How to PREDICT offspring? Punnett squares How to PREDICT offspring?

Traits Your characteristics Can be PHYSICAL – how your body LOOKS eye color & hair color Can be PHYSIOLOGICAL – how your body WORKS cystic fibrosis, sickle cell anemia, diabetes

Alleles Different forms of a gene Think of the word OPTIONS!! Alleles for eye color Blue, brown, green, hazel, etc. Think of the word OPTIONS!!

Dominant t T The allele that SHOWS Written with a CAPITAL letter In pea plants, tall is DOMINANT over short T = Tall t = Short t T

Recessive The allele that is HIDDEN unless you get it from BOTH parents. Written with a lowercase letter If Yellow is dominant…what letters do we use? If Yellow is dominant…what letters do we use? Y – yellow y - green Y – yellow y - green If Round is dominant…what letters do we use? If Inflated is dominant…what letters do we use? R – round r - wrinkled I – inflated i - constricted

Homozygous/Pure Homo means SAME When both alleles are the SAME TT or tt

Heterozygous/Hybrid Hetero means DIFFERENT When both alleles are DIFFERENT Tt

If these two mice have different alleles…why do they look EXACTLY ALIKE? Because the dominant allele HIDES the recessive allele.

Phenotype PHenotype – PHysical features Use descriptive words ONLY!! Tall, short, yellow, green,etc. TT = tall tt = short Tt = _______ tall

Genotype Genetic make-up for a trait ‘Type-o-Genes’ To figure out genotype, ask 2 questions: Homozygous or Heterozygous? Dominant or Recessive? TT – Homozygous Dominant Tt – Heterozygous tt – Homozygous Recessive

Genotype Determines Phenotype

Punnett Square A tool used to PREDICT offspring outcome Shows the cross between two parents If a heterozygous tall plant is crossed with a short plant (Tall is dominant), what kind of offspring would be possible? Tt x tt T t t Genotype Phenotype Tt tt 2/4 Heterozygous 2/4 Tall Tt tt 2/4 Hom Recessive 2/4 Short

Punnett Square TT TT Tt Tt T t T T The letters on the OUTSIDE of the Punnett Square represent the SPERM and EGG of the parents P generation TT TT Tt Tt The letters on the INSIDE of the Punnett Square represent the OFFSPRING (Babies) F1 generation

Practice Problem Bb Bb Bb Bb In rabbits Brown fur is dominant to White fur. What would the offspring be when a Homozygous brown rabbit mates with a white rabbit? B = brown b = white BB x bb B B Genotype Phenotype Bb Bb b 4/4 Heterozygous 4/4 Brown Bb Bb

Practice Problem In Pea plants, tall plants are dominant over short plants. What would the offspring be if two hybrid pea plants pollinated?

Practice Problem In rose bushes, straight thorns are dominant over curved thorns. If a homozygous dominant straight-thorned rose bush pollinates a homozygous dominant curved-thorned rose bush what kind of thorns would their offspring have?

Practice Problem In rabbits, brown fur is dominant to white fur. If two white rabbits mate and have offspring with brown hair, what do we know about both parents? Show the Punnett square to prove your answer.

Practice Problem In beagles, white snouts are recessive to brown snouts. What would the offspring look like if a white snout beagle mates with a hybrid brown snout beagle?