Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCAT Biology > Genes > Flashcards

Genes Flashcards

Exam Krackers MCAT Biology Lecture 2

You may prefer our related Brainscape-certified flashcards:
MCAT flashcards AP® Biology flashcards Biology 101 flashcards
1
Q

What is a gene?

A
  • a series of nucleotides that generally codes for the production of a single polypeptide or RNA.
  • repetitive sequence
  • eukaryotes have more than one copy of some genes - unique-sequence
  • prokaryotes have only one copy of each gene.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Purines

A
  • Adenine and Guanine
  • 2 ringed structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Pyrimidines

A
  • Thymine, Cytosine, Uracil
  • single ringed structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

DNA

A
  • a polymer of nucleotides, each made of a phosphate group, a 5 Carbon sugar, and a nitrogenous base
  • Nucleotides are bound to the next by Phosphodiester bonds between the 3 C of one ribose to the 5th C of the next
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The double strands of DNA are held together by _________ bonds between the nitrogenous bases.

A
  • Hydrogen
  • A2T

A-T 2 H-bonds

  • C3G

C-G 3 H-bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

DNA Replication

A
  • Semiconservative (1 original, and 1 new strand)
  • Bidirectional (proceeds in both drections from an origin)
  • semidiscontinuous (formation of one strand is continuous”leading strand” and the other is fragmented”lagging strand”)
  • DNA paddles upstream (reads 3’ to 5’) and it synthesizes downstream (creates the new strand 5’ to 3’)
  • each nucleotide added to the new strand requires the removal of a P-group from a deoxynucleotide triphosphate, which some of the E is used to drive the replication
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

DNA Helicase

A

unwinds the double strand (like a teenage boy, unzips the genes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

DNA polymerase

A
  • can only add nucleotides to existing strands in the 5’ to 3’ direction thus making it necessary for the leading and lagging strand
  • It needs an RNA primer (approx. 10 nucleotides to initiate the strand)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

5 Steps of Replication

A
  1. Helicase unzips the double helix
  2. RNA Polymerase builds a primer
  3. DNA polymerase assembles the leading and lagging strands

4 Primers are removed

  1. Okazaki fragments are joined
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Okazaki fragments Lagging strand Leading Strand

A
  • disconnecting strands that make up the lagging strands
  • interrupted strand
  • continuous new strand
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

DNA ligase

A

moves along lagging strand and ties Okazaki fragments together to complete the polymer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Exonuclease

A
  • one of the enzymes in DNA polymerase that proofreads by removing nucletides from the strand.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Telomere

A
  • protect chromosome from being eroded through repeated rounds of replication
  • repeating 5 nucleotide units from 100 to 1000 units long
  • telomerase catalizes the lengthing of telomeres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is RNA different from DNA?

A
  • single stranded
  • U not T
  • Uses ribose (not deoxyribose)
  • not confined to the nucleus (DNA is in nucleuos and mitochondrial matrix) RNA is can be in cytosol
  • produced by transcription (DNA by replication)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the different types of RNA?

A

mRNA - delivers DNA code for AAs to the cytosol where proteins are made

rRNA - combines proteins to from ribosomes(cellular complex directs protein synthesis) - synthesized in the nucleulus

tRNA - transports AAs from the cytosol to the ribosomes for incorporation into proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

‘Transcription

A
  • requires a Promoter(a spot on DNA that tells RNA polymerase where to begin transcription
  • Initiation- is the beginning of transcription
  • only the template strand of DNA is transcribec
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

consensus sequence

A
  • the most common nucleotide sequence of a promotor reccognized by RNA polymerase of a given species.
  • variation from this sequence causes less tight and less often bond of RNA polymerase to the specific promoter resulting in decreased frequency of those genes being transcribed.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Most genetic regulation occurs at ________.

A

Transcription

  • the amt of a specific protein in a cell is most likely determined by the amt of its mRNA is transcribed.
  • many proteins can be transcribed from a single mRNA
  • mRNA is has a short half-life in the cytosol, it degrades shortly after transcription
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 3 steps of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What occurs during the Initiation phase of Transcription?

A
  • Transcription initiation complex containing RNA polymerase is made when initiation factors find the promoter on the DNA strand
  • RNA Polymerase binds to promoter, and begins to unzip the DNA, forming a transcription bubble -
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How many types of polymerases do prokaryotes have verses eukaryotes?

A
  • Prokaryotes have just 1
  • Eukaryotes have 3 ( 1 for each of the 3 types of RNA)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What occurs during the Elongation phase of Transcription?

A
  • only the template(antisense) strand is transcribed. The coding (sense) strand is there to protect against degredation
  • (Like DNA Polymeraase) RNA Polmerase reads from 3’ to 5’ creating 5’ to 3’ RNA.
  • RNA Polymerase does not contain a proofreading mechansm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What occurs during the Termination phase of Transcription?

A
  • a special terminattion sequence and proteins are required to dissacociate RNA Polymerase from DNA. ? (not sure when) 5’cap and poly A tail is put on the 5’ and and 3’end of mRNA repectively. They protect against degradiont from exonucleases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the difference between prokayotic and eukaryotic mRNA?

