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B4 Flashcards

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1
Q

What is a gene?

A

A section of DNA that contains a code for making a polypeptide and functional RNA.

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2
Q

What is a locus?

A

The location of a particular gene on a chromosome.

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3
Q

What is an allele?

A

A different version of the same gene.

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4
Q

What is a chromosome?

A

A threadlike structure composed of tightly coiled DNA wrapped around histones (if it is a eukaryotic cell).

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5
Q

What is a start codon?

A

3 bases at the start of an mRNA sequence which help to initiate translation.

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6
Q

What is a stop codon?

A

3 bases at the end of every gene that do not code for an amino acid, causing ribosomes to detach and therefore stops translation.

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7
Q

What is the genetic code?

A

An amino acid is coded for by 3 DNA bases which are described as the ‘triplet code’.

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8
Q

What does it mean that the genetic code is degenerate?

A

Each amino acid is coded for by more than one triplet of bases.

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9
Q

What is a homologous chromosome?

A

A pair of chromosomes that have the same genes and therefore are the same size.

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10
Q

What is eukaryotic DNA?

A

DNA stored as linear chromosomes inside the nucleus, tightly coiled and wrapped around proteins called histones.

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11
Q

What is prokaryotic DNA?

A

DNA molecules that are shorter and circular, not wound around histones but supercoiled to fit in the cell.

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12
Q

What is a codon?

A

3 bases on mRNA that code for an amino acid.

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13
Q

What is the advantage of the genetic code being degenerate?

A

If a substitution mutation occurs, the new triplet of bases may still code for the same amino acid, so the mutation will have no impact on the final protein produced.

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14
Q

What is the advantage of the genetic code being universal?

A

Genetic engineering is possible; a human gene can be inserted into another organism, e.g., human gene for insulin inserted into bacteria to make insulin.

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15
Q

What is the advantage of the genetic code being non-overlapping?

A

If a point mutation occurs, it will only affect one codon and therefore one amino acid.

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16
Q

What is a triplet code?

A

An amino acid is coded for by 3 bases.

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17
Q

What is meant by ‘the genetic code is universal’?

A

The same triplet of bases codes for the same amino acid in all organisms.

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18
Q

What is meant by ‘the genetic code is non-overlapping’?

A

Each base in a gene is only part of one triplet of bases that codes for one amino acid. Therefore, each codon is read as a discrete unit.

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19
Q

What are introns?

A

Non-coding sequences of DNA.

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20
Q

What is an anticodon?

A

3 bases on the tRNA which are complementary to the codon on mRNA.

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21
Q

What is the structure of mRNA?

A

Single-stranded and made up of codons.

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22
Q

What is the structure of tRNA?

A

Single-stranded, folded to create a cloverleaf shape, held in place by hydrogen bonds, has an anticodon and amino acid binding site.

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23
Q

What is the function of mRNA?

A

A copy of a gene from DNA created in the nucleus, and it then leaves the nucleus to carry the copy of the genetic code of one gene to a ribosome in the cytoplasm.

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24
Q

What are exons?

A

Sequences of DNA that code for amino acids.

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25
What is splicing?
Post-transcription modification removing introns.
26
What is a genome?
The complete set of genes in a cell.
27
What is a proteome?
The full range of proteins that a cell is able to produce.
28
What is the function of tRNA?
A specific amino acid attaches at the binding site and transfers this amino acid to the ribosome to create the polypeptide chain.
29
What is transcription?
The first stage in protein synthesis where one gene in DNA is copied into mRNA, occurring in the nucleus.
30
What is translation?
The second stage in protein synthesis where the polypeptide chain is created using both the mRNA base sequence and the tRNA, occurring on ribosomes in the cytoplasm.
31
Which enzymes are involved in transcription?
DNA helicase and RNA polymerase.
32
What is a mutation?
A change in the DNA, which can be a gene or chromosome mutation.
33
What is the function of helicase?
Catalyses the breaking of hydrogen bonds between the two strands of DNA.
34
What does RNA polymerase do?
Joins adjacent RNA nucleotides together, forming a phosphodiester bond.
35
What is pre-mRNA?
mRNA in eukaryotes that still contains the introns. ## Footnote The introns are removed by a protein called a spliceosome, leaving just the exons.
36
How is pre-mRNA modified?
Introns are removed by a spliceosome, leaving only exons.
37
What is independent segregation?
Homologous pairs of chromosomes randomly line up opposite each other at the equator of the cell.
38
What is crossing over?
Parts of the chromatids twist, break and recombine with another chromatid, resulting in new combinations of alleles in the gametes.
39
What are gametes?
Sex cells (sperm and egg).
40
How does meiosis introduce variation?
Through crossing over and independent segregation.
41
What is ATP used for in translation?
Forming the peptide bond between amino acids.
42
What is a haploid?
One copy of each chromosome in a cell.
43
What is a diploid?
Two copies of each chromosome in a cell.
44
What is meiosis?
Cell division that creates genetically different gametes, involving two nuclear divisions.resulting in four haploid daughter cells
45
What are the types of gene mutations?
Deletion and substitution.
46
What is a frameshift?
The removal of one base changes all of the subsequent codons, causing all the bases to shift back one position.
47
What is a chromosome mutation?
Change in the number of chromosomes, occurs during meiosis.
48
What is a deletion mutation?
A base is removed from a sequence, causing a frameshift.
49
What is the function of helicase?
Catalyses the breaking of hydrogen bonds between the two strands of DNA.
50
What does RNA polymerase do?
Joins adjacent RNA nucleotides together, forming a phosphodiester bond.
51
What is pre-mRNA?
mRNA in eukaryotes that still contains the introns. ## Footnote The introns are removed by a protein called a spliceosome, leaving just the exons.
52
How is pre-mRNA modified?
Introns are removed by a spliceosome, leaving only exons.
53
What is independent segregation?
Homologous pairs of chromosomes randomly line up opposite each other at the equator of the cell.
54
What is crossing over?
Parts of the chromatids twist, break and recombine with another chromatid, resulting in new combinations of alleles in the gametes.
55
What are gametes?
Sex cells (sperm and egg).
56
How does meiosis introduce variation?
Through crossing over and independent segregation.
57
What is ATP used for in translation?
Forming the peptide bond between amino acids.
58
What is a haploid?
One copy of each chromosome in a cell.
59
What is a diploid?
Two copies of each chromosome in a cell.
60
What is meiosis?
Cell division that creates genetically different gametes, involving two nuclear divisions. results in four haploid daughter cells
61
What are the types of gene mutations?
Deletion and substitution.
62
What is a frameshift?
The removal of one base changes all of the subsequent codons, causing all the bases to shift back one position.
63
What is a chromosome mutation?
Change in the number of chromosomes, occurs during meiosis.
64
What is a deletion mutation?
A base is removed from a sequence, causing a frameshift.

B4 (1 decks)

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