Genetics Chapter 7 Mr. Femia Biology Mr. Femia Biology
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 allele or 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