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A Level Biology AQA > UNIT 4, Topic 4A & 4B - DNA, Protein Synthesis, Diversity, and Classification > Flashcards

UNIT 4, Topic 4A & 4B - DNA, Protein Synthesis, Diversity, and Classification Flashcards

1
Q

a gene occupies…

A

a fixed position called a locus on a particular DNA molecule

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2
Q

gene

A

A gene is a base sequence of DNA that codes for : amino acid sequence of a polypeptide, and, a functional RNA (including ribosomal RNA and tRNA)

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3
Q

functional RNA

A

Functional RNAs areRNA molecules that are not translated into proteins

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4
Q

ribosomal RNA

A

Ribosomal RNA arethe subunits on a ribosome.

Ribosomes are the organelles where proteins are formed in a cell. It consists of a large and small subunit that is made up of ribosomal RNA (rRNA).

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5
Q

DNA

A

A chemical polymer (polynucleotide) that stores genetic information for a cell

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6
Q

loci

A

a fixed position a gene occupies on a chromosome

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7
Q

allele

A

alternative form of a gene (in the same loci and chromosome) that’s caused by random mutations mostly

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8
Q

codon

A

3 mRNA molecules
“3 bases code for one amino acid”

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9
Q

primary structure of protein…

A

the UNIQUE sequence of amino acids

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10
Q

genome

A

the complete set of genes / genetic make up in a cell

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11
Q

proteome

A

the entire set of proteins expressed by a genome: all the proteins a cell is able to code for

  • use this phrasing as not all proteins can or are made at the same given time
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12
Q

give 3 features of eukaryotic DNA

A
  • linear (and enclosed in a nucleus)
  • long
  • bundled into chromosomes
  • contains histones (proteins)
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13
Q

Give 3 features of prokaryotic DNA

A
  • short
  • circular DNA (plasmids)
  • does not contain/ associated with proteins (histones)
  • found in the cytoplasm (no nucleus)
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14
Q

histones

A

The protein that DNA molecule wraps around, also provides structural support for a chromosome

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15
Q

introns

A

sections of a gene that are not expressed in final RNA products (aka dont code for amino acids)

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16
Q

exons

A

coding regions of a gene that code for a protein / amino acid sequence (they are the reason for splicing)

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17
Q

what is the genetic code?
what’s a triplet code?

A

Described as a sequence of bases (adenine, guanine, cytosine, thymine) which, when arranged in a certain order, code for specific amino acids.
A triplet code describes how an amino acid is coded for by a group of 3 bases.

(note that codons actually code for an amino acid during transcription, hence the codon table. The tRNA, anticodon, is just essentially used as a carrier for the amino acid because it’s complementary to the mRNA’s codon)

18
Q

What determines the sequence of amino acids?

A

the order of bases to form a polypeptide (each with a different amino acid sequence).

19
Q

after the primary structure, how does the tertiary structure help define the protein / polypeptide chain?

A

Hydrogen, ionic, and disulfide bonds form between the R groups on the amino acid causing the chain to fold further and form a protein, and this gives it its function, such as an enzyme

20
Q

why do different species have different base sequences?

A

(mutations)
In terms of proteins, they need different Gene’s to be able to make different proteins

21
Q

read…

A

correct order:
1. DNA base sequence codes for…
2. (after transcription and translation) amino acid sequence determines…
3. polypeptide chain determines…
4. (after folding) protein structure and function

22
Q

practice some Exam Qs

A

.

23
Q

bonds in polypeptide chain

A

peptide

24
Q

3 code words used to describe DNA

A

degenerate, universal, non-overlapping

25
Q

degenerate code
why is this advantageous?

A

Several base triplets can code for the same amino acid.
- e.g. only 20 amino acids but 64 possible combinations of triplets

Its advantageous as despite mutations, theres a chance that the mutation won’t have an affect in the amino acid coded for in the end

26
Q

non-overlapping code

A

Each base in sequence is read only once!
So the base cytosine in ATC, for example, would not be read twice for the next triplet

27
Q

read

A

DNA: triplet
mRNA: codon
tRNA: anticodon

28
Q

universal code
- what does this suggest about evolution?

A

the same specific base triplets code for the same amino acids - in all living things.
- Suggesting we all have a common ancestor.

29
Q

heterozygous

A

(might not be on spec)
non identical alleles

30
Q

Extra features of eukaryotic DNA

A
  1. wrapped around histones
  2. mitochondria and chloroplasts have their own DNA
  3. most DNA doesn’t code for polypeptides
31
Q

What are the 2 purposes of histones

A
  1. Allows large DNA molecule to be stored compact by wounding the linear DNA around it. Then, associated proteins and DNA are coupled up tightly to form a chromosome
  2. They help support the DNA
32
Q

Describe the DNA found in mitochondria and chloroplasts (organelles only have their own DNA in eukaryotic cells)

A

It’s similar to prokaryotic: short, circular, and not associated with proteins. (can link to suggests commona ancestor)

33
Q

Explain why most DNA in eukaryotes doesn’t code for polypeptides

A

some genes code for functional RNA instead of polypeptides (which is also ribosomal and tRNA).
Additionally, the genes that do code for polypeptides contain non-coding regions as well as coding (introns and exons).

34
Q

Multiple repeats?

A

These are regions in eukaryotic DNA base sequences that occur outside of Gene’s. They repeat many times but do not code for amino acids.

  • non-coding repeats
    e.g. CGCGCGCGCGCG and you would describe this repeating sequence of GC to be 12 bases long.
35
Q

in the definition of a gene you dont have to include…

A

the fact exons and introns exist

36
Q

2 types of non coding DNA

A

non- coding/ multiple repeats and introns

37
Q

genome

A

the complete set of genes in a cell.

38
Q

proteome

A

full range of proteins that the cell can code for / produce

39
Q

what’s the link between the genome and proteome?

A

Proteome is as a result of the full genome; as it contains genes that code for specific proteins.

40
Q

protein synthesis definition, and define translation and transcription

A

The production of polypeptides (that fold to form proteins) within the cell using the genetic code, 2 parts: transcription and translation.

Transcription: the production of mRNA from DNA (different in prokaryotes and eukaryotes)
Translation: the production of polypeptides from the sequences of codons carried by mRNA.
- DNA and RNA are involved in these stages

41
Q

what are the 3 different terms used to describe a group of 3 bases

A

triplet, codon and anticodon

A Level Biology AQA (6 decks)

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