Genes traits and this guy named Mendel Biology

Genes, traits, and this guy named Mendel Biology Mr. D

Meiosis n Before meiosis begins, the cell has __ chromosomes or two sets of __ – 46 chromosomes – 2 sets of 23 n So, let us take for example, chromosome 5 codes for hair color n How many copies of chromosome 5 do we have? – 2

Meiosis n Where did we get each chromosome? – One from our mom – One from our dad Let’s pretend Chromosome 5 has the gene for hair color n Let’s say that your mom blonde hair and your dad has brown hair n If I tell you that allele means different form of a gene, how many forms of hair color could you have? n – 2

Genes n n Let’s say your dad’s side of the family all have brown hair. Also, let’s say that all your mom’s side has blonde hair. Therefore, your parent’s hair color is purebred (only one color ever appears in their family) What will the hair color be when they have a child? – The child ends up with brown hair. So, which allele (different form of a gene) is dominant? – Which is recessive?

Genes n Now we know which allele for hair color is dominant (brown) and which is recessive (blonde). n Dominant alleles are capital letters like “H” n Recessive alleles are small letters like “h” n How many forms of a gene do we have for each trait (ex. hair color)? n What are some possible combinations?

Different combinations n Homozygous – genotype of identical alleles, ex. HH or hh n Heterozygous – genotype of different alleles, ex. Hh n So, how can we figure out the traits passed on to each generation (heredity)? n Now we can talk about Punnett squares

Gregor Mendel n n Monastery of St. Thomas, Brno, Czech Republic. Taught physics and natural science. Performed experiments 18561868, published in 1866. Used pea plants

How Mendel performed his crosses with pea plants

Fig. 8. 5

Gregor Mendel “I like to pea…I mean I like pea plants” n Why peas? – Easy to grow – Self-fertilize or can hybridize artificially – Matures quickly – Contrasting traits are easy to see n

Mendel’s Laws n Law of dominance – Some alleles (variation) are dominant over other alleles n Law of segregation – Each gamete gets one copy of the gene n Law of independent assortment – Each trait separates independently during formation of gametes

Mendel’s 7 traits 1. 2. 3. 4. 5. 6. 7.

Probability n Sometimes we want to know how often something will occur n What is the chance of getting tails when you flip a coin? n How about 2 tails in a row? n For example

Probability and punnett squares n Punnett squares can help us determine genetic crosses

Punnett square Predicts possible offsprings n Capital letter = dominant allele (ex. “H”) n Lower case letter = recessive allele (ex. “h”) n Same letter used for dominant/recessive n – HH, not HM, HL and so on n Expressed traits called phenotype – What you see/observe n Genetic makeup = genotype – The type of alleles

O. J. Simpson capital murder case, 1/95 -9/95 • • Odds of blood in Ford Bronco not being R. Goldman’s: • 6. 5 billion to 1 • Odds of blood on socks in bedroom not being N. Brown-Simpson’s: • 8. 5 billion to 1 Odds of blood on glove not being from R. Goldman, N. Brown-Simpson, and O. J. Simpson: • 21. 5 billion to 1 • Number of people on planet earth: • 6. 1 billion • Odds of being struck by lightning in the U. S. : • 2. 8 million to 1 • Odds of winning the Illinois Big Game lottery: • 76 million to 1 • Odds of getting killed driving to the gas station to buy a lottery ticket • 4. 5 million to 1 • Odds of seeing 3 albino deer at the same time: • 85 million to 1 • Odds of having quintuplets: • 85 million to 1 • Odds of being struck by a meteorite: • 10 trillion to 1

Punnett Square n n n This is a simple Punnett square. It looks like a window pane You put the alleles on the outside P 1 and F 1 generations It helps us figure out what offspring we get §H nh nh H

Cross the following n Count the number of genotypes and phenotypes – HH x hh – HH x Hh – Hh x Hh – Rr x Rr – Cross a heterozygous brown haired male with a homozygous recessive blonde female