Chapter 15 Flashcards
what is a poly morphism?
common genetic variants.
what is the definition for genetic variation?
the genetic variation that exist among individuals in a population at a particular point in time
what is a genotype and a phenotype?
genotype- the genetic makeup of a cell or organism
phenotype- an individuals characteristics and traits.
How did differences in genotypes between individuals originate?
by mutations that occurred and are commonly found now in a population (polymorphism)
what is an allele?
different forms of a gene that correspond to different DNA sequences in the genes (different versions of the same gene)
how many new mutations are produced every generation from parent to child?
~ 30-150
if an allele has a dramatic effect on the amino acid sequence what is the result?on the function of a protein what happens to that protein?
the function of the protein is changed since the amino acid sequence determines the shape of the protein which determines the function.
What is a homozygous allele?
when an individual inherits the same type of allele from each parent. Or an
What is a heterozygous allele?
when an individual inherits different types of alleles from each parent.
What is the maximum number of alleles of a given gene you can carry and what is the maximum amount of possible alleles a gene can have?
2 but there are 3 different alleles available in a population.
is it better to be homozygous or heterozygous for a given allele if that allele is potentially harmful?
heterozygous
what are examples of phenotypes effected by the environment?
- skin pigmentation: sun exposure
- adult height: nutritional state and health as child
- rate of lung cancer: smoke exposure
- body weight: food availability& amount of physical activity.
what occurs during the polymorphism of the OCA2 gene?
G-C allele- blue eyes (absence of pigment)
T-A allele- Brown eyes
what occurs during the polymorphism of the MC1R gene?
C allele codes for Arg= black/brown/blonde
T allele codes for Cys= red (failed melanin)
What does Nondisjunction mean?
the failure of a pair of chromosomes to separate during anaphase of cell division.
Which checkpoint in the cell cycle usually prevents nondisjunction from happening?
Spindle assembly checkpoint (before anaphase are all chromosomes attached to the spindle?)
When Nondisjunction occurs in mitosis what happens?
leads to cell lineages with extra or missing chromosomes (often in cancer cells)
When Nondisjunction occurs in meiosis what happens?
the result is that the gametes have either an extra or missing chromosome.
what is the difference between first-division nondisjunction and second-division nondisjunction?
first-division nondisjunction: more common, homologous chromosomes fail to separate and all resulting gametes have an extra or missing chromosome.
second-division nondisjunction: sister chromatids fail to separate, giving rise to to products with a normal number of chromosomes, 2 gametes will be normal and the other 2 gametes have either an extra chromosome, or missing chromosome.
If a cell experiences a nondisjunction event in meiosis I, will any of the 4 daughter cells be normal?
no 2 have no chromosomes and 2 have extra chromosomes.
If a cell experiences a nondisjunction event in meiosis II, will any of the 4 daughter cells be normal?
yes 2 will be normal and 1 will have an extra chromosome while the other will be lacking a chromosome.
if a nondisjunction fails to happen in meiosis I, what is it that failed to separate properly from each other?
the homologs have failed to separate properly.
if a nondisjunction fails to happen in meiosis II, what is it that failed to separate properly from each other?
The sister chromatids have failed to separate from each other.
What are the 3 possible ways an allele can be? also what may effect this?
-harmful
-beneficial
-neutral
sometimes the environment where the carrier lives can effect the allele.
