GeneticsChapter 7GeneticsChapter 7

Mr. FemiaBiology

Mr. FemiaBiology

Heredity

• Heredity – characteristics inherited from parents to offspring through genes

Genetics

• The study of genes and heredity

Traits

• Characteristics that are inherited through genes

Gregor Mendel

• A monk in the 1800s

• First to identify heredity

Garden Peas

• Studied the traits in garden peas– Tall/short– Round/wrinkled– Green/yellow pods– Purple/white

flowers

Background information

• Each trait or characteristic has 2 copies of DNA that code for that trait

• Each copy of the trait is called an allele

• Each organism has two copies of each allele

Conclusions

• Mendel had certain rules for heredity– Characteristic, unit

factor/gene/height– Two contrasting

traits/alleles/tall or short• Another example pod

color – green/yellow

The Rule of Dominance

• Alleles can be either dominant or recessive (strong or weak)– Dominant alleles are observable– Recessive alleles are not usually

observable, when the dominant allele is present

The Law of Segregation

• Alleles for a gene separate when forming a sperm and egg

Law of Independent assortment

• Alleles for different genes are distributed to sperm and egg independently

• Could be – tall and fat– Short and thin– Tall and thin– Short and fat

• Why all siblings do not look exactly alike

Dominant

• The allele that is expressed – you can see it

• Use the first letter of the word and capitalize it

• C curly hair• B brown hair

**Recessive**

• The allele that is not expressed• It is covered up by the dominant

allele• It is there you just cannot see it• Use the lower case for of the

dominant allele• c for straight hair• b blonde hair

Phenotype

• The way an organism physically looks– Brown hair, tall

Genotype

• The copies of alleles or genes that an organism has

• BB, Bb, bb/ TT, Tt, tt

Homozygous – (homo same)

• Pure• When an organism has 2 copies of

the same allele• BB – homozygous dominant• bb – homozygous recessive

Heterozygous (hetero means different)

• Hybrid• When an organism has 2 different

alleles for a gene• Bb, Gg etc.

Parent Generation P1

• The 2 organisms that are used to reproduce

F1 generation

• The offspring - babies

F2 generation

• The babies of the F1 or the grandchildren of the P1

Incomplete dominance

• There is no dominant alleleor recessive allele• The 2 alleles are blended and make up a new physical

appearance• Ex. A red allele and a white allele

can make a pink flower

Co dominance

• There is no dominant or recessive allele but both are expressed

• Ex: a chicken with white feathers mates with a chicken with black feathers and they have offspring with black

and white feathers

**Punnett Square**

• A way of organizing genetics so that scientist can determine the genotype of the offspring of 2 individuals

• If 2 plants have a baby – predict what it would look like!

Monohybrid

• One cross because you are looking at only one trait

Dihybrid

• Two crosses - you are looking at 2 traits

Pedigree

• A diagram representing a family tree

• The alleles that each person in the family has

Monohybrid Punnett Square Problems

• Height – tall is dominant to short• Symbol for tall _______• Symbol for short _____• Phenotype –

– Homozygous tall male X short female

• Genotype– Male _____ X Female ______

P1 Punnett Square

– F1 genotype ratio

– F1 phenotype ratio

Monohybrid Punnett Square Problems

• Height – tall is dominant to short• Symbol for tall _______• Symbol for short _____• Phenotype – • _______ male X _______ female• Genotype

– Male _____ X Female ______

F1 Punnett Square

– F2 genotype ratio

– F2 phenotype ratio