New answers tagged

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Thalassemia is a recessive trait. That means individuals with only one copy of the allele (Heterozygotes) have the "normal" phenotype (they don't have Thalassemia). If an individual is homozygous for the recessive allele they will have Thalassemia. Heterozygotes are often referred to as carriers as they can transmit the allele to their offspring, but do ...


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The first definition is correct. A sex-linked trait is a trait caused by a locus that is on a sexual chromosome. If you google sex-linked trait, you will find this same definition (not the exact same words) over and over again. The definition of sex-linked trait is NOT restricted to traits that are not unrelated to primary or secondary sexual organs. Any ...


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Sex linked traits are those controlled by genes on the sex chromosomes, regardless of whether or not they are related to reproduction. This can be the major (e.g. X or Z) or minor (e.g. Y or W) sex chromosomes. "Sex linkage applies to genes that are located on the sex chromosomes. These genes are considered sex-linked because their expression and ...


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I assume that you mean changing the amino acid sequence in a single protein in an organism to one that no longer reflects the sequence predicted from the DNA sequence. In that case, I would suggest using ADAR (Double-stranded RNA-specific adenosine deaminase) or similar enzymes. ADAR deaminates adenosine to inosine, which is read by the ribosome as a ...


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To a certain extent, maybe. However RNAi would not work as you describe because it causes the whold mRNA to be degraded not just a portion of it. If the gene in question is spliced, you could probably influence the splicing pattern by triggering certain signalling pathways. But this is limited to producing different splicing variants of your gene and is ...


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In programming, if you need to ensure your data has integrity, a single array won't do. We have cyclic dependency checks in programing to determine if the data is corrupt. We have hamming codes to permit detecting a fixing one bit corruption. If we want to really fix multi-bit corruption, we need at least one copy of the data. Lossless compression ...


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Your individual questions here are reasonable enough - although you could do a bit better at knowing some more details of the systems you are dismissing as 'flawed'. However, I think the bigger problem is your overall approach, which seems to be to make analogies between human-made computers and biological systems and then critiquing the 'missing' parts from ...


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From wikipedia If the genetic pattern of homozygotes can be distinguished from that of heterozygotes, then a marker is said to be co-dominant. This definition seems to be different from the one used to explain allelic effects. For example, as you would know a SNP is basically a feature of the DNA sequence. It is more of a genotype rather than a ...


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"Note that interaction effects among genes also depend on their physical distance." I think that's more of a pragmatic assumption, because we tend to associate regulatory features with their closest downstream TSS, though it's certainly not a hard and fast rule. e.g., in certain organisms like budding yeast, its known that the most transcription factor ...


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This is an open-ended question and will be impossible to correctly answer. I am voting "to close as too broad". Note also that the question in the title is not the same as the question in the post. But I still wanted to give you some information that may help you. Here are just a few examples for which knowing gene density matters. Background selection ...


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Largely an informed guess based on properties of distributions rather than specific knowledge of statistical genetics: a beta distribution is useful for modeling the frequencies of two alleles at one locus. A Dirichelet distribution, which is a multivariate generalization of a beta distribution, would thus be useful for modeling a set of loci. The flip side ...


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Expression of the double-sex gene is rather unusual, so it is not surprising that you are having difficulty understand mutations in it. The simplified diagram below (adapted from Gilbert’s Developmental Biolgy — available on-line) should help clarify the matter. The key concept is that although the double-sex gene (dsx) is expressed in both male and ...


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I have done lots of research on this in the past few hours and would like to record this for future students to have a look at if they ever require help with a similar question. a) Complete a genetic cross of F2 to show the genotypes and phenotypes of the offspring. We have a two by two grid, with the centre results being TT, Tt, tT, and tt. The phenotypes ...


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I can answer this for mammals. The mammalian oocyte (egg) is surrounded by a layer called the zona pellucida. There are three well-characterized proteins in this layer, called ZP1, ZP2 and ZP3 (not very imaginative, I know). I don't know much about ZP1 but ZP2 and ZP3 are involved in fertilization. The sperm's outer surface has receptors for ZP2 and ZP3. ...


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I would say that first exception might be White gene in Drosophila Melanogaster, described in 1910 by Thomas Hunt Morgan and Lilian Vaughan Morgan. At least, is the first exception we study in genetics since sex linkage its so fundamental. These experiments established the chromosomal theory of inheritance. Thomas Hunt Morgan, an embryologist who had ...


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The first exception to Mendelian genetics was probably discovered by Mendel. As a followup to his pea experiments, Mendel used hawkweed, in which his rules do not seem to apply due to some unusual aspects of hawkweed development; see Apomixis in hawkweed: Mendel's experimental nemesis for details. Mendel eventually abandoned his biological experiments, ...


