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Marker
| What it's not: |
A pre-Euro German trader in foreign exchange. |
| What it is: |
A segment of DNA that can be tracked from one generation to the next one. Markers can be entire genes or a single letter of code (see polymorphism). |
Meiosis
| What it's not: |
The experience of one’s own extremely bad breath. |
| What it is: |
The other kind of cell division that creates gametes (sex cells). The cell divides so that four individual cells are produced, each with half the number of chromosomes that the original cell had. (See haploid). In humans, these little guys (male sperm cells) and gals (female egg cells) ‘find their other half’ when the sperm fertilizes the egg. Since every gamete is unique, this ‘recombination’ during fertilization produces an even ‘more’ unique offspring with the required number of chromosomes (46 in humans: ½ that number from the sperm cell & the other ½ from the egg cell. |
Mendelian Ratio
| What it's not: |
The mathematical formula used by the
fire department to figure out the maximum occupancy |
What it is:
|
Ths ratio is the proportion of offspring
that are expected to have a particular phenotype or genotype,
based on Mendel’s laws of independent assortment and segregation.
For example, assume at a particular locus the ‘R’ allele is the
dominant allele and codes for a flower to be the colour red. At the
same locus the ‘r’ allele is the recessive allele and codes for
a white flower. If a red heterozygous plant (Rr) is crossed with another
red heterozygous plant (Rr) then according to Mendel’s laws the fraction
of offspring that are expected to be the colour red vs. the colour white
would be 3:1, as shown by the Punett square below. The mendelian ratio
for the phenotype produced by this cross is therefore 3:1.
|
R |
r |
| R |
RR (red
flower) |
Rr (red
flower) |
| r |
Rr (red
flower) |
rr (white flower) |
For more information on Mendel’s ratios,
check out our information on inheritance patterns
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Messenger RNA (mRNA)
| What it's not: |
A new parcel delivery company, similar to UPS. |
| What it is: |
This is the processed RNA, ready for translation. DNA has all kinds of information hidden in the sequence and if the RNA were to take all that information out of the nucleus, it would be too long. So it splices out the ‘good parts’ = the exons, which are required for the functional product, usually proteins. Then a 5’ cap and a polyA tail are added to the ends for stability and to help ribosome recognize the transcript – and you have your mature or messenger RNA. It takes the message of the DNA out into the cytoplasm.
mRNA is similar to the final blueprints for building a new house – you don’t want to take all of the information about the house to the job site every day but the just the needed information.
DNA = architect team
Nucleus = office
RNA = entire file on the job
mRNA = essential information to build from the file
5’cap and poly tail = protective covering to protect the plans and direct to the right job site
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Metabolism
| What it's not: |
A type of food poisoning that you get from eating too many mandarins. |
| What it is: |
Metabolism describes how the body processes the food that we eat into the energy that we need to live. It is not just the rate of burning calories but how food is used. Many things can affect the body’s metabolism, including gene variants and environmental factors. Inborn errors of metabolism can happen when someone can’t process particular foods effectively – these errors often have a genetic basis. |
Microarray
| What it's not: |
A Japanese karaoke term, roughly translated as “Be ever so kind as to keep the microphone away from him (or her).” |
| What it is: |
A microarray is a slide or membrane with small bits of DNA fixed to it. Microarrays can collect data at thousands of points in one experiment, so they will be useful if you want to survey a large number of genes quickly. The slide with target sequences is incubated with a test sample. If the sequences are complementary, they will hybridize and cause a colour change that analyzing computers can read and interpret.
Microarrays are generally used for 2 main purposes: to detect genomic variation and to analyze gene expression. If you want to test genomic variation, the small pieces of DNA (oligonucleotides) on the slide are genomic DNA and you use genomic DNA as your test samples. To test expression, the oligonucleotides fixed to the plate are cDNA and your test samples are mRNA. By noting where the mRNA in your test binds to the cDNA on the plate, you can identify the mRNAs in your sample and determine what genes are expressed. |
Mitochondria
| What it's not: |
Hallucinations caused by dust mites. |
| What it is: |
These are the small, self-replicating organelles found in the cytoplasm of every cell expect red blood cells. Mitochondria are the “powerhouse” of the cell because they generate ATP, the energy currency of our bodies. Interestingly, it is believed that mitochondria were originally independent aerobic bacteria that colonized the inside of the eukaryotic ancestor and a symbiotic relationship developed. |
Mitochondrial DNA (mtDNA)
| What it's not: |
What makes a man a mama’s boy. |
| What it is: |
This is the circular DNA found in the eukaryote’s mitochondria. It is 16,569 bp in length and encodes 37 genes. mtDNA follows a genetic code similar to bacteria when translating codons, supporting the idea that mitochondria were once independent aerobic bacteria.
