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Biology > DNA, Genes and Chromosomes > Flashcards

DNA, Genes and Chromosomes Flashcards

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1
Q

Gene

A

A section of DNA that contains the coded information for a polypeptide and functional RNA

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2
Q

What is functional RNA?

A

RNA which has a use in protein synthesis (tRNA and rRNA)

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3
Q

How many amino acids regularly occur in the genetic code?

A

20

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4
Q

Was does a triplet code for?

A

An amino acid

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5
Q

What do a small number of triplets code for?

A

A STOP codon

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6
Q

Why must the genetic code be in triplets?

A

One base per A.A results in only 4 A.As
Two bases per A.A results in only 16 A.As
Three bases per A.A results in 64 A.As

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7
Q

Why are all 64 combinations of triplets used for 20 amino acids?

A

Most amino acids are coded for by more than 1 triplet. STOP codons must also have triplets

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8
Q

What does a degenerate genetic code mean?

A

Multiple codons code for the same amino acid

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9
Q

What does a non-overlapping genetic code mean?

A

The DNA strand is only read one-way and each is base is only read once

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10
Q

What does a universal genetic code mean?

A

The same codons code for the same amino acids in all organisms

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11
Q

Exon

A

Coding gene region

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12
Q

Intron

A

Non-coding gene region

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13
Q

Where are chromosomes not used?

A

Prokaryotes, mitochondria and chloroplasts

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14
Q

Where chromosomes are not used what is the DNA like?

A

Short, circular and without histone proteins

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15
Q

What is a Eukaryotes’ DNA like?

A

Linear, long DNA wrapped around histones. Condenses into a chromosome

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16
Q

How many molecules of DNA make up a chromosome?

A

One molecule per chromatid

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17
Q

When are chromosomes visible?

A

Prophase

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18
Q

What happens to the DNA double helix once associated with histones?

A

The DNA-histone complex is coiled
The coil is looped further
The loops are then packed into a chromosome

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19
Q

Homologous Chromosomes

A

A pair of the same chromosome one from the mother and one form the father

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20
Q

How many homologous chromosomes are there?

A

2n (46 in humans)

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21
Q

What happens to the homologous chromosomes in Meiosis?

A

The are split and then recombined with another organism’s gametes in fusion

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22
Q

Where in humans are a pair of chromosomes not homologous?

A

Male sex chromosomes (XY)

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23
Q

Allele

A

One of a number of alternate forms of a gene

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24
Q

Where are alleles from?

A

One is inherited from each parent

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25
Do alleles produce the same polypeptide?
They produce different polypeptides
26
Genome
The complete set of genes in a cell including mitochondria and chloroplasts
27
Proteome
The full range of proteins produced by the genome
28
Why is DNA not used in protein synthesis?
It is too large to leave the nucleus
29
What is used instead of DNA in protein synthesis?
Ribonucleic acid (RNA)
30
What is an RNA monomer made up of?
A ribose sugar, a phosphate group and a nitrogenous base
31
What are the nitrogenous bases in RNA?
Cytosine C, Adenine A, Guanine G, Uracil U
32
Where in the cell does splicing of pre-mRNA occur?
The nucleus (before released through the nuclear pore)
33
What is the shape and size of an mRNA molecule?
1000s of bases long in a single helix shape
34
What is mRNA's function
To act as a template for protein synthesis
35
Through what process is mRNA made?
Transcription
36
How does mRNA perform its function?
It associates with ribosomes to allow tRNA molecules to form the polypeptide
37
Is it mRNA or tRNA which determines the polypeptide sequence?
mRNA as it corresponds to the DNA base sequence
38
What is the shape and size of an tRNA molecule?
80 nucleotides folded into a clover shape
39
What are the 2 most important parts of a tRNA molecule
Point of attachment Anticodon
40
Point of attachment
The point on a tRNA molecule where an amino acid is held, ready to form peptide bonds
41
Anticodon
The three bases on tRNA which are complementary to the codon on mRNA
42
What is the function of an anticodon?
The specific anticodon is specific to one amino acid
43
Which bases are pyrimidines?
Uracil, Thymine and Cytosine
44
Which bases are purines?
Adenine and Guanine
45
Transcription
The process of making pre-mRNA using DNA as a template
46
Step 1 of transcription
RNA polymerase acts on a specific DNA region causing the strands to separate and the bases to expose
47
Step 2 of transcription
One of the strands of DNA is used as a template strand
48
Step 3 of transcription
The template strand pairs with complimentary free floating nucleotides
49
Step 4 of transcription
RNA polymerase moves along the strand of complementary nucleotides, joining them into pre-mRNA
50
Step 5 of transcription
RNA polymerase reaches a stop codon and it detaches
51
How many bases are exposed during transcription?
12 as the DNA rejoins itself behind the RNA polymerase
52
Splicing
The conversion of pre-mRNA into mRNA (in eukaryotes)
53
Why is splicing only occurring in eukaryotes?
In prokaryotes there are no introns
54
What happens in splicing?
The base sequence of the introns are removed from the pre-mRNA. This makes mRNA
55
Translation
The process where mRNA is read in the ribosomes and translated into an amino acid sequence
56
Step 1 of translation
A ribosome attaches to the start codon of an mRNA molecule
57
Step 2 of translation
The tRNA molecule with the complementary anticodon to the start codon moves up to the ribosome and pairs with the codon. It carries an amino acid
58
Step 3 of translation
Another tRNA molecule pairs with the next codon on the mRNA. It carries another amino acid
59
Step 4 of translation
The ribosome moves across the mRNA joining the 2 amino acids by peptide bonds.
60
How are the peptide bonds formed in transcription?
By an enzyme and the hydrolysis of ATP
61
Step 5 of translation
The ribosome releases the 1st tRNA molecule and gaining a 3rd tRNA molecule with a 3rd amino acid
62
Why can translation produce many proteins so quickly?
50 ribosomes can translate one mRNA molecule at once at the rate of 15 amino acids a second
63
When does translation stop?
At the STOP codon on the mRNA
64
Supercoiling
The process of prokaryotes coiling their DNA to fit in the cell
65
Which enzyme manages supercoiling in prokaryotes?
DNA gyrase
66
Compartmentalisation
The separation of different parts of the cell with different functions by using membranes
67
What are the advantages of compartmentalisation in eukaryotes?
Enables the building of more complex proteins and RNA products
68
Endosymbiotic theory
Bacterial cells were engulfed by larger organelles and evolved to be organelles
69
What does endosymbiotic theory explain?
The presence of DNA in mitochondria and chloroplasts
70
What is DNA used for in mitochondria and chloroplasts?
Production of respiration enzymes in mitochondria Production of photosynthesis enzymes in chloroplasts
71
If the DNA triplet is GAT what is the mRNA codon?
CUA
72
If the mRNA codon is CUA what is the tRNA anticodon?
GAU
73
WHich type of RNA has paired bases in its structure?
tRNA (to form the clover leaves)
74
Spores
Haploid cells formed only by asexual reproduction in some plants and all fungi
75
What binds homologous chromosomes together and maintains their alignment?
Synaptonemal complex
76
What is the percentage difference in the amino acid sequence between mammals and insects?
33%
77
Missense mutation
If the new codon codes for a different amino acid
78
Nonsense mutation
If the new codon is a STOP codon

Biology (11 decks)

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