DNA & RNA Flashcards
DNA and RNA are ____________.
Polynucleotides
What are the 3 parts of a nucleotide?
- 5 carbon sugar (Pentose)
- Nitrogenous base (ATCG)
- One or more phosphate groups
What are pyrimidines?
C, T, U
- has one 6 membered ring
What are Purines?
A, G
- has a 6 membered ring fused to a 5 membered ring
What is the sugar for DNA?
What is the sugar for RNA?
What are their differences?
Deoxyribose
Ribose
Deoxyribose lacks an oxygen atom
In Animals, some DNA is found in the __________.
In Plants, some DNA is found in the __________.
Mitochondria
Chloroplasts
What are the 3 phases of Translation? Describe what happens in each one
Initiation
- initiator tRNA carrying the first amino acid binds to the mRNA start codon. The small and large units of the ribosome come together and translation begins.
Elongation
- Elongation Factor (EF) proteins recruit charged tRNAs to form more amino acids
Termination
- Release Factors (RF) bind to a stop codon in the A site and releases the polypeptides
A-T base pair has ___ hydrogen bonds
G-C bade pair has ___ hydrogen bonds
2
3
What is polycistronic mRNA?
mRNA that contains 2 or more genes
Why is the genetic code in triplets instead of doublets?
If the genetic code was in doublets, it would only produce 16(4^2) combinations of codons, which is not enough to specify 20 amino acids.
What are synonymous codons?
Codons that specify the same amino acid
Define Third-base Wobble
The flexibility of nucleotide pairing in the 3rd position of the codon and its anticodon
Eg,
UCC, UCU, UCA, UCG all code for Ser
- the 3rd base doesn’t matter
For translation, tRNAs need to be charged. What are they charged by? What does this do?
They are charged by Aminoacyl-tRNA Synthetases
- these contact multiple points on tRNA to identify the proper tRNA to charge with an amino acid
What are the differences in transcription for prokaryotes and eukaryotes?
- Eukaryotes have 3 RNA Polymerases, prokaryotes have 1
- Eukaryotes form an initiation complex with transcription factors, prokaryotes don’t
- RNA is transcribed first in the nucleus and second in the cytoplasm is eukaryotes, in prokaryotes they are done simultaneously
- Eukaryotes have 5’ capping and polyadenylation, prokaryotes don’t
Define monocystronic
One gene in one mRNA
Define polycystronic
Many genes on one mRNA
What is alternative pre-mRNA splicing?
When different mRNAs can be produced from the same gene, using different promoters or polyadenylation sites or by removal of different exons
What are introns?
Segments of DNA that do NOT code for proteins and are spliced out
What are exons?
Segments of DNA that DO code for proteins and are joined together after splicing
What are alternative promoters?
Promoters that can initiate transcription at distinct start points in different cell types
What is alternative polyadenylation?
When a gene has different polyadenylation signals (at the poly-A tail) to encode multiple mRNA transcripts
What are the 4 components of PCR (Polymerase Chain Reaction)?
- Double stranded DNA
- 4 DNA Nucleotides
- Heat stable DNA Polymerase
- 2 different DNA primers
How many cycles is PCR run through?
30-35
Each PCR cycle _________ the number of copies of the target sequence
Doubles
What DNA polymerase is used in PCR?
Taq polymerase (it is heat stable)
What is autosomal inheritance?
Hereditary transmission of genes carried on autosomes
Autosomes are non sex chromosomes
Dideoxynucleotides are used for ___________ because they are _________.
Sequencing, chain terminating
What is true reversion?
Reverting the mutation at the same site or within the same codon
What is intragenic reversion?
Reverting the mutation at a different part of the gene
What is second-site reversion?
Reversion at a different site to generate original function
Suppressor mutations because they suppress mutated phenotype
What is euchromatin?
Chromosome regions containing chromatid that is not densely compacted. The most expressed genes are located here
(These genes are more actively transcribed)
What is heterochromatin?
Chromosome regions where chromatin is tightly condensed
Fewer expresses genes here
Which DNA is more likely to hold repetitive DNA, euchromatic or heterochromatic?
Heterochromatic
What is a nucleosome core particle?
A heterooctameric protein complex that contains two molecules each of the four histones H2A, H2B, H3 and H4.
What are “beads on a string”?
Chromatin that consists of nucleosomes and linker DNA
What’s the diameter of a nucleosome?
10 nm
After chromatin has been condensed from a 10nm-fiber, what state is it next condensed into?
30nm-fiber (solenoid structure)
Which RNA polymerase makes mRNAs in Eukaryotes?
RNA polymerase II
Scaffold proteins condense chromatin into 300nm-fiber and it forms into _________ in metaphase.
Sister chromatids