The genetics of mitochondrial diseases is complex. First, mtDNA is inherited from the mother because the egg is the main source of mitochondria. Generally, every cell has multiple mitochondria and every mitochondrion has multiple copies of circular DNA. During cell division, mitochondria do not divide equally between daughter cells so mutant mtDNA can vary significantly between cells. Then add the fact that mitochondria do not have a good repair mechanism, it means mutations accumulate.
Due to multiple mtDNA and mitochondria per cell and tissue, there is a threshold effect requiring a minimum of mutations before clinical symptoms appear. Because mitochondria produce energy, it shouldn’t be surprising that mtDNA diseases first affect the energy-craving brain and muscles. |
Mitosis
| What it's not: |
The tendency to have smelly feet. |
| What it is: |
The kind of cell division that produces two daughter cells with DNA identical to the parent. Living organisms (like us) produce new cells via this process to grow and repair damage. So natural cloning has long been a fact of life. |
Mode of Inheritance
| What it's not: |
The way in which your beloved and belated grandmother divided up her estate. |
| What it is: |
The different modes of inheritance describe how genetic traits are passed down from parent to offspring. X-linked, autosomal recessive and autosomal dominant are the three basic modes of inheritance seen in single gene disorders. Multifactorial inheritance is another mode of inheritance that depends on both genetic and environmental factors. Plus, our mitochondria are primarily inherited from our mothers so defects in mitochondrial genes have a mother to child (maternal) inheritance pattern. |
Molecular Chaperones
| What it's not: |
Your Math and English teachers supervising your high school dance. |
| What it is: |
Molecular chaperones are proteins that assist in the correct folding or transport of other proteins. This helps to make sure that proteins are assembled properly and in the right place so they are useful to the cell. |
Monosomy
| What it's not: |
The zombie-like state students are in when they have to get up early to get to class. |
| What it is: |
The term monosomy is used to describe when one copy (or part of) of a chromosome is present instead of the typical two copies (disomy). As a rule, only one chromosome (monosomy) is lethal except in Turner’s syndrome where women have one X chromosome instead of the usual two X chromosomes. |
Mosaic
| What it's not: |
An art style combining many little parts into a bigger work of art |
| What it is: |
An individual or tissue is said to be mosaic if it contains at least two cell lines that differ genetically but that have been derived from the same fertilized egg. Just like the bricks that make up a house might consist of a patchwork of two colours, a mutation that happens in a single cell soon after conception may lead to an individual who is made up of some cells with a functional copy of a gene, and some cells that contain the mutation. |
Mouse Model
| What it's not: |
The next Kate Moss. |
| What it is: |
In genetics related research, experiments are often performed on organisms other than humans for safety and ethical reasons. The mouse is an organism that is commonly used in genetic research because its genome has been well studied, the genome can be easily altered and new generations of mice can be bred quickly. There are currently many mouse models available for research that mimic human diseases like obesity, cancer and neurological conditions like Huntington’s disease. |
Multifactorial
| What it's not: |
An adjective applied to industrial parks. |
| What it is: |
This generally means ‘many factors’. In terms of inheritance patterns, multifactorial can be confusing when you are first learning about genetics because it is often thrown about and defined vaguely. Because the many ‘factors’ referred to include multiple genes and/or environmental influences, how the term is precisely defined changes depending on the situation. For example, in some cases multifactorial could mean 2 genes plus environment; in others, 7 seven genes working together.
Most common traits like skin colour and height are multifactorial. Although your genes give a rough estimate of your height, environment also plays an obvious role in your stature because if you don’t have adequate nutrition during childhood, you will be shorter.
To see how genes and environment both affect a trait, please try this short activity. |
Mutation
| What it's not: |
A term of endearment for one’s younger brother or sister. |
| What it is: |
Basically, mutations are mistakes; specifically, errors in copying the code of bases DNA molecule when the cells is dividing either by mitosis or meiosis. Most mistakes at this level are largely unnoticed - happily, like most of the little mistakes many of us make regularly. That is to say, most mutations are silent: they don’t mess up the protein the gene codes for.
Mutations can also arise from external damage to DNA. For example, sunlight causes two thymines (see base pairs) to stick together. When this is ‘fixed’, a different base can be inserted. As well, there are several disorders where an individual is predisposed to mutations; for instance, having defunct repair genes means more mistakes can go unnoticed until it’s too late. |
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