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2. MCBG > 2.1, 2.2 Introduction To DNA and precision med > Flashcards

2.1, 2.2 Introduction To DNA and precision med Flashcards

1
Q

What is a DNA molecule and its function? (3)

A
  1. Deoxyribonucleic acid
  2. Double helix
  3. Contains genes - Length of DNA that codes for a protein
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2
Q

How is DNA packaged to form a chromosome?

A
  1. DNA wrapped around a histone forming ‘beads on a string’
  2. Further compressed into a solenoid
  3. Further folds to form our chromosome
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3
Q

What is a piece of DNA wrapped around a singular histone called?

A

A nucleosome

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4
Q

What is chromatin?

A

DNA + histone proteins

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5
Q

Describe the structure, function and colour on microscopy of heterochromatin (2)

A
  1. Solenoid form of DNA and histones
  2. Genes are not expressed
  3. Darker
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6
Q

Describe the structure, function and colour on microscopy of euchromatin (2)

A
  1. Beads on a string
  2. Genes are expressed
  3. Lighter
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7
Q

What are genes?

A
  1. Distinct sequence of nucleotides that carry a code for proteins
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8
Q

What is the human genome?

A

Entire DNA sequence in humans i.e. Humans - 23 pairs of chromosomes

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9
Q

What are autosomes and how many do we have? (2)

A
  1. Chromosomes that contain genes that relate to anything but sex determination
  2. We have 22 autosomal pairs (i.e. 44) and 1 pair of sex chromosomes (i.e 2)
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10
Q

Name and describe the structure of the two pentose sugars that can be found within our bodies. Where are these located?

A
  1. Ribose - pentose sugar with OH group on 2nd Carbon within ring - located in RNA
  2. Deoxyribose - pentose sugar with H group on 2nd carbon within ring - located in DNA
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11
Q

What is the difference between a nucleotide and nucleoside?

A

Nucleotide - phosphate + sugar + base

Nucleoside - sugar + base

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12
Q

What are the two types of nitrogenous bases, name the base pairs that associate with them and how many rings each base has.

A
  1. Purines - Adenine, Guanine - 2 rings

2. Pyramidines - Thymine, Cytosine, Uracil - 1 ring

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13
Q

How many hydrogen bonds do the base pairs A and T and G and C make?

A

A and T - 2

G and C - 3

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14
Q

Describe the two DNA strands that bond together forming our DNA molecule.

A
  1. DNA strands are COMPLEMENTARY
  2. run ANTI-PARALLEL to each other
  3. By convention, top strand always written 5’ to 3’
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15
Q

What bonds join nucleotides to each other forming the DNA strands? What parts of the nucleotide make this bond? (2)

A
  1. Phosphodiester bonds
  2. 3’ Carbon to the oxygen to the Phosphate
  3. Distinct ends, 5’ Phosohate and 3’ OH
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16
Q

Where does DNA replication occur within a cycle of mitosis?

A

Within the S phase

17
Q

What is the term describing the DNA replication process and the fact that each new molecules has 1 recycled strand?

A

Semi-conservative

18
Q

Describe the DNA replication process in eukaryotes

A
  1. Initiation
    - DNA helicase unwinds DNA at origin of rep
    - single strand binding proteins keep strand separated
    - DNA primase kick starts addition of nucleotides by adding short sequences of RNA called primers
  2. Elongation
    - leading strand - DNA polymerase takes over and elongates
    - lagging strand - okazaki fragments formed as DNA polymerase works in 5’ to 3’ direction continuously only on 3’ to 5’ strand.
  • Exo/endonuclease proof reads replication
  • polymerase reverses and corrects
  • DNA ligand seals okazaki fragments into one continuous strand
  1. Termination
    - two facing replication forks meet and DNA ligase joins final fragments
19
Q

Name a difference in prokaryotic and eukaryotic DNA rep

A

Eu - many origins of replication

Pro - 1 origin of replication

20
Q

Describe the DNA replication process in prokaryotes

A
  1. Recognition of origin of replication
  2. Primase
  3. DNA polymerase + other specific proteins
21
Q

What drives the addition of nucleotides onto elongating strand?

A

Loss of pyrophosphate (PPi)

22
Q

One DNA molecule is called a chromosome, what are the two DNA molecules after replication called?

A

A chromosome too! Have sister chromatids which are identical.

23
Q

Briefly describe precision medicine

A

Moving from one-size-fits-all medicine to tailored therapy.

Involves pharmacogenetics - Study of how a persons genes affect their response to a drug

24
Q

What are immunotherapeutic checkpoint inhibitors?

A

Immune checkpoint inhibitors unleash a patients own T cells to kill tumours (e.g. For cancer)

25
Q

What is DNA ligase?

A

Joins nucleotides together by catalysing the formation of phosphodiester bonds

26
Q

What are okazaki fragments?

A

Newly synthesised DNA fragments formed on lagging parent strand during DNA replication

27
Q

What is epigenetics?

A

Study of changes in organisms caused by modification of gene expression as opposed to alteration to genetic code itself

2. MCBG (18 decks)

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