Topic 1- DNA Flashcards
What are the 4 nitrogenous bases in DNA?
Adenin-Thymine, Guanine-Cytosine
What molecular components make up a nucleotide?
Phosphate
Deoxyribose sugar group
Nitrogenous Base
How is DNA stored in eukaryotes?
Wrapped around histones in the form of chromosomes in the nucleus
How is DNA stored in prokaryotes?
As free-floating circular chromosomes and as plasmids in the cytoplasm
Nitrogenous Bases in RNA
Adenine-Uracil, Guanine-Cytosine
What are the 3 stages of DNA replication?
Initiation: helicase unwinds DNA double helix to create replication fork. Single strand binding proteins stabilise the separated strands and primase synthesises RNA primers to provide started points for DNA polymerase.
Elongation: DNA polymerase adds nucleotides to the RNA primer in 5’ to 3’ direction synthesising the new DNA strand. The leading strand in synthesised continuously while the lagging strand is synthesised in short fragments (Okazaki fragments) due to 5’ to 3’ direction relative to fork’s movement.
Termination: Once replication is complete, the RNA primers are removed and replaced with DNA. DNA ligase seals the gaps between the Okazaki fragments on the lagging strand resulting in two identical DNA molecules.
What enzyme is responsible for unwinding the DNA in replication?
Helicase
What enzyme is responsible for copying the DNA?
DNA Polymerase
What is the leading strand?
The strand where continuous DNA replication occurs
What is the lagging strand?
The strand where discontinuous DNA replication occurs
In which direction does DNA replication occur?
5’ to 3’
Centromere
Centre of chromosome
What are homologous chromosomes?
A pair of the same chromosomes one having come from each parent
What are sister chromatids?
An identical copy of the original chromosome that occurs after DNA replication
What is formed after meiosis I?
2 diploid daughter cells
What is formed after meiosis II?
4 haploid daughter cells
What 3 processes create diversity in meiosis?
Independent assortment, recombination (crossing over), random fertilisation
What is the difference in output of spermatogenesis and oogenesis?
Spermatogenesis creates 4 viable spermatozoa, oogenesis creates 1 viable ovum and 3 polar bodies
What is a gene?
A small section of DNA constituting the basic unit of heredity
What molecule is created from transcription?
mRNA
Where does translation occur?
Ribosome
What is created from the process of translation?
A polypeptide Chain (protein)
What is removed during RNA splicing?
Introns
What is transcription?
The process of copying a section of DNA into an RNA