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Assuming... The parents are the real biological parents (no cheating allowed!) There is a purely dominance/recessivity relationship between the alleles and no individual can express the disorder without being homozygous for the disease causes allele De novo mutations for the disorder are rare enough to be ignored in the calculation of this probability ...


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[H]ow exactly we mark out genotype in science? Do we use D's and r's? General rule The general rule is to indicate the dominant allele with a upper-case letter and the recessive allele with a lower-case letter. The most commonly used letter is the first letter of the alphabet. The two possible alleles are a and A and the four possible genotypes here ...


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Is there evidence of selection against long proteins and long genes? I am not aware of any such evidence and cursory googling did not reveal studies that researched a correlation between gene selection and gene size. However, the larger a gene, the larger the probability of a deleterious mutation within said gene so I expect that there is some limit to ...


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In population genetics, with a simple one-locus two-allele model, we consider the frequency of the two alleles to be $p$ and $q$ where $p + q = 1$ (and thus $1-p=q$ and $1-q=p$). When an allele is recessive it is only expressed at the phenotypic level when the individual carries two copies of the allele. Following from your example, gene $A$ might be ...


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Usually relatedness is described via the coefficient of relationship because it is natural, relatively simple to calculate, and corresponds well to the actual amount of DNA likely to be inherited. In this system, you are 50% related to your mother, and your mother is 50% related to her full brother (your uncle), so you are 50% $\times$ 50% $=$ 25% related ...


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The coefficient of relationship between you and your uncle is 25% (see wiki > coefficient of relationship for more info). However, the percentage of similarity depends on the genetic diversity in the population of interest. If you were studying a population of fully homozygous clones (no genetic diversity), then no matter what the coefficient of ...


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To some extent, it depends on what you mean by "dominance". If you take a phenotypic definition of dominance, then the answer is (technically) yes, you could imagine such a gene system. That is, imagining alleles p, q, and r, and three phenotypes P, Q, and R, with the following homozygous behavior: pp ➞ P qq ➞ Q rr ➞ R Then you could theoretically ...


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Dominance by silencing the other allele The mechanisms by which dominance work are still very much unknown. One type of mechanism that will be of particular interest to this question is the modifier of dominance where the protein product of an allele silence the expression of the other allele in order to cause dominance relationship. Is the pattern you ...


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Issues with the post Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection). This question has nothing to do with sexual selection. What do you mean by ...


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Mutations are not performed targeting a specific new phenotype. There is no way an organism can "know" the impact of a specific future mutation anyway. A mutation is just a mistake in the replication process. As a consequence the majority of mutations are deleterious and only a handful of mutations are beneficial. It is true though that the mutation rate ...


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This kind of question is what developmental genetics is all about. The answer turns out to be, in general, 'no'. There is no neat mapping between spatial dimensions of an organism and its genome. (There is one exception to this in some organisms called the Hox cluster, but they are kind of a freak case). The reason for this is that in general you should ...


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To add to Remi b's answer - this question is confusing because 'null' and 'recessive' are terms emerging from two very different levels of analysis. The concept of 'recessive' existed before we knew what genes were, or how they worked. It just describes the patterns of inheritance you see in a gene's effects. The concept of a 'null' allele however came ...


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If you mean to say why DNA is in the form of chromosomes, then obviously answer is simple: For Compression and Packaging - Around 2metre long DNA must be compressed (at an unbelievably high ratio) to let it fit in the tiny nucleus (order of micrometers)


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Both TALEN and ZFN gene editing technologies use a pair of single-strand endonucleases that ultimately lead to a double strand break. Cas9 in CRISPR-Cas technology, however, cuts both the DNA strands (there are some Cas enzymes in certain bacterial species that cut only a single strand [ref]).       Image courtesy: ...


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Basically, a recessive allele leads to formation of a product that has a low activity or no activity, which is complemented in the presence of the dominant allele (there can be effects related to dosage, in some cases). This can be easily understood in terms of an enzyme; a dominant allele would code for an enzyme with full activity whereas the recessive ...


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Good question +1. Unfortunately, the mechanisms by which dominance work is relatively poorly understood and it is likely that the mechanism differs from one locus to another. You might want to have a look at the posts Why are some genes dominant over others? What is the mechanism behind it? Evolution of dominance or some papers such as Llaurens et al. ...


