Mendelian Genetics

VOCABULARY Genetics: _______________________________ Heredity: the passing on of characteristics (traits) from parents to offspring Genes: chemical factors that determine traits located on chromosomes, they control how an organism develops Alleles: different forms of the same gene (AA,Aa,aa) Traits: specific characteristics that varies from one individual to another; EX: seed color and height _______________: the uniting of male and female gametes (sperm and egg) Cross: combining gametes from parents with different traits

___________________ + = + = Male Zygote Female Zygote Autosome: chromosomes that are not sex chromosomes + = 22 + Y 22 + X 44 + XY Male Zygote + = 22 + X 22 + X 44 + XX Female Zygote

Gregor Mendel Mendel (1822): crossed pea plants to study the inheritance of traits. ________________________ Why did Mendel use pea plants? They reproduce sexually They have two distinct, male and female, sex cells called gametes Their traits are easily to isolate

Mendel Cont. Mendel crossed (fertilized) the pea plants and studied the results Mendel concluded 2 things: Inheritance is determined by factors that are passed from one generation to the next __________________________________

Phenotype and Genotype Phenotype: They way an organism looks EX: red hair, brown hair, short, tall Genotype: the gene combination of an organism EX: AA or Aa or aa

Principle of Dominance Dominant Trait: the trait that is expressed traits always appear; uppercase letter (A) Recessive Trait: the trait that is unexpressed traits that dissappear; lowercase letter (a) for a recessive trait to appear, both parents must give the recessive allele Homozygous: The two alleles for a trait is the same; EX: (AA or aa) Heterozygous: The two alleles for a trait is different; EX: (Aa)

Solving Crosses ____________ = A (AA or Aa) Recessive = a (aa) Solve crosses using Punnett Square Punnett Square: diagram used to determine the probability of an offspring having a particular genotype Does not show what the offspring will be. Answer questions based on results from the Punnett Square _______ _______ _______ _______

Monohybrid Crosses Monohybrid Cross: Cross that involves one pair of contrasting traits. Ex: hair color ______________________________ Sample problems: Red hair (R)is dominant to white hair (r) RR x rr → red hair x white hair Rr x rr → red hair x white hair Rr x Rr → red hair x red hair Rr x RR → red hair x red hair

Sample Problems R r 1. R R 2. r r Rr Rr r r Rr Rr 4. R r R r 3. R R R _________ _________ _________ _________ r r Rr Rr _______ _______ r r Rr Rr _______ _______ 4. R r R r 3. _________ _________ _________ _________ R R _______ _______ R r _______ _______

Sample Question Short hair (L) is dominant to long hair (l) in mice. What is the genotype and phenotype ratio of a heterozygous short-haired mouse crossed with a long-haired mouse?

Sample Answer Short hair = dominant = L (LL or Ll) long hair = recssive = l (ll) Ll x ll (heterozygote parent = Ll) Punnett Square: Genotype ratio: _______________________ Phenotype ratio: ______________________ Ll x ll L l