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Genetics Flashcards

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1
Q

What is the primary role of a transcription factor?

A

A protein that binds specific DNA sequences to regulate the rate of transcription.

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2
Q

Give an example of a transcription factor and its role.

A

GATA4 – important in cardiac development and differentiation.

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3
Q

What are the two main types of chromatin and their functions?

A

Euchromatin (loosely packed, active genes), Heterochromatin (tightly packed, silent genes).

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4
Q

What are histone modifications and why are they important?

A

Chemical changes to histone proteins (e.g., acetylation, methylation) that influence gene expression by altering chromatin structure.

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5
Q

What effect does histone acetylation generally have on gene expression?

A

Promotes transcription by loosening chromatin.

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6
Q

What enzyme adds acetyl groups to histones?

A

Histone acetyl transferase (HAT).

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7
Q

What enzyme removes acetyl groups from histones?

A

Histone deacetylase (HDAC).

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8
Q

What is the role of DNA methylation in gene regulation?

A

Represses gene expression by condensing chromatin.

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9
Q

Where is constitutive heterochromatin found in the genome?

A

Centromeres and telomeres – always highly condensed and inactive.

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10
Q

What are Lamin-Associated Domains (LADs)?

A

Regions of heterochromatin located at the nuclear periphery associated with the nuclear lamina.

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11
Q

What is real-time RT-PCR used for?

A

Quantifying mRNA levels in a sample.

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12
Q

What are the key steps in real-time RT-PCR?

A

Isolate RNA → reverse transcribe to cDNA → amplify with specific primers and fluorescent probe → quantify in real time.

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13
Q

What control should be used in RT-PCR?

A

Housekeeping gene (e.g., GAPDH) as a loading control.

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14
Q

What is Western blotting used for?

A

Detecting and quantifying specific proteins in a sample.

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15
Q

What are the key steps in Western blotting?

A

SDS-PAGE → transfer to membrane → probe with primary and secondary antibodies → detect signal.

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16
Q

Why is GAPDH used in a Western blot?

A

As a loading control to ensure equal protein loading.

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17
Q

What is immunofluorescence used for?

A

Visualising the location of proteins in cells or tissues using fluorescently tagged antibodies.

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18
Q

What control should be used in immunofluorescence?

A

Negative control without primary antibody; DAPI for nuclear staining.

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19
Q

What is Next Generation Sequencing (NGS)?

A

A high-throughput method to sequence entire genomes or transcriptomes.

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20
Q

How is NGS different from Sanger sequencing?

A

NGS sequences millions of fragments in parallel; Sanger sequences one at a time.

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21
Q

What can RNA-Seq (a form of NGS) be used for?

A

Measuring gene expression, identifying differentially expressed genes, SNPs, or mutations.

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22
Q

What is RNA interference (RNAi)?

A

A technique using siRNA or shRNA to knock down gene expression by degrading mRNA.

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23
Q

What is a common limitation of RNAi?

A

Temporary and incomplete knockdown; potential off-target effects.

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24
Q

What control is used in RNAi experiments?

A

Negative control siRNA that doesn’t target any gene.