A

Prokaryotic - mRNA is polycistronic (several genes in 1 transcript)

Eukaryotic - mRNA is monocistronic(1 gene per transcript)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Define Operon

A
  • entire transcript of a prokaryotic gene
  • sequence of bacterial DNA containing an operator(additional regulatory site), promoter, and related genes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

a decrease in glucose causes an _________ in cAMP

A

increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the three ways post-transcriptional modification occurs?

A
  • addition of nucleotides
  • deletion of nucleotides
  • modification of bases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

primary transcript

A
  • the initial mRNA after transcription
  • contains introns (nonsense) and exons(code for proteins)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Whats the difference in post-transcriptional between prokaryotes and eukaryotes?

A

Prokaryotes - occur in rRNA and tRNA, the mRNA here is mostly transcribed

Eukaryotes - occurs in all three (mRNA, rRNA, and tRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are snRNPs

A

Small Nuclear Ribobucleoproteins

associates w/other proteins to for the Spliceosome(loops entrons, while spliceing exons together)

  • may form diff seuquences
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Denatured DNA

A
  • can occur from heating, high salt or pH solution,
  • the breaking of H- bonds thus separating the double strand
  • DNA with more CG (triple h-bonds) pairs will have a higher Tm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is Nucleic Acid Hybridization?

A
  • Separated strands will spontaneously associate with original partners or other complementary nucleotide sequence
  • there can be DNA-DNA, DNA-RNA, RNA-RNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How can bacteria defend themselves against viruses?

A
  • cutting the DNA with restriction enzymes
  • protecting their own DNA from the restriction enzymes with methylation(adding -CH3)
34
Q

Restriction Enzymes(endonucleases)

A
  • digest(cut) nucleic acids at certain nucelotide sequences(restriction sites)
  • Restriction sites are usually palindromic (same backwards and forwards)
35
Q

Sticky Ends

A

Most restriction endonucleases cleave the DNA strand unevenly that can later recconnect by DNA ligase.

36
Q

Recombinant DNA

A
  • when 2 DNA fragments can be joined together regardless od the origin of the DNA , as long as they were cleaved by the same endonuclease
37
Q

DNA Library 1: How do you make a DNA library

A
  1. use a vector to insert a DNA fragment into a bacterium
  2. Reproduce the bacterium to create a clone of bacteria with the DNA fragment.
38
Q

DNA Library 2: How do you screen DNA libraries for appropriate clones?

A
  • include the gene for resistence to a certain antibiotic in the original vector, and include lacZ gene(enables bacteria to metabolize the sugar X-gal)
  • When an antibiotic is added to the library of clones clones without resistance will be eliminated, thus the clones with resistance must not have taken up the vector.
39
Q

DNA Library 3: How do you screen out clones that contain the original vector and not the DNA Fragment?

A
  • use an endonuclease that inserts the DNA fragment into the middle of the lacZ gene and inactivates it (a recognition site that cuts the lacZ gene in two)
  • (so the lacZ gene will not work) While a normally active lacZ gene would turn blue in the presence of X-gal.
40
Q

Describe cDNA

A

Complementary DNA

  • bacteria has noe mechanism for removing introns, so we clone DNA with no introns
  • mRNA is reverse transcribed using revers transcriptase to make cDNA (single stranded?)
  • DNA Polymerase is added to to prod the double strand of desired DNA (with no introns)
41
Q

What are the benefits of PCR?

A

** Polymerase Chain Rxn**

  • fast way to clone DNA, while reusing a small amt of heat resistantpolymerase
  • PCR requires that the base sequence flanking the ends of the DNA fragment be known, so that the complementary primers can be chosen.
42
Q

What is the process of PCR?

A
  1. Double strand of DNA to be cloned is placed in mixture with many copies of DNA primers one for each strand.
  2. Mixture is heated to 95oC to denature the DNA
  3. Mixture is cooled to 60oC, primers hybridize(anneal) to their complementary ends of DNA primers
  4. heat-resistant polymersases is added and the mixture is heated to 72oC (to activate the polymerase) - polymerase clones the complementary strands, Doubling the amt. of DNA
43
Q

Describe Southern Blotting

A

- identifies specific sequences of DNA by nucleic acid hybridization

  1. DNA is cleaved into restriction fragments
  2. Gel electrophloresis is used to spread fragments according to size (large fragments move slower than small)
  3. Blot onto membrane
  4. Radio labeled probe made from DNA or RNA 5. Visialize with radiographic film
44
Q

Describe Nothern Blotting

A
  • same as southern blotting , but for RNA
45
Q

Describe Western Blotting

A
  • detects proteins with antibodies
46
Q

What is RFLP

A

Restriction Fragment Length Polymorphisms

  • DNA finger prints used to identify criminals in court cases -
47
Q

SNPs

A

** Single Nucleotide Polymorphisms**

  • genome of one human differes from another at about one nucleotide in every 1000. These differences are SNPs
48
Q

What are the stop and start codons respectivly?

A

Start: AUG (methionine)

Stop: UAA, UAG, UGA (signal the end of protein synthesis)

49
Q

3 consecutive nucleotides on a strand of mRNA represent a _________.

