Sex Determination And Linkage

Question 1

What are the assumptions of the chi square goodness of fit?

Answer 1

Random sample

Sample size (sufficiently large to prevent small sample error)

Independence - the observations are independent of each other.

Question 2

What are degrees of freedom?

Answer 2

The number of values (characteristics such as different flower colors) that are free to vary minus 1

Question 3

How are the princples of segregation and independent assortment related and how art they different?

Answer 3

Genes encoding different characteristics separate and assort independently of one another when they are not located close together on the same chromosome.

During this process, two alleles of the same gene encoding one characteristic still have to be segregated from each other during the formation of gametes.

Question 4

In male spermatogenesis, the Y chromosomes always segregate ___.

Answer 4

Together.

Question 5

True or false: sexual reproduction alternates between haploid and diploid states.

Answer 5

True

Question 6

What is an example of non-homologous chromsomes pairing during meiosis?

Answer 6

X and Y chromosomes pair during meiosis even though they are not homologous.

Question 7

What is hermaphroditism?

Answer 7

Both sexes in the same organism.

This is mostly seen in invertebrates, snails, slugs and earthworms.

Question 8

What is monoecious?

Answer 8

When an organism has both male and female reproductive structures.

This includes corn, sagebrush and buttercup.

Question 9

What is dioecious?

Answer 9

Either male or femal reproductive structures but not both in one organism.

Question 10

What chromosomes contains genetic information essential for both sexes?

Answer 10

The X chromosomes

Question 11

The absence of what chromosome reults in a female phenotype?

Answer 11

Chromosome Y

Question 12

How does the heterogametic sex differ from the homogametic sex?

Answer 12

Gametes of the heterogametic sex have different sex chromosomes; gametes of the homogametic sex have the same sex chromosome.

Question 13

What gender is manifested in some organisms that have a haploid set?

Answer 13

Males

Question 14

What gender is manifested in some organisms with a diploid set?

Answer 14

Female

Question 15

True or false: in some organisms, sex is determined by temperature.

Answer 15

True

Question 16

What is the X:A ratio?

Answer 16

X:A; x = number of X chromosomes

A = number of haploid sets of autosomes

Question 17

What is the theory of Bridges?

Answer 17

A theory that the sex of a fruit fly is determined by the relative number of x chromosomes and autosomal sets.

The Y chromosome does not determine sex, just fertility.

Question 18

What is the sexual phenotype of a fruit fly that has XXYYY sex chromosomes and two sets of autosomes?

Answer 18

Female. X:A ratio is 1.

Question 19

What gene on the Y chromosome determines maleness?

Answer 19

SRY gene.

Question 20

What sex chromosomes are present in Turner syndrome?

Answer 20

XO

Question 21

What are the possible combinations of sex chromosomes for Klinefelter syndome?

Answer 21

XXY, XXXY, XXXXY, XXYY

Question 22

What are signs and symptoms of Turner Syndrome?

Answer 22

XO

Short stature

High-arched palate

Ears protrue, neck low hairline

Lazy eye

Broad chest

Question 23

What is the male-determining gene in humans?

Answer 23

SRY gene

Question 24

What happens if the SRY gene gets translocated to the X chromosome?

Answer 24

Testicular disorder of sex development, SRY on X results in male phenotype.

Question 25

What are some X-linked characteristics?

Answer 25

X linked white eye in Drosophila

X linked color blindness in humans

Question 26

What was the genotype of the few-lived F1 red-eyed males obtained by Bridges when he crossed a white-eyed female with a red-eyed male?

Answer 26

X^WX^+Y

Question 27

Hemophilia (reduced blood clotting) is an X-linked recessive disease in humans. A woman with hemophilia mates with a man who exhibits normal blood clotting. What is the probability that their child will have hemophilia?

Answer 27

1/2

Question 28

XYY how does XYY sondrome prove that the Y chromosome has few genes that determine human structure?

Answer 28

Patients with XYY haven no specific physical features except perhaps increased height.

They may have learning disabilities, aggressive behavior and severe acne.

Question 29

What is dosage compensation?

Answer 29

Inactivation of 1 X chromomes to compensage for different X dosage between the sexes.

Question 30

What is the Lyon hypothesis?

Answer 30

A hypothesis that suggests that dosage compensation in mammales by inactivation of all but one X chromosome inc ells with more than one X chromosome.

The Barr body, is an inactivated X chromosome.

Question 31

What is mosaicism?

Answer 31

A condition in which cells within the same person have a different genetic makeup.

Question 32

What occurs when 2 or more Xic inactivation centers are present?

Answer 32

Xist is turned on and its RNA product coats the X chromsome.

Additional proteins recognize the inactive X and cause condensation and permanent inactivation.

This process in done during meiosis.

Question 33

What is the chi-square goodness of fit?

Answer 33

A statistical test that indicates the probability that the difference between the observed and expected is due to chance.