Content Review: Nucleotides, DNA, genes, chromosomes, and codons are all terms used to describe our genetic information. Take each pair of terms and describe their relationship. Nucleotides and genes Genes and Chromosomes DNA and codons Chromosomes and DNA

Lesson 12: Single Gene Inheritance relate your understanding of genes and DNA to chromosomes; relate your understanding of alleles to Mendelian concepts of segregation and dominance; understand how meiosis leads to the production of haploid gametes; relate the outcome of meiosis to the establishment of Punnett squares; extend your understanding of genetics to include incomplete dominance (leaving pedigree analysis to Lesson 14)

What did we inherit from our parents? In organisms like humans, chromosomes come in matched pairs.

How do we refer to the GENES we inherited from our parents? Genes come in different forms, called alleles Example: A, B vs. O alleles for blood type HOMOZYGOUS for U gene UU HETEROZYGOUS for W gene Ww A B

How are chromosomes randomly passed on to offspring? 5.9 Matched chromosomes pair up Matched chromosomes separate Sex cells = gametes. Ours are HAPLOID

G Meiosis g G g G g G g

What happens after chromosomes are divided in meiosis? Haploid + Haploid = Diploid

Meiosis followed by fertilization G g G g You try it first G GgGggg GgGg

Take a minute to talk about probability G g G g What is the probability of getting Gg? GG? gg? 1/4

What did Mendel tell us about the inheritance of traits? Crossed peas for seven contrasting characteristics Looked at offspring and “grand” offspring Carefully, mathematically, analyzed the data CONCLUSION Traits are controlled by factors (alleles) that come in pairs

What else did Mendel tell us about the inheritance of traits?

How are phenotype and genotype related? Flower color is the phenotype (appearance) Pp is the genotype (makeup of alleles) PP pp PpPp P P p p Pp

Punnett squares predict offspring from parents genotypes Pp P p Parent’s haploid gametes PpPp PpPp PpPpPpPp PP pp Diploid progeny

If I cross Pp purple by the white parent, what kinds of “kids” will I see? Try it! Pp x pp p p p p P PpPp PpPp pp

Do you know any human single gene traits? Check your partner’s phenotype for these traits. Can you determine their genotype?

First Thing Mendel Didn’t Know Two doses of “R” allele – very red One dose of “R” allele – pink No doses of “R” allele - white RR Rr rr

Mendel would have been surprised! RR Rr rr “R” vs. “r” now refers to whether or not allele makes a protein, and “contributes” to phenotype “R” is contributing “r” is non-contributing

You mate two pink snapdragons. ____ is the proportion of red offspring from this trait that shows ________________. Try it!

Try another one! A gene called “Insulin-like growth factor” (I) controls size in dogs. A Great Dane is homozygous for the I allele, whereas a toy poodle is homozygous for the “i” allele. A mating between the two gives a middle sized dog. Assume there is only this one gene that influences size and determine what sizes (and in what proportion) would be seen if the Great Dane mated with the middle-sized GreatOodle.

C1 = Curly hair C2 = straight hair Can you think of any traits in humans controlled by incomplete dominance? Try it! Cross two heterozygous parents.

Another example: not just ONE ethanol- response gene: ADH ALDH GOOD ADH function = contributing allele GOOD ADH function = Increased dosage desired GOOD ALDH function = contributing allele GOOD ALDH function = Few side effects

With SOME Alcohol response genes ADH ALDH Alcohol dehydrogenase Aldehyde dehydrogenase Therefore, if ALDH works poorly, aldehyde builds up. Drinker Feels more sick.

How to designate alleles for incompletely dominant traits? Rapid metabolism of aldehyde Slow metabolism of aldehyde ALDH2*2 alleleALDH2*1 allele Why not “A” vs. “a”? “Brain Storm” by alexiuus.deviantart.com

SNPs and alcoholism PMID: Very low frequency of ALDH2*2 allele Mongolian Chinese Somewhat higher frequency of ALDH2*2 allele Han Chinese Rapid metabolism of aldehyde Slow metabolism of aldehyde PROTECTS from ethanol abuse