Mutations,
the changes in the sequences of genes in DNA
, are one source of genetic variation. Another source is gene flow, or the movement of genes between different groups of organisms. Finally, genetic variation can be a result of sexual reproduction, which leads to the creation of new combinations of genes.
What are different versions of the same gene that arise through mutation?
When genes mutate, they can take on multiple forms, with each form differing slightly in the sequence of their base DNA. These gene variants still code for the same trait (i.e. hair color), but they differ in how the trait is expressed (i.e. brown vs blonde hair). Different versions of the same gene are called
alleles
.
Can the same trait arise from different genetic changes?
Mutations
could arise in the same gene and give rise to the same trait because many nucleotides contribute to controlling the expression of a gene. Mutations in a different gene could also give rise to the same trait.
Lactase-persistence alleles vary in their geographic distributions. Within European and populations of European ancestry, they are almost entirely correlated with the presence of
the −13,910 C/T mutation in the enhancer region of the lactase
gene (LCT).
Are genetic changes random?
In other words,
mutations occur randomly with respect to whether their
effects are useful. Thus, beneficial DNA changes do not happen more often simply because an organism could benefit from them.
What are the 4 types of mutation?
- Germline mutations occur in gametes. Somatic mutations occur in other body cells.
- Chromosomal alterations are mutations that change chromosome structure.
- Point mutations change a single nucleotide.
- Frameshift mutations are additions or deletions of nucleotides that cause a shift in the reading frame.
What are 3 causes of mutations?
A mutation is a change in a DNA sequence. Mutations can result from
DNA copying mistakes made during cell division, exposure to ionizing radiation, exposure to chemicals called mutagens
, or infection by viruses.
What is lactase persistence can you still drink milk without having any problems?
People who are lactase persistent continue to produce the enzyme lactase beyond infancy and generally
throughout life
. As a consequence, they are able to digest lactose and drink milk at older ages without adverse effects.
Is lactose intolerance a recessive trait?
The type of lactose intolerance that occurs in infants (congenital lactase deficiency) is inherited in an
autosomal recessive pattern
, which means both copies of the LCT gene in each cell have mutations.
Why would a mutation leading to lactase persistence become common in certain populations but not others?
The lactase-persistence mutation would become common if
it provided a survival and reproductive advantage in a particular environment
. For example, in a population with domesticated cows, where milk is available, the ability to drink milk might have been advantageous in periods of drought or when food was limited.
Why do most changes to DNA have no effect at all?
Many kinds of somatic mutations have no obvious effect on an organism,
because genetically normal body cells are able to compensate for the mutated cells
. Nonetheless, certain other mutations can greatly impact the life and function of an organism.
What is the only random aspect of evolution?
Evolution by natural selection is a two-step process, and only the first step is random:
mutations are chance events
, but their survival is often anything but.
What is an example of silent mutation?
Silent mutations are base substitutions that result in no change of the amino acid or amino acid functionality when the altered messenger RNA (mRNA) is translated. For example, if the
codon AAA is altered to become AAG
, the same amino acid – lysine – will be incorporated into the peptide chain.
What is the difference between a silent mutation and a neutral mutation?
silent or synonymous mutation – does not change the amino acid sequence encoded by a particular gene. A
neutral mutation is neither adaptive nor deleterious
.
What is the most rare genetic mutation?
KAT6A syndrome
is an extremely rare genetic neurodevelopmental disorder in which there is a variation (mutation) in the KAT6A gene. Variations in the KAT6A gene can potentially cause a wide variety of signs and symptoms; how the disorder affects one child can be very different from how it affects another.