A

codon

50
Q

Describe the Genetic Code

A
  • Degenerative
  • more than one series of three nucleotides may code for the same amino acid.
  • Unambiguous- any single series of 3 nucleotides will code for one and only one amino acid
  • Almost universal- nearly every living organism uses the same code
51
Q

Describe Ribosomes…

A
  • large and small sub-unit (40S and 60S for a combined sedimentation coefficient of 80S in eukaryotic)
  • made in nucleolous
52
Q

What are the three steps of Translation?

A
  1. initiation
  2. elongation
  3. termination
    - polypeptide begins folding as it is translated (assisted w/ chaperones)
    - can take place on free floating or attached ribosomes.
53
Q

Describe the Initiation step of Translation…

A
  1. mRNA enters cytosol from nucleus through nuclear pores
  2. ‘Initiation factors’ assist 5’ end attach to small subunit of ribosomes
  3. tRNA w/ 5’-CAU-3’ sequesters methionine and settles at the P-site - this signals the large subunit to join forming the initiation complex
54
Q

Describe the Elongation process of Translation…

A
  1. a tRNA (with corresponding AA, attaches to the A-site, at the cost of 2 GTPS
  2. peptidyl transferase catalyses the dehydration rxn of the C-terminus of methionine attaching to the N-terminus of the amino acid at the A-site.
  3. Translocation
55
Q

P- site A-site E-site C- terminus N-terminus

A

P-site - peptidyl site

A-site - aminoacyl site

E-site - (exit)

C- terminus - Carboxyl end

N-terminus - Amine end

56
Q

What happens during translocation (elongation of translation)

A
  1. ribosome shifts 3 nucleotides along the mRNA towad the 3’ end
  2. the tRNA that carried the methionine moves (from the P-site) to the E site where it is then discarded.
  3. A 2 peptide chain is formed at the P-site and the A-site is cleared for the next tRNA.
    - Translocation requires expenditure of another GTP.
    - elongation process repeats until a stop codon reaches the P-site
57
Q

Describe the Termination process of Translation…

A
  1. a stop codon reaches the A-site
  2. a Release Factor binds to the stop codon causing H2O to to add to the end of the polypeptide chain.
  3. polypeptide is freed (from mRNA and ribosome), ribosome breaks up into subunits to be used again
58
Q

What is a mutation?

A
  • any alteration in the genome(total complement of DNA) that is not genetic recombination.
  • may occur at chromosomal or nucleotide level
59
Q

what are mutagens?

A
  • chemical or physical agents that can induce mutations.
60
Q

Point mutation

A
  • mutation changes single base pair of nucleotides
61
Q

missense mutation

A
  • base pair mutation occures in AA coding sequence of gene.
  • may or may not alter AA sequence
62
Q

sickle cell anemia

A
  • dz caused by a single AA difference in hemoglobin
63
Q

What is the difference between a ‘neutral’ and a ‘silent’ mutation?

A

Neutral no change in protein function Silent AA is not changed (yet may be significant by changing the rate of transcription)

64
Q

Frameshift mutation

A
  • deletions or insertions in non-multiples of 3
  • results in completely nonfunctional protein
65
Q

Nonsense mutation

A
  • when a stop codon is created
  • prevents translation of a functional protein entirely
66
Q

chromosomal deletion

A
  • dna fragment breaks off from chromosome
67
Q

chromosomal Duplication

A
  • dna fragment breaks free off one chromosome and incorporates into a homologous chromosome.
68
Q

down syndrome

A

result of aneuploidy( concerning an entire chromosome) where there are 3 chromosomes at chromosome 21

69
Q

Translocation (chromosome)

A
  • when a segment of DNA from one chromosome is inserted into another chromosome
70
Q

Inversion (chromosome)

A

orientation of a section of DNA is reversed on the chromosome.

71
Q

Describe Transposition (chromosome)

A
  • DNA segments called transposons can excise themselves from a chromosome and reinsert at another location.
72
Q

Forward mutation

A
  • Mutation further away from Wild type(original state)
73
Q

Backward mutation

A
  • mutation back towards wild type
74
Q

oncogenes

A
  • genes that cause cancer
75
Q

protooncogenes

A
  • can be converted to oncogenes by mutagens (UV, chemicals, random mutations)
76
Q

Carcinogens

A
  • mutagens that cause cancer
77
Q

Describe Chromatin

A
  • entire DNA/protein complex
  • By mass: 1/3 DNA 2/3 protein small amt of RNA
78
Q

nuclesome

A
  • 8 histones wrapped in DNA
  • nucleosomes wrap into coils called solenoids that further wrap in supercoils
79
Q

Euchromatin

A

chromatin that can be uncoiled and transcribed

80
Q

Chromosome

A

chromatin associated with (in human somatic cells) the 46 double stranded DNA molecules

81
Q

homologues

A

pair of chromosomes with same traits( can be different genes)

  • cells with homologous pairs are ‘Diploid’ if not htey are considered ‘Haplloid’
82
Q
A

MCAT Biology (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions