Good Morning! Do now: Think about the following questions How is DNA packaged? Where do you get your DNA from? Do you have more, less or the same amount of chromosomes (DNA) as your parents? If you get DNA from mom and dad, why don’t you have twice as much DNA as them?

Chromosomes Chromosomes are how DNA is packaged in our cells Shaped like an X Each piece of the X is called an arm Under normal conditions humans have 46 chromosomes, stored in pairs (23 pairs) ARM

Chromosomes in The Cell Cycle (Mitosis) Normal human cells have 46 chromosomes During interphase a cell doubles its DNA to 92 chromosomes During mitosis, the cell divides (PMAT), splitting the chromosomes in half, giving each cell 46 chromosomes (just like the parent) Interphase PMAT

Where do we get our DNA from? If we get our DNA from our parents, why don’t we get twice as many chromosomes? We only take half the DNA from mom (23 chromosomes) and half the DNA from dad (23 chromosomes) in a process called MEIOSIS

Overview of Meiosis Meiosis – division of Gametes Gametes- sex cells Male gamete- sperm Female gamete- egg/ovum Sexual Reproduction Two parents DNA from both parents  genetically DIFFERENT

Meiosis A. Interphase Parent Cell B. PMAT I C. PMAT II ` *This picture does not show every step of meiosis, it is a general overview*

Human Chromosomes in Meiosis Interphase PMAT 1 PMAT 2

Tricky vocabulary Monoploid/Haploid- one set of chromosomes (n) Diploid- two sets of chromosomes (2n) Polyploid- more than two sets of chromosomes (xn where x= number of sets)

Human Chromosomes in Meiosis Interphase PMAT 1 PMAT 2

What can go wrong During Meiosis? Crossing Over Occurs during Prophase/Metaphase I During crossing over, arms from different chromosomes get tangled, and pieces of DNA (genes) can get switched/mixed up

What can go wrong during meiosis? Non-disjunction During non-disjunction, chromosomes do not divide or split evenly Causes there to be some sperm/egg cells with extra Chromosomes Makes some sperm/egg cells with not enough chromosomes Normal Meiosis Non Disjunction Meiosis

Karyotype A karyotype is an organized profile of a persons chromosomes 23 pairs of homologous chromosomes 22 autosomes 1 pair of sex chromosomes XX- female XY- Male Homologous: Same size, shape and genes/instructions

Karyotyping When scientists arrange chromosomes into pairs to determine if there is a chromosome disease/mutation

Mitosis vs Meiosis MitosisMeiosis Type of cellsSomatic (Body)Gametes (Sex Cells) Type of reproductionAsexualSexual PMATOccurs 1 timeOccurs 2 times CytokinesisOccurs 1 timeOccurs 2 times Daughter cells produced 24 Chromosomes in daughter cells 46, Diploid (2n)23, Haploid (n) Cells areIdenticalGenetically different ProblemsCancerCrossing over, Non-disjunction