and across into the empty spaces. B B b B b B b b B b B b

Punnett Squares Now that we have learned the basics of genetics lets walk through some examples using Punnett Squares.

W w W w W W W w W w w w Cross 2 parents are heterozygous (Ww). Usually write the capital letter first W w W W W w Lets say: W- dominant white w- recessive violet W w w w Cross 2 parents are heterozygous (Ww). What percentage of the offspring will have violet flowers? ANSWER: 25% (homozygous recessive)

Red hair (R) is dominant over blond hair (r) Red hair (R) is dominant over blond hair (r). Make a cross between a heterozygous red head and a blond. r R r r R r r r r What percentage of the offspring will have red hair? 50%

T t t t t t T t t What are the percentage of phenotypes? 50% tall Let’s try some more… In pea plants, tall pea plants (T) are dominant over short pea plants (t). Construct a Punnett Cross a heterozygous tall pea plant and a short pea plant. T t What are the percentage of phenotypes? T t t t t 50% tall 50% short t t

Black eyes (R) is dominant over red eyes (r) in rats Black eyes (R) is dominant over red eyes (r) in rats. Make a cross between a homozygous rat with black eyes and a rat with red eyes. R R What is the possibility of a red eye off springs? Rr r Discuss with students other possible answers 0% 

Classwork: Let’s try this together