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Biology 152 > Genetics-Exam 2 > Flashcards

Genetics-Exam 2 Flashcards

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1
Q

What is the transforming principle?

A

substance can be transferred from non-living cells to living cells, that substance being DNA. Two important experiments lead to this Griffith (1928) and Avery (1944–confirmation that DNA was the genetic material.

In the Griffith experiment infected rats with S=virulent and R=non-virulent strain pneumonia. When mixed heat-killed S-strain with living R-strain, mouse died. Finding: non-virulent R strain TRANSFORMED into virulent S-strain. But there was not enough evidence to see that DNA was the genetic material.

Avery experiment subjected heat-killed S-bacteria and put them into various enzymes that destroyed said macromolecule. Transformation of R-strain happened in RNAase and Protease but NOT in DNAase. Showed DNA was REQUIRED for genetic change.

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2
Q

What was the Hershey-Chase experiment?

A

Wanted to know what was exchanged between bacteria and bacteriophage, either molecule, protein or DNA. Phages injected with two radioactive solutions, phosphorus for new DNA sulfur for new proteins. The solution was centrifuged and bacteria ONLY showed phosphorus solution (32P)

Finding: found bacteriophage infects bacteria injects DNA and take over bacteria to make more phages.

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3
Q

What is the structure of DNA?

A

Deoxyribonucleic acid (2’ missing hydroxyl group-OH) each DNA strand is a polynucleotide composed of multiple nucleotides. Each nucleotide has a 5’ carbon sugar, phosphate group, 1 of 4 nitrogenous bases, and a double helix

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4
Q

What are the characteristics of genetic material

A
  1. must contain info for phenotype
  2. must be able to replicate
  3. must have ability to change

DNA satisfies these conditions!

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5
Q

What is the structure of prokaryotic chromosomes?

A

circular chromosomes found in cytoplasm

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6
Q

What is the structure of eukaryotic chromosomes/genomes?

A

linear chromosomes found in nucleus

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7
Q

What are the differences between haploid and diploid cells?

A

haploid= n (one set of chromosomes)

diplpoid=2n (2 sets of chromosomes, mom and dad)

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8
Q

Why are mitochondrial and chloroplast DNA important? What are the origins of the two organelles?

A
  1. have own circular genomes like bacteria
  2. Multiple copies of the genome in mitochondria and chloroplast
  3. Similar ribosome size and structure
  4. replicate independently of the cell (they divide on own via binary fission) partioned into daughter cells @ random

Most likely originated from bacteria, eukaryote swallowed a proteobacteria

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9
Q

What is the endosymbiont theory?

A

organelles like chloroplast and mitochondria were once free living prokaryotes/proteobacteria but swallowed by eukaryotic cell and evolved into modern day chloroplast and mitochondria; why these organelles have lots of similarities with bacteria

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10
Q

What is the difference between heteroplasmy and homoplasmy

A

Heteroplasmy: presence of more than one type or organellar genome; mixture of normal and abnormal mitochondria (mitochondrial DNA or plastid DNA) within cell or idnvidual
Homoplasmy: presence of uniformally normal or abnormal mitochondria in a tissue
* different cells have different metabolic needs, so some cells are okay with some non-functioning mitochondria mixed with normal mitochondria

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11
Q

What makes the backbone of DNA?

A

sugar-phosphate backbone, formed by 5’ to 3’ phosphodiester bonds (type of covalent bond)

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12
Q

What is the central dogma?

A

DNA—»>RNA (tranciption)—»> Protein (translation)

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13
Q

What is a purine?

A

adenine and guanine (ketone- double bonded O); have two rings

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14
Q

What is a pyrmidine?

A

thymine and uracil (RNA) have two ketone groups

cytosine has one ketone group; have one ring

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15
Q

How did Avery demonstrate transforming principle is DNA?

A

Griffith experiment did not show that DNA is the genetic material, subjected heat-killed S strain into different enzymes along with R strain, S-virulent transformed R strain in RNAase and Proteinase, but didn’t in DNAase/ it degraded indicating that DNA is required for genetic change

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16
Q

What bases pair with each other?

A

purine always pairs with a pyrmidine; G and C have 3 hydrogen bonds; A and T(U) have 2 hydrogen bonds

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17
Q

What is the significance of the major and minor grooves of DNA?

