Ch. 12 Genetics

Essential QuestionEssential Question

What controls the inheritance of traits in

organisms?

A. Gregor Mendel (1822-1884) – The father of

Genetics Mendel discovered the

basic principles of heredity by breeding garden peas in carefully planned experiments.

Mendel defined different types of hybridization

1. P generation – parental; true breeding parents

2. F1 generation – 1st generation of offspring3. F2 generation – 2nd generation

of offspring

TraitTrait Dominant Dominant ExpressionExpression

Recessive Recessive ExpressionExpression

Form of ripe seed Form of ripe seed (R)(R)

SmoothSmooth WrinkledWrinkled

Color of seed Color of seed albumen (Y)albumen (Y)

YellowYellow GreenGreen

Color of flower (P)Color of flower (P) PurplePurple WhiteWhite

Form of ripe pods Form of ripe pods (I)(I)

InflatedInflated ConstrictedConstricted

Principles of genetics

Traits are handed down from one Traits are handed down from one generation to the nextgeneration to the next

Traits are controlled by genesGenes are inherited in pairs, one

from each parent

Some genes are dominant some are recessive

Dominant genes can mask recessive genes when one of each is inherited

Some genes are not dominant or recessive but blend when inherited together

B. Genetic Vocabulary1. Chromosomes: hereditary units of an organism

2. Allele – One gene of gene pair for a trait.

for example: In the gene pair Bb for hair, color both B & b are alleles

3. Homozygous – pair of identical alleles for a character

BB = Brown

4. Heterozygous – having 2 different alleles for a character.

5. Haploid = contains one copy of each chromosome (meiosis)

6. Diploid = contains two copies of each chromosome (mitosis)

Bb = Brown

7. Genotype – an organism’s genetic makeup.

BB or Bb

8. Phenotype – an organism’s outward appearance.

9. Mutations: changes in genetic material

Brown eyes

10. Karyotype: an enlarged photograph of the chromosomes in an organism

Above is a karyotype of a normal human male.

11. Multiple alleles - when more than 2 alleles control a trait. Example human blood. A dominant, B dominant, O recessive

Phenotype ( blood group) Genotype

A AA or Ao

B BB or Bo

AB AB or ABo

o oo

12. Sex linked traits - gene for a trait is carried on one of the sex chromosomes. example color blindness, hemophilia

XX- Female XY - Male13. Meiosis - production of gametes

(sperm or egg cells) which contain half the normal number of chromosomes

C. Ways to determine inherited traits - Predicting

traits1. Punnett square – a square used to

show all the possible combinations of gametes.

A homozygous brown–eyed mother mates with a blue – eyed father. What ratio of brown–eyed to blue–eyed children will they have?

Brown eyes is the dominant trait

B- brown eyes b- blue eyes BB x bb

B B

b

b

genotypic ratio is:

phenotypic ratio is:

Bb

Bb Bb

Bb

100 % Bb

100 % Brown

b

b

B

B

BB Bb

Bb bb

2. Determining parental genotypes

Pedigree Test – Test in which you look at the offspring of parents to determine the genotypes of the parents.

The squares are for males and the circles are for females.

If the symbol has been darkened it says the person carries the trait.