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biology year 1 > genetic information > Flashcards

genetic information Flashcards

1
Q

define gene

A

a sequence of DNA nucleotide bases that codes for a polypeptide or a functional RNA

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2
Q

structure of DNA

A

double stranded molecule
each strand is a polynucleotide made up of individual nucleotides

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3
Q

what is a DNA nucleotide composed of?

A

phosphate group
deoxyribose sugar
nitrogenous base

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4
Q

describe the DNA in prokaryotes

A

circular DNA
some have smaller loops of plasmid
DNA is naked
not associated with histone proteins

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5
Q

describe the DNA in eukaryotic chloroplasts and mitochondria

A

short circular molecule
not associated with histone proteins

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6
Q

describe the DNA in the nuclei of eukaryotic cells

A

very long linear molecule
associated with histone proteins
DNA molecule and histone proteins forms a chromosome

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7
Q

describe a homologous chromosome

A

-same genes of same loci
-centromeres at same place so same shape and size
-one maternal, one paternal

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8
Q

how is a chromosome formed?

A

-DNA molecule is wrapped around histone proteins to fix in place
-DNA histone complex is coiled into solenoids

this means a very long molecule of DNA can be condensed into a single chromosome (a lot of info)

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9
Q

what do humans have a diploid number of?

A

2n=46

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10
Q

what do genes code for?

A

either:
-the amino acid sequence of a polypeptide
-a functional RNA (including rRNA and tRNA)

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11
Q

where do genes occupy?

A

locus (fixed position)

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12
Q

what is an exon?

A

parts of a gene which codes for amino acid sequences

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13
Q

what are introns?

A

non-coding sequences

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14
Q

define genome

A

complete set of all the genes in a cell

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15
Q

define proteome

A

the full range of all the proteins that a cell is able to produce using its genome

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16
Q

define allele

A

two or more versions of a genetic sequence coding for a different polypeptide

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17
Q

define gene pool

A

all the different alleles of all the genes found within a population

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18
Q

which amino acid does the start triplet always code for

A

methionine

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19
Q

define triplet

A

every three bases in the sequence of a gene

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20
Q

what does a triplet code for?

A

a specific amino acid

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21
Q

how many different nucleotides are there in DNA?

A

4

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22
Q

how many possible combinations of triplets are there to code for 20 amino acids?

A

4^3= 64

23
Q

define degenerate

A

in the genetic code, most amino acids are coded for by more than one triplet

24
Q

how many triplets dont code for amino acids in DNA?
what are they called?

A

3
stop triplets

25
Q

define universal

A

the same triplet always codes for the same amino acid

26
Q

define non-overlapping

A

each base is only read once, each base is part of only one triplet

27
Q

RNA structure

A

single stranded polynucleotide
nucleotides composed of phosphate,ribose sugar and nitrogenous base (Uracil instead of Thymine)

28
Q

how long is messenger RNA?

A

few thousand nucleotides long

29
Q

what is every 3 bases called in mRNA?

A

codon

30
Q

what is the shape of mRNA?

A

linear molecule as bases don’t bond to each other

31
Q

how long is transfer RNA?

A

about 75 nucleotides long

32
Q

describe the structure of tRNA

A

-strands fold back on themselves
-hydrogen bonds form between complementary base pairs
-shape is called clover leaf
-one end is an amino acid binding site
-3 of the bases are exposed called an anticodon

33
Q

how many different types of tRNA are there?

A

61

34
Q

why are there not 64 triplets?

A

because there are 3 stop codons which dont code for any specific amino acid

35
Q

how is a protein made in eukaryotes?

A

-specific gene is transcribed (introns and extrons)
-this makes pre-mRNA
-this is spliced to form mRNA
-this is a copy of the exons of the gene only
-mRNA is translated to make polypeptides

36
Q

describe transcription in the nucleus

A

-gene unwinds as hydrogen bonds between complementary bases broken by RNA polymerase
-one strand acts as a template
-complimentary free RNA nucleotides bind to exposed bases
-in a condensation reaction, sugar phosphate backbone is joined using RNA polymerase
-both inton and exon are transcribed to make pre-mRNA

37
Q

what disengages the RNA polymerase?

A

the stop triplet marking the end of a gene

38
Q

describe splicing in eukaryotic cells

A

pre-mRNA is spliced
the non-coding sections (transcribed from the introns) are cut out and coding sections are edited together to produce mRNA

39
Q

what types of DNA dont need splicing?
why?

A

prokaryotic DNA
chloroplast and mitochondria DNA
because they dont have introns

40
Q

where does translation happen? and what does it make?

A

cytoplasm

makes polypeptides

41
Q

describe translation

A

-mRNA moves out of nucleus and attaches to ribosome.
-tRNA carrying amino-acids bind by their anticodons to the mRNA - by complementary base pairing.
-Another molecule of tRNA with another amino-acid attaches to the mRNA on the next codon along.
- The two amino-acids on the tRNA form a peptide bond.
-The first tRNA now moves away and a new tRNA attaches.
- This process repeats, adding more amino-acids to the polypeptide-chain. -Process ends when a ‘stop signal’ is reached and completed polypeptide detaches.

42
Q

what does a gene mutation involve?

A

a change in the base sequence of a chromosome

43
Q

what are neutral mutations?

A

when the change in amino acid sequence does not affect the function of the protein

44
Q

why might some substitutions not result in any change?

A

genetic code is degenerate
the new triplet may code for the same amino acid

45
Q

what are silent mutations?

A

in substitution mutation when the mutation causes no change

46
Q

what happens to the length of the polypeptide chain when the new triplet is a stop triplet?

A

shorter

47
Q

what does addition result in?

A

a frame shift

48
Q

what’s the consequence of a frame shift?

A

new sequence of amino acids
changes position of hydrogen and disulphide bonds

49
Q

what 2 mutations result in a frame shift?

A

addition
deletion

50
Q

how can the rate of mutations be increase?

A

mutagenic agents

51
Q

x4 examples of mutagenic agents?

A

-high energy radiation
-ionising radiation
-chemicals eg tar in cigarette smoke
-viruses

52
Q

what are carcinogens?

A

substances which cause mutations in oncogenes which cause the cell to become cancerous

53
Q

whats non-disjunction?

A

when homologous chromosomes do not separate in meiosis

54
Q

whats down syndrome caused from?

A

non-disjunction of chromosome 21

biology year 1 (7 decks)

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