Bell Work: Draw and label a chromosome Chromatids Centromere

More Vocabulary Centromere- holds the chromatids together Chromatids- identical sides of the chromosomes Contain same genetic information on both sides Sister chromatids = when two chromatids are bound by a centromere

DNA, CHROMOSOMES, & Karyotypes

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

Let’s start with vocab. Cell cycle = the life cycle of a cell Interphase = all the time between cell divisions Mitosis = division of the nucleus Cytokinesis = division of the cytoplasm

Stages of the Cell Cycle Interphase M-phase (Mitosis) Cytokinesis

Draw it out With your table group, draw a chart of the cell cycle on your desk

DNA & Chromosomes in Interphase G1 phase – Interphase DNA is in the form of chromatin S phase – Interphase DNA chromatin coils itself tightly into chromosomes [ l shaped] Each chromosome duplicates itself [X shaped]

Chromatin DNA wrapped around histone proteins Structure of DNA between cell divisions. Chromosomes are only present during cell division.

Rod or X- shaped structures made of tightly wound DNA & Proteins Histones - sphere shaped proteins that the DNA wraps around DNA CHROMOSOMES Proteins

Chromosomes Rod shaped prior to S phase X- shaped after S phase (duplication) Rod shaped after Anaphase

Follow the DNA Early S phase

Draw it out As a table group, draw out the process of the cell cycle on your desks Show the DNA in each step

Chromosomes come in matching sets -these are called homologous pairs

Karyotype after DNA replication Each homologous pair duplicates itself = homologous chromosomes

PROKARYOTIC VS EUKARYOTIC CHROMOSOMES Larger rod shaped in Nucleus Prokaryotic: Circular Smaller NOT in Nucleus Chromosome

Which is more complex in terms of DNA? Adders Tongue Fern Human OR

Which is more complex in terms of DNA?

Chromosome Numbers Organism # of chromosome Fruit Fly 8 Carrot & Lettuce 18 Cat 32 Earthworm 36 Human 46 Gorilla 48 Sand Dollar 52 Adder’s Tongue Fern 1262

Two Types of Chromosomes SEX Determine the gender of the individual The 23rd pair 2 of the 46 chromosomes AUTOSOMES The other 44 out of 46 chromosomes

Autosomes vs. Sex Chromosomes

SEX Chromosomes XX = XY =

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 Description Both sets of homologous chromosomes present Only one of each homologous chromosome present Type of Cell All cells but sex cells (egg or sperm) Only sex cells- Egg or Sperm Abbreviation 2n 1n