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Molecular genetics Flashcards

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1
Q

What is the central Dogma and what is involved?

A

a phrase to describe the flow of genetic info through a biological system. Involves the DNA- > RNA -> and the proteins and processes to make the flow of info possible

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2
Q

Explain the structure of DNA and its properties

A
  • It is anti-parralel from the 5’-3’ directions and 3’ -5’ direction
  • Double helix
  • bases inside are H-bonded
  • ## the phosphate backbone outside has phosphodiester bonds (Covalent)
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3
Q

What are the three functions of the DNA Structure?

A
  • ## Store genetic info
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4
Q

How does Semiconservative replication work?

A

Each parental strand is a template for a new strand

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5
Q

during DNA synthesis, which end of the DNA is the new nucleotides added on?

A

the 3’ end of the new strand

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6
Q

which direction is the DNA template read and which direction is the new DNA Built

A

it is read 3’ to 5’ and it is built 5’ to 3’

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7
Q

DNA replication begins in the

A

ori( Origin of Replication)

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8
Q

What does the helicase do?

A

unwinds the DNA

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9
Q

After the DNA is unwound how do the primase and primer work together?

A

DNA replication starts with a short primer or starter strand of RNA, and the primase synthesizes the complementary DNA

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10
Q

What exactly are okazaki fragments?

A

the small spaces in the synthesis of the lagging strand

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11
Q

what are the enzymes in DNA replication and what is their function?

A

Helicase(Unzipping enzyme) - Breaks the Hydrogen bonds connecting the bases
DNA Polymerase(Builder) - replicates DNA Molecules
Primase(Initializer) - makes the primer so polymerase can figure out where to start replicating
Ligase(Gluer) - connect DNA fragments together

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12
Q

what is the difference between leading Strand and lagging strand?

A

In the leading strand, the primer is placed once and DNA polymerase is able to consistently replicate from the 5’ to 3’ direction
In the lagging strand, primers have to keep being placed for the DNA polymerase to build. Okizaki fragments are made here and ligase glues the fragments together.

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13
Q

What happens with the single stranded bit of DNA is left at each end

A

They are cut and the chromosome is slightly shortened after each replication

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14
Q

What are Telomeres and what are they made by?

A

They are structures that have short repeated sequences of DNA made by telomerase.

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15
Q

where are telomeres found?

A

the ends of eukaryotic chromosomes

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16
Q

How are the chromosomes protected form being joined to other chromosomes?

A

the sequence of DNA in the telomeres bind a protein complex called Shelterin.

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17
Q

What does telomerase do?

A

catalyzes the addition of lost telomeric sequences. (an enzyme that adds nucleotides to telomeres) It has an RNA sequence that acts as a template for the telomeric DNA.

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18
Q

What are the two repair mechanisms and how do they work?

A

ProofReading
- if bases are paired incorrectly the nucleotide is removed. Done by DNA polymerase and it is checked right before adding it to the DNA sequence.
Mismatch repair
- after replication, other proteins scan for mismatched bases missed in proofreading and replace them

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19
Q

What is Polymerase chain reaction?(PCR)

A

Making copies of DNA sequences.
A cyclic process in which a sequence of steps is repeated over and over again

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20
Q

What does PCR use?

A
  • double stranded DNA sample
  • Two primers complementary to the ends of the sequence to be copied
  • Four dNTPs
  • A DNA polymerase that works in high temps
  • Salts and a buffer for pH
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21
Q

How do mutations occur and what are they?

A

Mutations are changes in the nucleotide sequence of DNA that is passed down
they can occur from replication errors that are not corected

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22
Q

what are the 5 different types of mutations?

A

Somatic Mutations
Germ line mutations
silent mutations
Loss of function mutation
Gain of function mutation

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23
Q

what are somatic mutations?

A

A mutation occuring in somatic cells. Passed on by mitosis but not to sexually produced offspring

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24
Q

what are germ line mutations?

A

occur in germ line cells that give rise to gametes. A gamete with a mutation passes it on to the new organism at fernlization

25
Q

Silent mutation?

A

Mutation that doesent affect protein function

26
Q

Loss of function mutation?

A

prevents gene transcription or produce nonfunctional proteins
Almost always recessive

27
Q

Gain of function mutation?

A

Leads to protein with altered function
Usually dominant
Common in cancer cells

28
Q

What are conditional mutations?

A

They cause phenotypes under restrictive conditions, like temp.

29
Q

What is a point mutation?

