Kaitlyn Li
Author: Science Daily
Date: Jan. 3 2014
URL: http://www.sciencedaily.com/releases/2014/01/140103204424.htm
Summary:
Recently scientists have found a genetic deletion that affects both fertility and milk yield in dairy cattle. For many years milk yield in dairy cattle such as the Scandinavian dairy cattle have been rising. This has resulted from targeted breeding programs and modern breeding methods. Although milk yield has risen, there has been almost no improvement in fertility. This unfavorable correlation between fertility and milk yield is partially affected by a deletion of a gene sequence. This has been recently discovered by scientist from Aarhus University, University of Liège, and MTT Agrifood Reasearch Finland. Before this discovery people have assumed that the reduction in fertility is due to the negative energy balance of high-producing cows at the peak of their lactation. The deletion of four genes is a recessive embryonically lethal mutation leading to calves to die while they are still embryos. Since the mutation is recessive both parents must have the gene and pass it to their calf, for the calf to be affected. This mutation has become common among in Nordic Red cattle and has caused many embryos to die in Finnish Ayshire, Swedish Red, and Danish Red cattle. The mutation has become widespread since it has a strong positive affect on milk yield. Breeder selecting for high milk yields have inadvertently also selected embryo mortality.
Relevance:
This article relates to our Hereditary Unit and Molecular Genetic Unit. In the hereditary unit we learned that traits were passed down from generation to generation. A parent contains two alleles. One allele from each parent is given to their offspring. In the article the mutation is recessive meaning that not having the mutation is dominant. When passing down traits if both parents contain the recessive trait then there is a chance their offspring will die as an embryo. Yet if one parent doesn't contain the recessive trait and has the dominant non mutated trait, the offspring will still develop. Since an organism is heterogeneous, the dominant trait is expressed. We also learned that mutations in a gene sequence occur when a change occurs, either a deletion, insertion or substitution. In the article a deletion occurred which lead to embryos being unable to develop. This mutation is a frameshift mutation and also must be carried in the gametes because it's inherited. This article also gives an example of artificial selection where humans breed domesticated plants and animals to produce offspring with genetic traits that humans valued. For dairy cattle, humans would choose the cattle that best yield milk. These cattle are inadvertently carried with the mutation where fertility is lowered and milk yield is raised. Since these cattle are the ones selected to reproduce, the mutation would occur more and more in the gene pool.
Author: Science Daily
Date: Jan. 3 2014
URL: http://www.sciencedaily.com/releases/2014/01/140103204424.htm
Summary:
Recently scientists have found a genetic deletion that affects both fertility and milk yield in dairy cattle. For many years milk yield in dairy cattle such as the Scandinavian dairy cattle have been rising. This has resulted from targeted breeding programs and modern breeding methods. Although milk yield has risen, there has been almost no improvement in fertility. This unfavorable correlation between fertility and milk yield is partially affected by a deletion of a gene sequence. This has been recently discovered by scientist from Aarhus University, University of Liège, and MTT Agrifood Reasearch Finland. Before this discovery people have assumed that the reduction in fertility is due to the negative energy balance of high-producing cows at the peak of their lactation. The deletion of four genes is a recessive embryonically lethal mutation leading to calves to die while they are still embryos. Since the mutation is recessive both parents must have the gene and pass it to their calf, for the calf to be affected. This mutation has become common among in Nordic Red cattle and has caused many embryos to die in Finnish Ayshire, Swedish Red, and Danish Red cattle. The mutation has become widespread since it has a strong positive affect on milk yield. Breeder selecting for high milk yields have inadvertently also selected embryo mortality.
Relevance:
This article relates to our Hereditary Unit and Molecular Genetic Unit. In the hereditary unit we learned that traits were passed down from generation to generation. A parent contains two alleles. One allele from each parent is given to their offspring. In the article the mutation is recessive meaning that not having the mutation is dominant. When passing down traits if both parents contain the recessive trait then there is a chance their offspring will die as an embryo. Yet if one parent doesn't contain the recessive trait and has the dominant non mutated trait, the offspring will still develop. Since an organism is heterogeneous, the dominant trait is expressed. We also learned that mutations in a gene sequence occur when a change occurs, either a deletion, insertion or substitution. In the article a deletion occurred which lead to embryos being unable to develop. This mutation is a frameshift mutation and also must be carried in the gametes because it's inherited. This article also gives an example of artificial selection where humans breed domesticated plants and animals to produce offspring with genetic traits that humans valued. For dairy cattle, humans would choose the cattle that best yield milk. These cattle are inadvertently carried with the mutation where fertility is lowered and milk yield is raised. Since these cattle are the ones selected to reproduce, the mutation would occur more and more in the gene pool.
Your summary states that "although milk yield has risen, there has been almost no improvement in fertility", which makes it seem like there's a cause-and-effect relationship between the two. If there's an increase in milk yield, should fertility improve?
ReplyDeleteThrough the past years Milk Production has increase significantly, while fertility has not. From studies of cows, it seems as if there would not be an improvement in fertility. Factors, such as the mutation which increases milk yield but kills embryos which would give the idea that fertility would not improve.
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