Eukaryotic cells have nucleus delimited by two juxtaposed membranes that continue with the membrane of the endoplasmic reticulum. The nuclear membrane, or karyotheca, presents pores through which substances pass. There are also ribosomes adhered to its external surface.
The nucleolus is a small and optically dense region in the interior of the cell nucleus. It is made of ribosomic RNA (rRNA) and proteins. One nucleus can have one or more nucleolus.
Cell Nucleus Review - Image Diversity: nucleolus
The number of chromosomes typical of each species is proximal for phylogenetically proximal species (for example, orangutan, gorilla, chimpanzee and human). But it is not impossible that evolutionary distant species, like rat and oat, bears similar karyotypes and the same total number of chromosomes.
Even presenting equal number of chromosomes evolutionary distant species have radically different characteristics since the quantity and the sequence of nucleotides that compose their respective DNA molecules are quite different.
The human haploid cell is the gamete (egg cell and sperm cell). The human gamete has 22 autosomes and 1 allosome, i.e., 23 chromosomes. The diploid cell is the somatic cell and it has 44 autosomes and 2 allosomes, i.e., 46 chromosomes.
Gametes have one sex chromosome and somatic cells have two sex chromosomes.
Sex chromosomes are also called allosomes (the other chromosomes that are not sex chromosomes are called autosomes).
Sex chromosomes get such name because they have genes that determine the sex (male or female) of an individual. Sex chromosomes also have genes related to other biological functions.
Webmaster 20th of May 2012
Tell us what you feel about Cell Biology Interview Questions and Answers
All comments will be published after review. No login or registration is required to post a comment on Cell Biology Interview Questions and Answers We offer and invite you to submit your valuable comment now; Please be respectful of others when commenting. Insulting others, self-promotional comments, website promotional comments, marketing stuff, SEO Techniques, SMS-style content and off-topic comments will not be approved at this information portal.
So start sharing your thoughts regarding Cell Biology Interview Questions and Answers
Thank you.