Mẹo What is the term for any change in the nucleotide sequence of DNA?
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Hoàng Quang Hưng đang tìm kiếm từ khóa What is the term for any change in the nucleotide sequence of DNA? được Cập Nhật vào lúc : 2022-11-26 06:50:09 . Với phương châm chia sẻ Bí quyết về trong nội dung bài viết một cách Chi Tiết Mới Nhất. Nếu sau khi Read Post vẫn ko hiểu thì hoàn toàn có thể lại phản hồi ở cuối bài để Mình lý giải và hướng dẫn lại nha.Mutation. Mutations are happening in our cells all the time, but almost none of these affect our health. This is very different than what we often see in science fiction in movies. In real life, a mutation is never so beneficial that it turns a person into a superhero or does something bizarre like cause them to grow wings. There are many reasons that mutations usually don't have major consequences. One reason is that our cells have very sophisticated machinery for repairing mutations very quickly. So there's not enough time for them to cause problems. Another is that most mutations occur in somatic cells like muscle cells or skin cells and can only affect the cell where the mutation occurred and cells that grow from that cell. On the other hand, when mutations occur in germline cells, eggs and sperm, they will be present in every cell that develops from that egg or sperm, an entire person, and can have larger effects.
Nội dung chính Show- What is any change in DNA sequence called?What is it called when one nucleotide is changed?Which term is used when referring to a change in the nucleotide sequence of a DNA molecule multiple choice question?Which term is used when referring to a change in the nucleotide sequence of a DNA molecule quizlet?
It's not a mistake when we say that ATG is a start codon. Scientists generally consider AUG to be a start codon in mRNA sequence and ATG to be a start codon in a DNA sequence.
But...
If AUG on an mRNA molecule means "start,"
and mRNA is copied from a DNA template,
and the DNA template is complementary to the mRNA copy,
then why isn't a DNA start codon TAC?
The key thing to remember is that DNA is double stranded.
Here's a DNA sequence, with the start codon in red:
GC ATG CTG CGA AAC TTT GGC TGA
We've shown the sequence of just one of the DNA strands. It's a shortcut, and it's tidier to look , and it's how DNA sequences are typically written. If we wanted to, we could include the sequences of both strands:
GC ATG CTG CGA AAC TTT GGC TGA
CG TAC GAC GCT TTG AAA CCG ACT
While our shorthand version shows just the top strand, it's actually the bottom strand that RNA polymerase reads to build an mRNA molecule. And if we're being literal about the actual nucleotides in the DNA strand that are read to build the mRNA's AUG start codon, we might consider the start codon on a DNA molecule to be TAC.
But that's not quite right. The chemical structure of DNA gives it a polarity, and the two complementary DNA strands are anti-parallel. That is, the 5' (5-prime) and 3' (3-prime) ends of the two DNA strands face in opposite directions:
5' GC ATG CTG CGA
AAC TTT GGC TGA 3'
3' CG TAC GAC GCT TTG AAA CCG ACT 5'
The scientific standard is to write a nucleotide sequence from 5' to 3'. That means we'd have to write the sequence of the bottom strand like this:
5' TCA GCC AAA GTT TCG CAG CAT GC 3'
It would be more accurate to say that the DNA sequence of the "start codon" on the bottom strand is CAT. But that's an inconvenient way to talk about a protein-coding DNA sequence: everything's not only complementary but also backwards.
For the sake of ease and clarity, scientists tend to ignore the bottom strand (they call it the "non-coding" or "antisense" strand). Instead, they refer to the sequence of the "coding" or "sense" strand: the one that's almost identical to mRNA—the difference of course being that every T in DNA is replaced by a U in RNA. They know there's another strand, and they know how to figure out what its sequence is if they need to.
The DNA sequence of a gene can be altered in a number of ways. Gene variants (also known as mutations) can have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. Variant types include the following:
Substitution
This type of variant replaces one DNA building block (nucleotide) with another. Substitution variants can be further classified by the effect they have on the production of protein from the altered gene.
- Missense: A
missense
variant
is a type of substitution in which the nucleotide change results in the replacement of one protein building block (amino acid) with another in the protein made from the gene. The amino acid change may alter the function of the protein.- Nonsense: A
nonsense
variant
is another type of substitution. Instead of causing a change in one amino acid, however, the altered DNA sequence results in a stop signal that prematurely signals the cell to stop building a protein. This type of variant results in a shortened protein that may function improperly, be nonfunctional, or get broken down. Insertion
An insertion
changes the DNA sequence by adding one or more nucleotides to the gene. As a result, the protein made from the gene may not function properly.Deletion
A deletion
changes the DNA sequence by removing least one nucleotide in a gene. Small deletions remove one or a few nucleotides within a gene, while larger deletions can remove an entire gene or several neighboring genes. The deleted DNA may alter the function of the
affected protein or proteins.Deletion-Insertion
This variant occurs when a deletion and insertion happen the same time in the same location in the gene. In a deletion-insertion variant, least one nucleotide is removed and least one nucleotide is inserted. However, the change must be complex enough to differ from a simple substitution. The resulting protein may not function properly. A deletion-insertion (delins) variant may also be known as an insertion-deletion (indel) variant.
Duplication
A duplication
occurs when a stretch of one or more nucleotides in a gene is copied and repeated next to the original DNA sequence. This type of variant may alter the function of the protein made from the gene.Inversion
An inversion changes more than one nucleotide in a gene by replacing the original sequence with the same sequence in reverse order.
Frameshift
A reading frame consists of groups of three nucleotides that each code for one amino acid
. A
frameshift
variant occurs when there is an addition or loss of nucleotides that shifts the grouping and changes the code for all downstream amino acids. The resulting protein is usually nonfunctional. Insertions, deletions, and duplications can all be frameshift variants.Repeat expansion
Some regions of DNA contain short sequences of nucleotides that are repeated a number of times in a row. For example, a trinucleotide repeat is made up of sequences of three nucleotides, and a tetranucleotide repeat is made up of sequences of four nucleotides. A repeat expansion
is a variant that increases the number of times that the short DNA sequence is repeated. This type of variant can cause the resulting protein to function improperly.
What is any change in DNA sequence called?
A gene variant is a permanent change in the DNA sequence that makes up a gene. This type of genetic change used to be known as a gene mutation, but because changes in DNA do not always cause disease, it is thought that gene variant is a more accurate term.What is it called when one nucleotide is changed?
Substitution, as related to genomics, is a type of mutation in which one nucleotide is replaced by a different nucleotide. The term can also refer to the replacement of one amino acid in a protein with a different amino acid.Which term is used when referring to a change in the nucleotide sequence of a DNA molecule multiple choice question?
A mutation is a change in the nucleotide sequence of a short region of a genome, and phenotypic results may vary on the severity and location of the mutation. Mutations can result from errors during DNA replication or induced by exposure to mutagens (like chemicals and radiation).Which term is used when referring to a change in the nucleotide sequence of a DNA molecule quizlet?
Changes to the nucleotide sequence of a DNA molecule are called. mutations. Tải thêm tài liệu liên quan đến nội dung bài viết What is the term for any change in the nucleotide sequence of DNA?
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