A

Helical structure of the 2 alternating spaces, major groove and minor groove.

Major groove is wider with bases exposed, protein specific binding to DNA.

Minor groove is narrower with bases NOT exposed, proteins bind in general manner.

18
Q

What are some of the important implications of the STRUCTURE of DNA?

A
  1. Base pairing: A with T (U-RNA), G with C
  2. 5’ to 3’, anti-parallel strands
  3. deoxynucleic acid (missing hydroxyl -OH group)
  4. Each single nucleotide has a 5’ sugar, phosphate group, and 1 out of 4 nitrogenous bases
19
Q

What is maternal inheritance of organelles?

A

you inherit mitochondria from your mother; Mitochondrial DNA is inherited through the maternal lineage. All offspring inherit their mother’s mitochondria, and therefore the same mitochondrial DNA. As a result, all family members that share a maternal lineage would have the same mitochondrial DNA. Mitochondrial DNA can therefore be used to confirm or eliminate a person’s relationship within a maternal line, but cannot be used to identify a specific individual.

20
Q

What is the difference between conservative, semi-conservative, and dispersive replication models?

A

conservative: a new dna molecule is replicated from an old piece, meaning the WHOLE dna molecule is replicated
semi-conservatice: a new dna molecule consists of one old strand and a new strand in first generation
fragment: fragments break and are pieced together at random

21
Q

How is transcription different in bacteria and eukaryotes?

A
  1. Prokaryotes only contain 3 promoter elements: -10, -35, and upstream elements–eukaryotes have many different elements such as TATAA box, initiator elements, TFIIB recognition element, downstream core promoter element
  2. Trancription and translation occur simultaneously in prokaryotes while in eukaryotes RNA is first transcribed in the nucleus and translated in the cytoplasm
  3. eukaryotic DNA complexed with histone proteins and highly compressed into chromatin in order to protect DNA- while in bacteria DNA isis free flowing in the nucleus so doesn’t need to be decompressed like eukaryotes
    4.
22
Q

How is transcription different in bacteria and eukaryotes?

A
  1. Prokaryotes only contain 3 promoter elements: -10, -35, and upstream elements–eukaryotes have many different elements such as TATAA box, initiator elements, TFIIB recognition element, downstream core promoter element
  2. Trancription and translation occur simultaneously in prokaryotes while in eukaryotes RNA is first transcribed in the nucleus and translated in the cytoplasm
  3. eukaryotic DNA complexed with histone proteins and highly compressed into chromatin in order to protect DNA- while in bacteria DNA isis free flowing in the nucleus so doesn’t need to be decompressed like eukaryotes
  4. eukaryotes use 3 different RNA polymerases while prokaryotes use
23
Q

What was the Meselson-Stahl Experiment?

A

wanted to see if DNA replication was semi-conservative, conservative or fragments. Used two nitrogen isotopes, 14N and 15N (one light one heavy); initially grew DNA on heavy nitrogen then switched to light nitrogen then observed how much of isotope in each generation via gradient centrifugation. Found that DNA replicated in semi-conservative way.

24
Q

What is theta replication in prokaryotes?

A

Theta replication in prokaryotes: have circular genomes, replication begins at one location (OriC) so once DNA unwound replication bubble forms with 2 replication forks with replication proceeding in both directions

25
Q

What is linear replication in eukaryotes?

A

many origins of replication, bi-directional

26
Q

What is the architecture of DNA synthesis

A

antiparallel and proceeds in 5’ to 3’ direction, replication fork unwound from L to R, leading strand: in direction of fork providing continuous replication, lagging strand (okazaki fragments): proceeds opposite direction of fork resulting in discontinous replication

27
Q

What is the architecture of DNA synthesis

A

antiparallel and proceeds in 5’ to 3’ direction, replication fork unwound from L to R, leading strand: in direction of fork providing continuous replication, lagging strand (Okazaki fragments): proceeds opposite direction of fork resulting in discontinous replication

28
Q

What are the steps of DNA replication?