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Yes, it is perfectly possible for both pairs of non-sister chromatids to cross over in a single tetrad. The "standard textbook" depiction is a simplification, true tetrads can sometimes be very complicated and the nested crossing-over would be difficult for entry-level textbooks to cover. This microscope image clearly shows two chiasmata occurring on two ...


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After a lot of research, I've finally found an answer. In the case of humans, it is practically impossible. See this article from wikipedia: During gestation, the cells of the primordial gonad that lie along the urogenital ridge are in a bipotential state, meaning they possess the ability to become either male cells (Sertoli and Leydig cells) or female ...


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Metrics of interest The two metrics you are interested in are $\pi$ - the mean number of differences between two randomly sampled (with replacement) alleles in a population $d$ - the mean number of differences between two randomly sampled (with replacement) alleles coming from two different species Consider two sequences ATCGTCAAT ATAGTTAAT There ...


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I am assuming you are referring to the use of the software GTCA (which stands for Genome-Wide Complex Trait Analysis). Original paper: Yang et al. (2011). I looked to the papers who cited Yang et al. (2011) and quickly scanned through looking for "leg". I did not find anything on it. So my best guess is: No, nobody ever applied GTCA to leg length.


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Terminology is what is holding you back. What chromosome implies depends on context, i.e. is it replicated or not. In Meiosis. Gametes arise from Germline cells that have 23 PAIRS of chromosomes. That means, that while there are 23 different chromosomes they come in doubles/pairs. This is the typical X like shape we think about when we hear chromosomes. ...


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(For the direct answer to your question skip to the end!) Genetic linkage can affect the spread of other genes. The degree of linkage, affected by the rate of recombination between the point (nucleotide, gene etc.) directly under selection and the other point. If the rate of recombination between to given points is low then linkage between them is high and ...


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Genetic hitchhiking / genetic draft From wikipedia Genetic hitchhiking, also called genetic draft or the hitchhiking effect, is when an allele changes frequency not because it itself is under natural selection, but because it is near another gene on the same chromosome that is undergoing a selective sweep. The term "selective sweep" is used improperly ...


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The answer is a bit of a 'yes and no', though mostly 'no. The Y chromosome has very few genes, but arguably the most pivotal is the sex-determining region Y or SRY gene, also known as TDF or testis determining factor. The protein this gene codes for acts essentially as a master switch for male phenotypes by triggering the development of testes in the ...


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Yes, having a Y chromosome does cause specific alterations to facial structure. The Y chromosome doesn't contain much actual genetic information. Most of the information needed to activate the male developmental program (the female one is the default) is in just one gene 'SRT', the other genes on the Y chromosome aren't super important, such that you can ...


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If height was fully determined genetically (and no trait is), then concordance between monozygotic pairs would be almost perfect, modulo some variation due to somatic mutation in early development (e.g. a mutation happens in in cell directly after the embryo splits).


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So the term allele is a broad one, and simply refers to the different versions of any piece of DNA in circulation in the gene pool - it doesn't need to refer to a gene. I can talk about the alleles at a random place in the genome. But if we proceed with your question and ask - 'do nonsense mutations within coding genes also lead to the creation of different ...


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Allele is just a variant form of gene: independent of the final product of protein, so nonsense will also lead to new allele. I will quote Nature Scitable here: Alleles can also refer to minor DNA sequence variations between alleles that do not necessarily influence the gene's phenotype.


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They occur because there is no reason for them to be selected against. Except for a 25% chance of offspring not surviving, in the rare event that the other parent also has the mutation. That recessive, lethal genes can persist in the population is surprisingly one of the reasons that diploid organisms that sexually reproduce are so successful and diverse. ...


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It would be beneficial to a population for a lethal gene to evolve in incestuous situations because genetic diversity is then promoted through natural selection. Genetic diversity is necessary for a species to evolve which would improve the chance of survival.


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Lethal genes evolve simply because of random deleterious mutations and absence of strong selection. Recessive lethal genes Random mutations can make a gene product non-functional or reduce its activity. However, in diploid organisms the other fully-functional copy of the gene can compensate for the non-functional allele. Sometimes both the alleles can ...


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The term sister chromatids refers to the pair of chromosomes which have been produced from a single parent chromatid by DNA replication, while a homologous pair refers to chromosomes which are more distantly related (e.g. those inherited from one's mother and father, which I guess is what you mean by 'male and female chromosome'). So the two options you ...


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This is just loose terminology. By ‘lethal gene’ Dawkins means an essential gene with a mutation that renders it inactive. With a recessive gene, the one ‘good’ copy in the heterozygote provides enough gene-product to allow survival, in contrast to the situation in the homozygote where the total absence of gene-product is lethal. With a rare mutation, the ...



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