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MTM > Genetic Info > Flashcards

Genetic Info Flashcards

1
Q

Difference in dna and rna

A

DNA: double stranded, high molecular weight, deoxyribonucleic acid

RNA: single stranded, heterogenous in size, ribonucleic acid, uracil

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2
Q

Difference between ribonucleic and deoxyribonucleic

A

Ribo has hydroxyl group 2nd carbon

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3
Q

Why is RNA unstable?

A

Has extra hydroxyl group on 2nd carbon so can be attacked by water

Adv as cels change expression pattern

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4
Q

What is a purine?

A

A and G

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5
Q

What is T and C

A

Pyrimidines

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6
Q

Why can several mRNAs be transcribed from some genes

A

Because exons spliced differently

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7
Q

How many chromosomes

A

22 autonomies and 1 sex chromosome

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8
Q

How is dna packaged

A

Packaged into chromatin by histones and other chromosomal proteins

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9
Q

How can chromosomes be identified

A

By banding pattern

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10
Q

What is upstream and downstream

A

5’ upstream
3’ downstream
Read in 5’ to 3’ direction

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11
Q

Repeated sequences in dna

A

50%
Often occur in blocks of tandem repeats
Called satellite DNA

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12
Q

Types of satellite DNA

A

Minisatellite - highly polymorphic 1000 copies in one block. Found at telomeres.

Microsatellite - smaller. Usually intergenic/ Intronic

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13
Q

Importance of minisatellites at telomeres

A

-Repeats create heterochromatin at tips which helps protect chromosomes from being digested by nucleuses

-Allows replication of DNA to the tips

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14
Q

Repeats can have negative effects. How?

A

They can cause mispairing during cell division to give:
• Large scale duplication/deletion between homologous chromosomes
• Translocation of DNA between non-homologous chromosomes

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15
Q

Germline cells?

A

Cell that divide to generate the gametes

Oocytes (eggs females born with) and spermatogonium

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16
Q

RNA that isnt translated into proteins?

A

tRNA and rRNA involved in translation of mRNA

But some RNA molecules modify other RNA molecules (snRNA; snoRNA)
microRNA (miRNA)- Bind to 3’UTR of mRNA and inhibit translation

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17
Q

What does detergent treatment of nucleus cause

A

causes release of decondensed chromatin threads from non-dividing
(interphase cells)

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18
Q

What is the fundamental unit of chromatin?

A

Nucleosome - DNA wound around a histone core

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19
Q

How are Decondensed chromosomes still structurally organised in non- dividing cells

A
  • Attachment to nuclear skeleton
  • has a functional role, for example the clustering of ribosomal
    genes in the nucleolus
20
Q

Heterochromatin

A

Found at centromeres and telomeres

Highly condensed region of an interphase chromosome

Generally gene poor and transcriptionally inactive

21
Q

Euchromatin

A

Prevalent in gene rich areas
less compact allowing access for proteins involved in transcription

22
Q

Nucleolus

A

Large structure in the nucleus

Where ribosomal RNA is transcribed and ribosomal subunits are assembled

23
Q

Two types of chromatin in chromosomes

A
  1. Euchromatin
  2. Heterochromatin
24
Q

How many histone molecules in a nucleosome made of

A

8

25
Q

DNA packaging

A
  1. DNA wraps around histones
  2. Nucleosomes fold up into chromatin
  3. Fibres compressed further
  4. Fibres coil up to produce chromatid of a chromosome
26
Q

Why can protein synthesis not occur during mitosis

A

because the DNA is so
condensed so enzymes e.g. RNA polymerase can’t access it.

27
Q

Kinetochores

A

spindle microtubules attach to the two kinetochores (one for each sister
chromatid) at the centromere

28
Q

Two types of heterochromatin

A
  1. Facultative heterochromatin
    In temporarily inactivated (condensed) state
  2. Constitutive heterochromatin
    Always inactive and condensed. Preset at centromere and telomeres.
29
Q

What are dNTPs

A

Required for replication and repair of dna

They are the building blocks of DNA

they lose two of the phosphate groups when incorporated into DNA during replication via phosphodiester Bond

30
Q

What are replication origins

A

Sites where replication can start
Have certain sequences that are recognised
Start codon AUG

31
Q

Which end can DNA polymerase add nucleotides

A

3’

32
Q

What must DNA polymerase require

A

dNTPs
Template
RNA primer

33
Q

Okazaki fragment

A

Synthesised in opposite direction to movement of fork in small fragments
Fragments joined together by DNA ligase

34
Q

Leading strand

A

Synthesised in same direction of fork
continuous synthesis

35
Q

Lagging strand

A

Lagging strand synthesised discontinuously
In opposite direction to movement of fork
Requires new RNA primers
DNA polymerase adds to new RNA primers to start a new Okazaki fragment
RNA primers removed and replaced with DNA using DNA ligase

36
Q

What synthesises RNA primers

A

DNA primase

37
Q

Role of DNA polymerase

A

Add nucleotides on 3’ of new strand
Proof read

38
Q

Replication bubbles ?

A

Form at multiple origins along length of chromosome
Spread out in both directions until all unite
Efficient and fast replication

39
Q

Chemical reactions which manage dna

A

Dpurination - base is lost

Deamination - C to U

UV - adjacent thymines become a dimer

40
Q

What does Nucleosome consist of

A

Composed of 8 histones
of 4 types
Roughly 140bp of DNA

41
Q

DNA positively charged.

A

No. Negatively charge.
Sugar phosphate backbone is negatively charged

42
Q

Amino acids positively charged?

A

Yes

43
Q

Enzymes that involved in acetylation

A

Histone acetyl transferases add acetyl
Histone deacetylase remove acetyl

44
Q

What can be used to track a gene

A

Microsatellites in non coding regions

45
Q

Function of micro RNA

A

To repress synthesis of a protein

46
Q

Genomic imprinting

A

Epigenetic change
the process by which only one copy of a gene in an individual (either from their mother or their father) is expressed, while the other copy is suppressed

MTM (12 decks)

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