A
  1. Helicase unwinds double helix into two strands, cutting hydrogen bonds
  2. single strand binding proteins (ssBs) attach to the halves and keep the DNA from reannealing
  3. Replication fork forms with the leading and lagging strands
  4. In leading strand, RNA primase moves along nucleotides and coats with an RNA primer that will be used to bind with DNA polymerase
  5. DNA Polymerase III attaches after primase and moves along toward replication fork in the 5’ to 3’ direction, synthesizes new nucleotides to existing strands
  6. DNA Polymerase II replaces the primer with DNA nucleotides so all DNA is there (no RNA)
  7. ligase binds together Okazaki fragments
  8. Topoisomerase cuts and rejoins the helix
  9. Addition of telomeres with are noncoding DNA added by telomerase (only in eukaryotes)
29
Q

What are the enzymes required for replication? (specify for both leading and lagging strand)

A

Initiator Protein: binds to origin and separates strands of DNA to initiate replication
helicase: unwinds DNA
Topoisomerase: relieves tensions from unwinding DNA
single-strand binding proteins: stops separated DNA strands from reannealing
Primase: make an RNA primer so DNA polymerase III can extend, one on leading strand, multiple times on lagging strand
DNA gyrase: moves ahead of replication fork, making and resealing breaks in the double-helical DNA to release the stress that builds up as a result of unwinding at the replication fork
DNA ligase: seals nicks on the lagging strand
DNA polymerase I: removes RNA primers
DNA Polymerase III: elongates a new nucleotide strand from 3’

30
Q

What is proof-reading?

A

DNA Polymerase I and II have proof-reading ability to synthesize new DNA, without it DNA polymerases would make 1 mistake per 10,000 bps, going 3’ to 5; exonuclease activity for both Polymerases

31
Q

What is the structure of RNA, how is it different from DNA?

A
  1. RNA is single stranded, DNA is double
  2. 2’ OH on RNA, 2’ H on DNA
  3. Uracil instead of thymine in RNA
32
Q

What are the types of RNA?

A

Many types of RNA including: mRNA, tRNA, rRNA

33
Q

What are the transcription factors in prokaryotes and eukaryotes?

A

Eukaryotes have more + complex transcription factors.
Prokaryotes have 3: -10, -35, upstream elements
Eukaryotes:TATAA box, initiator elements, TFIIB recognition element, downstream core promoter element

34
Q

What is the transcriptional unit?

A

a gene is the transcriptional unit, see picture in notes

35
Q

What is template vs non-template; sense vs anti-sense?

A

sense strand= non-template= coding strand carries translatable code in 5’ to 3’ direction complimentary to antisense= template= non-coding which does NOT carry translatable code in 5’ to 3’ direction

36
Q

What are the promoter consensus sequences?

A

The promoter consensus sequences is a sequence of DNA where proteins can bind which initiates transcription

37
Q

What is a sigma factor? Where is it used?

A

A sigma factor is used in prokaryotes, it recognizes the consensus sequences in a promoter region. The sigma factor will then bind to the promoter leading to the loading of DNA polymerase, one DNA Poly- attached then sigma factor will unbind

38
Q

What is RNA Polymerase, what are the differences in Eukaryotes and prokaryotes?

A

RNA Poly

39
Q

What is the ribosome and the sites on a ribosome?

A

Ribisomes make the proteins that are encoded by the mRNA created during transcription.

40
Q

What are Shine-Dalgarno sequences?

A

Near the start codon in prokaryotes. Helps to initiate translation by binding the mRNA to the ribosome near the first AUG. It base pairs with the 16s rRNA. It can be on the end or it can be in the middle of an RNA (it’s polycistronic).

41
Q

What are the phases of translation?

A

Initiation, Elongation, Termination
Initiation: SSU
Elongation:
Termination:

42
Q

What are the phases of translation?

A

Initiation, Elongation, Termination
Initiation: Small subunit binds to mRNA at RBS (sequence that’s complimentary to sequence in 16S rRNA of small ribosomal subunit; large subunit loads and ribosome is ready to go
Elongation:2nd tRNA enters A site and if anticodon binds to 2nd codon of mRNA it stays, ribosome then moves exactly three nucleotides down mRNA
Termination: when stop codon reached, no tRNA will match and instead there are protein release factors that recognize stop codon and signal to ribosome to stop translation

Biology 152 (4 decks)

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