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Genetics Final

Lecture 3

Bacteriophages Viruses that infect bacteria and take over their cellular biochemistry to make them produce more viruses
Hershey and Chase Radioactively labelled some phages and let them infect bacteria cultures. Found no viral DNA in the fluid, but did in the infected bacterial cells. Showed that DNA and not protein was hereditary material
In what organisms is RNA the hereditary material? Certain animal, bacterial, and plant viruses
Three parts of a nucleotide Phosphate group, pentose sugar, and nitrogenous base
Difference between deoxyribose and ribose Ribose has one more oxygen and deoxyribose
Purine structure Double ring
Pyrimidine structure Single ring
Nucleoside Sugar and a base
Phosphodiester bonds Phosphate groups link together the sugars in a polynucleotide chain
What holds A and T together? Two hydrogen bonds
What holds C and G together? Three hydrogen bonds
Oligomers Short DNA molecules of defined sequences
A DNA Closest to DNA in cells. Right-handed, short and wide
B DNA Watson and Crick model. Right-handed. Long and thin.
Z DNA Left-handed. Zigzag sugar phosphate backbone.
RNA in cell Single stranded
RNA secondary structure Regions of double-stranded RNA separated by short segments of unpaired RNA
Prokaryote genome Single circular chromosome
Organelle genomes Mitochondrial in all eukaryotes and chloroplast in plants
What do viruses consist of? Nucleic acid fragments surrounded by proteins
Virus genetic material Can be single stranded or double stranded, RNA or DNA, circular or linear
Genome of T-even bacteriophage Single linear chromosome of double stranded DNA, surrounded by protein coat, with chromosome in head of phage
Genome of X174 phage Single circular chromosome of single stranded DNA
Genome of lambda phage Linear chromosome of double stranded DNA, when it infects a cell it becomes circular due to sticky ends pairing together, becomes linear again when it reproduces
RNA virus Virus that either uses RNA as genetic material or whose genetic material passes through an RNA intermediate
Hepatitis B virus Genome is double stranded DNA but is transcribed into RNA during replication
Plasmid When the minor chromosome is dispensable to the life of the prokaryotic cell
Chromosome in archaea and bacteria Arranged as a dense supercoiled clump in a membraneless nucleoid region
Negative supercoiling Twisting left-handed against helical conformation. Untwisted so it has fewer twists
Positive supercoiling Twisted right-handed even tighter until the helix knots. More twists added
Topoisomerases Enzymes that control DNA supercoiling
Why do chromosomes become compacted? DNA is organized into looped domains
C value Amount of DNA comprising the haploid genome of a species
C-value paradox There is often no correlation between C value and evolutionary complexity
Nucleosomes DNA wound around histone proteins
What connects nucleosomes? Linker DNA and linker histone
Beads-on-a-string 10-nm nucleofilament chromatin fiber
30-nm chromatin fiber Nucleosomes wound together and bound by H1 linker histone. Solenoid model
What are SARs Scaffold-associated regions. Stretches of DNA that bind to nonhistone proteins to determine loops in a chromosome scaffold
700-nm fiber Scaffolded chromosome
Euchromatin Regions of the chromosome that show the normal cycle of chromosome condensation (beads-on-a-string). Can be expressed
Heterochromatin Regions of chromosomes that usually remain condensed. Usually inactive
Constitutive heterochromatin Present in all cells at identical positions on both homolouges. Mostly repetitive DNA and exemplified by centromere regions
Facultative heterochromatin Varies in state. Condensed sections of euchromatin such as a Barr body
Barr body Inactivated X chromosome in somatic cells of XX female mammals
Centromeres Accurate segregation of replicated chromosomes into daughter cells
Telomeres Constitutive heterochromatic. Provide chromosome ends with stability. Sequences loop back to form t-loop.
Unique-sequence DNA One to a few copies in a genome
Moderately repetitive DNA A few to 10 to the fifth copies in genome
Highly repetitive DNA 10 to the fifth to 10 to the seventh copies in genome
Dispersed repeated or interspersed repeated DNA sequences arranged at irregular intervals within genome
Tandemly repeated DNA sequences clustered together so they repeat many times in a row
What are SINEs? Short interspersed repeated sequences. Sequences are 100-500 bp in length
What are LINEs? Long interspersed repeated sequences. >5000 bp in length
Created by: iragland