molecular genetics

Question 1

what are the differences between RNA and DNA

Answer 1

RNA (ribonucleic acid)
- single stranded
- uracil instead of thymine
DNA (deoxyribonucleic acid)
- double stranded
- thymine instead of uracil

Question 2

what are the nitrogenous bases? which are pyrimidines and purines?

Answer 2

pyrimidines (single ring)
- thymine (DNA) [uracil in RNA]
- cytosine
purines (double ring)
- adenine
- guanine

Question 2

what makes up a nucleotide?

Answer 2

Pi - sugar [ribose; 5C sugar, deoxyribose; ribose minus one oxegyn] - nitrogenous base [AUCG, ATCG]

Question 3

how does DNA condense in eukaryotes?

Answer 3

• DNA gets wrapped around histones (protein)
• Organize histone packets into a nucleosome
• nucleosomes are looped
  2 of those make a metaphase chromosome

Question 4

how does DNA condense in prokaryotes?

Answer 4

super coiling

Question 4

topoisomerase

Answer 4

relieves tension/prevents DNA from breaking (also known as gyrase)

Question 5

helicase

Answer 5

cuts H-bonds (unzips DNA)

Question 6

SSBP

Answer 6

(single strand binding proteins)
keep H-bonds from re arranging

Question 7

DNA polymerase III

Answer 7

synthesizes new DNA strands
BUT
- cannot start on its own
- can only add new nucleotides to free 3 end
- only synthesized in 5 to 3 end direction (new strand goes 5 to 3)

Question 8

primase

Answer 8

lays down RNA primer 5 to 3 for DNA polymeraise to start

Question 9

what are telomeres? and what do they do?

Answer 9

protects eukaryotic genes from losing important DNA when primers are removed

telomerase: can restore telomeres BUT as you age telomerase is less active

Question 9

DNA polymerase I and II

Answer 9

excises primers and replace with nuceotides + proofread and excise typos

Question 9

ligase

Answer 9

makes phosopdiester bonds between DNA fragments (okazaki fragements)

Question 10

what it the difference in the synthesis of the leading and lagging strands

Answer 10

the leading strand is synthesized continuously whereas the lagging strand is synthesized in okazaki fragments since DNA poly can only work off a free

Question 11

what is more harmful a base pair substitution and a frameshift mutation? and why?

Answer 11

frameshift mutation because an addition or deletion of a base affect all the codons after

Question 12

what are the three kinds of base pair substitutions?

Answer 12

base pair substitution: A instead of C (for example)
- nonsense: STOP codon
- missense: differents AA
- silent: no change (redundant codon)

Question 12

what is a gene

Answer 12

section of DNA that codes for a protein

Question 13

central dogma of biology???

Answer 13

gene – trancribed to — mRNA — translated to —protein (sequence of AA)

Question 14

what enzyme is responsible for transcription?

Answer 14

RNA polymerase: reads the template strand from 3 - 5 so that mRNA runs 5 - 3

Question 15

what direction do the coding and template strands run

Answer 15

template (anti sense): 3 - 5
coding (sense): 5 - 3

Question 16

what does tRNA do

Answer 16

tRNA brings AA to the ribosome, it has anticodons specific to the AAs needed

Question 17

in eukaryotes what needs to happen to the mRNA before entering the cytoplasm

Answer 17

mRNA modification:
- cap and tailing: GGGG cap and poly A tail
- splicing: SnRNPs exise the introns (non coding region)
- alternative splicing: introns are not always introns, regulated with regulatory proteins

Question 18

why do eukaryotes need to do mRNA modification

Answer 18

because the mRNA starts to degrade in the cytoplasm and must be protected from that with the caps
splicing so that the ribosome creates the right protein

Question 19

explain translation

Answer 19

1. mRNA settles into P (peptide) site of the ribosome
2. tRNA brings AA to A site (acceptor)
3. ribosome makes peptide bond
4. ribosome shifts (3 codons over)
5. process repeats until stop codon)

exit site of the ribosome: tRNA id removed/leaves to get other AAs

Question 20

what are the components of an operon?

Answer 20

CAP, promoter (ex. TATA box), operator, structural genes

Question 21

explain an example of the off model

Answer 21

lactase: LacI inhibitor blocks RNA polymerase from transcribing by binding. lactose binds to the inhibitor to remove it once there is lots of lactose to be digested

Question 22

tryptophan is an explain of what model of regulation?

Answer 22

on model: always on unless you dont need it
tryp activates the inhibitor when there is lots of tryp already in your system (when u have another source, ex chicken)

Question 23

gene regulation in eukaryotes?

Answer 23

much messier, not neatly organized

transcription factors: regulator proteins that binds to a part of DNA to regulate transcription
- activators
- inhibitors

Question 24

difference in DNA/DNA replication in pro and eukaryotes?

Answer 24

prokaryotes:
- small, circular
- no junk DNA (no mRNA modification)
- supercoiling
- single origin of replication
- don’t lose length cuz of primers cause circular (no telomeres)
- translation starts when transcription is occuring

eukaryotes:
- large, linear
- lots of “junk” DNA (repetitive sequences, genome stability, and evolution, introns) [mRNA modification]
- DNA coils around histones
- many origins of replication
lose a few nucleotides at endsm [telomeres]
- translation and transcription happen at some time (mRNA must be transported)

Question 24

explain DNA replication

Question 25

the genetic code is… (explain)

Answer 25

universal and redundant

Question 26

Explain how you could use genetic technology to insert a gene into a different organism?

Question 27

What is a plasmid

Answer 27

A same circular section of dna inside bacteria, commonly used for cloning bacteria, separated from bacterial DNA

We can insert genes into a plasmid using restriction endonuclease