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Cells and Macromolecules > Genes, chromosomes and the genetic code > Flashcards

Genes, chromosomes and the genetic code Flashcards

1
Q

What are the DNA double helix forms (4)

A
  1. A
  2. B
  3. Z
  4. depend on how hydrated the surrounding area is
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2
Q

What happens to DNA in a very aqueous environment (2)

A
  1. DNA coils up
  2. Sugar-phosphate backbone = hydrophilic with hydrophobic core
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3
Q

What is the size of DNA (4)

A
  1. full width of DNA molecule - 2nm
  2. Full length of DNA - 2m
  3. 10-11 full pairs in a twist
  4. Humans have over 3 billion bp (~2m of DNA) per each cell
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4
Q

What is Chargaff’s rule of nucleotide bases (3)

A
  1. Adenine - Thymine (DNA)
  2. Adenine - Uracil (RNA)
  3. Guanine - Cytosine
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5
Q

What is the genome like in prokaryotes (4)

A
  1. Single circular
  2. Chromosome in nucleoid
  3. Non essential genes in plasmids
  4. Genome is v compact, mostly coding genes
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6
Q

What is the genome like in eukaryotes (6)

A
  1. linear chromosomes
  2. 2 copies of each chromosome
  3. One set of chromosomes from each parent
  4. Contain mitochondrial genome
  5. Proportionally much smaller than DNA found in the nucleus
  6. Maternal inheritance
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7
Q

What is a genome (2)

A
  1. Whole of DNA sequence
  2. 3 billion base pairs - 25’000 coding genes
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8
Q

What are genes (2)

A
  1. code for something
  2. basic physical and functional unit of heredity
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9
Q

What are the types of genes (6)

A
  1. Structural - codes for polypeptide chains
  2. RNA - code for RNA molecules
  3. Regulator - regulate gene expression
  4. Pseudogene - dead, non-coding
  5. Exon - coding
  6. Introns - intervening, non-coding sequences
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10
Q

What are alleles

A

different forms of the same gene

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11
Q

What is the structure of genes (9)

A
  1. start at 5’
  2. Promoter region
  3. Transcription initiation codon on exon 1
  4. Translation initiation codon on exon 1
  5. Interon 1
  6. More exons and codons
  7. Translation termination codon
  8. Polyadenylation signal on end of last exon
  9. Transcription termination at 3’ end
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12
Q

How is DNA packaged (6)

A
  1. DNA double helix wraps around histone proteins = nucleosome
  2. Nucleosome + H1 histone = chromatosome
  3. Nucleosomes fold = 30nm fibre
  4. Loops are formed
  5. Fibres are compressed
  6. Tight coiling = Chromatid of a chromosome
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13
Q

What is a nucleosome (5)

A
  1. Fundamental unit of chromatin compaction
  2. Consists of DNA + nucleosome protein core
  3. 1.7 left hand super helical turns
  4. Nucleosome protein core = Histones (small basic proteins)
  5. Linker DNA = sections of DNA between nucleosomes
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14
Q

What are histones (3)

A
  1. Globular proteins
  2. 5 members in the family: H1, H2A, H2B, H3 and H4
  3. H3 & H4 are x2 in a histone.
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15
Q

How are chromosomes arranged in humans (6)

A
  1. Humans have 46 chromosomes in every somatic cell - DIPLOID
  2. 22 pairs of autosomes
  3. 1 pair of sex chromosomes
  4. karyotype is map of all the chromosomes arranged in size.
  5. Every cell has same genetic information
  6. GAMETES are reproductive cells and only have one set of chromosomes - HAPLOID
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16
Q

What is a genotype (2)

A
  1. genetic potential of an individual
  2. One gene codes for a trait, but there are different versions (alleles) of that gene
17
Q

What is the phenotype (2)

A
  1. expression of the genotype as it interacts with the environment
  2. the detectable characteristics of organisms that can be determined by multiple alleles and the influence of the environment
18
Q

What is epigenetics (3)

A
  1. Study of the changes in gene expression (phenotype) that is not due to change in genotype
  2. Change influenced by environment, age, lifestyle, disease state…
  3. Caused by chemical changes:
19
Q

What chemical changes cause changes in gene expression (not due to genotype) (3)

A
  1. DNA (methylation of DNA)
  2. Gene silencing by non-coding RNA (ncRNA)
  3. Histone modification
20
Q

What is transgenerational epigenetics

A

three generations at once are exposed to the same environmental conditions

21
Q

What is the genetic code (6)

A
  1. 3 nucleotide sequence = CODON
  2. 1 CODON = 1 amino acid
  3. 4 nucleotides (A, U, C and G) in a 3 nucleotide code = 64 (43) combinations
  4. 20 essential amino acids
  5. DEGENERATE (multiple codons that mean the same amino acids)
  6. UNAMBIGUOUS (any codon will only mean one amino acid).
22
Q

What is the start codon

23
Q

What are the stop codons (3)

24
Q

What is a missense protein

A

the change of a single base pair causes the substitution of a different amino acid in the resulting protein.

25
Q

What is a nonsense protein

A

a change in DNA that causes a protein to terminate or end its translation earlier than expected

Cells and Macromolecules (29 decks)

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