✅8 - DNA, Genes and Protein Synthesis Flashcards

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1
Q

What is a gene?

A

A section of DNA that contains the coded information for making polypeptides and functional RNA

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2
Q

What is a locus?

A

The particular positions of a gene in a section of DNA

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3
Q

Why was it suggested that there were a minimum of three bases coding for each amino acid?

A

Only 20 amino acids occur in proteins
Each amino acid must have its own code
There are only four bases
4^2 is 16, while 4^3 is 64 amino acids

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4
Q

Why is the code degenerate?

A

Because most amino acids are coded for by more than one triplet

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5
Q

How is the triplet always read?

A

In one direction

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6
Q

What is always the first triplet in an amino acid sequence?

A

That coding for the amino acid methionine

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7
Q

Why is the code non-overlapping?

A

Because each base sequence is only read once, as triplets rather than individually

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8
Q

Why is the code universal?

A

Because with a few minor exceptions each triplet codes for the same amino acid in all organisms - indirect evidence for evolution

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9
Q

What are introns?

A

Triplets which do not code for any amino acids

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10
Q

What are exons?

A

Triplets that are expressed

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11
Q

What are histones?

A

Proteins associated with DNA

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12
Q

What is a chromatid?

A

A thread of DNA which makes up a chromosome

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13
Q

What are homologus pairs?

A

One chromosome from each parent in a pair, with the same genes but not necessarily the same alleles

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14
Q

What is the human chromosome number?

A

46

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15
Q

What is an allele?

A

One of a number of alternative forms of a gene

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16
Q

What is mRNA?

A

Messenger RNA

17
Q

What is the relative size of mRNA?

A

Small enough to leave the nucleus through the nuclear pores and to enter the cytoplasm

18
Q

What is a codon?

A

A sequence of three bases on mRNA that codes for a single amino acid

19
Q

What is a genome?

A

The complete set of genes in a cell, including those in mitochondira and/or chloroplasts

20
Q

What is a proteome?

A

The full range of proteins produced by the genome

21
Q

What is RNA made up of?

A

Ribose
One organic base
A phosphate group

22
Q

What are the two types of RNA important to protein synthesis?

A

mRNA

tRNA

23
Q

What is the base sequence of mRNA determined by?

A

The sequence of bases on DNA

24
Q

What are the complementary base pairings for RNA?

A

C + G

A + T/U

25
Q

What is transcription?

A

When a complementary section of part of the DNA sequence is made in the form of a molecule of pre-mRNA

26
Q

What is translation?

A

The mRNA is used as a template to which complementary tRNA molecules attach and the amino acids they carry are linked to form a polypeptide

27
Q

How is mRNA made from pre-mRNA?

A

Through splicing

28
Q

Which enzyme builds the pre-mRNA strand?

A

RNA polymerase

29
Q

Why do mRNA molecules leave the nucleus via nuclear pores?

A

Because they are too large to diffuse out

30
Q

Where does the ribosome attache to?

A

The starting codon at the end of the mRNA molecule

31
Q

Where does the tRNA molecule move to?

A

The ribosome, and attaches to the complementary codon on the mRNA

32
Q

How many tRNA molecules does the ribosome bring together at once?

A

Two

33
Q

What is used to form peptide bonds between the two amino acids?

A

An enzyme and ATP

34
Q

What happens as the third amino acid is attached to the sequence?

A

The first tRNA is released and it is free to collect another amino acid

35
Q

How many ribosomes can pass behind the first?

A

Up to 50