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25
What is CRISPR-Cas9?
A genome editing tool that introduces double-stranded breaks at specific DNA sequences.
26
What guides the Cas9 enzyme to its DNA target?
A synthetic single guide RNA (sgRNA) complementary to the target DNA sequence.
27
What happens after Cas9 cuts DNA?
Cell repairs the break via NHEJ (error-prone) or HDR (precise but less efficient).
28
What are potential issues with CRISPR-Cas9?
Off-target effects, inefficient HDR in non-dividing cells.
29
Which method would you use to study gene expression levels of one gene?
Real-time RT-PCR.
30
Which method would you use to study protein levels of a transcription factor?
Western blotting.
31
Which method would you use to see where a protein is located in the cell?
Immunofluorescence.
32
Which method would you use to identify all genes expressed in a cell type?
RNA-Seq (NGS).
33
Which method would you use to knock out a gene permanently?
CRISPR-Cas9.
34
Which method would you use for temporary gene silencing?
RNAi.
35
What are the key principles of inheritance in genetics?
- Dominance/Recessivity: One allele masks the effect of the other. - Epistasis: One gene masks or modifies the expression of another gene. - Sex-Linkage: Genes located on sex chromosomes (X or Y) follow distinct inheritance patterns.
36
What does the term 'epistasis' mean?
Epistasis occurs when one allele at one locus can mask or modify the effects of alleles at one or more other loci. It adds complexity to inheritance and phenotypic expression.
37
How are genes on different chromosomes inherited?
Genes located on different chromosomes are inherited independently (Mendel’s Law of Independent Assortment). This results in a 9:3:3:1 phenotypic ratio in dihybrid crosses.
38
What is the expected phenotypic ratio in a self-cross of heterozygous individuals for genes on different chromosomes?
The expected phenotypic ratio is 9:3:3:1.
39
What is the significance of recessive epistasis in genetics?
Recessive epistasis occurs when a recessive allele at one gene masks the phenotypic effects of another gene. For example, in Labrador Retrievers, the homozygous ee genotype for the E gene hides the effects of the B gene, resulting in a yellow coat.
40
How does dominant epistasis work?
In dominant epistasis, a dominant allele at one locus (e.g., I for white coat color) masks the effects of alleles at another locus (e.g., E for darker coat colors).
41
What is polygenic inheritance?
Polygenic inheritance refers to traits controlled by multiple genes, each contributing to the phenotype. Examples include skin color, Alzheimer’s disease, and diabetes.
42
How does skin color inheritance demonstrate polygenic inheritance?
Skin color is controlled by multiple genes (3 genes), with each contributing allele adding a unit of color. This results in a continuous variation of skin tones.
43
What is copy number variation (CNV)?
Copy number variation refers to differences in the number of copies of a particular gene in different individuals. CNVs can affect genes involved in immune function and brain development.
44
What are the potential effects of CNVs on health?
CNVs can have both beneficial and harmful effects depending on the gene involved and the context. For example, CNVs in genes involved in immune function may provide adaptive advantages but can also contribute to disease.
45
How do environmental factors influence genetic traits?
Environmental factors, such as temperature or nutrition, can influence the expression of genetic traits. For example, the coat color of Siamese cats depends on temperature, with darker colors appearing in cooler areas of the body.
46
47
What does genetic linkage refer to?
Genes located close together on the same chromosome tend to be inherited together.
48
What is a recombinant?
An offspring with a different combination of alleles than either parent, due to crossing over.
49
What does a recombination frequency of 50% suggest?
Genes are on different chromosomes or very far apart on the same chromosome.
50
What is a linkage map?
A genetic map showing the relative positions of genes based on recombination frequencies.
51
What unit is used to measure genetic distance?
Centimorgan (cM).
52
How do double crossovers affect genetic mapping?
They can underestimate actual distance because some recombinants appear as parental.
53
What is karyotyping used for?
To visualize and analyze the number and structure of chromosomes.
54
What is aneuploidy?
The presence of an abnormal number of chromosomes (e.g., trisomy 21).
55
What causes structural chromosome abnormalities?
Errors during meiosis or DNA repair, such as deletions, duplications, inversions, and translocations.
56
What is the Philadelphia chromosome associated with?
Chronic myeloid leukemia (CML), resulting from a translocation between chromosomes 9 and 22.
57
What is FISH used for?
Fluorescent in situ hybridization; detects specific DNA sequences on chromosomes.
58
What are the clinical implications of balanced vs. unbalanced translocations?
Balanced may be silent; unbalanced often lead to developmental issues or miscarriage.
59
What is epistasis?
One gene masks or modifies the effect of another gene.
60
What is recessive epistasis?
A recessive allele at one locus masks the effect of alleles at a second locus.
61
What is dominant epistasis?
A dominant allele at one locus masks the effects at another locus.
62
What are modifier genes?
Genes that influence the phenotypic expression of other genes.
63
What is polygenic inheritance?
Traits influenced by multiple genes, often showing continuous variation (e.g., skin color, height).
64
What is copy number variation (CNV)?
Variations in the number of copies of a particular gene between individuals.
65
What are multifactorial traits?
Traits influenced by both genetic and environmental factors (e.g., diabetes, heart disease).
66
Why are multifactorial traits complex to study?
They don't follow Mendelian inheritance and involve numerous genes and environmental inputs.
67
What does the complementation test determine?
Whether two mutants with the same phenotype are defective in the same or in different genes.
68
What type of mutations does the complementation test work for?
Recessive mutations only.
69
What is the key result in a complementation test that indicates mutations are in different genes?
F1 progeny show wild-type phenotype.
70
What does it mean if F1 progeny in a complementation test still show the mutant phenotype?
Mutations are in the same gene.
71
What is auxotrophy?
The inability of an organism to synthesize a particular organic compound required for its growth.
72
What type of media can prototrophic yeast grow on?
Minimal medium (MM).
73
What does growth on MM + histidine indicate about a yeast strain?
It is a histidine auxotroph (His-).
74
Why is the complementation test considered simple and universal?
It does not require prior knowledge of the genes involved and is cost-effective.
75
Why must mutations be recessive for the complementation test to be informative?
Dominant mutations will always show the mutant phenotype regardless of gene identity, making the test uninformative.
76
What is the genotype result when two mutants defective in different genes are crossed?
F1 progeny are double heterozygotes (e.g., a-/A+ b-/B+).
77
What are model organisms used for genetic complementation tests?
Commonly yeast (Saccharomyces cerevisiae).
78
What is the purpose of dropout medium in yeast experiments?
To test for specific auxotrophies by removing one supplement at a time.
79
What does it mean when two albino parents have no albino children?
They carry mutations in different genes that complement each other.
80
What is Zellweger's Syndrome an example of?
A condition caused by recessive mutations in any one of multiple genes with the same phenotype.
81
What is the limitation of complementation testing with dominant mutations?
The test becomes uninformative as all F1s show the mutant phenotype regardless of gene identity.

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