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Biology > DNA, genes and protein synthesis > Flashcards

DNA, genes and protein synthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a gene?

A

A section of DNA that contains the coded information for making polypeptides and functional RNA, located at the locus

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2
Q

How do genes control the characteristics of an organism?

A

Genes code for proteins (enzymes) and these control chemical reactions and therefore the development and activities of an organism

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3
Q

What is the minimum number of bases that must code for one amino acid?

A

3

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4
Q

How many different amino acids regularly occur in proteins?

A

20

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4
Q

What is a triplet?

A

Three bases code for each amino acid

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5
Q

What is a degenerate code?

A

Multiple different codons will give the same amino acid

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6
Q

How many triplets code for amino acids that need more than one?

A

2-6

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7
Q

What happens to the starting codon on the polypeptide?

A

If not needed in the final molecule, it is removed at the end

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8
Q

What are the ‘stop codes’?

A

Three triplets don’t code for any amino acids and they mark the end of the polypeptide chain

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9
Q

What is non-overlapping?

A

Each base in the sequence is only read once

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10
Q

Why is the code universal?

A

Few minor exceptions, but each triplet codes for the same amino acid in all organisms

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11
Q

What are exons?

A

Coding sequences of DNA

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12
Q

What are introns?

A

Non-coding regions of DNA

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13
Q

What else do genes code for?

A

rRNA and tRNA

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14
Q

What is the DNA in a prokaryote like?

A

Shorter, form a circle and aren’t associated with proteins, therefore they don’t have chromosomes

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15
Q

What is the DNA in a eukaryote like?

A

Longer, form a line and are associated with histones to form chromosomes

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16
Q

When are chromosomes visible?

A

Distinct structure when cells are dividing

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17
Q

How are chromosomes seen at the start of cell division?

A

Two threads, joined at a single point

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18
Q

What is each thread of the chromosome during cell division called?

A

Chromatid as DNA has already replicated

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19
Q

What is a locus?

A

A specific position of a gene on a DNA molecule

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20
Q

What are homologous pairs?

A

Where one of each chromosome is derived from the mother and father

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21
Q

What is the diploid number?

A

The total number of chromosomes in an adult cell, not the number of pairs

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22
Q

What is the diploid number in humans?

A

46

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23
Q

What is the difference between the chromosomes in a homologous pairs?

A

Carry the same gene but not always the same allele

24
Q

What is an allele?

A

One of the number of alternative forms of a gene

25
Q

What happens when the alleles are different?

A

Each allele has a different base sequence, therefore a different amino acid sequence, so produces a different polypeptide

26
Q

What is a mutation?

A

Changes in the base sequence of gene, which creates a new allele of that gene

27
Q

How do mutations affect the protein produced?

A

May not function properly or at all, enzymes may have a different shape and not be able to form ES complexes

28
Q

How is DNA transferred into the cytoplasm to make proteins?

A

Transcribed onto mRNA

29
Q

What is a codon?

A

Sequence of three bases on mRNA that codes for a single amino acid (complimentary to DNA)

30
Q

What is the genome?

A

The complete set of genes in a cell, including those in the mitochondria/chloroplasts

31
Q

What is the proteome?

A

Proteins produced by a given type of cell under a certain set of conditions

32
Q

What is the complete proteome?

A

The full range of proteins produced by the genome

33
Q

What are the nucleotides of RNA made up of?

A

Pentose sugar ribose, AUCG bases and a phosphate group

34
Q

What determines the base sequence of mRNA?

A

Transcription of DNA

35
Q

What does mRNA do once it leaves the nuclear pores?

A

Associates with the ribosomes, where it acts as a template for protein synthesis

36
Q

How many mono-nucleotides make up mRNA?

A

Thousands

37
Q

How many mono-nucleotides make up tRNA?

A

Around 80

38
Q

What is the structure of tRNA?

A

Single-stranded chain folded into a clover-leaf shape, with one end of the chain extending beyond the other

39
Q

Why are there many different tRNA molecules?

A

Each attach to a different amino acid

40
Q

What is an anticodon?

A

Three bases at the opposite end of a tRNA molecule, on the anticodon loop

41
Q

What happens during protein synthesis with tRNA?

A

An anticodon pairs with the three complimentary organic bases that make up the codon on mRNA, tRNA attaches to amino acids and lines them up on the mRNA template

42
Q

In what form does DNA provide instructions?

A

Long sequences of bases

43
Q

What is transcription?

A

The formation of pre-mRNA from part of DNA sequences

44
Q

How does pre-mRNA become mRNA?

A

Splicing

45
Q

What is translation?

A

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

46
Q

What enzyme forms pre-mRNA?

A

RNA polymerase

47
Q

How many base pairs are exposed on a DNA molecule at once?

A

About 12

48
Q

When is splicing necessary?

A

In eukaryotic cells, as there are introns

49
Q

Why must introns be removed?

A

They would prevent the synthesis if polypeptides

50
Q

How many different tRNA molecules are there?

A

60

51
Q

What does the ribosomes attach to on the mRNA molecule?

A

The starting codon

52
Q

What happens when the ribosome and mRNA attach?

A

The tRNA molecule with the complimentary anticodon sequences moves and pairs up with the codon on mRNA

53
Q

How many tRNA molecules act at once on mRNA?

A

2

54
Q

How are two amino acids joined together?

A

By a peptide bond, using an enzyme and ATP which is hydrolysed

55
Q

How many amino acids are added to a polypeptide chain each second?

A

Up to 15

56
Q

What happens when the ribosome reaches stop codon?

A

Ribosome, tRNA and mRNA separate and the polypeptide chain is complete

57
Q

Why do up to 50 ribosomes pass immediately behind the first?

A

So many identical polypeptides can be assembled simultaneously

Biology (22 decks)

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