Warm up One cat carries heterozygous longhaired traits

Warm up: • One cat carries heterozygous, long-haired traits (Ss), and its mate carries homozygous short-haired traits (ss). Use a Punnett square to determine the probability of one of their offspring having long hair. – A. 25% – B. 50% – C. 75% – D. 100%

Practice 2: • In pea plants, spherical seeds (S) are dominant to dented seeds (s). In a genetic cross of two plants that are heterozygous for the seed shape trait, what fraction of the offspring should have spherical seeds? –¼ –½ –¾ – 4/4

Practice 3 • A white flowered plant is crossed with a plant that is heterozygous for the trait. Purple is dominant to white. What is the phenotypic ratio? – A. 2: 2 – B. 3: 1 – C. 1: 3 – D. 4: 0

Practice: • A homozygous red cow (R) is crossed with a purebred white cow (r). Draw a Punnett Square depicting this cross, and write down the genotypic and phenotypic ratios resulting form this cross.

This is actually the phenotype for heterozygous roan cows!

Alternative Patterns of Inheritance • Not every trait works out perfectly-that is, one trait is dominant, one recessive • Exceptions to Mendel’s principles (one dominant, one recessive)

Co-dominance • Pattern of inheritance where both alleles are dominant and therefore both phenotypes are expressed – Usually shown by two capital letters – Example: roan cows, chicken feathers

Ex. 1 • Cross two roan cows and give the phenotypic and genotypic ratios

Co dominance Practice: • In a certain fish, blue scales and red scales are codominant. When a fish has the genotype BR, it has a patchwork of blue and red scales. What happens if you breed this fish with a fish that only has Blue Scales.

Incomplete Dominance • Incomplete dominance-one allele is dominant to another only to a certain extent, so it can’t completely express its phenotype – This results in phenotypes that are intermediate – Example: snap dragons:

Incomplete Dominance Practice: • Cross one white and one pink snapdragon. Give phenotypic and genotypic ratios. • Cross two heterozygous snapdragons.

Multiple alleles • When there are more than two forms of one gene • Ex: Blood type, A B and O forms Note-this is also an example of what type of inheritance?

Multiple Alleles practice: • Give the phenotypic and genotypic ratios of the offspring a parent who is heterozygous for type A and heterozygous for type B • Mom has type O blood. Dad has type AB blood. What percentage of their kids will inherit type B blood?

Sex Linked Traits • Humans have 23 pairs of chromosomes • One of your 23 pairs are your sex chromosomes – Females: have XX – Males: have XY Karyotype

Sex linked Traits • Genes carried on X Chromosome – Females have two alleles – Males only have one allele (y doesn’t have much) • Ex. Blood clotting factor (XH) found on X chromosome, individuals with defective allele for blood clotting factor (Xh) have hemophilia

Ex. 1 • Cross a female who is heterozygous with a male who is normal • Carrier-Does not display disease but carries defective allele (heterozygous) – What is chance the female offspring will be carriers? – What is the chance they will have a male with hemophilia? – Can males ever be carriers for sex-linked disorders? – Who is more likely to have a sex-linked disorder?

Ex. 2 • Colorblindness is a recessive X-linked disorder. Cross a mom who is a carrier with a dad who is colorblind. • What is the likelihood they will have a child who is color blind? • What is the chance the male children will have normal vision?

Polygenic traits • When a trait is controlled by more than one gene • Results in spectrum of phenotypes • For example eyecolor-look around – Not just blue, green, brown, varying degrees Eye color

Genes and the environment • Environment can influence expression of genes – Genes contain information, environment can determine how much of that information is expressed – Example: Western white butterflies, Siamese cats

Closure: • Go back to warm up problem. Using what you learned about co-dominance, fix your genotypic and phenotypic ratios-hand into me before you leave

Alien Genetics • You are to create your own species of Alien. For your alien, you must create 3 traits – One trait must show normal dominant/recessive relationships – One must be co dominant – One must be incompletely dominant • Cross two purebred individuals showing the different forms of these characteristics and the resulting hybrid offspring – Draw a Punnett square for each cross – Draw each organism, showing the traits