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OCR A-Level Bio > gentetics > Flashcards

gentetics Flashcards

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1
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2
Q

What are mutations?

A

Mutations are changes in the sequence of nucleotides in DNA molecules.

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3
Q

What are insertion/deletion mutations?

A

Insertion/deletion mutations involve one or more nucleotide pairs being inserted or deleted from the sequence, altering the sequence after the mutation point, known as a frameshift.

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4
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What is a point mutation/substitution?

A

A point mutation/substitution occurs when one base pair is replaced by another.

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5
Q

What is a nonsense mutation?

A

A nonsense mutation is one where translation is stopped early, resulting in a truncated polypeptide due to the premature introduction of a stop codon.

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6
Q

What is a missense mutation?

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A missense mutation is a codon change that results in the production of a different amino acid, altering the tertiary structure of the protein.

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7
Q

What is a silent mutation?

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A silent mutation is a codon change that does not affect the amino acid sequence produced, possible due to the degenerate nature of the genetic code.

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8
Q

What are the effects of mutations?

A

Mutations can have neutral effects, be beneficial, or harmful depending on the environment and context.

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9
Q

What is an example of a beneficial mutation?

A

An example of a beneficial mutation is the development of trichromatic vision in humans.

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10
Q

What is an example of a harmful mutation?

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A harmful mutation includes a mutation in the CFTR protein which causes cystic fibrosis.

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11
Q

How can gene expression be controlled?

A

Gene expression can be controlled at the transcriptional, post-transcriptional, and post-translational levels.

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12
Q

What is the lac operon?

A

The lac operon is a length of DNA that controls the expression of beta-galactosidase responsible for hydrolysis of lactose in E. coli.

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13
Q

What happens when glucose is high and lactose is low in the lac operon?

A

Transcription of the structural genes is inhibited due to the binding of the repressor to the operator region.

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14
Q

What happens when glucose is low and lactose is high in the lac operon?

A

Lactose binds to the repressor, changing its shape and making it ineffective, allowing RNA polymerase to bind to the promoter region and transcription to occur.

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15
Q

What are transcription factors?

A

Transcription factors are proteins that can switch genes on and off by interacting with the promoter sequence of DNA.

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16
Q

What is post-transcriptional control?

A

Post-transcriptional control involves editing the primary mRNA transcript by removing introns to create a mature transcript of exons.

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17
Q

What is post-translational control?

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Post-translational control involves activating proteins, such as adrenaline, with the help of cyclic AMP.

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18
Q

What are homeobox genes?

A

Homeobox genes are involved in controlling the development of body plans by coding for transcription factors that regulate gene expression.

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19
Q

What is apoptosis?

A

Apoptosis is programmed cell death that controls the development of body plans and tissue development in both plants and animals.

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20
Q

What is the difference between discontinuous and continuous variation?

A

Discontinuous variation can be assigned to specific categories, while continuous variation involves quantitative differences between phenotypes.

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21
Q

What is meiosis?

A

Meiosis is a form of cell division that produces haploid gametes and generates genetic variation.

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22
Q

What is crossing over in meiosis?

A

Crossing over occurs when pairs of homologous chromosomes exchange genetic material.

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23
Q

What is independent assortment in meiosis?

A

Independent assortment refers to the various combinations of chromosome arrangements during meiosis.

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24
Q

What is an allele?

A

An allele is an alternative form of a gene.

