Genetics

An organism’s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its parents. To varying degrees, genes interact with each other and environmental factors to generate traits. The distribution of alleles and traits within a population is influenced by a number of factors, including natural selection, migration, and random genetic drift.In this video, JoVE introduces some of the foundational discoveries in genetics,...

To dissect genetic processes or create organisms with novel suites of traits, scientists can perform genetic crosses, or the purposeful mating of two organisms. The recombination of parental genetic material in the offspring allows researchers to deduce the functions, interactions, and locations of genes. This video will examine how genetic crosses were influential in developing Mendel's three laws of inheritance, which form the basis of our understanding of genetics. One genetic crossing...

Genetic screens are critical tools for defining gene function and understanding gene interactions. Screens typically involve mutating genes and then assessing the affected organisms for phenotypes of interest. The process can be “forward”, where mutations are generated randomly to identify unknown genes responsible for the phenotypes, or it can be “reverse”, where specific genes are targeted for mutation to observe what phenotypes are produced.Here, JoVE reviews various types of genetic...

Many human diseases are associated with mutations or variations in genetic sequences. Some of these genetic variants are heritable, passed down from generation to generation, while others arise sporadically during an organism’s life and cause diseases such as cancer. Researchers are trying to identify and characterize these genetic alterations in the hopes of improving diagnosis and therapeutic options for patients.In this video, we will examine the history of genetic disease research, and...

Single nucleotide polymorphisms, or SNPs, are the most common form of genetic variation in humans. These differences at individual bases in the DNA often do not directly affect gene expression, but in many cases can still be useful for locating disease-associated genes or for diagnosing patients. Numerous methodologies have been established to identify, or “genotype”, SNPs.JoVE’s introduction to SNP Genotyping begins by discussing what SNPs are and how they can be used to identify...

Cytogenetics is the field of study devoted to chromosomes, and involves the direct observation of a cell’s chromosomal number and structure, together known as its karyotype. Many chromosomal abnormalities are associated with disease. Each chromosome in a karyotype can be stained with a variety of dyes to give unique banding patterns. More recent techniques, including comparative genomic hybridization and fluorescence in situ hybridization (FISH), allow for detecting specific chromosomal...

Gene expression is the complex process where a cell uses its genetic information to make functional products. This process is regulated at multiple stages, and any misregulation could lead to diseases such as cancer. This video highlights important historical discoveries relating to gene expression, including the understanding of how distinct combinations of DNA bases encode the amino acids that make up proteins. Key questions in the field of gene expression research are explored, followed by a...

Microarrays are important tools for profiling gene expression, and are based on complementary binding between probes that are attached to glass chips and nucleic acids derived from samples. Using these arrays, scientists can simultaneously evaluate the expression of thousands of genes. In addition, the expression profiles of different cells or tissue types can be compared, allowing researchers to deduce how the expression of different genes change during biological processes, and thus gain...

Source: Pablo Sanchez Bosch2, Sean Corcoran2 and Katja Brückner1,2,3 1Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research 2Department of Cell and Tissue Biology,  3Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA, USA     Rapid Amplification of cDNA Ends (RACE) is a technique that allows amplification of full-length cDNA from mRNA by extending to the 3’ or 5’ end, even without prior knowledge of the sequence (Frohman et al.,...

Among different methods to evaluate gene expression, the high-throughput sequencing of RNA, or RNA-seq. is particularly attractive, as it can be performed and analyzed without relying on prior available genomic information. During RNA-seq, RNA isolated from samples of interest is used to generate a DNA library, which is then amplified and sequenced. Ultimately, RNA-seq can determine which genes are expressed, the levels of their expression, and the presence of any previously unknown transcripts.

Since the early days of genetics research, scientists have noted certain heritable phenotypic differences that are not due to differences in the nucleotide sequence of DNA. Current evidence suggests that these “epigenetic” phenomena might be controlled by a number of mechanisms, including the modification of DNA cytosine bases with methyl groups, the addition of various chemical groups to histone proteins, and the recruitment of protein factors to specific DNA sites via interactions with...

Methylation at CpG dinucleotides is a chemical modification of DNA hypothesized to play important roles in regulating gene expression. In particular, the methylation of clusters of methylation sites, called “CpG islands”, near promoters and other gene regulatory elements may contribute to the stable silencing of genes, for example, during epigenetic processes such as genomic imprinting and X-chromosome inactivation. At the same time, aberrant CpG methylation has been shown to be associated with...

Histones are proteins that help organize DNA in eukaryotic nuclei by serving as “scaffolds” around which DNA can be wrapped, forming a complex called “chromatin”. These proteins can be modified through the addition of chemical groups, and these changes affect gene expression. Researchers use a technique called chromatin immunoprecipitation (ChIP) to better understand which DNA regions associate with specific histone modifications or other gene regulatory proteins. Antibodies are used to isolate...

Genetic engineering – the process of purposefully altering an organism’s DNA – has been used to create powerful research tools and model organisms, and has also seen many agricultural applications. However, in order to engineer traits to tackle complex agricultural problems such as stress tolerance, or to realize the promise of gene therapy for treating human diseases, further advances in the field are still needed. Important considerations include the safe and efficient delivery of genetic...

One of the most widely used tools in modern biology is molecular cloning with restriction enzymes, which create compatible ends between DNA fragments that allow them to be joined together. However, this technique has certain restrictions that limit its applicability for large or complex DNA construct generation. A newer technique that addresses some of these shortcomings is recombineering, which modifies DNA using homologous recombination (HR), the exchange between different DNA molecules based...

A well-established technique for modifying specific sequences in the genome is gene targeting by homologous recombination, but this method can be laborious and only works in certain organisms. Recent advances have led to the development of “genome editing”, which works by inducing double-strand breaks in DNA using engineered nuclease enzymes guided to target genomic sites by either proteins or RNAs that recognize specific sequences. When a cell attempts to repair this damage, mutations can be...