Chromosomes and Cell division Mitosis Flashcards
What is found on chromosomes?
DNA
DNA is found in the nucleus of prokaryotic cells. It has to be wound up to fit into chromosomes.
What are homologous pairs?
Humans have 23 homologous pairs of chromosomes. One from each pair comes form your mother and the other from your father.
Both chromosomes are the same size and carry the same gene. But usually have different alleles (different version of the gene)
How are chromosomes often shown as?
They are often shown as x-shaped, which is actually one chromosomes attached to an identical copy of itself.
They are only x-shaped after the DNA has been replicated in call division.
Each side of the the X is referred to as a chromatid and the bit in the centre is the centromere.
Why is mitosis needed?
It is needed for growth and repair, if you have damaged tissue, the cells around the damaged area divide by mitosis to produce new tissue for growth.
Cells also divide by mitosis to produce new tissue fro growth.
How does asexual reproduction involve mitosis?
a single organism produces offspring by dividing into two organisms or by splitting off pieces of itself.
All the offspring are genetically identical to each other and the parent.
How many stages is mitosis split into and what are they?
5 stages : interphase, prophase, metaphase, anaphase and telophase
What is interphase?
Interphase is before the cell starts to divide, every DNA molecule must replicate so that each new cell has a full copy of DNA. The new molecule remains attached to the original one at the centromere.
What is phrophase?
AT this stage mitosis can now begin, each molecule becomes supercoiled and compact. Each chromosome can now been seen with a light microscope and appears as two chromatids lying side by side, joined by the centromere.
What is metaphase?
The nuclear membrane breaks down and the chromosomes line up along the the equator of the cell.
What is anaphase?
The centromere split and the chromatids seperate and are dragged to opposite ends of the cell.
What is telophase?
A nuclear membrane forms around each set of chromatids and the cytoplams divides.
