1. Chromosomes
Chapter 8

2. DNA Contain Genetic information
Long, thin molecule that consists of three billion nucleotides.
If stretched out would be 20 miles long
How does it fit into a nucleus?

3. DNA within a Cell Chromosome Chromatin
Rod-shaped structures made of DNA and proteins
Visible in a cells nucleus only during cell division
Chromatin
Less tightly coiled DNA-Protein complex
Chromatin structure allows long strands of DNA to be condensed into ordered, accessible arrangements
Chromatin coils up to form visible chromosomes during cell division

4. DNA Packing to form Chromosome
Chromosomes are coated with histone and non-histone proteins
Histone
organize and maintain the shape of chromosomes
are responsible for packing the DNA into a compact form.
Nonhistone
control the activity of specific regions of the DNA

5. Chromosome Structure Each half of a chromosome is called a chromatid
Chromatids are held together by a centromere

6. Chromosome structure Genes include: Exons-coding regions
Introns- non-coding regions interspersed between exons
In addition to genes, chromosomes have lots of “non-coding” sequence
Complete Eukaryote Chromosome Structure PSSA worksheet together.

7. Chromosome number DNA of a genome is divided
into chromosomes (variable
size and number)
Diploid 2n
Two sets or homologous pairs of chromosomes
Haploid n
One set or half of a homologous pair
Gametes (sperm & egg)
Complete Act. #1 Graphing activity

8. Karyotypes & Medical Genetics
Use blood or amniotic fluid to obtain cells.
Cells are cultured for three days and stopped during metaphase of mitosis with the drug colchicine.
Cultured cells are stained and examined under a microscope.
A micrograph of the chromosomes, (metaphasic
spread) are arranged by:
Length
Position of centromere
Pattern of bands
Humans have 22 autosome pairs and 1 sex chromosome pair!
Complete Karyotype Demo

9. Chromosome- rod-like structure composed of DNA and protein that’s visible only during cell division
Chromatid- one of the two strands of a chromosome
Chromatin- loosely coiled strands of DNA and protein found in the nucleus of the cell
Autosome- any chromosome that is not a sex chromosome
Sex chromosome- one of a pair of chromosomes that determine the sex or an individual
Haploid- describes a cell, nucleus, or organism that has only one set of unpaired chromosomes;n
Diploid- a cell that contains two haploid sets of chromosomes;2n
Karyotype- a graphical display that shows an individuals chromosomes
Centromere- region of the chromosome that holds the two sister chromatids together
Homologous chromosome- chromosomes that have the same sequence of genes and structure that pair during meiosis
Histone is not on your vocabulary quiz

10. Review
What is the difference between a chromosome, chromatid, and chromatin?
How is all the DNA of an organism crammed into the nucleus of a cell?
How is chromosome number related to intelligence?
What types of chromosomal traits do scientist look at when completing a karyotype?
Handout and Complete Karyotype Activity #2
Don’t forget Vocabulary Quiz #1 is tomorrow!