Exam 1: Sex Determination and Sex-Linked Traits

Question 1

How does the X and Y chromosome pair up during meiosis even though they are not homologous?

Answer 1

They are homologous at pseudoautosomal regions near the telomeres (ends)

Question 2

Dioecious

Answer 2

EITHER male OR female reproductive structures in one organism

Question 3

How can diecious reproductive strucutres be determined?

Answer 3

Chromosomally, genetically, or environmentally

Question 4

Monoecious

Answer 4

BOTH male AND female reproductive structures seperatly on the same plant/organism

Question 5

Hermaphroditism

Answer 5

BOTH sexes in the same organism on the same flower

Question 6

XX-XO definition

Answer 6

XX = females XO = males

Question 6

XX-XO Examples

Answer 6

Some insects

Question 7

XX-XY definition

Answer 7

XX = female XY = males

Question 8

XX-XY Examples

Answer 8

Mammals

Question 9

Which parent is the offsprings sex determiend by?

Answer 9

Heterogametic organism - ZW (female birds), XY (male mammals), XO (male insects)

Question 10

ZZ-ZW definition

Answer 10

ZW = female ZZ= male

Question 11

ZZ-ZW Examples

Answer 11

Birds

Question 12

Which organisms have their sex determined by sex-determining genes instead of sex chromosomes

Answer 12

Fish

Question 13

Evolution of the Y chromosome

Answer 13

A mutation arose in the chromosome that caused maleness, suppression of crossing over, keeping genes for male traits on one chromosome. This lack of crossing over leads to the degeneration of the Y chromosome.

Question 14

Complete Dominance

Answer 14

Heterozygous phenotype is the same as the homozygous dominant phenotype

Question 15

Incomplete Dominance

Answer 15

Heterozygous phenotype is an intermediate in the middle of the homozygous phenotypes

Question 16

Codominance

Answer 16

Heterozygous phenotype expresses both homozygous phenotypes phenotypes but not blended together (flower has some red petals and some white pedals)

Question 17

CFTR

Answer 17

Cystic fibrosis transmembrane conductance regulator

Question 18

What occurs if someone is recessive for CFTR?

Answer 18

Membrane channels that line the lungs are closed

Question 19

What occurs if someone is heterozygous for CFTR?

Answer 19

Some proteins are closed and some are open, but enough CFTR is produced to prevent cystic fibrosis - codominance and mutation is recessive at the physiological level

Question 20

Penetrance

Answer 20

The percentage of offspring that have a particular genotype that actually express the expected phenotype

Question 21

Variable penetrance

Answer 21

When an individual has the allele for a trait but doesn’t express it

Question 22

Variable expressivity

Answer 22

The degree to which a trait is expressed

Question 23

How to calculate updated percent chances of phenotypes with a % penetrance?

Answer 23

normal change x % penetrance
ex: 1/4 x 8/10 =0.2 1/5 or 20% updated chances for a phenotype given a 80% penetrance

Question 24

Lethal allele phenotype ratio

Answer 24

2:1

Question 25

Epistasis

Answer 25

Gene interaction that affects gene expression

Question 26

Epistatic

Answer 26

The gene that stops the expression of another gene

Question 27

Hypostatic

Answer 27

The gene whose expression that is stopped or masked

Question 28

Recessive epistasis ratio

Answer 28

9:3:4

Question 29

Dominant Epistasis Ratio

Answer 29

12:3:1

Question 30

Recessive Epistasis

Answer 30

The trait that is associated with the hypostatic locus will not be expressed when the epistatic locus has a homozygous recessive genotype no matter the genotype at the hypostatic locus

Question 31

Dominant Epistasis

Answer 31

The trait associated with the hypostatic locus will not be expressed when the epistatic locus has a heterozygous or homozygous dominant genotype, regardless of the genotype at the hypostatic locus