biology 5th year

what does cell continuity mean

cell continuity means that the division of pre- existing living cells has produced all cells living today

what are chromosomes

chromosomes are thread- like structures made up of DNA and protein that contain genetic information

what is a karyotype

the karyotype is the complete set of chromosome of an individual and what it looks like under a light microscope

what are homologous chromosomes

pairs of chromosomes with the same size and shape and contain genes for the same characteristics

what is a genome

all the genetic information of an organism

what is the diploid number of humans

46

what is the haploid number of organisms

23

what does diploid mean

when there are two sets of chromosomes one from the mother and one from the father (shortened to 2n)

what does haploid mean

when an organism has one set of chromosomes

what cells in the human body are not diploid

gametes (sperm and egg cells)

what are examples of haploid organisms

yeast and fungi cells

what are triploid organisms

organisms with three sets of chromosomes

what are tetraploid organisms

organisms with four sets of chromosomes e.g salmon

what happens in part1 of the interphase (not apart of mitosis)

the cell grows to its normal size makes proteins and carries out its daily functions while that is happening the cell organelles such as the mitochondria and chloroplasts replicate

what happens in part 2 of interphase

the DNA replicates

what happens in part 3 of interphase

the cell makes final preparation for division (mitosis)

what is mitosis

the process in which the nucleus divides to form two cells genetically identical to its parent cell

what kind of cells use mitosis

prokaryotic cells (cells with membrane bound organelles such as mitochondria and chloroplasts)

what is the equivalent process of mitosis in other types of cells

eukaryotic cells use binary fission

what is the function of mitosis in unicellular organisms

in unicellular organisms such as amoeba the main function is reproduction

what is function of mitosis in multicellular organisms

growth and repair of cells

what are the four main stages of mitosis

prophase, metaphase, anaphase, telophase

what happens in the prophase

• chromatin condenses and becomes visible as rod shaped structures

• nuclear membranes break down

• the centrioles move toward opposite poles

• spindle fibres start to form

what happens in the metaphase

• the chromosomes line up on the equator

• the spindle fibres attach to the centromeres

• and the nuclear membranes have completely disappeared

what happens in the anaphase

• the spindle fibres contract

• chromosomes are pulled apart

• one copy of each chromosome is pulled towards each pole

what happens in the telophase

• the nuclear membranes reappear

• the chromosomes begin to unwind

• and cell division begins

what happens in cytokinesis (not officially part of mitosis)

• cell division is complete

• in plant cells the cell plate begins to form

• in animal cells the cleavage furrow appears

what is meiosis

meiosis is the division of a diploid nucleus producing 4 haploid genetically different nuclei

what are the functions of meiosis

1. gamete formation (production of sperm and egg cells in human)

2. pollen grain formation (spore formation in flowering plants)

what is the end result of mitosis

• two cells that are genetically identical with the same number of chromosomes

end result of meiosis

four cells which are all genetically different and half the number of chromosomes as the parent cell

what is cancer

when the cells lose their normal control of mitosis leading to the formation of a tumour

causes of cancer

• ionising radiation e.g x-rays

• ultraviolet radiation e,g sunbeds

• excessive drinking of alcohol (spirits)

types treatments for cancer

1. surgery (removal of tumour)

2. chemotherapy: when chemicals are administered to attack and kill cells that are actively dividing

3. radiotherapy: using high energy radiation e.g gamma rays to shrink the tumour