8.2 - DNA + Chromosomes Flashcards

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1
Q

What are the characteristics of DNA in prokaryotic cells?

A
  • shorter
  • circular
  • not associated w proteins (histones)
  • no introns
  • contain plasmids
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2
Q

What are the characteristics of DNA in eukaryotic cells?

A
  • longer
  • linear
  • associates with proteins called histones
  • has introns
  • mitochondria + chloroplasts contain short, circular DNA not associated w proteins (similar to DNA in prokaryotes)
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3
Q

When are chromosomes visible as distinct structures and what do they look like?

A
  • when a cell is dividing
  • appear as 2 threads joined at 1 point
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4
Q

What protein is DNA associated with?

A
  • histones
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5
Q

How is a chromosome formed?

A
  • double helix of DNA is wound around histones fixing it in position
  • DNA-histone complex then coiled
  • coil is looped + further coiled then packed into chromosome
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6
Q

What is a homologous pair of chromosomes?

A
  • 2 chromosomes carrying the same genes
  • 1 maternal chromosome, 1 paternal chromosome
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7
Q

What is the total number of chromosomes known as?

A
  • diploid number
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8
Q

What is the total number of chromosomes in humans?

A
  • 46
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9
Q

What is an allele?

A
  • 1 of a number of alternative forms of a gene
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10
Q

What happens when an individual inherits different alleles?

A
  • each allele has a diff. base sequence
  • diff. AA sequence
  • diff. polypeptide produced
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11
Q

What is a mutation?

A
  • any change in base sequence of gene which produces a new allele of that gene
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12
Q

What happens when there’s a mutation?

A
  • causes diff. sequence of AA
  • diff. polypeptide
  • diff. protein: may not function properly/at all
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13
Q

What determines the sequence of amino acids in a protein?

A
  • the sequence of nucleotide bases in DNA
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14
Q

Describe how a gene is a code for the production of a polypeptide.

A
  • a gene is made up a sequence of bases
  • that is read in triplets
  • which determines the sequence of AA forming the primary structure in a polypeptide
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15
Q

How is a phosphodiester bond formed between 2 nucleotides?

A
  • from a condensation reaction (where 1 molecule of water is released)
  • between the phosphate group + the pentose sugar (deoxyribose or ribose)
  • catalysed by DNA polymerase
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16
Q

How is DNA in eukaryotic cells similar to the DNA in prokaryotic cells?

A
  • nucleotide structure is identical
  • nucleotides joined by phosphodiester bonds
  • chloroplasts + mitochondria in eukaryotic cells contain short, circular DNA not associated w proteins which is similar to DNA in prokaryotes
17
Q

Describe the structure of a DNA molecule?

A
  • a double helix w 2 polynucleotide chains
  • held together by hydrogen bonds
  • between specific complementary base pairs
18
Q

What are ribosomes formed from?

A
  • RNA
  • proteins
19
Q

How are ribosomes formed?

A
  • a complementary strand of mRNA is transcribed from DNA in nucleus
  • mRNA travels from nucleus to the ribosomes in the cytoplasm
  • ribosomes (proteins) translate mRNA into AA forming a polypeptide