Cells And Chromosomes Flashcards
What are the two type of cells?
Somatic- all cells that aren’t somatic
and reproductive cells (gametes)
Prokaryotes def
Organisms whose cell lack a nucleus and their DNA is floating loosely. Divide and reproduce via simple mitosis
Eukaryotes def
Organisms that have a well defines nucleus adhere DNA resides and is protected. Eukaryotes divide by mitosis for somatic cells and by meiosis for sexual reproduction.
Major differences between eukaryote and prokaryote
Prokaryotes lack a nucleus and are much smaller. Prokaryotes have one circular DNA molecule whereas eukaryotes have multiple linear DNA molecules. Prokaryotes have DNA that isn’t complexed with histones in eubacteria or some histones in archae and eukaryotes have DNA complexed with histones.
Similarities between prokaryotes and eukaryotes
Both have DNA, ribosomes, a cell membrane and contain cytoplasm
Differences in packaging of DNA for prokaryotes and eukaryotes
In eukaryotes, DNA is closely associated with a special class of proteins, histones, to form chromosomes, this complex is termed chromatin. Mechanisms required to ensure a copy of each chromosome is transmitted to each new cell.
Genes of prokaryotic cells are generally on a single, circular molecule of DNA.
Three fundamental events for cell to reproduce successfully
- The genetic info must be copied
- The copies must be separated from each other
- The cell must divide.
All cells must do these steps but the processes differ for prokaryotes and eukaryotes.
Prokaryotic cell reproduction
The circular chromosomes of bacteria replicates and the cell divides by binary fission. two newly replicated chromosomes move away to opposite ends and a new cell wall forms between them, producing two cells, both identical to the parent.
Eukaryotic cell reproduction
Eukaryotic chromosomes are separated from the cytoplasm by the nuclear envelope . The nucleus has the nuclear matrix , which consists of a network of protein fibres that maintain precise spatial relations amount components and take part in replication.
Homologous pairs
Eukaryotes have 2 copies of each chromosome, one from mother, one from father. The two chromosomes in a homologous pair are alike in size and structure and carry the same set of hereditary characteristics, except the sex chromosome.
Allele def
Allele is the term used to describe the different version of a gene.
What three essential elements must a functional chromosome have?
- A centromere: the attachment point for spindle microtubules (responsible for moving chromosomes) ,. Before cell division, a kinetochore assembles on the centromere.
- A pair of telomeres: the natural ends of a linear chromosome, help protect and stabilize the chromosome.
- Origins of replication: sites where DNA synthesis begins. Each chromosome replicates itself and the two chromatids are held together at the centromere.
Classification of centromere location
Metacentric- centromere in middle
Submetacentric- centromere halfway between middle and top.
Acrocentric- centromere basically right at the top
Telocentric- centromere at the very top of chromosome, nothing on other side.
Chromatin def
A substance found in the cell nucleus that’s composed primarily of DNA and proteins. There are two types of chromatin:
1. Euchromatin- undergoes the normal process of condensation and decondensation in cell cycle
2. Heterochromatin- remains in a highly condensed state throughout the cell cycle, even interphase.
Chromatids def
Chromatin condenses when the cell divides to form chromosomes which split into two identical strands called chromatids. Each chromatid then becomes a chromosome in each new cell that is formed.
