Lecture 2+3 Flashcards
What is a neucleotide?
Contains a deoxyribose sugar, attached to 5 carbon, a phosphate group, attached to the 1 carbon is the base
What does a phosphodiester bond do?
it’s the link of the 5’ carbon and the 3’ carbon
Complementary base pairing
Thymine (pyrimidine) double carbon bond with adenine (purine). Cytosine (pyrimidine) triple carbon bond with guanine (purine)
Antiparallel DNA?
the strands are antiparallel because the bases on one polarity is the opposite to the other strand
What is 5 prime and 3 prime?
The carbons on the sugar
Where are chromosomes found? and when are they visible
In prokaryotes in cytosol
In Eukaryotes in nucleus
Only visible during cell division
Where are genes found?
on chromosomes, (also mitochondria, chloroplasts and plasmids. Position of a gene on a chromosome is a locus
when are chromosomes single and double stranded
Single - one molecule of DNA
Double - Chromatid two molecules of DNA
S phase important
What is a nucleosome?
DNA wrapped around histone: protein molecules
When does DNA replicate
when the nucleosome
Heterochromatin?
Euchromatin?
Heterochromatin = tightly packed chromatin Euchromatin = lightly packed chromatin
PCR?
Polymerase Chain reaction to get lots of copies of a piece of DNA. Heating takes them apart
DNA replication is
Semi conservative
DNA enzymes
Helicase unzips
Ligase
DNA topoisomerase (gyrase) - relieves supercoiling
Single stranded binding proteins - keep old strands apart
DNA polymerase III - can only replicate in one direction thus the strand grows 5’–> 3’, needs short double-stranded region to start DNA replication = Primer RNA
Clamp
Primase
Differences in eukaryote = enzymes, speed and length of Okazaki fragments
What is a leading strand?
5’ to 3’ –> opening up the DNA going into the fork
What is the lagging strand?
Still 5 to 3 but DNA polymerase III does it in small chunks leaves Okazaki fragments (discontinuously) because of this the primers are removed, gaps are filled with complementary bases (DNA polymerase I) and the fragments are joined by Ligase
What are Telomeres and their function?
Protect the ends of chromosomes, (particularly with lagging strand) can lose genes/ erode away
What can Telomerase do to help?
extends the lagging strand, primer attaches and DNA polymerase completes the replication. can be seen in cancer cells!
Genetic consequences of Meiosis
Segregation of alleles
independent assortment of chromosomes
crossing over and recombination of alleles
Incomplete dominance is where
A blended phenotype, 1:2:1 ratio
Codominance is where
the full effect of both alleles is seen in the phenotype of the heterozygote
1:2:1 ratio
Complete dominance ratio
3:1 ratio
