ODWS icon

The Open Door Web Site
HOMEPAGE BIOLOGY HOMEPAGE CHEMISTRY PHYSICS ELECTRONICS HISTORY HISTORY OF SCI & TECH MATH STUDIES LEARNING FRENCH STUDY GUIDE  PHOTO GALLERY
IB BIOLOGY HOMEPAGE SCIENTIFIC INVESTIGATIONS DRAWING IN BIOLOGY DRAWING TABLES ERROR ANALYSIS IN BIOLOGY ALL ABOUT GRAPHS ICT IN BIOLOGY STATISTICS SCIENTIFIC POSTERS MOLECULAR IMAGES
WS

Powerpoint Presentation: Chromosomes and Sex Determination
Powerpoint Presentation: Replication

 

Genetics Index

Meiosis
Meiosis: Crossing over
Mitosis and Meiosis
Introduction to Mendelian Genetics
Test Cross
Codominance
Multiple Alleles
Pedigree Charts
Twin Studies
The dihybrid cross
Dihybrid Cross : Test Cross
Autosomal Linkage
The Genetic Diagram for Linked Genes
Calculating the cross over value using a test cross
Sex determination and sex linkage
Sex linkage
Genetic diagram for sex linked genes
Blood Clotting and Haemophilia
The Retina and Daltonism
Genetic Modification
Cloning Animals
Cloning Plants

Topic Chapters Index

 

Numbers of chromosomes

  • Constant for each cell in the body (except sex cells which only have half sets).

  • Constant throughout the life of an individual (you don't lose or gain chromosomes)

  • Constant for all members of a species

Organism

Chromosome numbers

Human

46

Chimpanzee

48

House Mouse

40

Fruit fly

8

Crayfish

200

Maize

20

Garden Pea

14

 

 

GENETICS

Custom Search

Chromosomes

Chromosomes in eukaryotes and prokaryotes are different

 

Prokaryotes

Eukaryotes

single chromosome plus plasmids

many chromosomes

circular chromosome

linear chromosomes

made only of DNA

made of chromatin, a nucleoprotein (DNA coiled around histone proteins)

found in cytoplasm

found in a nucleus

copies its chromosome and divides immediately afterwards

copies chromosomes, then the cell grows, then goes through mitosis to organise chromosomes in two equal groups

 

Chromosomes in eukaryotes

Condensed and visible during mitosis.

At the beginning of mitosis they can be seen to consist of two threads (sister chromatids) joined by a centromere.

The sister chromatids are identical copies.

During mitosis the sister chromatids separate and are placed into two nuclei.

 

Identifying chromosomes

Chromosomes can be identified by:

  • Their size

  • Their shape (the position of the centromere) NB Chromosomes are flexible.

  • Banding patterns produced by specific stains (Giemsa).

 

Chromosomes and cell division

  • Multicellular organisms copy their chromosomes before cell division.

  • They must grow to a mature size.

interphase

  • The nucleus divides, distributing the chromosomes into two equal groups (mitosis).

  • The cytoplasm then divides (cytokinesis) each part taking a nucleus.

The cell cycle

the cell cycle

 

Cell type

Cell cycle / hours

Bean root tip

19,3

Mouse fibroblast

22

Chinese hamster fibroblast

11

Mouse small intestine epithelium

17

Mouse oesophagus epithelium

181

 

The Open Door Web Site is non-profit making. Your donations help towards the cost of maintaining this free service on-line.

Donate to the Open Door Web Site using PayPal

SITE MAP
WHAT'S NEW?
ABOUT

PRIVACY

COPYRIGHT

SPONSORSHIP

DONATIONS

ADVERTISING

© Paul Billiet 2018
Any questions or problems regarding this site should be addressed to the webmaster

Hosted By
Web Hosting by HostCentric


SiteLock