Chapter 8

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?

• Chromosome
– 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

• 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

Each half of a chromosome is called a chromatid
Chromatids are held together by a centromere

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.

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

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

Chromosome - rodlike 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 chromosomeone 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 chromosomechromosomes that have the same sequence of genes and structure that pair during meiosis
Histone is not on your vocabulary quiz

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!