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25
What is a locus?
A locus is the specific position of a gene on a chromosome.
26
What is a phenotype?
A phenotype is the observable characteristics of an organism resulting from its genotype and environment.
27
What is a genotype?
A genotype is the alleles present within the cells of an organism for a particular trait.
28
What is a dominant allele?
A dominant allele is one that is expressed in the phenotype even if only one copy is present.
29
What is a recessive allele?
A recessive allele is expressed only if there is no dominant allele present.
30
What is homozygous?
Homozygous refers to having two identical alleles for a trait.
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What is heterozygous?
Heterozygous refers to having two different alleles for a trait.
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What is codominance?
Codominance occurs when both alleles contribute to the phenotype.
33
What is linkage?
Linkage is the phenomenon where genes for different characteristics are located at different loci on the same chromosome and are inherited together.
34
What is monogenic inheritance?
Monogenic inheritance is when a phenotype is controlled by a single gene.
35
What is a dihybrid cross?
A dihybrid cross involves the inheritance of two genes.
36
What is sex linkage?
Sex linkage is the expression of an allele dependent on the gender of the individual, as the gene is located on a sex chromosome.
37
What is autosomal linkage?
Autosomal linkage refers to genes located on the same chromosome that tend to be expressed together.
38
What is epistasis?
Epistasis is the interaction of different loci on the gene, where one gene locus affects the expression of another.
39
What is recessive epistasis?
Recessive epistasis occurs when the presence of a recessive allele prevents the expression of another allele at a second locus.
40
What is dominant epistasis?
Dominant epistasis occurs when a dominant allele at one locus completely masks the alleles at a second locus.
41
What is the chi-squared test?
The chi-squared test is a statistical test used to determine whether the difference between observed and expected results is due to chance.
42
What is the Hardy-Weinberg principle?
The Hardy-Weinberg principle estimates allele frequencies in a population and checks for changes over time.
43
What is evolution?
Evolution is the process by which the frequency of alleles in a gene pool changes over time due to natural selection.
44
What is natural selection?
Natural selection is the process where fitter individuals survive and pass on advantageous alleles to future generations.
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What is genetic drift?
Genetic drift is a phenomenon where small changes in allele frequency occur due to the fact that not all individuals in a population reproduce.
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What is a genetic bottleneck?
A genetic bottleneck is a rapid reduction in population size that affects genetic variation in future generations.
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What is the founder effect?
The founder effect is a decrease in genetic diversity that occurs when a population descends from a small number of ancestors.
48
What is speciation?
Speciation is the process by which new species arise after a population becomes separated and cannot interbreed.
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What is allopatric speciation?
Allopatric speciation is caused by a physical barrier that separates populations, leading to reproductive isolation.
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What is sympatric speciation?
Sympatric speciation occurs when new species evolve from a single ancestral species while inhabiting the same geographic region.
51
What is artificial selection?
Artificial selection is the process where selection pressures are artificially created by humans to breed desired characteristics.
52
What is the process of DNA sequencing?
DNA sequencing begins with mapping the genome, fragmenting DNA, and using chain-termination techniques to read the base sequence.
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What is the significance of comparing genomes?
Comparing genomes allows for determining evolutionary relationships between species and developing personalized medicine.
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What does gene sequencing allow for?
Gene sequencing allows for genome-wide comparisons between individuals and between species.
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Why is comparing genomes between species significant?
It allows evolutionary relationships between species to be determined and is beneficial to medical research.
56
What can comparing genomes of individuals enable?
It enables differences to be identified for the development of personalised medicine and studies of human diseases.
57
What has gene sequencing allowed in terms of polypeptides?
It has allowed for the sequences of amino acids in polypeptides to be predicted.
58
What is DNA profiling?
DNA profiling is a forensic technique used to identify individuals by characteristics of their DNA.
59
What is the main technique used in DNA profiling?
The main technique is the Polymerase Chain Reaction (PCR).
60
What is the first step in PCR?
A reaction mixture is set up by mixing the DNA sample, primers, free nucleotides, and DNA polymerase.
61
What happens during the heating step of PCR?
The mixture is heated to 95 degrees to break the hydrogen bonds and separate the two strands.
62
What is the purpose of cooling the mixture in PCR?
It allows primers to bind to the strands at a temperature between 50-65 degrees.
63
What temperature is optimal for DNA polymerase activity?
The temperature is increased to about 70 degrees.
64
How does DNA polymerase create a copy of the sample?
It uses complementary base pairing with free nucleotides.
65
How many cycles are typically repeated in PCR?
This cycle is repeated around 30 times.
66
What is gel electrophoresis used for?
It is used to separate DNA fragments and proteins according to their size using an electric current.
67
What do restriction enzymes do?
They cut DNA at specific base sequences, useful in genetic engineering.
68
What are common vectors used in genetic engineering?
Plasmids and viruses are the most common vectors.
69
How are isolated DNA fragments placed in plasmids?
Plasmid and gene are cut with the same restriction enzyme to create complementary ends.
70
What is electroporation used for?
It is used to stimulate bacterial cells to take up plasmids.
71
How can bacteria that have taken up a plasmid be identified?
With the help of marker genes, such as antibiotic resistance genes.
72
What is gene therapy?
Gene therapy is the insertion of a normal allele into target cells to replace a faulty allele.
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What are the two types of gene therapy?
Somatic gene therapy and germ line gene therapy.
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What is the difference between somatic and germ line gene therapy?
Somatic gene therapy is a short-term solution, while germ line therapy is a permanent solution passed down to offspring.
75
What are some benefits of genetic engineering?
Insect resistance in crops and genetically modified animals used to produce pharmaceuticals.
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What are some objections to genetic engineering?
Concerns about environmental effects and accessibility of genetically modified seeds for poorer farmers.

OCR A-Level Bio (53 decks)

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