Chapter 15

Question 1

what is a poly morphism?

Answer 1

common genetic variants.

Question 2

what is the definition for genetic variation?

Answer 2

the genetic variation that exist among individuals in a population at a particular point in time

Question 3

what is a genotype and a phenotype?

Answer 3

genotype- the genetic makeup of a cell or organism

phenotype- an individuals characteristics and traits.

Question 4

How did differences in genotypes between individuals originate?

Answer 4

by mutations that occurred and are commonly found now in a population (polymorphism)

Question 5

what is an allele?

Answer 5

different forms of a gene that correspond to different DNA sequences in the genes (different versions of the same gene)

Question 6

how many new mutations are produced every generation from parent to child?

Answer 6

~ 30-150

Question 7

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?

Answer 7

the function of the protein is changed since the amino acid sequence determines the shape of the protein which determines the function.

Question 8

What is a homozygous allele?

Answer 8

when an individual inherits the same type of allele from each parent. Or an

Question 9

What is a heterozygous allele?

Answer 9

when an individual inherits different types of alleles from each parent.

Question 10

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?

Answer 10

2 but there are 3 different alleles available in a population.

Question 11

is it better to be homozygous or heterozygous for a given allele if that allele is potentially harmful?

Answer 11

heterozygous

Question 12

what are examples of phenotypes effected by the environment?

Answer 12

• 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.

Question 13

what occurs during the polymorphism of the OCA2 gene?

Answer 13

G-C allele- blue eyes (absence of pigment)

T-A allele- Brown eyes

Question 14

what occurs during the polymorphism of the MC1R gene?

Answer 14

C allele codes for Arg= black/brown/blonde

T allele codes for Cys= red (failed melanin)

Question 15

What does Nondisjunction mean?

Answer 15

the failure of a pair of chromosomes to separate during anaphase of cell division.

Question 16

Which checkpoint in the cell cycle usually prevents nondisjunction from happening?

Answer 16

Spindle assembly checkpoint (before anaphase are all chromosomes attached to the spindle?)

Question 17

When Nondisjunction occurs in mitosis what happens?

Answer 17

leads to cell lineages with extra or missing chromosomes (often in cancer cells)

Question 18

When Nondisjunction occurs in meiosis what happens?

Answer 18

the result is that the gametes have either an extra or missing chromosome.

Question 19

what is the difference between first-division nondisjunction and second-division nondisjunction?

Answer 19

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.

Question 20

If a cell experiences a nondisjunction event in meiosis I, will any of the 4 daughter cells be normal?

Answer 20

no 2 have no chromosomes and 2 have extra chromosomes.

Question 21

If a cell experiences a nondisjunction event in meiosis II, will any of the 4 daughter cells be normal?

Answer 21

yes 2 will be normal and 1 will have an extra chromosome while the other will be lacking a chromosome.

Question 22

if a nondisjunction fails to happen in meiosis I, what is it that failed to separate properly from each other?

Answer 22

the homologs have failed to separate properly.

Question 23

if a nondisjunction fails to happen in meiosis II, what is it that failed to separate properly from each other?

Answer 23

The sister chromatids have failed to separate from each other.

Question 24

What are the 3 possible ways an allele can be? also what may effect this?

Answer 24

-harmful
-beneficial
-neutral
sometimes the environment where the carrier lives can effect the allele.

Question 25

When someone has sickle cell anemia, what allele is present?

Answer 25

homozygous SS for B-globin.

Harmful if 2 copies of the S allele

Question 26

When someone has a sickle cell trait, what allele is present?

Answer 26

heterozygous AS for B-globin

Question 27

The S allele of the B-globin gene have what 3 different effects?

Answer 27

harmful- if carried in the homozygous state
beneficial- in heterozygous state, malaria
neutral- heterozygous state where malaria isn’t a problem.