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dna & protein synthesis Flashcards

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1
Q

what is DNA?

A
  • dna is the molecule that carries genetic information for the development & functioning of an organism
    -dna found in all living things and codes for the instructions that makes an organism
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1
Q

what does DNA stand for?

A
  • Deoxyribonucleic acid
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2
Q

nucleotides are made up of?

A
  • made up of 3 parts
  • phosphate group + deoxyribose sugar + nitrogenous base
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3
Q

nucleotides

A
  • A= adenine, T= thymine, G= guanine, C= cytosine
  • joined together by their sugar phosphate backbones
  • hydrogen bonds (weak bonds) hold together the nitrogenous bases
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4
Q

how genes make a protein

A
  • enzyme: a protein that speeds up chemical reactions
  • DNA polymerase: an enzyme that helps copy dna during cell division (mitosis) DNA -> DNA
  • RNA polymerase: an enzyme that helps copy dna during protein synthesis. its converts DNA to RNA
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5
Q

RNA

A
  • rna uses ribose sugar instead of deoxyribose
  • has 4 base pairs: instead of thymine it has uracil
  • A pairs with U and G pairs with C
  • single stranded and short
  • RNA can leave the nucleus and travel into cytoplasm
  • 3 types: mRNA, rRNA, tRNA
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6
Q

two steps of protein synthesis

A
  • transcription (DNA -> mRNA)
  • translation (mRNA -> protein)
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7
Q

what is mRNA

A
  • stands for messanger RNA
  • mRNA carries the instructions for one gene
  • mRNA is synthesised in the the nucleus
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8
Q

what is the function of mRNA

A
  • its function is to make a copy of a gene and take it to a ribosome (found in cytoplasm), where amino acids are assembled to make a protein
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9
Q

transcription- DNA to mRNA

A
  • transcription is the first of gene expression/protein synthesis
  • it is broken into three major steps
    1. initiation
    2. elongation
    3. termination
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10
Q

initiation

A
  • initiation is the beginning of transcription. it occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter
  • this signals the DNA to unwind so the enzyme can ‘read’ the bases in one of the DNA stands (known as the template strand)
  • the enzyme is now ready to make a strand of mRNA and complementry sequence of bases
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11
Q

elongation

A
  • elongation is when complementary nucleotides are added to synthesise an mRNA strand
  • RNA polymerase reads the unwound DNA strand & builds the mRNA molecule, using complementary base pairs
  • adenine pairs with uracil & cytosine pairs with guanine
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12
Q

termination

A
  • termination is the ending of transcription, and occurs when RNA polymerase crosses a termination sequence in the gene
  • the mRNA strand is complete, and it detaches from RNA
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13
Q

the three steps together

A
  • the mRNA strand is now ready to leave the nucleus, travel into the cytoplasm, attach a ribosome and to be translated into a protein
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14
Q

first three steps of translation- mRNA to protein

A
  1. the mRNA moves through the nuclear pore to the cytoplasm
  2. the mRNA attaches to the ribosome. the ribosome moves along the mRNA strand, reading 3 nucleotides (condon) at a time. translation begins at the START condon.
  3. transfer RNA (tRNA) molecules ferry the amino acids to the mRNA at the ribosome
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15
Q

last three steps of translation- mRNA to protein

A
  1. tRNA links with the ribosome and matches its anticondon of mRNA
  2. a peptide bond forms between the adjoining amino acids, forming a polypeptide. The tRNA is removed to be used again
  3. the protein production stops when a STOP condon is reached. the mRNA breaks away from the ribosome. STOP condons are UAA, UGA, UAG. THey aer STOP condons because they don’t code for anything
16
Q

how does the coding work?

A
  • each codon codes for an amino acid
  • there are 20 amino acids, so some are coded for by multiple codons
17
Q

DNA mutations (causes & how common)

A
  • mutations occur at a frequency of about 1 in every billion base pairs
  • everybody has about 6 mutations in their body
  • mutations aren’t always seen, the affected gene may still be able to function
  • muations may be: harmful, beneficial
18
Q

how does mutations impact protein synthesis?

A
  • DNA affect= substitution, insertion, deletion
  • mRNA copied incorrectly
  • codes for wrong amino acids
  • formation of incorrect protein/part of polypeptide is missing/ not functioning protein
19
Q

what are mutations

A
  • mutations are changes in genetic material; changes in DNA and gene/s
  • in mutations, the DNA code can have 1 or more bases: added, deleted, or exchanged
20
Q

causes of mutations

A
  • mutations may occur randomly & spontaneously due to errors in DNA replication
  • they may be induced by mutagens. e.g. x-ray and uv lights
21
Q

names of genetic mutations

A
  • Huntingtons disease (insertion DNA mutation)
  • Sickle cell anaemia (substitution DNA mutation)
22
Q

what is huntingtons disease?

A
  • a progressive brain disorder that affects the central area of the brain
  • movement, mood and thinking skills are affected as a consequence
23
Q

changes in DNA segment for huntingtons disease

A
  • mutation involves a DNA segment of cytosine, adenine, and guanine that appears multiple times in a row
  • normally CAG segment is repeated 10 to 35 times within a gene
  • in people with huntingtons the segment is repeated more than 120 times
24
Q

what is sickle cell anaemia?

A
  • only one amino acid changes in the haemoglobin
  • the haemoglobin still functions but it folds differently, changing the shape of the red blood cell
  • this affects the way the haemoglobin can carry oxygen
25
Q

what are some possible genetic disorders?

A
  • cystic fibrosis
  • klinefelter (XXY)
  • tourette syndrome
  • turner syndrome
  • down syndrome

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