DNA & CHROMOSOMES Mrs. Stewart Honors Biology Central Magnet School

Standards CLE Investigate how genetic information is encoded in nucleic acids. CLE Describe the relationships among genes, chromosomes, proteins, and hereditary traits.

Objectives Evaluate the structure of a chromosome Differentiate between prokaryotic and eukaryotic chromosomes Infer the complexity of an organism based on chromosome number Identify gender based on chromosomes

How big is the unseen world of cellular biology? Cell Sizes – Scale Scale of the universe

What is DNA? DNA – contains all the genetic (hereditary) information necessary to build and maintain an organism

DNA and Genes Genes – specific sections of DNA that code for a trait

How much DNA is in most of the cells in a human body? Approx. 2 meters in every diploid cell 2 meters = ___6.5___ Feet Approx 6 billion base pairs of DNA per cell

Each of us has enough DNA in our bodies to reach from here to the sun and back - more than 300 times How is all of that DNA packaged so tightly and squeezed into a tiny nucleus?

Activity Materials needed: –Yarn = DNA –Easter Egg = Nucleus Question: What do the differently colored sections of yarn relate to in DNA? Mission: Make all the DNA fit into the nucleus in a way that it would still be “organized”

Chromatin Definition: Histones:  DNA that is tightly wrapped around proteins  found in the nucleus of Eukaryotic cells A sphere-shaped protein that DNA wraps around o Not found in Eubacteria

Chromosome Vs. Chromatin Chromosomes are only present during cell division. In between cell divisions, chromosomes are unraveled and called Chromatin

Chromosome Vs. Chromatin Chromosome: Chromatin: Tightly coiled DNA & proteins during cell division; DNA cannot be “read” while in this form. Loosely coiled DNA & proteins during the cell’s life other than cell division. DNA can be “read” to direct activities of the cell.

Chromosomes Definition: –Rod-shaped or X-shaped structures made of tightly coiled chromatin in preparation for the cell to divide

CHROMOSOMES

Chromosomes What do they look like? How many do humans have? They look like an “X” after the DNA has been duplicated (just before the cell divides) They look like an “I” after they divide and between cell divisions 23 Pairs of chromosomes (23 from mom, 23 from dad) = 46 chromosomes

What does a chromosome look like?

Chromosomes Centromere Chromatids

Chromosome Terminology Centromere- Connecting point between two chromatids - holds the chromatids together Chromatids- identical strands of a duplicated chromosome –become visible at the beginning of Mitosis or Meiosis –Contains same genetic information on both

Prokaryotic vs. Eukaryotic Chromosomes Prokaryotic Circular Only one No histones (except Archaebacteria) Not in a nucleus Eukaryotic Rod or X shaped Many Histones In nucleus Chromosome

Think – Pair – Share Which is more complex in terms of DNA?

Adders Tongue Fern OR Human

Think – Pair – Share Which is more complex in terms of DNA? Potato OR Sand Dollar

Chromosome Numbers Organism# of chromosome Fruit Fly8 Carrots & Lettuce18 Cat32 Earthworm36 Human46 Gorilla / Chimpanzee48 Potatoes / Plums48 Sand Dollar52 Horse64 Adder’s Tongue Fern1262

Two Types of Chromosomes SEX –Determine the gender of the individual –Carry a few other traits –2 out of our 46 chromosomes AUTOSOMES –Carry most of the traits that we inherit –44 of the 46 chromosomes

SEX Chromosomes XX = XY =

HOMOLOGOUS CHROMOSOMES A pair of autosomes that are the same size and shape and code for the same genes One comes from ____________ Humans have 44 autosomes, so they have 22 pairs of homologous autosomes Mom Dad

KARYOTYPE A picture taken from a microscope of all the chromosomes within a cell. The chromosomes are then arranged in homologous pairs and given a set of numbers

Diploid vs Haploid Cells DiploidHaploid Description Both sets of homologous chromosomes present Only one of each homologous chromosome present Type of CellAll cells but sex cells (egg or sperm) Only sex cells- Egg or Sperm Abbreviation2n1n

Standards CLE Investigate how genetic information is encoded in nucleic acids. CLE Describe the relationships among genes, chromosomes, proteins, and hereditary traits.

Objectives Evaluate the structure of a chromosome Differentiate between prokaryotic and eukaryotic chromosomes Infer the complexity of an organism based on chromosome number Identify gender based on chromosomes

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