CH 15 Genetic Variation Reading Guide Flashcards Preview

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Flashcards in CH 15 Genetic Variation Reading Guide Deck (22):

Define Genotype

The genetic makeup of a cell


Define phenotype

an individuals observable characteristics or traits


How did differences in genotype between individuals originate?



Does a difference
in genotype between two individuals necessary translate into a difference in phenotype?



Define polymorphism

Genetic difference among individuals that is sufficiently common ie. present in a group of 50 randomly chosen people


Define allele

Different forms of any gene that correspond to different DNA sequences


What is the maximum number of alleles of a given gene that you can carry? Explain.

2. You can be homozygous AA of heterozygous Aa


Define homo and heterozygous

Homozygous: Has the two same types of alleles AA
Heterozygous: Has two different alleles Aa


What determines whether you are homozygous or heterozygous for a particular gene?

It depends what alleles you inherit from your parents


Is at always
best to be homozygous for a given allele? or is it always better to be heterozygous? Can
we make such a ‘rule of thumb’ when it comes to allelic combinations in general?

No. Some homozygous pairings can lead to life threatening conditions like sickle cell anemia


Define nondisjunction

is the failure of a pair of chromosomes to separate during anaphase. Results in one daughter cell receiving an extra set of chromosomes and one daughter receive no copy of that chromosome


Which checkpoint in the cell cycle is there to prevent nondisjunction from happening?

Spindle assembly checkpoint


If nondisjunction happens during meiosis, does it matter for the outcome if the error
happens in the first or the second meiotic division?

In the first-division non disjunction you get two daughter cells with an extra set of chromosome and two empty daughter cells
In the second-division non disjunction you get 1 daughter cell with an extra chromosome, 1 empty daughter cell and 2 normal daughter cells


If nondisjunction happens in meiosis I, what is it that fails to separate properly from
each other?

The homologous chromosomes fail to seperate


If nondisjunction happens in meiosis II, what is it that fails to separate properly from
each other?

The sister chromatids


What causes down syndrome?

An extra chromosome of one of the smallest sets. Usually a trisomy of chromosome 21


Why don’t we observe trisomy of chr 1, 2, 3, etc in live born infants?

Because trisomies involving these chromosome result in still births


What makes human males male? Is it the presence of the Y chromosome or the fact that
they just have a single X chromosome?

It's because of the presence of a Y chromosome


What explanation does the textbook give for the fact that XYY males are phenotypically

The extra Y chromosome contains only a few functional genes that an extra Y is essentially non detectable.


What explanation does the textbook give for the fact that XXX females are phenotypically

Due to X-inactivation


What causes Turners Syndrome?

45 chromosomes with just one X chromosome


What causes Klinefelter syndrome?

Two X and one Y chromosome on 47