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Karan - MBBS Year 1: Principles Week 1 > Introduction to the Human Genome > Flashcards

Introduction to the Human Genome Flashcards

1
Q

In DNA nucleotides, what is the nitrogenous base attached to?

A

Attached to deoxyribose 5′-phosphate

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2
Q

Outline complementary base pairing.

A
  • 2 hydrogen bonds between adenine and thymine
  • 3 hydrogen bonds between cytosine and guanine
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3
Q

What stabilises the nucleotides and what binds them together?

A
  • Sugar-phosphate backbone
  • Phosphodiester bonds
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4
Q

What direction is DNA read in?

A

5’ to 3’

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5
Q

Outline DNA coiling

A
  • Double helix coils around histones to form nucleosomes
  • Nucleosomes coil to form solenoids to form chromatin loops
  • Chromatin becomes condensed and forms chromosomes
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6
Q

Outline the central dogma of molecular biology

A
  • TRANSCRIPTION - production of mRNA from DNA template
  • TRANSLATION - synthesis of protein from mRNA
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7
Q

Outline the principles of the genetic code

A
  • Read in triplets
  • Codons encode an amino acid
  • 64 possible combinations but 20 amino acids - code is degenerate
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8
Q

Define a gene

A
  • Basic unit of inheritance - passed to offspring
  • Regions that code for RNA
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9
Q

Outline the structure of the gene.

A
  • Enhancer site regulating transcription
  • Promoter region - TATA box in eukaryotes - RNA polymerase II binds upstream of first gene exon
  • Start of codon - start of translation
  • Also has UTRs
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10
Q

Define intron

A

Non-coding regions of a gene which are spliced out during
mRNA processing

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11
Q

Give examples of post-translational modifications

A
  • Cleavage into smaller polypeptide units
  • Combination with other polypeptides
  • Glycosylation
  • Acetylation

RELEVANT for function of protein - if a protein needs to become a glycoprotein, it will be glycosylated

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12
Q

Where does protein processing occur?

A
  • Cytoplasm
  • Golgi apparatus
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13
Q

What is the difference between tertiary and quaternary structure?

A
  • TERTIARY - three dimensional folding due to side chain interactions
  • QUATERNARY - occurs in proteins consisting of more than one amino acid chain
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14
Q

Outline the process of collagen fibril formation

A
  • Pro-alpha polyppetide chain is formed and undergoes hydroxylation and glycosylation
  • Three polypeptide chains assemble into triple helix and secreted out of cell
  • Portions at each end of procollagen are cleaved, forming a mature molecule
  • Form collagen fibrils
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15
Q

Describe osteogenesis imperfecta

A
  • Caused by mutations in gene encoding type 1 collagen
  • CLINICAL FEATURES - recurrent bone fractures, short stature and scoliosis
  • Subsitution of glycine to another amino acid
  • Glycine sits in centre of triple helix structure –substitution leads to instability
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16
Q

Define mitosis

A
  • Cell division in which two genetically identical diploid cells form
  • Involves interphase, prophase, metaphase, anaphase, telophase and cytokinesis
17
Q

Define meiosis

A

Formation of haploid gametes from diploid cell

18
Q

Outline steps in meiosis.

A
  • INTERPHASE I - replication
  • PROPHASE 1/METAPHASE 1 - pairs of homologous chromsomes line up at centre of cell - crossing over at chiasmata and exchange genetic material
  • MEIOSIS I - REDUCTION DIVISON - 1 cell forms 2 cells with 1 chromosome
  • Meiosis II – sister chromatids segregate - get 1 chromatid in each cell
19
Q

Outline the process of DNA replication. PART 1

A
  • Helix unwound using topoisomerase
  • Hydrogen bonds between bases break (helicase enzyme)
  • Single DNA strands – become templates
  • DNA polymerase travels along DNA strand adding free nucleotides from 5’ to 3’ end
20
Q

Outline the process of DNA replication. PART 2

A
  • Whole length of DNA strand replicated = replication fork
  • Newly added nucleotides checked to make sure complementary to base
  • If not – nucleotide excised and replaced with correct nucleotide
  • When DNA replication error not successfully repaired = mutation
21
Q

Outline the process of DNA repair

A
  • DNA repair enzymes recognise altered base
  • Excise by cutting DNA strand (endonuclease)
  • Replace with correct base (using complementary base-pairing) –DNA polymerase
  • Re-seal DNA backbone - DNA ligase
22
Q

What causes genetic variation?

A
  • Crossing over
  • Mutations
  • Random fertilisation

Karan - MBBS Year 1: Principles Week 1 (14 decks)

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