Ch. 8 HeredityGLE 0707.4.3 Explain the relationship among

genes, chromosomes, and inherited traitsTB 234-240

What You’ll Learn…

• Explain how traits are inherited• Identify Mendel’s role in history of genetics• Use Punnett Squares to predict the results of the

crosses• Compare and contrast the difference between an

individual’s genotype and phenotype

Why You Need To Know It…• Heredity and genetics help explain why people

are different

I. Inheriting Traits1. Heredity – passing of traits from

parent to offspringA. What is Genetics?1. Genes on chromosomes control

organism’s form, function, and traits2. Different forms of traits that make

up a gene pair = alleles3. Meiosis = pair of chromosomes

separate, alleles also separate into different sex cells

4. Every sex cell has 1 allele for each trait

5. Study of how traits are inherited through interactions of alleles = science of genetics

II. Mendel: Father of Genetics1. Gregor Mendela. Austrian Monkb. 1865- studied pea plants to

predict possible types of flowers and fruits resulting from cross breeding

c. 1st to trace on trait through several generations

d. 1st to use math = probability to explain heredity

http://www.brainpop.com/science/cellularlifeandgenetics/heredity/

III. Genetics in a Garden1. Mendel studied specific traitsa. Crossed 2 plants with different expressions of that traitb. New plants all looked like one of the 2 parentsc. New plants called hybrids = received different genetic information (Diff. Alleles)

for a trait from each plant2. Organism that always produces the same trait generation to generation = purebredEX: Tall plants that always produce tall plants = purebred

A. Dominant and Recessive Factors1. Cross pollination- pollinate one trait with opposite traitEx: Purebred tall plants with purebred short plants2. Dominant Allele = trait that covers up/dominants other form of that traitEx: Tall gene covered short gene in plants3. Recessive Allele = trait that is covered by the dominant traithttp://www.brainpop.com/health/geneticsgrowthanddevelopment/genetics/

III. Genetics in a Garden

Dominant and Recessive Factors

B. Using Probability to Make Predictions1. Probability- math that helps you predict

the chance of something happeningEx: Coin toss – heads or tails – 50/50 chance2. Mendel worked with a large number of plants – helped make predictions more accurate. Also increased the chances of seeing a repeatable pattern3. Valid science conclusions need to be based on results

III. Genetics in a Garden

C. Punnett Squares1. Letters represent dominant and

recessive alleles2. Uppercase letter = dominant allele3. Lowercase letter = recessive letter4. Letter – A code (genotype) =

Genetic make-up5. The way an organism looks or

behaves is a result of genotype = phenotype

Ex: Brown hair = phenotype of hair color = brown

III. Genetics in a Garden

D. Alleles Determine Traits1. Most cells have 2 alleles for

every trait2. Alleles are located on

chromosomes in nucleus of the cell

3. Organism with the same 2 alleles = homozygous trait

EX: both tall alleles ( TT )4. Organism with that has 2 different traitsEX: 1 tall and 1 short ( Tt )5. Mendel produced heterozygous hybrids for height = Tt

III. Genetics in a Garden

E. Making a Punnett Square1. Letters representing 2 alleles

from 1 parent are written along the top of the grid

2. Those of the 2nd parent are placed down the side of the grid

(1 letter per section )3. Each square of the grid is filled with 1 allele donated by each parent 4. Letters represent genotypes of possible offspring that parents could produce

III. Genetics in a Garden

T

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F. Principles of Heredity1. Traits are controlled by alleles on chromosomes2. An allele’s effect is dominant or recessive3. When a pair of chromosomes separates during

meiosis, the different alleles for a trait move into separate sex cells

https://www.khanacademy.org/science/biology/heredity-and-genetics/v/punnett-square-fun

III. Genetics in a Garden