genetic information Flashcards

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1
Q

how is DNA stored in eukaryotes

A

long
linear
associated with proteins (histones)]
tightly coiled into chromosomes

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2
Q

how is DNA stored in prokaryotes

A

short
circular
not associated with proteins

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3
Q

how is DNA stored in chloroplasts and mitochondria

A

short
circular
not associated with proteins

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4
Q

describe the features of DNA which make it a stable molecule

A
  1. two strands with specific base pairing
  2. large no. of hydrogen bonds between strands
  3. helix/coiling reduces chance of molecular damage
  4. strong sugar-phosphate backbone
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5
Q

describe the molecular structure of DNA

A
  • Long polymer of nucleotides;
  • composition of a nucleotide (pentose sugar, phosphate and N containing base)
  • 4 bases named (A, T, C and G) (Uracil (U) is a base in RNA that replaces T), A, G are purine bases (2 ring structure) T, C and U are pyrimidine bases (single ring structures)
  • sugar-phosphate ‘backbone’;
  • two (polynucleotide) strands;
  • specific base-pairing;
  • example e.g. A–T / C–G; there are 2 H bonds between A/t and three H bonds between C/G
  • hydrogen bonding between bases
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6
Q

explain how the structure of DNA is related to its function

6

A
  • sugar - phosphate backbone gives strength (phosphodiester bonds)
  • (coiling gives) compact shape;
  • sequence of bases allows information to be stored;
  • long molecule stores large amount of information;
  • information can be replicated/complementary base pairing;
  • (double helix protects) weak hydrogen bonds/double helix makes molecule stable prevents code being corrupted;
  • chains held together by weak hydrogen bonds;
  • chains can split for replication / transcription
  • Complementary base pairing enables information to be replicated/transcribed
  • Many hydrogen bonds together give molecule stability;
  • Hydrogen bonding allows chains to split for replication/transcription OR molecule unzips easily for replication / transcription.
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7
Q

what are genes

A

sequence of DNA

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8
Q

what do genes code for

A

amino acid sequence of a polypeptide

functional RNA

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9
Q

what does a gene occupy and what is this called

A

a fixed position

locus

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10
Q

what does a sequence of triplets code for

A

sequence of amino acids

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11
Q

describe the nature of the genetic code

A

degenerate
-same amino acid can be coded for by more than one triplet

universal
-same specific triplet codes for same specific amino acid in all living organisms

non-overlapping
-each base can be used only once and in one triplet , in a sequence

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12
Q

Explain why, in eukaryotes, much of the DNA doesn’t code for polypeptides.

A
  • Between genes…
    • Non-coding multiple repeats
  • Within genes
    • Only exons code for amino acid sequences,
      which are separated by one or more non-coding sequences, called introns
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13
Q

what is a locus

A

position of a gene

on a strand of DNA

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14
Q

what are genes

A

sections of coding DNA

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15
Q

what is a mutation

A

change in base sequence of a gene

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16
Q

define codon

A

triplet coding for a specific amino acid

17
Q

what determines amino acid sequence of a polypetide

A

base sequence of gene

18
Q

define exons

A

sequence of bases in gene

coding for a polypetide

19
Q

what are introns in

A

eukaryotes

20
Q

define introns

A

sequences of bases in a gene

not coding for a polypeptide

21
Q

define genome

A

complete set of genes in a cell

22
Q

define preteome

A

full range of proteins a cell is able to produce

23
Q

what are alleles

A

different versions of the same genes

24
Q

what is a homologous pair of chromosomes

A

same size chromosomes with same genes

but different alleles

25
Q

what are the two stages of protein synthesis

A
  1. transcription

2. translation

26
Q

what happens in transcription

A
  1. mRNA made from DNA

2. happens in nucleus

27
Q

what happens in translation

A
  1. production of polypeptides from codons carried by mRNA

2. happens in ribosomes in cytoplasm

28
Q

what is the function of mRNA

A

acts as template for translation in cytoplasm

29
Q

what is a triplet code on mRNA called

A

a codon

30
Q

why does mRNA breakdown after a few days

A

chemically unstable