Molecular Genetics Flashcards
What are the complementary base pairs in nitrogenous bases
AT double bond
CG triple bond
Nucleoside vs nucleotide
Side = base + ribose sugar Tide = base + sugar + phosphate ( t = t)
Explain the semi conservative process of DNA replication
Helicase unzips Parent DNA
RNA polymerase creates an RNA primer.
DNA polymerase 3 adds complementary nucleotides on the 3’ end (5’-3’)
RNAse H removes primers
Gaps are filled by DNA polymerase 1 and any nicks are sealed by ligase
Explain the difference between leading and lagging strand and why that’s a thing
Nucleotides can only be added from 5’ - 3’
Leading is continuously synthesized only requiring one primer
Lagging stars and has Okazaki fragments that require many primers
Difference between prokaryote and eukaryote DNA replication
Pro - 1 origin of replication on each circular chromosome (plasmid)
Euk - multiple origins on each linear chromsome
All nucleotide processed go in which direction
5’ to 3’
What does telomerase do
Lengthen the end of eukaryotic chromosome with telomeres
Define gene vs genome
Series of DNA nucleotides that code for an RNA product
Genome contains the entire DNA sequence of an organism
what is the central dogma *****
DNA is transcribed into RNA which is translated into amino acids (proteins)
4 differences of RNA to DNA
can leave the nucleus (DNA only in nucleus and mitochondria
Uracil instead of thymine
Has an OH group
Single stranded
Primary rna
Immature strand of mRNA
Messenger rna
Primary rna is processed to encode for a blueprint used in translation
Ribosomal rna
Rna component of a ribosome
Transfer rna
Transfer amino acids to growing polypeptide
3 phases of transcription
Initiation , elongation, termination
Initiation phase of transcription
RNA polymerase binds to promoter or TATA box then unzips DNA and forms a transcription bubble
Elongation phase of transcription
RNA polymerase transcribes the template (antisense) strand adding nucleotides 5’-3’ creating a primary RNA transcript with the same sequence as the coding strand (sense)
mRNA strand made in transcription is complementary to _____ and the same as ______
Complements the template strand
Same as the coding strand
** uracil instead of thymine
Termination phase terminates transcription which it hits which sequence
UAA UAG UGG
Remember on the template strand UAA would be ATT and coding strand would be TAA
Do page 59 in classroom companion**
Ok
3 types of post transcriptional modification
Does this occur in bacteria mRNA?!
MRNA in bacteria are translated directly into a protein. eukaryotes undergo
- 5’ cap methyl guanine cap is added to 5’ end protects from degradation by exonucleases
- Poly A tail on 3’ end , the string of adenin protects from degradation
- Splicing - introns are cleaved and Exxon’s are spliced together by snRNPs
What is a ribozymes
RNA molecule that can catalyze reactions , one of the few enzymes that’s not a protein
What happens to mRNA after post transcriptional modification
Exons Exit the nucleus into cytoplasm to undergo translation
Start codon
AUG
MRNA nucleotides strung together form the genetic code which has 3 key features
Unambiguous - codes from a specific amino acid
Degenerative - an amino acid can have more than one code
Universal - all living organisms use the same code except the mitochondria
What are the sedimentation coefficients of prokaryotic and eukaryotic ribosome
Pro - 30 + 50 (70)
Euk - 40 + 60 (80)
Describe translation process
TRNA with methionine enters P site to form initiation site. C end binds to N end of amino acid in a dehydration reaction. That tRNA goes to E site and exits while a new tRNA comes to A site until a stop codon reaches the A site
Ditrection of translation
5’ to 3’ and N to C
Is there proof reading in translation , transcription , replication
No
Reduced
High and fast
Key differences between prokaryotes and eukaryotes in transcription/translation
Pro - not membrane bound so can occur simultaneously therefore less regulation and control
Euk - transcription in nucleus, translation in cytosol
When you come across a membrane bound protein (functions in ER rather than cytosol) how was it created
First couple of amino acids form a signal peptide that is recognized by RNA signal recognition particle that binds and then carries the ribosome complex to SRP receptor protein on the endoplasmic reticulum
The N terminus of the peptide is orientated into the lumen (interior) and translation resumes with the peptide growing inside the lumen!
Difference between posttrascriptional control and posttranslational
Transcript - 5’cap, poly A tail, splicing
Translat - how proteins are folded, carbs or lipids added, exported
Silent point mutation
Codon codes for same amino acid
Missense point mutation
Codon codes for different amino acid that may or may not impact the protein
Nonsense
Changes to stop codon resulting in non functional protein
Frameshift
Insertion not in a multiple of 3 alters the reading frame
Nonframeshift mutation
Multiple of 3 nucleotide inserted into gene sequence
Explain what goes wrong that cancer cells form
No apoptosis
Proto-oncogene is a normal gene that becomes an oncogene due to a mutation often caused by a carcinogen
Loss of tumor suppressor gene
How does DNA become a chromosome
DNA wraps around his tones to form nucleosides which become a solenoid then chromatin which become chromosomes
What is a chromosome
Organized DNA+protein structure in the nucleus
Single double helix of coiled DNA that contains genes
Cell cycle for somatic cells consists of mitosis and interphase , what are the stages of interphase
after mitosis G0 = cell arrest
G1 = growth
S = 46 chromosomes duplicated into sister chromatids
G2 = double check
What is mitosis and what does it produce
Nuclear cell division * no genetic change
2 genetically identical daughter cells with 46 chromosomes
4 phases of mitosis
Prophase - chromosome condenses, spindle forms
Metaphase - chromosomes align
Anaphase - sister chromatids separate, cytokinesis begins
Telophase - new nuclear membrane forms
What does diploid mean
Cell has homologous pairs
In the nucleus of a human cell there are 46 chromosomes before replication, how many are there after replication
46 chromosomes still!!!!
Refer to duplicates as sister chromatids, this is a very important concept
What is the result of meiosis
Four haploid gametes from a single diploid germ cell
What happens during prophase 1 of meiosis
Homologous chromosome s(same genes) form a tetrad which is held together at the chiasmata where crossing over of genetic material occurs
Product after meiosis 1
Haploid 23 chromosomes / 46 chromatids
3 ways eukaryotes increase genetic diversity
Crossing over in prophase 1
Random assortment in metaphase 1
Fertilization
What is nondisjunction and how serious is it
Failure of chromosome pairs to separate at anaphase resulting in aneuploid cells which is not much of an impact on somatic cells but can be severe in embryogenesis
Monopoly vs trisomy
Mono - loss of single chromosome in zygote - often not viable
Tri - addition of chromosome in zygote
See page 90 for differences between mitosis and meiosis
Ok
how are dna nucleotides linked
covalent phosphodiester bond formed by dehydration between OH of 3’ carbon and the phosphate attached to the 5’ carbon
