1 Dividing & Delivering Distributing genetic information How?Why? Lab 7

Windows on the gene: eyes Find a brown- and a blue-eyed person. Look deep into their eyes & try to figure out the difference What does it mean genetically when we say ‘brown eyes are dominant’? – One gene, two alleles Why should that be so? What do brown alleles got that blue do not?

‘Ripped’ from Headlines Blue eyes arise from a DNA change that prevents creation of melanin in the eye specifically Mutation appears identical in all blue-eyed folks Headline: Blue eyes result of ancient genetic ‘mutation’ Headline – It’s not a ‘mutation’; it’s a mutation Meaning?

4 Blinding you with Science (jargon) KNOW THESE Gene: A stretch of DNA that represents all the information for a product as well as when and where to make the product Allele: A version (or flavor) of a gene; two alleles of the same gene my differ by a nucleotide or dozens of them- -generally a small number Dominant/recessive: Two alleles enter; one allele leaves (which version manifests in the organism) – NOT which version is more common! More in the lab manual & Vocab exercises!

5 Scaling A gene is ~1, ,000 basepairs* A chromosome is tens or hundreds of thousands of genes A genome is 1-100s of chromosomes A genotype refers to the alleles present in a given genome A human genome is ~3,000,000,000 basepairs A human genome is (currently guesstimated at) ~20-30,000 genes** A human genome is ~1 meter of DNA *Includes control regions & stuff that won’t make it into the final product **We keep finding stuff that matters

Genes are on chromosomes (chromosomes are bunched up DNA) Alleles are different “flavors” of genes There are two alleles for each gene

Mitosis and Cell Division Goals: - Scaling: Nucleotide, Gene, Chromosome--and how many of each Differences between mitosis and meiosis - Predict and describe meiotic results - Master concepts referred to by: allele, dominant, recessive, linkage

It’s all in a name Chromosome Gene Chromatid Allele Homologous Dominant Recessive Spindle Fiber Centromere

1 “Chromatid” can also be a chromosome; it has all the genes on it.

1 “Chromatid” can also be a chromosome; it has all the genes on it.

1 “Chromatid” can also be a chromosome; it has all the genes on it. This

1 “Chromatid” can also be a chromosome; it has all the genes on it. This Is just a copy of this

So, in this scenario…

From Mother Chromosome 1 Chrm 2

From Mother Chromosome 1 Chrm 2 From Father Chromosome 1 Chrm 2

This is a DIPLOID Nucleus/Cell

Chromosome 1 (from mother) Chromosome 1 (from father)

Chromosome 1 (from mother) Chromosome 1 (from father) Copied during Interphase Copied during Interphase

Chromosome 1 (from mother) Chromosome 1 (from father) Copied during Interphase Copied during Interphase

So after replication…

Chromosome 1 (from mother) Chromosome 1 (from father) Condensed versions during mitosis/meiosis Chrm 2

This is a DIPLOID Nucleus/Cell

This is ALSO a diploid nucleus/cell

Mitosis and Cell Division Why are chromosomes usually shown like this?

25 Touching mitosis & meiosis

26 Your brain: A lousy place to think You can do a lot of fuzzy math (and fuzzy biology and fuzzy chemistry and fuzzy...) up there Drawing/speaking/writing forces precision; reveals missing bridges

Mitosis and Cell Division You run a cake-making company Order comes in for a cake What information do you need? – It’s ‘old-fashioned’- no photos

28 Symbolism String of beads = chromosome = double-stranded DNA bead = gene Pay close attention to the nipples! Every group gets two long (maternal & paternal version of chromosome I) and two short (maternal & paternal chromosome II). each bead is a GENE--i.e. thousands of nucleotides. The ‘oddball’ beads highlight separate alleles

Mitosis and Cell Division What comes after MITOSIS?

Clear your mind Go outside & take a lap around the floor Do I look like I’m kidding? Ok, lets watch a youtube video of people getting hit in the nuts… Its relavent-ish. Ch-oIX8

35 Genotype, phenotype Pick two traits Pick a dominant & recessive outcome arising from different alleles Always have one heterozygous You choose who you’re mating with (homozygote or heterozygote)…

Meiosis: the other cell division Point to what cells are producing through meiosis? Don’t be shy….

37 Throwing the dice “Sexual reproduction has been compared to a game of roulette in which the players throw away half their chips at every spin of the wheel.” Jonathan Silverton, ‘An Orchard Invisible’ p. 22

Doing it (making sex) It’s a huge waste of time… even when other people are involved Exhausting (sometimes enough is enough already and you just want to go to sleep)… Science calls this “metabolically expensive,” psychology calls it the “refractatory period,” you may call it “get out, I’m going to sleep”

Jack Sprat and his lipase-deficient disease Jack Sprat could eat no fat. His wife could eat no lean. And so between them both, you see, They licked the platter clean

40 Why have sex? Suppose I’m Jack Sprat; you’re my wife. – I have the mutant form of the fat-eating gene; you of the lean-eating gene – If we reproduce asexually (mitotically), how long until some descendant can eat a whole pig? – If sexually, i.e. by taking parts of our holdings & throwing them together in an offspring?

41 Thinking it through How much are you ‘like’ your ma & pa? How much of your genome should you give your child if he/she is not uni- parental?

Meiosis Let’s do it How diverse are your ‘gametes’? Is that enough?

Meiosis Recombination ‘Homologous’ chromosomes can exchange genes

Meiosis Where should the circled site on Chromo1 recombine with Chromo2? 1 2 3

Meiosis Pick two ‘traits’ What is dominant/recessive?

Meiosis First, make a copy--b/c that’s the way it happens Pair the pairs: duplicated mom’s & dad’s contributions pair Recombine (randomly)

Meiosis Now we’ve recombined; how to separate? When is a cell haploid? Select a gamete, go fuse with a classmate Stop by and show me the genotype

Meiosis Diversity? Two chromosomes with recombination How many possibilities?

Meiosis Crossing Over is GREAT for genetic diversity!!! What are the ‘costs’?

Things go wrong during Meiosis Non-disjunction Insertion Deletion Inversion

Clean Up No, we’re NOT done

More Vocab… We’ve talked about chromosomes, mitosis, and meiosis… Recombining genes via Crossing Over How likely do you suppose it is that genes are inherited together?

More Vocab… Linkage’ - referring to whether genes are inherited together because they are ‘close’ on a chromosome ‘Linked’ - referring to the resulting behavior of traits encoded by such genes

Gameter Open Gameter Move things around, work with the buttons Notice A and a go together End up with: ‘A’ and ‘B’ on Chrm II, with A farther right than B Ab and AB

Gameter Explore – One meiosis – 200 meioses – Move ‘em around and try again Observe Hypothesize Test Evaluate

Homework Genetics Words Gameter : Linkage (S'ware) Gameter Revised Proposals

What happens in each “Stage?”

What if a cell isn’t “listening”? Malignant Tumor – grows aggressively, invades surrounding tissue, metastasizes Benign Tumor – lacks malignant tumor’s properties Benign tumors CAN cause “mass effects”

What if a cell isn’t “listening”? Carcinoma - external/ internal coverings of body Sarcoma - support tissues (bone, muscle) Leukemia, lymphoma - blood-forming tissue cancers

And now, back to our program