Nice animation, includes recombination

Mitosis and Cell Division

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

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

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 Human genome is ~3,000,000,000 basepairs Human genome is (currently guesstimated at) ~20-30,000 genes** Human genome is ~1 meter of DNA

Mitosis and Cell Division

Gene: Segment of DNA that represents all 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! Mitosis vs Cell Division More in the lab manual & Vocab exercises!

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?

A Couple Things to Think About…

Mitosis and Cell Division How many cells –When you were “0”? –Now? What do cells DO?

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

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 ALSO a diploid nucleus/cell

This is a DIPLOID Nucleus/Cell

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

Back to program

Pay attention to the ‘nubbins’

Mitosis and Cell Division What do our bead models represent?

Mitosis and Cell Division SHOW ME 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 links

Mitosis and Cell Division Pick two traits Pick a dominant & recessive outcome arising from different alleles You all start off heterozygous

Mitosis and Cell Division Point at some of your cells that ‘do’ mitosis? What’s the goal/purpose of this thing called ‘mitosis’? So what must the first step be? Do it.

Mitosis and Cell Division Let’s do it What are ‘homologous’ chromosomes? How does ‘cell’ know they go together?

Mitosis and Cell Division Point at some of your cells that ‘do’ mitosis? What’s the goal/purpose of this thing called ‘mitosis’? So what must the first step be? Do it. Now what must be achieved? –Any half? If not, how pick the appropriate half? How do your final results compare with starting?

Mitosis and Cell Division What comes after MITOSIS?

Meiosis Why have sex? What do you want the cells to look like at the end of meiosis? How much are you ‘like’ your mom and dad? Do ‘mother’ chromosomes have to stay together?

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

Meiosis

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

Disease Presentation

Research Project

Where we’re headed Your proposal is an answerable, interesting question It will reflect causation Follow rubric – choose a proposal

Take a look Onion root tip – make it a squash Grasshoppers testes

Mitosis (with just ONE set of chromosomes) looks like this…

+ Two IDENTICAL DIPLOID cells

+ Both cells are still DIPLOID because they have TWO chromosome #1s When they replicate their DNA, each will look just like the parent cell

Show Me

MEIOSIS (with TWO sets) looks like this…

+ Each of these cells is HAPLOID as it only has ONE set of chromosomes (1 of each; chrm 1 and chrm 2) Meiosis 1

Meiosis 2 Four DIFFERENT HAPLOID cells

Back to the Cell Cycle

Cells spend most of their “lives” like this

They only look like this after they replicate their DNA in order to divide (mitosis)

HOMEWORK Proposal!!!!!!!