A

Results from the gain, loss, or substitution of a single nucleotide

30
Q

What do point mutations usually arise from?

A

replication errors or be caused by enviromental mutagens like radiation

31
Q

what are chromosomal mutatoin?

A

extensive changes in genetic material involving whole chromosomes

32
Q

what are the 4 types of chromosomal mutations?

A

Deletions - loss of a chroomosome segment
duplications - homologous chromosomes break in different places and recombine with wrong partners
Inversions-result from breaking and rejoining but the segment is flipped
Translocations - segment of DNA breaks off and is inserted into another chromosomes

33
Q

Spontaneous mutations?

A

occur with no outside influence
- Replication errors by DNA polymerase

34
Q

induced mutations?

A

caused by mutagens(something that causes mutations)
- Chemicals can alter nucleotide bases

35
Q

what are the benefits mutation could have?

A

it provides the raw material for evolution in the form of genetic diversity
- Diversity may benefit the organism immediately (in somatic cells)
- Mutations in germ line cells can cause an advantage in offspring

36
Q

What happens from DNA –> RNA?
what happens from RNA –> Polypeptide?
explain these

A

DNA to RNA is transcription - Information from a DNA sequence is copied to a complementary RNA sequence.
RNA to Polypeptide is translation - converts the RNA sequence to an amino acid sequence

37
Q

What are the three types of RNA? and what do they do?

A

mRNA - carries the DNA message to a ribosome and gets translated
rRNA - makes up ribosomes
tRNA - Transfers an amino acid to polypeptide chain. base pairs with mRNA

38
Q

What are the components transcription needs?

A
  • DNA template for base pairings
  • the 4 nucleoside triphosphates ( ATP, GTP, CTP, UTP)
  • An RNA polymerase
39
Q

What is the difference between DNA polymerase and RNA polymerase?

A

RNA polymerase dont need primers

40
Q

What are the 3 steps of Transcription?

A

Initiation
Elongation
Termination

41
Q

In transcription, what does initation require and what does it do?

A

Requires a promoter (Tissue specific) – tells RNA polymerase where to start transcription and which strand to transcribe

42
Q

In transcription, what is Elongation?

A

RNA polymerase unwinding DNA and reading the template in a 3’ to 5’ direction

43
Q

in transcription, what is termination?

A

specified by a specific DNA sequence

44
Q

What are coding regions?

A

sequences of DNA that are expressed as proteins

45
Q

after transcription, what are the noncoding sequences and translated regions called? What happens to them in the final mRNA

A

The introns are noncoding and the translated are exons. The introns are removed

46
Q

What does RNA splicing do>

A

removes the introns and connects the exons together

47
Q

What are consensus sequences and what are they bound by?

A

They are short sequences between exons and introns
first bound by snRNPs

48
Q

how are the ends of Pre-mRNA modified?

A

5’ cap is added to the 5’ end and it facilitates binding to a ribosome
poly A tail is added to the 3’ end and it assists in the export from the nucleus and contributes to stability.

49
Q

What does Translation do and where does it occur?

A

It is the sequence of an mRNA into an amino acid sequence which occurs at ribosomes.

50
Q

what are the start and stop codons?

A

Start codon: AUG
Stop codons: UAA, UAG, UGA

51
Q

What are missense mutations?

A

result in a change in one amino acid sequence

52
Q

What is a nonsense mutation?

A

results in a premature stop codon

53
Q

What is a frame-shift mutation?

A

insertion or delition of one or more bases
usually causes a new order of triplets to be read and all the amino acids after the mutation are shifted.

54
Q

What must tRNA do to link the codon in an mRNA codon with a specific amino acidd?

A

the tRNA must read mRNA codons corrrectly

Then it must deliver the correct amino acids that correspond

55
Q

What are the three functions of tRNA?

A
  • Binds to a specific amino acid and becomes charged
  • Binds to mRNA codon at the tRNA anticodon - atriplet that is complementary to the mRNA codon for the particular amino acid
    Interact with ribosomes non covalently
56
Q

What is wobble and what does it allow?

A

It allows the cells to produce fewer tRNA species but does not allow the genetic code to be degenerate.

It is because specifity for the base at 3’ end of the codon is not always observed

57
Q

identify and explain the three tRNA binding sites in the subunit

A

A Site binds with the anti codon of a charged tRNA
P site is where tRNA adds its amino acid to the polypeptide chain
E site is where tRNA sits before being released from the ribosome

58
Q
A

Biology (2 decks)

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