2. DNA Replication Flashcards
What are homologous chromosomes?
Chromosomes in eukaryotic cells come in pairs called homologous chromosomes. One of each homologous pair (HP) comes originally from each parent. They are the same length and size and contain genes for the same characteristic however they are not genetically identical (as each pair comes from two different people).
What is the difference between leading and lagging strands?
The leading strand runs in the 5’ to 3’ direction. DNA polymerase builds the new strand in 3’ to 5’ direction, by moving along the strand and adding bases continuously. Whereas, the lagging strand runs in 3’ to 5’ direction. Because DNA polymerase only works by adding bases from the 3’ to 5’ direction, RNA polymers need to keep being placed for the DNA polymerase to add the DNA bases in sections.
What is the purpose and process of DNA Replication?
Since DNA contains the genetic information required to synthesise proteins that carry out life processes. DNA is passed on to daughter cells during cell division. The DNA in the parent cell needs to be replicated before cell division, to ensure each daughter cell receives an exact copy of the genetic information.
- An enzyme called helicase unzips DNA along weak hydrogen bonds between complementary bases.
- The bases along both sides of the DNA molecules become exposed.
- The 2 exposed strands become templates for new strands to be built on.
- Free-floating DNA nucleotides dissolved within the cell randomly come into juxtaposition with their complementary partners by re-establishing the hydrogen bond. The result is a semi-conservative strand, half new DNA and half old DNA
What are Eukaryotic cells and how does the DNA within it differ from other cells?
Eukaryotic cells are larger, more complex cells found in plants, animals, fungi, and protozoa. Have a nucleus and other organelles such as mitochondria and chloroplasts.
- DNA is packaged into linear chromosomes found in the nucleus.
- DNA is in the form of chromatin, the DNA is tightly coiled around globular proteins called histones.
- Chromosomes become visible when the chromatin condenses before cell division.
- DNA is also found in chloroplasts (plants) and mitochondria (plants and animals) the structure is similar to prokaryotic cells.
What are Prokaryotic cells and how does the DNA within it differ from other cells?
Prokaryotic cells are bacteria cells, smaller than eukaryotic cells and more simple. Do not contain a nucleus.
- Have a single circular chromosome located in a region of cytoplasm called the nucleoid.
- Do not have histones but have proteins that assist in organization.
- May contain plasmids - small, extrachromosomal DNA molecule
