The Cell, DNA and Chromosomes Flashcards
what is a cell?
- basic units of all living matter
- essential for life
- fundamental components of structure, development, growth and life processes in the human body
what are the components of normal human cells?
cell membrane
cytoplasm
cytoplasmic organelles
nucleus
what are the parts of the nucleus?
DNA and nucleolus
what are the cytoplasmic organelles?
- endoplasmic reticulum
- Golgi apparatus or complex
- mitochondria
- lysosomes
- ribosomes
- centrosomes
what is the atomic composition of the body?
60% hydrogen, 25.7% oxygen, 10.7% carbon, 2.4% nitrogen and <1% calcium, phosphorus and sulphur
what is the molecular composition of the body?
80% water, 15% proteins, 2% lipids, 1% carbohydrates, 1% nucleic acids, and 1% other
what is nucleic acid?
nucleic acid (DNA) is considered to be the most critical and radiosensitive target molecule
- comprise of 1% of the cell
- large and very complex macromolecules
what is a purine?
2 carbon-hydrogen rings
Adenine and Guanine
what is a pyrimidine?
1 carbon-hydrogen ring
Thymine and Cytosine
what is the physical, chemical composition of DNA
- Composed of two long sugar-phosphate chains, which twist around each other in a double-helix configuration and are linked by pairs of nitrogenous organic bases at the sugar molecule of the chain
- Hydrogen bonds attach the bases to each other
- Contains all the information the cell needs to function
- Carries the genetic information necessary for cell replication
- Regulates all cellular activity to direct protein synthesis
- Determines a person’s characteristics by regulating the sequence of amino acids in the person’s constituent proteins during synthesis of these proteins
- Sequence of nitrogenous base pairs in a DNA molecule that constitutes the genetic code
- 2.9 billion base pairs
what are the base pairs?
A with T and G with C
What is a chromosome?
- Tiny rod-shaped bodies that under a microscope appear to be long threadlike structures that become visible only in dividing cells
- Composed of protein and DNA
- Normal human has 46 different chromosomes (23 pairs) in each somatic (non-reproductive) cell
- Reproductive cells (germ cells) have only 23 chromosomes each
What are genes?
- Distinct segments of DNA that serve as the basic units of heredity
- Each one contains information responsible for directing cytoplasmic activity, controlling growth and development of the cell, and transmitting hereditary information
- Control the formation of proteins in every cell through the intricate process of genetic coding
- Approximately 30000 genes capable of producing 90000 different proteins
Effect of ionizing radiation damaging the components of the cell involved in molecular synthesis beyond repair?
- cells behave abnormally
- cells die
what are somatic cells?
body cells
- 2 of each gene located on 2 different chromosomes (homologs)
- 23 pairs of homologous chromosomes
- 46 chromosomes (diploid, or 2n)
what are genetic or germ cells?
- Female: Oogonia (immature, 2n or 46) → ova or egg (gamete, n or 23)
- Male: Spermatogonia (immature, 2n or 46) → sperm or spermatozoa (gamete, n or 23)
what are the two types of cell division that occur in the body?
- mitosis and meiosis
what is mitosis?
- a process in which the nucleus first divides, followed by the division of the cytoplasm
- Process that occurs when all somatic cells divide
what is meiosis?
- a process of reduction cell division
- process that occurs when genetic cells divide
what are the phases of the cellular life cycle?
interphase
mitosis
what is interphase?
G1, S and G2 phases
what is S phase?
S phase is when each DNA molecule is replicated and then divided into two sister chromatids
- each DNA molecule is replicated into 2 identical daughter chromosomes
what are the 4 subphrases of mitosis?
prophase
metaphase
anaphase
telophase
what is the process of mitosis?
- During metaphase cell division can be stopped and chromosome damage caused by radiation can be visualized under a microscope
- Results in an approximately equal distribution of all cellular material between the two daughter cells
what is the process of meiosis?
- Meiosis and mitosis phases are similar
- The major difference begins at the end of telophase
- During meiosis, sister chromatids exchange some chromosomal material (genes) called crossover
- Crossover results in changes in genetic compositions and traits that can be passed on to future generations
ploidy?
- Ploidy is the number of sets of chromosomes in a cell.
- Usually a gamete carries a full set of chromosomes that includes a single copy of each chromosome.
- The haploid number is the number of chromosomes in a gamete (n).
- Two gametes form a diploid zygote with twice this number
Gametes: Egg (23 or n) + sperm (23 or n) = zygote (46 or 2n) - Zygote becomes an embryo
